Hot Rod Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
274 Posts
Discussion Starter · #1 · (Edited)
Here it is ,I've got exhaust valves touching pistons all 8 . 427 bbc 6-71 around 10 lbs boost. I can't get ahold of the guy who setup heads hes on vacation , Springs are at 145 closed.i think open was in the 380 Range, guage won't go that high to see like i said hes on vacation so i cant get the specifics but i know thats right in there. we got a head that we cut so u can bolt on and run it thru and watch the valves, I have got .200 zero lash no gasket , and i run a .090 copper so i'm past .300 clearance with gasket and lash. what the hell is going on??? same spring on intake ,the blower should try to push them open. and actually help shut the exhaust. no intake problems. yes this is just flat tappet forgot to tell you
 

·
Registered
Joined
·
274 Posts
Discussion Starter · #5 ·
I'm all for that solution easy fix. explain why when i've got plenty of clearance that it should work, it does have more lift on ex. and I did retard it 2 degrees. not arguing the point just don't get it with .300 clearance why are they hitting
 

·
Registered
Joined
·
274 Posts
Discussion Starter · #7 ·
flat tappet in the engine we have a head that has been cut so you can bolt on 1 cylinder and actually stick feeler guage between valve and piston. no head gasket and zero lash rolled engine over several times to check ,at the closest point stuck a stack of feeler guages and measured them with my calipers ,yes .200 that is correct and i run a .090 copper head gasket so that would be .290 and then .025 lash. they are tapping pistons . have had no probs with intake, same spring on both. doesn't make sense
 

·
Administrator
Joined
·
6,247 Posts
Doesn't make sense at all, I agree, I don't recall having seen that much clearance, even on a short lift setup. Is the contact being made just rolling the motor over or running? Any chance it's valve float? And we assume the checking/cut head is the same head you run?
 

·
Registered
Joined
·
274 Posts
Discussion Starter · #10 ·
no doesn't hit turning it over, just running , thats what i was assuming was valve float , I just don't understand why, intake is bigger plus boost thats trying to open intake and yet no problems there. we heard it making a kind of whistling noise turning it over put your hand over no.5 zoomie and it got quiet we thought it was a ex valve sticking, we ran it anyway 2 -1/8 mile passes checked lash before and after each run everything was fine still ran 125 mph in 1/8 with a 5 foot wheelstand and a 3 foot back tire wheelstand after front came down. put the air to each cylinder and blew air like crazy out of each zoomie, tore it down and this is were i'm at. I clayed this combo before running it . just borrowed the head to actually watch things as i turned it over by hand.
 

·
Registered
Joined
·
274 Posts
Discussion Starter · #11 ·
Had a brainstorm at 11:30 tonite. Tell me if i'm correct, installed heigth 1.900 checked, .639 lift on ex leaves me 1.261, so i put spring and the .030 shim that was in it, put in vise ran it down to the 1.261 measured with good calipers I had .025 between coils - and maybe why no intake probs YET ,.579 lift on intake ,set up at 1.321 and had .050 between coils , does anybody think this is a little tight for a blown race car or even street, I thought min of .060 and even .100 on high rpm . could this be the problem? my head guy ordered everything ,never even thought of checking it out
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top