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Thread: Captain Sensable YBT

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    Captain Sensable YBT

    after a few twists and turns, ive finally started working on daves YBT in earnest.
    its not going to be anything radical , without the big bucks budget to build or run a monster 500bhp motor, were essentially bulding a pretty std engine. it will leave dave near the bottom of the race yb power stakes, but hopefully we can make it super responsive so it really fires out the corners and thus makes up for the lack of outright grunt

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    Re: Captain Sensable YBT

    Sounds interesting, like anything though a nice responsive turbo motor is only going to be any good if the gearing suits it, then ofcourse you have the issue with traction so you need nice linear power delivery and not tons of low down boost.

    Personally I see a stock compression YB on a modern Garrett turbo with a half sharp ecu giving you everything you could ever need on a reasonable budget, also couldn't see it being overly expensive to run simply as the engine doesn't need to be a all singing and dancing spec.

    Either way though always interesting to see things done a bit different

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    Re: Captain Sensable YBT

    straight away im not sure this engine deserves the sensible tag!
    but only from the point of view that i've spent hours and hours porting the head!

    infact 3 times i finished the inlets then went back and took a whole chunk more material out! how much? 5mm out the inlets, they have grown from 22mm to 27mm which is a vast increase in area. i know a yb will do 400 odd bhp on a std head, but my reasoning for porting is that for any given cam or turbo or boost combo a ported head should give more power and the ability to hang onto the power at the top end for longer, its also free power as there was no cost involved other than about 30 meters of emery paper loads of time. and theres no loss of power or reduction of power band unlike fitting cams.

    why 27mm, well that was mostly a result of my flow testing when looking at doing an n/a engine, where i'd established that 25/26mm was still restricting airflow, some of it was simply a case of looking down teh port and seeing that removing more material would expose more of the back of the valve which can only be good for air flow, incidently after finishing it i then had a quick flick through des hammells book,he recomends 27mm, i actually think that it you took the ports out to 28mm or larger still you could downdraft the port a little more and gain a bit more flow, although in sensible turbo spec i dont think its worth it, not to mention risking breaking through somewhere.



    pic showing how much more valve back you can expose

    almost std head used for reference, i say almost std its had the "usual" porting job which comprises of nothing but a bit of smoothing and polishing but actually does very little

    almost std exhaust


    modified exhaust

    modified inlet, note how much you can see of the end of the inlet port, a lot of material has come out of the short turn, not ideal if building an engine for dave roberts which you want to give max torque from about 3rpm, but great for a turbo on boost


    near std head for comparison




    25mm inlet port before i went the whole hog!



    std and modifed exhaust ports, i havent opened them out much, mainly just eased tight bits around guide boss and took a chuck of step out the short turn and laid it back, i could of taken a load more out, but its difficult without removing the guides, after putting a zillion hours into porting couldnt face risking breaking through or doing a shed load more grinding, apart from which when you see the tiny hole in teh turbo the exhaust gasses have to fit through carving loads out teh exhaust ports seems pointless



    i've probably given the impression i didnt do much to teh exhaust ports not so, it just doesnt show up very well in the pics, so the finger test is valid, this is as far as my finger would go in the the exhaust port of the near std head


    and the modified one, dunno who many cfm it flows but its gone up a whole knuckle!
    Last edited by Graham; 27-06-2012 at 22:33.

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    Re: Captain Sensable YBT

    Balls deep in that last photo Nice work G
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    Re: Captain Sensable YBT

    Lol @ ball deep

    Porting looks good

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    Re: Captain Sensable YBT

    Thanks for the hard work Graham and getting the thread going. We have the car booked into 'Pipe engineering' after the next race with the escort is out of the way so that a new engine loom can be made and any other final mods to accept the new engine. Just gotta sell my pinto pace dry sump kit now to fund a decent turbo..

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    Re: Captain Sensable YBT

    ok update time


    lapped the valves in, the inlets were pretty straight forward but on the exhausts i had to recut the seats in the head


    next cam time, what we have is a 4WD head and 2wd cams, as you see if you line the cam up with the valves and journals, the cam bearing wont fit its groove,


    i reasoned if 4wd cams fit 2wd heads with a spacer, the opposite must be true, so 5mm was turned off the cams



    the state of the cambolt washers that cam with the cams was a bit scary, someone must of really tightened them big time, i seem to recall engines with much thicker washers with recess machined in them??


    having machined the cams i wasnt too happy with the end of cam being almost flush with the verniers, which TBH im only using verniers because i have them, the cams are std 2wd and staying that way, well for now at least that said with skimmed head and block verniers will allow the cams to be timed in where they should be.


    i wanted to turn a bit off the nose of the cam, but struggled for a minute as to how to hold it in the lathe, most cams you can chuck up teh rear journal, something not possible with a yb cam because the only thing on the end is a lobe, the answer was screw a long bolt in it so i could hold in in the chuck but still get to the nose of the cam




    thats better cam not flush with the pulley

    Last edited by Graham; 19-08-2012 at 18:54.

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    Re: Captain Sensable YBT

    Good work Graham, glad the cams came out as you planned, cant wait for the next update

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    Re: Captain Sensable YBT

    any reason to why your using 2wd cams instead of just using 4wd ones that bolt straight in? cost reason?
    its not dead till it's buried!


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    Re: Captain Sensable YBT

    How did you use the emerypaper ?

    Some clever lathe work !

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    Re: Captain Sensable YBT

    Quote Originally Posted by caprimentle View Post
    any reason to why your using 2wd cams instead of just using 4wd ones that bolt straight in? cost reason?
    yeah because we had 2wd cams so no cost involved

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    Re: Captain Sensable YBT

    right block, nothing special just a plain and simple 205 jobbie,




    it was chemically cleaned, and looks like it has suffered minimal corrosion of the water jacket






    normally i strip an engine and take a good look at the mains and there backs and decide there and then if the main bearing housings are ok, as i got this block as a bare block i didnt have that luxuary, so had to do some measuring to see that the bearing housings were on size and not oval, neednt of bothered though!



    i dropped the pinto crank from linford in the block, this crank has never been ground, its still std/std as it came from ford, although it has been trufrided, and has the journals polished to yb size.


    after boring the block was refaced, i dunno how much was taken off, the machinest just took enough off to ensure a perfect surface, that said his boss did tell me they had to take more than normal off, 25 thou piston protrusion kinda hints at that, i checked the protrusion on no1 and no4, it was the same had it not been that would of indicated the block has had more off one end than the other, even with std cams im now a little worried about valve piston clearance!


    the valve piston clearance issue further highlighted, by the head having already had a fair bit off it and it needs another skim to clean it up, its currently 138.1mm and the valves only 5 thou below flush, me thinks i will be modifying the pistons!

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    Re: Captain Sensable YBT

    Blimey, looks like the pistons will need working. Will they need valve cut outs like linford or actually machining down? Good to see the crank all looks happy in there though

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    Re: Captain Sensable YBT

    What size valves has it got again? Really demonstrates how for a NA motor you're struggling with skimmed heads.

    Like your work with the cams.

    Shaun

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    Re: Captain Sensable YBT

    its got standard valves, for an n/a motor you have to have pistons with cutouts,

    i'll check the cr before deciding what to do, cutouts are obviously much harder to do, but will give a bigger safety margin for an over rev or poss cam swap later on

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    Re: Captain Sensable YBT

    Graham, sorry, my point was meant to illustrate how for NA you are struggling for valve size, clearance etc in the head.

    I like where you are headed with this one. Having driven a few late model 'high' comp (by traditional standards) turbo'd cars they have all been super responsive. Should do well on the track.


    Shaun

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    Re: Captain Sensable YBT

    You could always use a cometic gasket which can be different thicknesses as you know to overcome the piston protrusion issue.
    Mind you there close as std and if over revved they can cause the valves to hit the pistons on the inlet side.

    Interesting thread what bhp are you going for?

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    Re: Captain Sensable YBT

    the turbo will be a t34, with a .48 ex housing so its not going to make a zillion bhp, but should really haul arse out the corners assuming the tyres can find some grip,
    in interests of a long service life were not going to push hard on the boost front, but hopefully should still see an easy 350bhp.

    i've just done the maths, and as it stands the cr is 8.7:1, and thats before the heads had final clean up skim, knocking the piston protrusion back to flush brings that back a fraction to 8.5, so theres plenty of room to drop the pistons back some more or put some valve cutouts in.

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    Re: Captain Sensable YBT

    Will make for a good all round engine with that turbo. I use the same with 55lb siemens which is a nice set up imo.
    Should have some good torque too.

    Paul

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    Re: Captain Sensable YBT

    things on a bit of a go slow, as i've done my back again, also need to fix my milling machine,

    but what i have done is shorten the pistons by 20 thou, so they are only a fraction out the block, meaning if ever needed the engine could have a head gasket change using any old gasket without worrying about piston/ head clearance,






    even with a bit trimmed off the cr will still be higher than std, i could of took a chunk more off but perfered take less and give some "margin" for an over rev or possible future cam swap

    so next step is mend the mill and put some valve cutouts in them
    Last edited by Graham; 10-09-2012 at 20:04.

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    Re: Captain Sensable YBT

    not going to use the valve cutter in head method ?

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    Re: Captain Sensable YBT

    Quote Originally Posted by DarthVader View Post
    not going to use the valve cutter in head method ?
    probably not due to a lack of valves to modify and difficulty getting on the backs of the valve stems with a drill

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    Re: Captain Sensable YBT

    Quote Originally Posted by DarthVader View Post
    not going to use the valve cutter in head method ?
    would like to see some pics of this method if possible.

    Graham hope your backs ok been there its not fun

    Paul

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    Re: Captain Sensable YBT

    Quote Originally Posted by costina View Post
    would like to see some pics of this method if possible.
    http://www.turbosport.co.uk/showthre...+valve+reliefs
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    Re: Captain Sensable YBT

    I think we spoke on pms graham about this befor on some pms anyway std cams.port head,std 1261 head gasket std bolts [dont bother with cometic and arp crap unless you want it to cost you a crack block] t34 .48 ex ,7.6.1 t0 7.8.1 comp ratio will take the heat out so more ignition can be run ,valve cut outs so no valve bounce on change down ,set of greys and you will see 360 hp and about 380 lbs give me a shout if you need any info
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    Re: Captain Sensable YBT

    Quote Originally Posted by joe GSM View Post
    I think we spoke on pms graham about this befor on some pms anyway std cams.port head,std 1261 head gasket std bolts [dont bother with cometic and arp crap unless you want it to cost you a crack block] t34 .48 ex ,7.6.1 t0 7.8.1 comp ratio will take the heat out so more ignition can be run ,valve cut outs so no valve bounce on change down ,set of greys and you will see 360 hp and about 380 lbs give me a shout if you need any info
    Thanks Joe for the great info, where is the best place to source head bolts and gasket? Are the Victor reinz gaskets any good as there are some nice sets on ebay.

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    Re: Captain Sensable YBT

    Dont buy a gpr a make sure its a 1261 original victor reinz and use original std bolts
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    Re: Captain Sensable YBT

    Quote Originally Posted by joe GSM View Post
    Dont buy a gpr a make sure its a 1261 original victor reinz and use original std bolts
    Thanks Joe, where is the best place to buy bolts?

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    Re: Captain Sensable YBT

    Matt lewis
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    Re: Captain Sensable YBT

    Quote Originally Posted by joe GSM View Post
    I think we spoke on pms graham about this befor on some pms anyway std cams.port head,std 1261 head gasket std bolts [dont bother with cometic and arp crap unless you want it to cost you a crack block] t34 .48 ex ,7.6.1 t0 7.8.1 comp ratio will take the heat out so more ignition can be run ,valve cut outs so no valve bounce on change down ,set of greys and you will see 360 hp and about 380 lbs give me a shout if you need any info
    Thats a really good spec very similar to mine but im on std comp running 30psi peak on 55lb siemens.

    Like the arp remark been there done that.........

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    Re: Captain Sensable YBT

    well thers been a fraction of progress, the pics say it all really, install a piston at TDC, some valves with no springs, using a short length of rubber hose attached to a stud in a drill rotate the valves and it will give you contact patches on the piston so i know where to put the valve cutouts, just need to make the jig to actually do it now!








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    Re: Captain Sensable YBT

    we now have valve cutouts, far bigger than actually needed, infact you would normally use a smaller cutter for the exhuasts so they are quite a bit bigger than needed, but i didnt for one simple reason, we have more compression than needed so it made sense to make the cut outs bigger and deeper than nec, its drops the cr a bit more plus it allows bucket loads or margin if dave wrong slots it or if he wants to put cams in it later on.




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    Re: Captain Sensable YBT

    As I said before those cut outs look very neat and it will be interesting to see where youre at CR wise now..
    Have quite a build up of goodies to bring up to you now, including new INA high volume buckets, gaskets, head bolts, sump, pick up etc. Guess youll be needing some of these soon with a bit of luck

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    Re: Captain Sensable YBT

    volume in piston is now about 20cc, 1cc up on std, BUT pistons have been shortened which reduced the volume down from 4wd 19cc as std.

    so despite heavily skimmed head, decked block, pistons shortened and cut outs added we back around 8.0:1,
    the head needs another light skim to clean it up before it can be finally fitted, so i'll get that done then recheck the chamber volume and double check the cr.

    i know there are arguments for dropping the cr lower, i have to say im a bit reluctant though, all daves opposition will have BIG turbos, cams etc, but i think over a lap he will be able to live with them provided it spools instantly and punches real hard out the corners (assuming he has traction!)

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    Re: Captain Sensable YBT

    Along with big turbo,s and cams there also running pretty big compression ratios max boost low down tailing of as the revs rise. Harvey Gibbs does some awesome big power 600+ hp reliable engines that are running 10.5 and more !!!!!

    Assuming traction !

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    Re: Captain Sensable YBT

    Nice work with the pistons Graham, it is a wonder why std YB's didn't have valve reliefs to start with as every std piston I have seen are showing signs of valve to piston contact with std cams, most likely due to worn out valve springs and higher boost levels causing valve bounce at high rpm and the valves being very close to the squish band of the pistons
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    Re: Captain Sensable YBT

    Quote Originally Posted by RWD fords rule View Post
    Nice work with the pistons Graham, it is a wonder why std YB's didn't have valve reliefs to start with as every std piston I have seen are showing signs of valve to piston contact with std cams, most likely due to worn out valve springs and higher boost levels causing valve bounce at high rpm and the valves being very close to the squish band of the pistons
    I've only ever found this on 2wd pistons. Another possibilty is that someone at some point has timed it up like a pinto when replacing the cam belt all intake valves kiss the pistons

  43. #38
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    Re: Captain Sensable YBT

    That is true I have seen some of them timed miles out, but imho using valve reliefs is a wise move
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    Re: Captain Sensable YBT

    I have seen this on all cosworth engines, and one was a genuine standard 20k mile car I took the head of to upgrade the gasket!

    Should have had reliefs as standard.
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    Re: Captain Sensable YBT

    Exactly, completely agree, a rare mistake by cosworth
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