RealWorld Posted January 1, 2012 Share Posted January 1, 2012 As the time has come to re-work the race car, aiming for an April re-launch, I thought it was neater to start a new car thread than spread across the other forums. Please bear with my endless questions. There used to be a thread on the original build here, but it went missing on the old forum - terminally entangled in the GT debacle So - started stripping today. Smoke and flame damage all over the drivers side of the engine bay. Carbs are fubarred, melted chokes and seized butterflies - starting again there. Much of the wiring needs replacing, along with master cylinders, oil and fuel pressure lines. The head was removed back in April, just after the test day fire, to check for damage to pistons/head/bores etc. Fortunately all was well, so whichever bits of molten Weber chokes made it into the combustion chamber made it out again harmlessly. Just needs a surface clean up, new gasket and putting back together. Which brings me to gaskets. A NOS copper composite came off the engine, put there by GT when he rebuilt this engine. My understanding is that copper is 'best' for race applications as it withstands heat and pressure better BUT tends not to seal as well as say, a Payen. I have both, and can use either - so am interested in recommends - I'll wager GT6Steve has something to say. Link to comment Share on other sites More sharing options...
GT6Steve Posted January 1, 2012 Share Posted January 1, 2012 I never had any success sealing a solid copper head gasket on the long six block. Tried several times with two different products. No Joy. Four cylinder is likely going to work fine. I like the Payens (not the price). I reuse them and I like the recessed block version. I'm alone in that apparently... Link to comment Share on other sites More sharing options...
RealWorld Posted January 1, 2012 Author Share Posted January 1, 2012 See! Knew you would Thanks for the opinion. I'll probably try the copper first and see how it goes. The one I have is Stanpart by 'Coopers' - copper one side and a dull grey metal the other. I'd guess copper side up - but am I right...? Link to comment Share on other sites More sharing options...
RealWorld Posted February 21, 2012 Author Share Posted February 21, 2012 Engine top end assembly is imminent. Am cleaning up the head today - studying GTs work. Inlet 1 & 2, that suffered the majority of shite influx from the flaming carb are corroded in the port - around the elbow and onto the back of the valve. Stems seem ok, valves seem ok. I can remove the corrosion closer to the manifold face, but can't get around the elbow well without removing the valve. So the question is - is it worth doing this (don't have a spring compressor currently) or will things shake down? I wouldn't worry of this was the exhaust port - hot gases would clean it/soot it up. But cool fuel/air isn't going to - is it? Thoughts please... R Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted February 21, 2012 Share Posted February 21, 2012 Always ran Payen gaskets, the proper silicone ones, they can burn if the engine is lean, over hot or detonating, the copper/asbestos is safer maybe but a bit more of a pain in the back side. You really really want to remove all the valves Richard and lap them again, course then fine, I did that each time the head was off just as a matter of course and so to keep the engine as fresh as I can at each moment. Think that way about it. Optimal at each moment. Do it right as you can. Wire Wool will be your friend. Do exhaust ports. Richard you will actually find the exhausts worse as they get physical carbon on them not fluid. Inlets get scrubbed as fuel is abrasive, as in cleaning not metal eating. Link to comment Share on other sites More sharing options...
RealWorld Posted February 21, 2012 Author Share Posted February 21, 2012 Looks like I'm in the market for a spring compressor, some good paste (rough & smooth) and an applicator. Wise words - hope they don't come back to bite me on the arse! R Link to comment Share on other sites More sharing options...
Aar0sc Posted February 21, 2012 Share Posted February 21, 2012 Hmm.... This: Is considerably cleaner than my engine bay currently Link to comment Share on other sites More sharing options...
spitNL Posted February 21, 2012 Share Posted February 21, 2012 I hate to disagree with Dave, but I wouldn't use the course paste. You will screw up the seats with the course paste and no amount of lapping with the fine paste will clear it up. Only use fine paste, hand lapping for about 10seconds will do the trick. If you think you need the course paste you're better of having the seats recut. Link to comment Share on other sites More sharing options...
PeteClan Posted February 21, 2012 Share Posted February 21, 2012 I find fine adequate but initially with a drop of WD40. Pete Richards Link to comment Share on other sites More sharing options...
RealWorld Posted March 14, 2012 Author Share Posted March 14, 2012 So tonight is lapping night Just been through all the valves with fine paste - seems to be ok, getting a nice clean/grey edge on the seats and valves. BUT! I need experienced minds here. Some of the inlet valves seem to 'stick' when fully in the head. Others don't, and none of the exhausts do. There's a resistance to withdrawing them - feels just like a little vacuum pressure from the port, but of course isn't. There's nothing on the stems, and the guides are clear. My thoughts are that the seat is cut a couple of thou off centre to the guide, and as the valve sits into the seat, it's moved sideways slightly by that offset, and the tension put on the stem between seat and guide is the 'sticking' force I'm feeling. So - should I worry? Can it be lapped away with more vigorous effort? Your lapping wisdom please stout yoeman... R Link to comment Share on other sites More sharing options...
CHRIS211083 Posted March 14, 2012 Share Posted March 14, 2012 Rich im having the same problem with my two center inlet valves. Im off to the machine shop when i get back to have them recut the seats. GT has told me to do this and to leave them unleaded and only one angle on the valve 45deg. Would recommend you do the same mate. Chris. Link to comment Share on other sites More sharing options...
RealWorld Posted March 14, 2012 Author Share Posted March 14, 2012 Thanks Chris. Day by day I become more and more underwhelmed by the quality of what the 'genius' GT actually delivers, and impressed by his ability to charge. I spent a lot of money on this head - much of it on chamber mods and flow bench work, but I expected the seats to be cut accurately as a given. Disappointing. I'm open to alternative wisdom rather than taking boy wonder's advice and paying again to have a job done for which I've already paid Maynard's under GTs supervision. R Link to comment Share on other sites More sharing options...
spitNL Posted March 14, 2012 Share Posted March 14, 2012 No experience with that, but would swapping one of the valves tell you anything? Number them first of course, and not suggesting you run it like that, test fit only. If the problem moves with the sticky valve or a different valve doesn't stick it's the valve, if not look at the guide and seat? I do know running non-concentric seats increases wear. Don't think you can solve non-concentric valves by lapping. How's the seal? Don't know if you've got the vacuum testing equipment, but an easy test is to assemble the valve with it's spring and pour some fuel in the port. You'll see soon enough if it leaks. Fred Link to comment Share on other sites More sharing options...
CHRIS211083 Posted March 15, 2012 Share Posted March 15, 2012 Not a bad idea spitnl, this would let you know if one of the valves was faulty. Leak down test always good. Should still be full after 10 -15 mins. Rich i feel your pain mate but i didnt pay the price. However did you get multiangle valve seats? And at leastvyours has been tested to make good figures. Mine wont be tested now till i get the efi fitted. What compression ratio do you have Rich. Cheers Chris. Link to comment Share on other sites More sharing options...
mattius Posted March 15, 2012 Share Posted March 15, 2012 Why does GT reacomend single angle seats?? seems to go against all conventional wisdom Link to comment Share on other sites More sharing options...
spitNL Posted March 15, 2012 Share Posted March 15, 2012 (edited) Chis, wasn’t talking about doing a leak-down test because that would mean reassembling the engine. The vacuum testing equipment I was talking about pulls a vacuum on a port and can be used on an unassembled head. The amount of vacuum it pulls is an indication of the valve seal. Don't know if you have access to this equipment Richard and if it's a good idea if the seats are very concentric. (The vacuum or pressure could bend the stems) Perhaps someone more experience could give you some directions? Why does GT reacomend single angle seats?? seems to go against all conventional wisdom Without knowing the details, all we can do is speculate. Fred Edited March 15, 2012 by spitNL Link to comment Share on other sites More sharing options...
Andy Posted March 15, 2012 Share Posted March 15, 2012 I need experienced minds here. Some of the inlet valves seem to 'stick' when fully in the head. Others don't, and none of the exhausts do. There's a resistance to withdrawing them - feels just like a little vacuum pressure from the port, but of course isn't. There's nothing on the stems, and the guides are clear. My thoughts are that the seat is cut a couple of thou off centre to the guide, and as the valve sits into the seat, it's moved sideways slightly by that offset, and the tension put on the stem between seat and guide is the 'sticking' force I'm feeling. So - should I worry? Can it be lapped away with more vigorous effort? Your lapping wisdom please stout yoeman... R If they are offset then the lapping would show this up pretty quickly as it would grind away one side of the seat more than the other. I thought the guides were used in the cutting process so would have thought this unlikely anyway. Perhaps check by pushing the valve in until you meet resistance and probing round with a thin feeler gauge. Are the seats recessed a little so the edges are catching? or is the bottom of the valve stem just a smidgen larger than the top? Heres's a bit of lateral thinking, Is there a magnetic effect between the diferent steel types? Andy Link to comment Share on other sites More sharing options...
RealWorld Posted March 15, 2012 Author Share Posted March 15, 2012 Thanks for your time and indulgence chaps. So - it's looking more like a guide issue. Bear with me here... This only affect inlet valves 1 & 2. They run up and down the guides fine, and only 'stick' when fully mated with the seat. 3 & 4 do not do this. When inlet valve 1 or 2 is put in 3 or 4, they move freely and don't stick in the seats. When inlet valve 3 or 4 is put in 1 or 2, they 'jam' in the guide approximately half way up. Proper metal on metal jam. This suggests to me that guides 1 and 2 are tighter than 3 and 4; and too small for valves 3 and 4 (for some reason!). It also suggests the reason valves 1 and 2 are sticking when at the seat is a related problem - i.e. the guides are tight. Am I making sense? Remember, these are GTs valves - from ES Valves - so a swap out isn't easy. Maybe I could get my machine shop to open out guides 1 & 2 very slightly.... R Link to comment Share on other sites More sharing options...
CHRIS211083 Posted March 15, 2012 Share Posted March 15, 2012 Chis, wasn’t talking about doing a leak-down test because that would mean reassembling the engi Fred You miss understood. fuel in chambers leak test was meant. Rich any machine shop will be able to ream the guides a touch. As for single angle valves. Dont ask me as i dont know bit this is what he has done. Chris. Link to comment Share on other sites More sharing options...
spitNL Posted March 15, 2012 Share Posted March 15, 2012 Well this is called a leak-down test; http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/viewall.html so forgive me for misunderstanding. This suggests to me that guides 1 and 2 are tighter than 3 and 4; and too small for valves 3 and 4 (for some reason!). It also suggests the reason valves 1 and 2 are sticking when at the seat is a related problem - i.e. the guides are tight. Does indeed sound like the guides and seats are causing the problem. Just rambling here, but would reaming the valve guides keep the concentricity? Or are you going to have the seats re-cut anyway? F. Link to comment Share on other sites More sharing options...
GHR630 Posted March 15, 2012 Share Posted March 15, 2012 At the risk of sounding stupid again, have you tried simply passing a 5/16 hand reamer down the guides? This all that is done after installation of new guides 'cos the interference fit can cause slight distortion and symptoms like you describe. These little reamers cost a couple of quid on line are used with a tap holder. Link to comment Share on other sites More sharing options...
RealWorld Posted March 15, 2012 Author Share Posted March 15, 2012 George - I love it when you talk stupid. Will order a 5/16 reamer tomorrow. R Link to comment Share on other sites More sharing options...
Andy Posted March 20, 2012 Share Posted March 20, 2012 At the risk of sounding stupid again, have you tried simply passing a 5/16 hand reamer down the guides? This all that is done after installation of new guides 'cos the interference fit can cause slight distortion and symptoms like you describe. These little reamers cost a couple of quid on line are used with a tap holder. Talking about hand tools on this forum - how dare you!!!! Really good call though. or for a really cheap alternative just roll up a bit of wet-n-dry and run dowm the valve to take out any burrs. Link to comment Share on other sites More sharing options...
RealWorld Posted March 24, 2012 Author Share Posted March 24, 2012 I've gone for the middle option - ordered a hand reamer. The snob in me wouldn't do Andy's sandpaper trick, and I resisted the power tool urge... Anyway - another question for you lot - I'm running a Pacet fan on the race car, and am changing the blades/shroud etc because of fire damage. The motor has a blue and black wire - which is positive and which is earth? I assumed black = earth - but the fan doesn't push air the way I'd expect it to in this orientation. Wisdom? R Link to comment Share on other sites More sharing options...
jimes Posted March 24, 2012 Share Posted March 24, 2012 I think you have the choice depending on which way you want it to blow. If it's wrong you can just swap the wires. Link to comment Share on other sites More sharing options...
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