how much valve clearance?

Here's the specs: 455 with speed pro 9-1 forged pistons. Can't remember the exact amount shaved off the block and heads but they were just "cleaned up". Poston cam with .499 lift.

Here's the deal: I put about an 1/8 inch thick piece of clay on the #1 piston, torqued the head down, adjusted the push rods and turned the motor over a few times. When I pulled the head back off the valves hadn't even touched the clay.

The question: Is this normal? I figured it would have at least touched a little.



Also since I have you here...the little disc that came off the front of the crank...does it go on infront of the crank gear before you put the timing cover on? Does the balancer hold it in place? Its been so long since I disassembled the motor I kinda forgetou:

Thanks

 

Mike, without knowing the duration of the cam, can't say if your valve clearance deal is abnormal, but rule of thumb, with a zero deck block setup, until you get to around 235* duration and above, you typically don't need valve reliefs in the pistons. Yours, having the pistons in the hole some amount, will make this even less of an issue.

Oil slinger goes between the timing gear and the balancer, and yes, put it on before the timing cover goes on.

JW

 

If you had 1/8" of clay on there and the valves didn't touch the clay, you have a minimum of .125 of clearance. I believe the "books" call for a minimum of .080 on the intakes and .100 on the exhaust valves. Sounds like you are fine.

And for God's sake, don't forget the oil slinger. It helps protect the front main seal from leaking if you experience high pressure in your engine.

 

Thanks guys,

The specs on the cam are .490 lift intake and exhaust with 228* intake and 246* exhaust duration. Sounds like I could've gone with a little bit bigger cam. Oh well, I'll see how this one runs first. Jim, I think I saw you at Salem but you were always either in a car or working on one. Maybe I'll talk with ya next year.

Phil, thanks again for bringing that stuff for me. It felt kinda dumb to ask the oil slinger question but hey, its my first buick and these are things I won't forget the next time.

Thanks again

 

What are you using for lifters? Hydraulic with no oil in them? Solid? I think your compressing the lifter.

 

Scott makes a good point... you do have to either "solid up" an old hydraulic lifter, or use a solid for this check.

Thanks for pointing that out Scott. Did not occure to me to go into depth on the issue, since considering the lift spec he gave, I pretty much just went right to the "no it won't touch the clay" answer.

Even on small cams it's good to check, unless your absolutely sure that the cam is in right, and ground right.

A cam that is really advanced or retarded can cause valve interference.

JW

 

You know I thought about that. I was using the hydraulic lifters which had been soaking in oil. The engine is on the stand with no intake and I didn't notice any compression of the lifters and I watched the valves opening as I turned the motor but, now that you mention it, it does seem like hydraulic lifters would compress without the motor running to pump them up.

Anyhow, Phil (70gsconvt) is running the next biggest Poston cam with no problem so I went ahead and buttoned it up. Do you guys think that's OK? Or should I go back and check it again?

BTW, I did degree the cam in and checked and rechecked it so I'm sure its in right. (straight up)

Thanks

 

I seem to remember that when I had my engine mocked up to have it checked, I had about .140 on intake and exhaust. And I had my block zero decked to .003. Heads were just machined enough to flatten mating surface. I run TRW's aluminum, forgedfactory-style dished pistons and Poston's 113A cam with adj. pushrods.

You should be OK. You might want to degree your cam to make sure it's installed "straight up". I did my Poston cam and found it to be about 2 degrees off.

 

Thanks again Phil,

I did degree my cam (2 degrees off as well) so it should be OK.
Ah, learning to do things right. Gone are the days of just buying a cam, sticking it in "straight up" and runnin' it. Its a wonder none of those Chevys I built didn't blow up as soon as I fired them up.