Nathan
Club Retro Rides Member
Posts: 5,649
Club RR Member Number: 1
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Cylinder Head WoesNathan
@bgtmidget7476
Club Retro Rides Member 1
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Hi Guys
Right got a little issue, I have just replaced the cylinder head on the GT for a Big valve version, All being well I bolted her down to the new gasgets etc etc and fitted all the interconnecting bits ie carb, exahust manidold and the like. Filled up the Water, and thought hey lets give her a try, she turns over but does not sound quite right and will also not fire, Now i checked the fiing squence and this is fine all was well before i replaced the head, Could i Have missed something. Whats really got me thinking is the non-usual noise when the engine turns over just does not sound the same, (quite hard to describe)
Cheers
Nathan
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Cylinder Head WoesBenzBoy
@benzboy
Club Retro Rides Member 7
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The sound could be different because of the bigger valves - it's strange how you pick up on tiny changes like sounds with familiar cars isn't it? Have you done a compression check? I know you just bolted it down and all but it might be worth double-checking. Also all the daft things like earth strap, LT coil connections... all that sorta thing. Easy to miss but can screw everything up! Hope you sort it soon mate!
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Nathan
Club Retro Rides Member
Posts: 5,649
Club RR Member Number: 1
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Cylinder Head WoesNathan
@bgtmidget7476
Club Retro Rides Member 1
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Yer true, I Have cheked the HT Leads and Coil aso getting a good spark, However I have not adjusted the Valve clearences maybe this could be the issue as the rockers would of been set to the old cylinder head and if i remember there was not gap at the point of top dead center so humm maybe the valves are slightly open, Not done a compression check thin i will have a try with that tomorrow
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Davenger
Club Retro Rides Member
It's only metal
Posts: 7,272
Club RR Member Number: 140
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Cylinder Head WoesDavenger
@dminifreak
Club Retro Rides Member 140
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yeah, good point, if the valves aren't closing, you'll get no compression, and if they aint opening, no fuel. Not sure how different a big valve head would be on a B series, but it's still worth checking
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Cylinder Head Woesrustingdeathtrap
@GUEST
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Might be a silly question but did you turn the engine over by hand before starting it. It doesnt really bear thinking about but there is a possibility of the valves not clearing the pistons, especialy if its a second hand or recon head.
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racer86
Posted a lot
'72 BMW 2002 / '72 Alpine A110 Gordini
Posts: 2,184
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you should deffinatly re-do the valve clearances as the bigger valves could have longer stems so with the std clearance could be being held open( no compression and piston valve interelations) Failing that did you lap the valve seats in?
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Nathan
Club Retro Rides Member
Posts: 5,649
Club RR Member Number: 1
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Cylinder Head WoesNathan
@bgtmidget7476
Club Retro Rides Member 1
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The head Is new well not new just recon ;D, Erm From what the sound is when she turns over i am guessing its due to the Rockers. I am thinking racer your correct the valves are constantly slightly open and not closing fully, I do seem to remember checking the first cylinder at top dead center and there was no gap in the rocker they were tight together
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Last Edit: Jun 6, 2005 9:11:50 GMT by Nathan
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Nathan
Club Retro Rides Member
Posts: 5,649
Club RR Member Number: 1
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Cylinder Head WoesNathan
@bgtmidget7476
Club Retro Rides Member 1
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The head is a Fast road, with the addition of the bigger valves, so i think really a fast road is a standard one with at bit of porting and this just has that + the larger valves. I have driven one before and they seem better but that car did not have the high lift cam of DCOE so I and hoping for a little better perfromance. I am not expecting anywhere near as good performance as my Late Cross flow Roadster but if a little improvement would be nice
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Last Edit: Jun 6, 2005 9:12:44 GMT by Nathan
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mercmad
Posted a lot
Flush Hard,it's a long way to McDonalds.
Posts: 1,740
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You must ALWAYS adjust your valve clearances.Your new head will have been surfaced,thus the push rod length will be too long,the valves will all be open.You have torqued the head down on the new gasket,so this will also exacerbate the problem. Loosen the valve clearances to the manufacturers recommnendation,start the engine,get it warm and check them again.you will notice they have closed up. Your car will have recommendations as to whether the valves should be checked hot or cold. either way,if they are too tight,the valves will be ruined by the gas leaking past the seats,or NO compression and No start,or too loose and the tappet rattle will drive you nuts. With loose tappets you are actually altering the cam timing too,and of course you lose power. So spend a hour or two and get them set to specs.
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Many years ago I changed my driving style to cope with rising fuel prices; I have now reached the stage where I am contemplating keeping my eyes shut in order to lower wind resistance.
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Just as a guide, I always wound the rockers right off the adjusters before replacing / putting a new head on - I didn't do this once between taking off my old 998 head and putting on my new skimmed 1098 head. It took a lot of effort to torque the head down - realised it was bending the push rods at the same time!
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Last Edit: Jun 6, 2005 16:18:41 GMT by iRocco
I like long walks, especially when they're taken by people I don't like.
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Nathan
Club Retro Rides Member
Posts: 5,649
Club RR Member Number: 1
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Cylinder Head WoesNathan
@bgtmidget7476
Club Retro Rides Member 1
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Jun 10, 2005 21:02:42 GMT
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SHES ALIVE ALIVE I TELL YEEE, Well its working and seems all fine apart from a dodgy Thermostat cap bolt but will replace that on sun. Gave her a Run Seems a Bit better but of course the weber is not quite right yet but will be for RCS
Cheers guys
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