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Dave, that really sucks. Looks like you're on top of it and should be back together quickly.
That's pretty much a stock engine. When it goes back together, use the factory GM single-chain timing set and measure for proper pushrod length to make up for deck changes (probably fine with factory push rods too). The non-adjustable valvetrain is perfectly fine on that engine, but if you need a conversion set, I've got a Comp set that I bought for mine a while back - basically brand new. Piston-valve-clearance needs to be measured during timing events. Running up to TDC and checking doesn't give the whole story. Rolling it over on the stand, did it ever feel tight? I'm guessing something went very wrong with the Summit timing set. |
Originally Posted by Unlimited jd
(Post 4798955)
How did you measure piston to valve clearance? By the questions you’re asking I’m pretty sure you did it wrong.
I put clay on top of the piston, torque the head down, assemble the valve train for that cylinder, rotate the crank 2 revolutions, pull the head off, measure the compressed thickness of the clay. so unless you checked it with one set of pushrods and rockers, then ran the engine with different parts you’re piston to valve clearance didn’t change
Originally Posted by speicher lane
(Post 4798957)
Even more basic question, was the block milled and/or the heads decked and the actual measurements of clearance not accounted for as the components were "stock"?
Just throwing that out there as the pics are showing more than one piston contact. |
Originally Posted by TomZ
(Post 4798961)
Dave, that really sucks. Looks like you're on top of it and should be back together quickly.
That's pretty much a stock engine. When it goes back together, use the factory GM single-chain timing set and measure for proper pushrod length to make up for deck changes (probably fine with factory push rods too). The non-adjustable valvetrain is perfectly fine on that engine, but if you need a conversion set, I've got a Comp set that I bought for mine a while back - basically brand new. Piston-valve-clearance needs to be measured during timing events. Running up to TDC and checking doesn't give the whole story. Rolling it over on the stand, did it ever feel tight? I'm guessing something went very wrong with the Summit timing set. Definitely should have checked PTV with timing events, but shouldn't have had to with all stock parts. I made assumptions I shouldn't have with that. |
Originally Posted by SB
(Post 4798953)
My thoughts too
Also, there would have been evidence of oil starvation and there isn't. Guides are perfect and even the broken valve doesn't have any signs of an oil issue. I'm talking about the shaft left in the guide. |
Originally Posted by HawkX66
(Post 4798813)
The heads are stock L29 heads on an L29 block. The only change from stock was the mag cam which wasn't enough of a difference to do much of anything and a Summit timing set. Valves, rockers etc were stock.
The timing set was setup at zero and installed correctly, but I'm wondering if there was a problem with it. I couldn't degree the cam correctly for the life of me. I didn't have a cam card so I just went with it because it was a stock cam. Never had that problem before and I should have stopped right there I'm sure. The valve train noise was the intake lifters just barely kissing the pistons for sure. I checked my notes and I had plenty of ptv clearance. Intake .102" Exhaust .168". You where the one. Now I get it. Okay, so refresh us. When you where degreeing in the cam what issues where you having ? |
Originally Posted by SB
(Post 4798970)
Oh….,,,,,okay….,,(bright light over my melon) I remember TomZ asking in a thread about the person sho bought his Bbc mag cam having issues degreeing it, or something like that.
You where the one. Now I get it. Okay, so refresh us. When you where degreeing in the cam what issues where you having ? |
If i remember the mag cam, it has 115lsa (115.5 ?) and should be installed at like 111icl and 119ecl
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the non adjustable valvetrain will only work with the stock cam ,any cam with a different base circle diameter wont work.i suspect this is the cause for the failure.
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Originally Posted by HawkX66
(Post 4798962)
That's one way and common, but not the only way. My way was right for actual PTV clearance, but it doesn't take into account the rockers and pushrods.
I didn't have the block decked or the heads milled. I had a lot of PTD clearance. I should have been able to zero deck it if I wanted to. |
Never heard of doing it without mocking it up and using clay. How else can you measure it ?
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