Predicting potential piston to valve clearance issues - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 01-23-2013, 03:15 PM
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I was told by a local dealership parts department that the AC Delco HL-124 (GM 12499425) LSx lifters are the service replacement for the AC Delco HL-123 LT1, LT4 and L30, L31 Vortec lifters.

However, the original AC Delco HL-123 (GM 17120735) Vortec lifters are still available over the counter.

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Old 01-23-2013, 03:21 PM
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Okay well... I will look into the comp 875 lifters...
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Old 01-23-2013, 03:30 PM
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Can you explain the differance to me between the lifters I purchased and the comp 875 lifters?
I was under the impression the GMs were a nicer quality peice.

The comp 875's are the same price I payed for the GM kit so it wouldnt be a big deal to return the GMs to jegs.
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Old 01-23-2013, 03:40 PM
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The Comp Cams 875 lifters, for all practical purposes, are solid lifters. They only have a 0 to .005" pre-load only to keep the valve train quiet and as a safety margin to keep from popping out the push rod cups. You could set them at zero pre-load but it is not advisable. You must use full roller rocker arms and fully adjustable rocker studs with CC 875 and 15850 lifters. Since they are restricted oiling lifters, you must use full roller rocker arms to prevent burning out and seizing the pivot ball in stock or roller tip rocker arms. Restricted lifter oiling is necessary at high RPM to keep the rod and main bearings fully pressurized with oil.

If it was not for the extra cost of full roller rocker arms and the difficulty in setting the pre-load, more people would use Comp Cams 875 and 15850 lifters with high lift camshafts.
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Old 01-23-2013, 03:40 PM
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Dish pistons with d cups or not usally dont have tpv issues at all. There is always that remote chance but being .010 in the hole and dish and small cam you are way good.

Probably with dished you could run 1:6 or even 1:7 rockers without issue.

Never had a dish piston small block chevy With tpv issues. Flat tops zero decked with big vales and large roller cam maybe.

Why use dish pistons and mill the head why not use flat tops. They are cheaper and should be right where you need to be without cutting the heads.
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Old 01-23-2013, 09:06 PM
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Originally Posted by hcompton View Post
Dish pistons with d cups or not usally dont have tpv issues at all. There is always that remote chance but being .010 in the hole and dish and small cam you are way good.

Probably with dished you could run 1:6 or even 1:7 rockers without issue.

Never had a dish piston small block chevy With tpv issues. Flat tops zero decked with big vales and large roller cam maybe.

Why use dish pistons and mill the head why not use flat tops. They are cheaper and should be right where you need to be without cutting the heads.



Already have the heads. Short block is paid for but not built yet
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Old 01-24-2013, 05:13 AM
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Quote:
Originally Posted by 0trbo4myCHEVUICK View Post
Already have the heads. Short block is paid for but not built yet
Got ya.

I ran the numbers and it looks like with a .010 deck and felpro 1094 .015 head gasket will leave you with 9.4:1 cr should be pretty good with 64 cc heads. About the same with 59cc and .041 head gasket. 9.3:1 But with 0.041 head gasket and deck of .010 will be close to the point where the gap is too high. But at .050 it should be usable. .060 is the limit for quech distance any more and its not going to be right. .040 is ideal.

If you have not gotten the block decked yet zero deck it or .010 or less. With zero deck and 0.041 i come up with right around 9.2:1.
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Old 01-24-2013, 06:38 AM
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Quote:
Originally Posted by hcompton View Post
Got ya.

I ran the numbers and it looks like with a .010 deck and felpro 1094 .015 head gasket will leave you with 9.4:1 cr should be pretty good with 64 cc heads. About the same with 59cc and .041 head gasket. 9.3:1 But with 0.041 head gasket and deck of .010 will be close to the point where the gap is too high. But at .050 it should be usable. .060 is the limit for quech distance any more and its not going to be right. .040 is ideal.

If you have not gotten the block decked yet zero deck it or .010 or less. With zero deck and 0.041 i come up with right around 9.2:1.

I wanted to use a gm .028 gasket with. 010 deck and 9.5 compression. I was going to call today and see if the block has been decked. If it hasn't, I was thinking of going .005
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Old 01-24-2013, 06:43 AM
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Any more thoughts on the lifters i have? I plan on setting the limiter at 6500rpm...
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