Valvetrain help

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Feb 25, 2011 | 03:57 PM

atccracing

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From: Martins Creek, PA

Valvetrain help

I have a 1997 351w engine I am rebuilding. I put a new Comp Cams cam in (off the top of my head I think it was 35-349-8), everything else is stock. After installing the lifters, pushrods, and rockers and torquing them to spec. The rockers (at bottom travel) all seem to have excessive play. I know the lifters can bleed down and cause this, but looking at them, they appear to have their plungers all the way up. I'm panicing here......... I was supposed to be putting this in next week, and my budget is dwindling fast!
Do I need longer pushrods?

Feb 25, 2011 | 05:30 PM

lew52

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Are you going roller cam , to roller cam ??.....Lew

Feb 25, 2011 | 07:45 PM

atccracing

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From: Martins Creek, PA

Yes. At least it is supposed to be. I re-used the stock roller lifters.

Feb 25, 2011 | 07:48 PM

88n94

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From: South Dakota

Quote:

Originally Posted by atccracing

Now would be an excellent time to check the rocker arm to valve stem clearance. The Haynes manual lists the spec at between 0.112 and 0.172 inch with the lifters collapsed as they would be now. Of course you have to have the crankshaft(actually it would be the camshaft) in different positions to check different valves.

If you need some different length pushrods you can find them pretty reasonably priced if you shop around.

Feb 26, 2011 | 06:24 AM

atccracing

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From: Martins Creek, PA

by rocker arm clearance, do you mean valve lash.
Just want to make sure I'm on the same page. My head is swirling over this!

Feb 26, 2011 | 10:37 AM

88n94

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Yes, the distance between the top of the valve and the rocker arm. Do yourself a favor and check this NOW, so if for some reason the engine doesn't run right you will know this is not the problem. Make sure the lifters are completely bled down. The Haynes manual I have does a pretty good job of describing the procedure. If you have a Chiltons, it probably would too.

If you find you need some different length push rods, I think the rocker arm ratio is about 1.6 to 1. As an example if you changed the push rod length by .030, it would change the clearance by about .048.

Feb 26, 2011 | 11:05 AM

atccracing

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From: Martins Creek, PA

I have my original engine that spun a bearing at home (this engine is at my work) I am going to bring in the valvetrain from that and see if the results are the same. I will check the clearance, but it confuses me how it could get this way. The Cam shouldn't have mad a difference. This was a salvage yard engine my job purchased for me because I plow our lot. I ring & bearing'd it, with the new cam. The only thing I can think of, is... it was like this due to worn rockers or pushrods, or lifters, because I just tore it down, didn't check them.

Thanks for your help. I'll let you know what my clearances where on Monday when I come back to work.