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Thread: flow bench and head flow figures.

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    flow bench and head flow figures.

    the idea behind this section is along the same lines as the power plots, somewhere to post flow testing data, if you post up flow figures make sure to give some details of teh head specification, i.e valve sizes, modifications etc and the test depression so the figures are actually meaningfull.

    oh and its probably a good idea to start new threads for different head types
    Last edited by Graham; 26-02-2016 at 09:19.

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    Re: flow bench and head flow figures.

    2.0 pinto heads,

    std unmodified carb 2.0,
    std unmodified injection 2.0
    jems carb/non injection big valve, ported but a very sharp step to the short turn, sharper than std carb head
    as above but short turn reworked





    all tested @28inch depression, but figures converted to 10".

    TBH i found it difficult to beleieve that the Jems head was actually finished, it a fair bit of work had been done to it and had big valves 44.5mm inlet , but it looks like someone forgot to finish the short turn! before i reworked it it wasnt much better than an unmodifed injection head
    Last edited by Graham; 26-02-2016 at 09:16.

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    Spanner Monkey redhf's Avatar

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    flow bench and head flow figures.

    Looking good ! How does it now compare to Vulcan ?

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    Re: flow bench and head flow figures.

    thank you. Very interesting.
    normally, how do you shape/refine the short turn?
    I use a long string of abrasive cloth along the port, up and down with hands keeping the cloth at more than 90 respect to the valve seat.
    In this way th epattern left on the short turn is the one I prefer, instead of using wandering rollers and air tool.

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    Re: flow bench and head flow figures.

    Quote Originally Posted by redhf View Post
    Looking good ! How does it now compare to Vulcan ?
    never flowed a Vulcan head i would however expect another 10cfm or so over this example, but at least this head now flows about what the average 80's big valve non injection head did.

    most vulcan heads are on 45.6mm and presumably injection castings, the valves this are 44.5. with a non injection head and re angling the valves you can get upto about 115-120cfm, so its still a fair way short of that, and may never achieve that at all, increasing valve size will help, but all i did was a fairly quick rework of what i had in the first place to give a good gain
    Last edited by Graham; 26-02-2016 at 09:21.

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    Re: flow bench and head flow figures.


    origonal head as supplied, see very nasty square step to short turn



    modified, theres actually much less to the turn now it has a radius, taking more out the bottom corners of the ports would pick up high lift flow at the expense of low lift, but as it stands flow is well up throughout the lift range

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    Re: flow bench and head flow figures.

    its pretty safe to say in its origonal form this head would of only out flowed a standard head due to the better shaped larger valves the porting was doing nothing for it

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    Re: flow bench and head flow figures.

    I have just purchased the down draught head that Memphis was going to use on his 1700 Pinto project. It's on a 1600 GT casting with GP 2 inlet valves and GP 1 exhaust.

    It would be interesting at sometime to get it it on a flow bench and see what figures it produces.

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    Re: flow bench and head flow figures.

    The first time I saw this type of head was an article by Dave walker in ccc magazine around the early 1990's. A few years later I was asked by a boss of a garage if I could produce a cheap pinto head, so I came up with this type of head. A standard size valve is used,The inlet port has been ground in no more than 3/4" , a three angled valve seat cut, the valve has been recut plus a 30 degree back cut. The graph below shows what I have at the moment, but I am having trouble with my back, so I am having to get my wife to lift the head on and off the flowbench, I know a little bit more can be got out of this head, but it will have to wait while later. The port airspeed is .500 lift, 265fps, @ .400 lift I have 247fps, @.300 lift I have 222fbs, all at 28" test pressure




    ncoll
    Attached Thumbnails Attached Thumbnails diy spec pinto head.jpg‎  


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    Re: flow bench and head flow figures.

    Click image for larger version Name:	pinto head2 7.3.16.jpg Views:	375 Size:	122.1 KB ID:	78104

    Gary ?
    downdraft pinto cylinder head graph
    Attached Thumbnails Attached Thumbnails pinto head2 7.3.16.jpg‎  


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    Re: flow bench and head flow figures.

    graph looks good, would like tp see pics of the head, total flow isnt spectaculary special, but area under the curve looske very good

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    Re: flow bench and head flow figures.

    Probably time for me to chime in as it is the head that I made for the 1700 hillclimb engine!

    I agree that the maximum flow is a little disappointing, but actually quite understandable. Because it was for a 1700, I deliberately kept the internal diameter of the downdraught tubes quite small at 35mm, so that the gas speed would be high and aid cylinder filling at low and mid lift, and therefore (hopefully) give the engine some much needed mid-range torque. The head flows enough on the inlet for 200+bhp (which was my target figure for the 1700), but just going up 2mm on the internal diameter of the tubes gives another 11% of cross-sectional area, which I'm sure would have given a corresponding increase in maximum flow to well over 130cfm @10"

    It was always an experimental build, and if I had developed the head for a 2.0 litre engine, I would have used the larger tube. However, I still think the small port head would be pretty bloody good on a 2.0 litre plus engine, and mid range torque should be very good. Garry (aka Forest Rallying) will be using the head on his 2.0 litre rally engine, so we should see how it performs in the real world before too long.

    Cheers Chris.

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    Re: flow bench and head flow figures.

    Hi Chris how are the tubes held in place in the head and what are tubes made of cheers Mario.

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    Re: flow bench and head flow figures.

    Quote Originally Posted by MemphisTwin View Post
    Probably time for me to chime in as it is the head that I made for the 1700 hillclimb engine!

    I agree that the maximum flow is a little disappointing, but actually quite understandable. Because it was for a 1700, I deliberately kept the internal diameter of the downdraught tubes quite small at 35mm, so that the gas speed would be high and aid cylinder filling at low and mid lift, and therefore (hopefully) give the engine some much needed mid-range torque. The head flows enough on the inlet for 200+bhp (which was my target figure for the 1700), but just going up 2mm on the internal diameter of the tubes gives another 11% of cross-sectional area, which I'm sure would have given a corresponding increase in maximum flow to well over 130cfm @10"

    It was always an experimental build, and if I had developed the head for a 2.0 litre engine, I would have used the larger tube. However, I still think the small port head would be pretty bloody good on a 2.0 litre plus engine, and mid range torque should be very good. Garry (aka Forest Rallying) will be using the head on his 2.0 litre rally engine, so we should see how it performs in the real world before too long.

    Cheers Chris.
    very interesting, funny but i do recall a certain Mr walker saying that he had at some point tried a downdraft head ( sorry i dont have any more details) and not gained any power!

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    Re: flow bench and head flow figures.

    To be honest, "downdraught" is a bit of a misnomer, as it's actually only semi-downdraught and the ports are not really as steeply angled as those of, say, the MAE downdraught Pre-Crossflow head.

    The tubes enter the head at 31 degrees from the horizontal which gives @ 38 degrees at the valve. I fully realise that the round tube is not ideal, and a D shaped port with the straight edge at the bottom would flow more air, but I was working with the constraints of an easily purchased "off the shelf" tube and a fairly simple boring process into the head for the tubes to slide into. If I could have found a D shaped tube (do they even exist?) of the right dimensions, then I could have had it scanned and the port cut out of the head with a cnc machine. Expensive!

    For a first effort, and looking at the results again I'm not at all disheartened. I know where I can gain more flow; bigger port!

    Mario, the tubes are mild steel and glued in with epoxy.

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    Re: flow bench and head flow figures.

    I took the Head I bought off Chris ( Memphis) to Neil to see exactly where we were with flow figures, we haven't got a lot of figures to compare with at the moment, CNC Manchester figures seem to be around 10 CFM high on a std Pinto head so their results are difficult to compare to ours.

    We don't want to get carried away and going to a massive port size, the engine is for a Stage Rally car so mid range torque's the most important thing and not the very last HP that a Race Engine wants. Neil commented how fast the air speed was on the head so maybe it's not all about outright CFM.

    Since the head was tested on the flow bench I have made a few slight modifications on Neil's advice, there was a slight bump / ridge where the tube met the inlet throat, that's now been blended in.

    I would like to thank Chris for selling me the head and Neil and his family for putting up with me for most of the day whilst we tested it on the flow bench. There'll always be people out there that think they could have done a better job, if so why haven't they done it!

    All's that I need now is a set of forged pistons and the engine can be built up. It'll be very interesting when the engine gets to the Dyno to see what the Power and Torque figures are.

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    Re: flow bench and head flow figures.

    yes i'd noticed that CNC show a std pinto head being about 10cfm more than either my sanez or daves superflow meassued them as being

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    Re: flow bench and head flow figures.

    If I can find some tunnel section tube of about 41mm OD, I might do another one. Just for the hell of it!
    Last edited by MemphisTwin; 29-03-2016 at 00:14.

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    Re: flow bench and head flow figures.

    Yes, I too have noticed that CNC heads' standard Pinto inlet flow 10 cfm more than anyone else @ 10", and their standard 1.6 cross flow flows 12cfm more than Peter Burgess found. I'm not accusing them of anything; just saying their flow bench seems to read high, and needs to be born in mind when comparing flow rates of modified heads. Tbh, everyone's figures differ to some degree, but not by a margin of 12 to 15%.

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    Re: flow bench and head flow figures.

    i guess it could be a calibration issue, my bench reads about 1cfm high, although i always knock that and any leakage off before actually running the numbers. im my case im not particularly bothered about the numbers being bang on, im using if for before and after comparison only, but it is nice to know you have similar figures to others, bit like rolling roads, direct comparision with others is a bit iffy, but if one rolling road reads 30bhp high........

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    Re: flow bench and head flow figures.

    hi chris thanks for the reply cheers mario.

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    Re: flow bench and head flow figures.

    Neil did a first plot of my Pinto Cylinder Head this week. 45.7mm Rec 882 Inlets, Std Ex valves and JB Weld in the port floor.

    I made the roof to floor 30mm so that should give me a 36mm port into the inlet.



    The flow drops off dramatically because I haven't properly unshrouded the valves and there is an issue with the inlet exhaust seats, which I need to smooth out. First head you see....that's my excuse.

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    Re: flow bench and head flow figures.

    The other smoother curve is a pinto Neil did some time ago with no filler. Don't know the full spec.

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    Re: flow bench and head flow figures.

    Last Flow test, no more being done to the head. Just smoothed out some rough edges.


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    Re: flow bench and head flow figures.

    whats the correction factor from 28" to 10"vac? and if 28" is the standard why change it to 10"?
    if Im aloud to ask

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    Re: flow bench and head flow figures.

    Some benches wont produce 28" maybe?
    1970 Mk1 Escort Tarmac Rally Car

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    Re: flow bench and head flow figures.

    Quote Originally Posted by _PauL_ View Post
    whats the correction factor from 28" to 10"vac? and if 28" is the standard why change it to 10"?
    if Im aloud to ask
    multiply the 28" figure by 0.6 to get 10"

    there is no standard figure, most of the superflow benches in use work at 10". my bench works at 28" although for really high flowing heads it wont be able to pull 28" but by testing at a lower pressure i can test stuff that theoretically flows more than my bench can handle.

    my bench @28 in has showed same flow figure once pressure corrected as daves superflow @ 10 so i dont really see it matters.

    to keep things consistent i always test at 28, but correct to 10 because at 10 i know at a glance whether a head is any good or not.
    Last edited by Graham; 13-12-2016 at 10:26.

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    Re: flow bench and head flow figures.

    Hi graham at what lift point is important on a pinto head to make good power for eg 90% of valve lift cheers mario.

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    Re: flow bench and head flow figures.

    Quote Originally Posted by mariors2000 View Post
    Hi graham at what lift point is important on a pinto head to make good power for eg 90% of valve lift cheers mario.
    i dont all together understand your question, you want as much flow as you can get, but theres no point chasing every last fraction of flow at say 0.500 valve lift if the cam either doesnt lift that far or is only there for the smallest amount of time

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    Re: flow bench and head flow figures.

    hi graham so at 250 inch lift you want 80% of maxium flow at .500 inch lift is that about right cheers mario

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    Re: flow bench and head flow figures.

    you want as much as you can get at all valve lifts, trying to apply a percentage doesnt make any sense

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    Re: flow bench and head flow figures.

    i recently did a fast road vw abf engine, for a 2.0 n/a engine which makes 150bhp as std the head flow is poor



    at low lift it was hard to get much of a gain on the inlets, and the exhaust i actually lost a bit in the middle, but the average gain was enough that when combines with very mild cams i picked up 27bhp

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    Re: flow bench and head flow figures.

    thanks graham.

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