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Thread: Opinions wanted on quality of porting job

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    Opinions wanted on quality of porting job

    Hi Guys,

    I just bought a 2ltr Pinto head that has been extensively ported and was just keen to get some opinions on the job that has been done.

    Obviously, it's pretty had to just give an opinion based on pics but any feedback would be great.

    The guy who did the work has been porting engines for over 30 years and has been around the pintos for a while too so i trust he did a good job.

    The valve seats haven;t been done yet either.

    Here's some pics.

    Cheers

    Matt
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    Re: Opinions wanted on quality of porting job

    I would be happy with that !

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    Re: Opinions wanted on quality of porting job

    I have plans to run it on 40mm R1 Bike Carbs, steel rods, forged pistons and a cam with similar specs -

    Lobe Lift - Ex .297 In .292
    Timing Ad (open & close) - 80-38 & 43-81
    Duration @ .50 - 256
    Valve Clr - .012 / .010
    Valve Lift - 448 / .457
    Lobe Sep - 110
    Rocker ratio - 1.55 / 1.6

    Cheers,

    Matt

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    Re: Opinions wanted on quality of porting job

    hmm, shortened guide bosses but no seperate guides, not even guide liners, also the inlet has had loads of work done where it makes very little difference, but where it really wants reworking the short turn wants a lot more work, head looks more show than go to me

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    Re: Opinions wanted on quality of porting job

    Thanks for the input Graham. I forgot to mention that I will have the bronze valve guides installed. The guy building my engine for me has a flow bench so we plan to see what can be done to improve the head.

    Cheers

    Matt

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    Re: Opinions wanted on quality of porting job

    Looks unneccesarly ported but without knowing the cross sectional areas of the port, hard to comment more. Also, hard to see the important short turn. I personally do not port cylinder heads but I have a certain basic knowledge about a correctly prepared Pinto cylinder head. Here at TS, there is quite a few very very knowledgeable people about the Pinto head and Graham is one of them. I am sure there will be more posts coming.

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    Re: Opinions wanted on quality of porting job

    Just a quick update - head has now had the porting finished off and valvles installed.

    We are aiming for 120 kw at the wheels so time will tell how good the head is.

    Bottom end is next. 92mm Forged pistons and longer than standard steel conrods are coming.

    Cheers

    Matt

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    Re: Opinions wanted on quality of porting job

    The valve seats look good, the exhaust ports are massive, much too large, but the real issue with that head is that the inlet ports have what looks like a really poor short side turn, it is very shallow and much too narrow, that head is not going to give the power you are looking for, 120kw at wheels would be around 200bhp flywheel, an accurate rolling road will not give that power with 48's, 40mm bike carbs will never flow enough air for 200bhp, that is my honest opinion

    Has the head porter got a flowbench as it does not look like he has
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Hi Jason,

    Those photos were taken by me just after I got the head. It was done by a friend without the aid of a flow bench. As it stands in the pics it was 90% complete with more porting work to be completed to iron out the issues you have highlighted.

    This is my first race engine and I am by no means an expert with engine building but I trust the guy doing it (who does have a flow bench) as he has done a number or similar powered pinto's albeit using twin 45 & 48 webers to get those numbers. Here's a link to one of his build threads - http://www.classic-ford.org/cfp/tm.a...gh=pinto+build

    As i have the bike carbs it will be interesting to see how they compare and also maybe back to back them with the webers.

    Just curious, have you ever played around with bike carbs as my guy loves them and believes that we'll get very similar if not a little more power than if it were on 45's.

    Thanks for your response.

    Cheers,

    Matt

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    Opinions wanted on quality of porting job

    I too think the exhaust ports are way too big!!

    For me, I can understand the use of bike carbs as they are nice and cheap, however if you are looking for that kind of power, why bit just use 48 webers? Even 200bhp to the flywheel is quite a bit ask on 45's! It's false economy IMO
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    Re: Opinions wanted on quality of porting job

    I have seen that build thread before, some nice machinery there

    Beware of using those cheap SI valves with the 4 keeper grooves, I once used a set of them and can confirm that they have US 2.3 pinto keeper grooves that do not match the triple keeper pinto collets, it is not that just an extra 4th collet groove, that would be perfectly fine but the problem is that the distance between the keeper grooves are totally different to the 2.0 valves and they do not match, my engine started splitting the collets between the grooves as there was only 1 collet groove physically touching one of the grooves in the valve, also when taking out the valves after limited miles they had a very sharp burr worn into only one of the keeper grooves, I had to file down the burr to get the valves out and since then some 10 years ago I have beeing using REC / GS valve ever since with not reliability issues, it would be a good idea to pass this information on to your friend as it could save him dropping a valve, those valves are also very heavy vs decent quality valves

    About the bike carbs I have never used them but I would certainly be in favour of using race flatside slide throtlte carbs with a 45mm ID as I know for sure they flow more than 48's but unfortunately they are very expensive, they are the ultimate 1 barrel per cylinder carb setup money can buy

    The road bike carbs are a different story, the max throttle plate size is 42mm iirc on some of the old larger cc inline 4 bikes, I agree that 40mm carbs could deliver similar top end to a std unmodified 45mm carb but imho the 40mm throttle plate is going to restrict top end power, but as it happens I have a set of R1 carbs here that I could flow test vs a 45mm dcoe with different size chokes to see how the bike carbs flow at wot with the slide fully up, it would be an interesting test, I might get time to test it this weekend as I am already flow testing different 45 dcoe setups with custom chokes that flow a shit load of air, more than even 43mm chokes but with the same part throttle vacuum signal strength to the main jet galley as a std 40mm choke which is excellent
    I have choke sizes from 36 to 43mm in steps of 1mm up to 40mm so we will see how the bike carbs compare as accurately as I can measure them using a sharp edge orific, a std 45mm carb with 38mm choke and aux vent + trumpet is flowing a little more than a 51.80mm ID sharp edge orifice which I believe equals 239CFM @ 21.3" water depression (which is the std test pressure for flow testing carbs)

    Best regards
    Jason
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Buy David vizards book there is a lot of good info on porting

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    Re: Opinions wanted on quality of porting job

    I`ll look forward to reading your Flow Bench Test on the 45 Weber Chokes Jason! I shall be needing some shortly for a set of 45s on a Stage Rally Pinto Engine.

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    Re: Opinions wanted on quality of porting job

    38mm chokes are the best all round for rallying with 45's imho, although I have worked on a modification to the std aux venturi's that increases vacuum signal to the main fuel jet and will allow you to use 1mm larger main choke size without any trade off in low end performance, plus the wot vacuum signal gives better atomisation with the larger chokes, if you sent me a good set of 45 dcoe 4.5 aux vents I could modify them for you, I have not tested this particular modification in an engine yet but I would expect good results, with possibly some emulsion tube tuning at most

    Imho anything can be improved upon, Webers send in quite raw fuel, finer atomisation like Dellorto carbs give or better will make more power and if you can use larger chokes without sacrificing low end flexibility you are onto a winner
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Thanks for the reply's guys,

    Jason, I hear what you are saying about the collet grooves. I read in des hamil's book the same thing. I'll pass it along.

    Your results with back to backing to the differet carbs would be very interesting as may well dispell a few myths (or may not).

    I'll use the bke carbs as I have them but worse case I'll just get some webbers / delllortos.

    I'll start another thread to keep you informed of the build progress.

    Cheers

    Matt

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    Re: Opinions wanted on quality of porting job

    Bike carbs are used extensively on kit cars with exceptional results
    I was once approached at a kit car show by an Ex Caterham race car engineer who explained the value of variable Venturi carbs over fixed.
    What we tend to do is match carb rear port diameter to head inlet port diameter or larger with tapered manifold runners.
    I too will be interested in the flow rates if you do them Jason, nothing like some proper data to cut through the bull

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    Re: Opinions wanted on quality of porting job

    Yes it will be interesting and I agree that variable chokes are a better method, they have the potential to closer match the fuel needs to the air as the throttle is opened off idle to say 1/4 throttle which is where big std 48, 50, 55 webers suffer especially if they have large chokes fitted, using hte smallest throttle plate possible is certainly an advantage up until a point where the air flow past the throttle plate + spindle becomes the main flow restriction

    I do think that 40mm bike carbs can compete with unmodified 45's and could be a good option on a fast road car, I just don't think that a 40mm bike carb has a change of flowing the same air as a 48DCO/SP even with the smallest 38mm chokes, but we will see how they compare to 45's and we might get a nice surprise if they flow very well

    I will not be able to give 100% accurate CFM ratings with my current flowbench until the new one is built but what I can do is to give a good idea of the flow and a direct back to back test between the two, we might find for example that a 45mm carb with 38mm choke flows the same air as the 40mm bike carbs at wot, and we know what kind of power levels can be got with 45's so we will be able to give a good estimate of what peak bhp 40mm bike carbs can support from a 2.0 pinto
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Call me old fashioned if you like, but Bike Carbs on a X Flow or a Pinto just look so out of place on a period Engine. I can appreciate people wanting to fit them if they are on a very tight Budget, but how much cheaper are they than Twin side Draughts? Nothing beats the Induction note of Webers or Dellortos!

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    Re: Opinions wanted on quality of porting job

    Quote Originally Posted by Forest_rallying View Post
    Call me old fashioned if you like, but Bike Carbs on a X Flow or a Pinto just look so out of place on a period Engine. I can appreciate people wanting to fit them if they are on a very tight Budget, but how much cheaper are they than Twin side Draughts? Nothing beats the Induction note of Webers or Dellortos!
    I totally agree but they are good in conversions where webbers can not be fitted. My mrs has a set of 36mm r6 carbs on her 1.6 engine in her 106 we wanted to fit webbers like on the euro 205 rallye but there isn't as much room in the 106 bay.

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    Re: Opinions wanted on quality of porting job

    I think they look great. Here in Oz a new set of twin 45's are around $1500 plus manifold plus linkages etc. Then a dyno tune (rolling road to you poms) is around $500 so you are looking at over $2k AUD for webers.

    My bike carbs (R1) have set me back $500 all up inc manifold (bogg bros) and dyno tuning etc so it makes very good financial sense to fit them. Plus they aren't that common here which i like.

    Here's a pic of my set up currently

    Cheers

    Matt

    Click image for larger version Name:	20130302_091838 (Small).jpg Views:	706 Size:	98.9 KB ID:	63289

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    Re: Opinions wanted on quality of porting job

    Hey Jason,

    Any updates on the comparison of Bike Carbs to the 45's?

    Cheers,

    Matt

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    Re: Opinions wanted on quality of porting job

    Haven't got a chance to flow test the R1 carbs yet, I have to make up a new mounting plate for the flowbench to test the R1 carb

    From visual inspection I can say for sure 40mm bike carbs are going to flow a HUGE amount less air than 48's with say 42mm chokes, on the other hand the R1 carbs may flow quite well vs 45mm carbs and 36 or 38mm chokes, time will tell

    Have been flow testing 45mm carbs with 36, 37, 38, 39, 40 and 43mm chokes, also 48's with 38 and 42mm chokes, size 40, 44 and 46 will be arriving next week for some more testing, the part throttle and full throttle vacuum signal to the main jets is proving to be very interesting, it is telling me that even 40mm chokes in a 45mm carb can give "better" low rpm response than 48's with 38mm chokes, the 48 flows a lot more air with 38mm chokes than even with 43mm chokes in 45's bored out to the very last

    What I can say for sure also is that 45's and especially 48's 50's, 55's have a huge restriction to fuel flow at part throttle, the std 3 x 1mm holes or 1 x 0.80mm, 1 x 1.00mm, and 1 x 1.20mm progression holes are inadequate for competition engines, 4 or 5 holes will work much better, I have been trying different progression hole locations adding in new holes into a spare carb and have found the 45 152's need 1 hole closer to the engine side of the carbs which is done with 152G 4 progression hole 45's, a small 0.80mm hole is added so that when the engine is at idle rpm the 0.80mm hole is directly above the throttle plate and as soon as the throttle plate is feathered open the hole starts to become uncovered letting fuel in faster than 152 3 hole, also adding another 1mm hole towards the trumpet side of the carbs in a specific location increases vacuum signal to the progression phase and reduces the lean spot just off idle

    5 progression holes are ideal for any competition engine, I since discovered that some 40DHLA carbs had 5 progression holes right from the factory, the Dellorto carbs were actually a lot better than weber in ways, higher air flow, better atomisation (which suits most engines) and better part throttle response with the additional progression holes better bridging the gap between idle and main fuel circuits

    Why on earth Weber only drilled 3 x 1mm progression holes in 48, 50 and 55mm webers I will never know, there is never going to be enough fuel going into the engine as the throttle is pressed up to say 1/4 throttle when the main jet should be just about starting to work at 2500 to 3000rpm or so, the only thing you can do with std 48's, 50's etc is to use a large main jet to richen the progression phase, but that is really a band aid fix for not having enough progression holes or total volume to stop the engine going lean just off idle when driven normally and before the main fuel circuit kicks in

    Now going from 2000rpm to WOT in an instant with ANY carb is never going to give faultless pickup without a lean spike but having extra progression holes will definitely help gain more response and end up with a very crisp responsive engine that can perform very close to TB performance

    This testing is showing me that under competition use when driving with carbs you want to be nice and progressive on the throttle if the rpm's ever drop very low, not giving more than say 1/4 throttle until 3000rpm where you could give it WOT which is a quicker way to drive with carbs as you are giving the progression holes a chance to do their job, even with TB's being progressive at low rpm with the throttle is best as you are making best use out of the tyre grip rather than spinning out the wheels with TB's or bogging down the engine when using carbs by going to WOT too early with either system, progressive wins, and in order to get best progression with carbs from sub 3000rpm extra progression holes are needed imho, then you can have best performance, very close to TB performance with a well tuned distributor and high cylinder pressures etc, not excessive cam overlap etc

    Getting back to the bike carbs I can see that when using a variable choke this could potentially improve low end performance vs a fixed choke system, this would make sense to me as with a fixed choke you either have to choose a large choke for top end power or a small one for better low end power but there would seem to be less of a trade off with variable venturi's since the choke size can be very small at low rpm and wide open at max rpm, meaning that the main fuel system would be more tuneable and bring in the main system earlier vs whatever peak air flow rate you were using vs webers, but the issue is that a 40mm carb bore and throttle shaft can only flow so much air, an ideal shape 40mm ID bore is said to flow 147 CFM @28" per square inch, but a 40mm carb has a throttle shaft blocking some of the air path so it would flow more like say a 39mm ID bore at best = 272.18cfm @28" or 237.40cfm @21.3" which is the usual std flow test depression for carbs

    I think that is it going to End up that 40mm bike carbs are going to flow something like 45mm x 36mm choke at best, there is a remote chance it might flow as muhc as a 45mm carb with 38mm choke but we will see

    For sure I think that bike carbs are good value for money if the inlet manifold is well made and not flow restrictive with sharp bents, I would recommend using at least 40mm throttle bores, I think 42mm is the largest available, 42's could have a chance of beating std unmodified 45's with large chokes but imho no road carbs are going to be any kind of a match for std 48's or modified 45's, I view production bike carbs on car engines as for fast road use and not competition, there may be an issue with the variable venturi's not opening fast enough under acceleration away from tight corners I am note sure but I have never heard bike carbs pick up like webers can, all of that needs to be taken into account when choosing which carbs to use

    48's are really a big step up from 45's, the vacuum signal to the main jets with 48's is pretty rubbish in comparison to 45's tbh, I would sooner use modified 45's than std 48's if I could get the 45's to flow enough air and retain low end response that is an all round winner and what I am working on, 48 carb flow in a 45mm carb with regular 45 low end response, 50's and 55's are really only for mega hp 2.0 engines or 2.4+ 16V engines imho, a 48mm throttle plate is enough to flow a LOT of air per cylinder and the smaller the throttle plate the better in terms of throttle control out of corners

    Anyway we will see how the flow testing goes, at least I will be able to say R1 carb flows the same a a 45 with X choke size with both at WOT and the R1 variable venturi completely up and out of the air path
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Dellorto 40mm carbs, certain models with 5 progression holes, the hole location staggering and size looks spot on








    Remember this is a 40mm carb, on a 45+ carb 5 holes should really be the standard for competition engines especially for 48+ as the larger the throttle plate diameter the bigger the gap between idle and main fuel circuits as larger carbs have to flow more air to get the main fuel circuit working
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Great stuff Jason, I just wish you were a bit more thorough in your response.

    It is interesting about the diferences in the weber vs Dellorto progression holes as i have heard that Dellortos are easier to tune and this is probably why or has a lot to do with it. It may add some weight to the dellorto side of the dellorto vs weber debate.

    As per my previous comments my mechanic is expecting similar power to 45's with better performance part throttle on bike carbs.

    Thanks for your results and continuing help.

    Cheers,

    Matt

    P.S. May need to change the thread title to "R1 bike carbs vs 45 webbers"

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    Re: Opinions wanted on quality of porting job

    Lol yes, I don't half go into detail with testing and writing these things but that's how I like to do it, sometimes it is the smallest things that can make the biggest difference

    I feel some flow testing coming on today with the R1's, off to make an adaptor soon and we will see how it goes
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    looking well forward to the results!!

    My guess is the R1 BCs will flow similar to 45s with 38mm choke.!

    Also not mentioned is the BCs dont have a pump jet which I think will make a difference in the end especially for competition use. I dont get any lean spots on my AFR meter anywhere in the rev range using 40mm keihins but mines fast road only.

    45dhla D model dell carbs have 6 or even 7 progression holes and a powerjet circuit.. very very nice carbs

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    Re: Opinions wanted on quality of porting job

    Quote Originally Posted by Craigorypeck View Post
    looking well forward to the results!!

    My guess is the R1 BCs will flow similar to 45s with 38mm choke.!

    Also not mentioned is the BCs dont have a pump jet which I think will make a difference in the end especially for competition use. I dont get any lean spots on my AFR meter anywhere in the rev range using 40mm keihins but mines fast road only.

    45dhla D model dell carbs have 6 or even 7 progression holes and a powerjet circuit.. very very nice carbs
    Please compare apples with apples! You are comparing 'regular' road bike carbs with off-road derived carbs. If you want accelerator pump equipped carbs look at the Mikuni RS range 34, 36, 38, 40mm, the HSR 40, 42 45 and 48mm or Keihin FCR range 39 and 41mm. And all of these are slide carbs ie. without butterflies so NO restriction! Bet they would blast your best sidedraught set-ups into the also ran stakes! LOL

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    Re: Opinions wanted on quality of porting job

    hmm are we not comparing weber dcoe carbs with the much more budget friendly r1 road bike carbs..??

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    Re: Opinions wanted on quality of porting job

    Here we go guys.....

    I was right on the money with the best guess, the 40mm R1 carbs at WOT with the variable venturi fully up and everything else sealed off (vacuum lines etc) are flowing just a tiny bit more air than 45's with std 36mm choke and 4.5 aux vent, when 37mm chokes are fitted to the 45's they clearly flow more air

    I also tested them again the unique ventutri's I am developing and it is very clear the 45mm carbs can flow WAY more air with better designed venturi's I am not going to say any more than what I have right now is flowing a little more air than 48DCOSP's with 38mm chokes, that is pretty epic flow from a 45mm carb which having the same bottom end power as 45's with 38mm chokes in terms of throttle response

    I was surprised to see that the variable venturi's in the R1 carbs get sucked up out of the way quite quickly when the flowbench is turned on

    I believe the reason why bike carbs do not have an accelerator enrichment mechanism is because with the variable venturi they simply don't need it! in truth fixed venturi's work a lot different to variable choke, both systems have their pro's and cons

    For a road engine these bike carbs appear ideal, twin 40's will never flow as much as a 40mm bike carb that is for sure and at the same time 40mm bike carbs are very going to flow enough air for an engine that was needing 38mm chokes in 45mm carbs or greater, don't even mention 48mm carb flow that is in a totally different league when it comes to airflow, only the heavily modified 45's I am working on can compete and beat 48's

    As for larger race bike carbs they are incredibly expensive, did anyone price them, have a look and makes sure you are sitting down when you hear the price of anything race orientated lol! mega expensive and imho not making any sense at that stage as TB's and ECU could be bought for the same price or less!

    I do think that the best carbs on earth are slide throttle RACE bike carbs which have 45mm ID's, they would out flow 48's no problem and have higher air speed through them and more tuning potential, but the cost is just insane for carbs, TB's make way more sense when spending that kind of money


    The advantage you would have in a road engine with 40mm bike carbs would be that they flow just a tad more air than 45's with 36mm chokes (practically the same air flow) but the 40mm throttle plates would make a more progressive throttle when driving at low speed and the air speed through the 40mm carbs is going to be a lot better than 45's with their larger 45mm trumpet ID, throttle plate bore and inlet manifold entry, getting the same air flow with a smaller CSA always means higher air speed, cylinder filling would be better with bike carbs than 45's with 36mm chokes no question about that and I would certainly expect higher mid range torque and peak power 40mm bike carbs vs std 45mm DCOE with 36mm chokes

    But if we want more WOT air flow for competition engines 40mm bike carbs are not going to cut it on a high spec 2.0 pinto or 1.6 16V engine and up

    42mm bike carbs would be interesting to test, they would no doubt flow similar to 45's with larger 39 or 40mm chokes I am sure and be more suitable but there isn't a hope of them out flowing the new venturi's I am working on for the 45mm carbs, watch this space as you will soon be able to upgrade 45mm DCOE's to flow the same air as 48's but with no loss of low end response and finer fuel atomisation

    So now we can lay to rest some of the claims that bike carbs are as good as 48's etc and also it is clear that for fast road engines they are a very good option imho and better than some people might have thought

    There is one thing that I will add about bike carbs that is very important, using an inlet manifold with port runners as straight as possible that match the head ports, the carbs can flow all the air they want but if the manifold is reducing flow and air speed then this changes the situation and they cannot compete with 45's in terms of peak torque and hp

    Ideally the bike carbs would be spaced out to match the bore spacing of the engine and a simple inlet manifold made with one mandrel bend in them at most, that will give better results than using them with the original spacing that is much too narrow to suit most car engines, the straighter the port runners the better even if they flow well on a flowbench, flow and velocity are two different things, both are very important

    Pics to follow, just having a bite to eat and then I will take some pics
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Mechanic snapper1's Avatar

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    Re: Opinions wanted on quality of porting job

    Any comparison is a start
    The kit car boys are using bike carbs a lot I have Mikuni's on the car and R1's on the spares shelf
    The next step is bike throttle bodies

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    Re: Opinions wanted on quality of porting job

    Quote Originally Posted by Craigorypeck View Post
    45dhla D model dell carbs have 6 or even 7 progression holes and a powerjet circuit.. very very nice carbs
    Agreed, I now prefer DHLA carbs, just a pity they are not being made any more as I would hapily use them, however thankfully modified webers can perform a lot better than Dellorto's, the progression hole drilling's being modified for a start and also much increasing air flow
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Quote Originally Posted by snapper1 View Post
    Any comparison is a start
    I completely stand by the flow testing, when I have my new bench built I will be also to give proper CFM figures and air speed measurements

    Can't argue with flow testing
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Was just taking some pics and camera died lol, will post them later this evening

    No matter how many times I test the R1 vs 45 with 36mm choke they flow very similar air, with the R1 carb just flowing a tad more, with 37mm chokes fitted the 45's flow more air

    As I was thinking production bike carbs are fine for fast road but not for completion engines unless they are on something like a xflow but even then for a full spec engine I would be using 42mm carbs as 40's are a little on the small side, for a pinto engine 42's could potentially perform better than std 45's, but again 40mm is too small imho

    The flow with 48's and 38mm chokes is not comparable at all with bike carbs never mind 40, 42, 44 or 46mm chokes in 48's

    However I do like the bike carb's variable venturi/choke mechanism, if here was a production bike with 45mm throttle plates they could be an excellent choice vs webers but unfortunately 42 seems to be the maximum and 36 to 40mm is most common

    Tuning is another story, I do not have experience tuning bike carbs yet so can't comment on that, the needle shape is like changing your weber emulsion tube making it leaner or richer in different parts of the rpm range and they have main fuel and air jets as normal just not nearly as easy to get to at least on the R1's, carbs have to come off the manifold and take the fuel bowls off, still though they are a good cheap modification for road cars and 42's may well be able to out perform std 45's
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Sorry Matt I have completely hijacked your thread lol
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Here we go, a few video's of some back to back testing










    I might take some more videos of 45mm and 48mm carbs if anyone in interested in seeing how they flow vs these tests, 37mm chokes flow more air than the 40mm bike carbs

    Everything was sealed off completely and I have a large flared exit below the bike carb with a 40mm ID minimum bore flaring out to at least 60mm ID, adaptor is sealed with both clear sealer and I machined the plate to accept an O ring to seal against the 18mm thick wooden sheet, using a piece of cloth to seal the wood against the top of the flowbench all of this gives a good seal

    Notice how fast the variable venturi's open and also how restrictive the individual air filters are, your engine would loose at least a few bhp with those type filters and if the engine is under carbed it would loose a lot more with these filters, they simply don't have enough surface area to not restrict WOT air flow

    The results I am getting are very similar ever time, using a basic flowbench for now but it is quite useful for this kind of back to back testing as you can quickly find out what parts flow more than others

    Going a step further with this type of flowbench you can machine 2mm to 3mm thick steel plates with a razor sharp edge but with no burr, bore then out in a lathe with a 45* angle, rub a small honing stone along the top edge to know off the slight burr leaving it razor sharp, then you can calculate what CFM @28" it is flowing by measuring the ID, calculating the sqaure inch area of the orifice and using a flow coefficient of 0.62 to 1, an ideal shaped hole with flared entry and slightly flared exit would flow 147CFM @28" per square inch, this is regarded as 100% flow coefficient, multiply this by .62 for a sharp edge orifice which equals 91.14CFM @28" per square inch
    Making different size orifice plates and comparing them to the flow depression reading you are getting on a floating depression flowbench will tell you what CFM the test item is flowing

    A lot can be learned with basic equipment, sooner I build the new flowbench the better as I would sooner using 6 motors for flow testing the 48's and modified 45's when testing the part throttle vacuum signal to the progression holes and main fuel system
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    Nice one jason!
    Fire blade carbs are 42mm. I think
    Once main jet is settled on, needle and clip position are easily changed without removing the complete carbs.
    Thanks again lad for the findings.

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    Re: Opinions wanted on quality of porting job

    Cheers Craig, no problem, yes I remember reading about adjusting the needle clip position to alter the AFR curve, as I understand they are also different shape needles with different angles and also ones that have a more complex shape not just a simple taper angle, never tuned then before as I said but for sure I would think the needle shape has to suit the engine for best AFR consistency, I would be tempted to use 42mm bike carbs on an engine to see what they are like vs 45's, the slider venturi mechanism looks like it is quite a good idea, I believe blackbird CBR1100 have 42mm carbs, don't know of any other 42mm bike carbs so far

    Throttle bodies are another story, I have a set of Busa 46mm TB's here that have a 42mm minimum ID, they will flow plenty of air for a 200bhp pinto engine imho, just a pity they have a 50mm entry ID, I would sooner 45mm parallel bores but they do flow quite well
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    sorry to OP for the hijack too..
    the bike carbs can be easy enough to get going but can get fiddly when fine tuning, a watchmakers lathe would be handy!
    One plus with the BCs is some have a TPS on the side which is good for megajolt etc
    Good budget option IMO

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    Re: Opinions wanted on quality of porting job

    That is what I was thinking, fairly easy to tune them pretty close and would likely take quite a bit of time to get the AFR perfected but at least you would know a lean area needs the needle turned down in diameter slightly once you figure out what height it needs to be removed from, top of needle/largest end = low end fuel, bottom/smallest diameter = top end fuel with mid range surely being a bit more tricky, and air jet size for top end fuel also, larger = leaner top end

    An ER25 or ER32 collet chuck mounted in a 4 jaw chuck is a great way to hold small items, using big rpm's and a carbide with a small corner radius to get a decent finish + some emery paper to polish smooth afterwards, ER32 are a gift to use for milling drilling etc also as they have a decent 1mm clamping range rather than collets

    Good point about the tps, for sure bike carbs a good budget upgrade, a bit more hassle to tune I imagine vs webers but very inexpensive
    "Horsepower sells cars, torque wins races" - Enzo Ferrari

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    Re: Opinions wanted on quality of porting job

    You certainly have been busy Jason. Everything you have said makes perfectly good sense and good on you for spending the time to get some hard evidence to support the theory.

    As suggested I went down the BC route as I didn't want to fork out big bucks for 45's as they would cost over $2k AUD to be fitted and set up properly where as I am all set up with the bike carbs for about $800AUD.

    I bought them before I was bitten by the race bug and when my new race engine is built we'll see how the BC's go and then if / when I want more power I can look at other induction options then.

    Being that you are comparing modified 45's to the standard BC's is there a way to modify the BC's in order to improve flow or is just a case of the over ID of the carb body determines maximum flow potential?

    Cheers

    Matt

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