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Discussion Starter · #1 ·
So this winter I removed the cast iron heads from my 1990 350 roller motor, and replaced them with Dart SHP aluminum heads. Adjusted the rockers like I have always done with cast iron to zero lash plus 1/4 turn. Not a fan of a lot of preload, so I don't do the 3/4-1 turn thing.
The problem I have is that everything sounds perfect until the engine warms up, and then the lash sounds too loose. I'm wondering if the aluminum heads change lash through expansion as they heat up more than cast iron do?
I can shut it off and let it cool down and when I restart the rockers are quiet. But as soon as the engine gets hot they sound like solid lifters, not hydraulics. The cam is a Howards roller cam, with Howards hydraulic roller lifters. Never had this issue with my BBC and Edelbrock aluminum heads, with flat tappet cam and hydraulic lifters. Anyone have any thoughts about maybe aluminum heads need more preload to account for expansion when they warm up?
 

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So this winter I removed the cast iron heads from my 1990 350 roller motor, and replaced them with Dart SHP aluminum heads. Adjusted the rockers like I have always done with cast iron to zero lash plus 1/4 turn. Not a fan of a lot of preload, so I don't do the 3/4-1 turn thing.
The problem I have is that everything sounds perfect until the engine warms up, and then the lash sounds too loose. I'm wondering if the aluminum heads change lash through expansion as they heat up more than cast iron do?
I can shut it off and let it cool down and when I restart the rockers are quiet. But as soon as the engine gets hot they sound like solid lifters, not hydraulics. The cam is a Howards roller cam, with Howards hydraulic roller lifters. Never had this issue with my BBC and Edelbrock aluminum heads, with flat tappet cam and hydraulic lifters. Anyone have any thoughts about maybe aluminum heads need more preload to account for expansion when they warm up?
1/4 turn is all I do as well, never had any issues with any of my aluminum heads. I’ve used several sets of Liberty Performance and no issues, Could the lifters be the culprit …..seems to be the trend today?
 

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My experience is there's about .003" difference in lash cold vs. hot on a solid lifter on most aluminum heads. That's 1/16 of a turn with 20 thread/in rocker studs. That's also about the variation you'll have if you are just "eyeballing" the adjustment.
 

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Discussion Starter · #4 ·
1/4 turn is all I do as well, never had any issues with any of my aluminum heads. I’ve used several sets of Liberty Performance and no issues, Could the lifters be the culprit …..seems to be the trend today?
If they were flat tappets I'd consider lifters first. But since they're roller I figured it might be elsewhere.
 

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Discussion Starter · #5 ·
My experience is there's about .003" difference in lash cold vs. hot on a solid lifter on most aluminum heads. That's 1/16 of a turn with 20 thread/in rocker studs. That's also about the variation you'll have if you are just "eyeballing" the adjustment.
As I mentioned above these are hydraulic rollers, not solids.
 

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Wheel Motor vehicle Hood Automotive tire Tire

I’m building a retro roller 2pc now with aluminum heads I’ll keep you posted with results…..will be on a run stand for first fire , will do 1/4 turn and watch results.
I’ve never seen an issue yet , last pair of BBC had retro rollers with Aluminum heads and no Ill result.
 

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Does not matter. The difference is due to the head expanding, changing the location of the rocker arm mounting location relative to the cam and lifter.
It may be from expansion I understand totally but I can’t imagine it growing enough to make it start to clatter……
Question ? is all or just a few?
Poly locks or stock lock nut , if stock could they have unspun?
 

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Are you running poly locks or just stock interference nuts on your rockers? I kinda went through this myself on an SBC I built with a factory roller and Profiler aluminum heads. Tried the 1/4 turn deal (with stock interference nuts on standard style slot rockers). They kept coming loose actually...went to a half turn and the problem disappeared.

I know plenty of guys run a full turn even on hydro roller cams...can't hurt to try an extra 1/4 turn and see what happens.

This is one of those issues where you can get a lot of answers. If 1/4 turn aint working, just add some more. Within reason I highly doubt a little more pre-load will harm anything.
 

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Discussion Starter · #11 ·
It may be from expansion I understand totally but I can’t imagine it growing enough to make it start to clatter……
Question ? is all or just a few?
Poly locks or stock lock nut , if stock could they have unspun?
These are Howards Cam poly locks. It's all of them, and not really clattering, just sounding like solid lifter clearances. Haven't pulled a valve cover after it's warmed up to check them, but I'm sure they're looser than when I set them cold.
Guess I'll try another 1/4 turn preload on all of them and see if that fixes the problem.
 

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I have never ran a full turn usually a 1/3 to 1/2 and all good. My first build in the 70s I popped the V/C on my pulled 327 and counted haw many threads were protruding above the nut and tightened the ones on the new 350 with an old Hyd Crane Fireball the same. This was after trying to go a full turn and failure to start due to too tight. That old small b lock fired right up and ran great to 6000. Same motor got a .500 lift Comp Stage II hyd. a few years later.
 

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Discussion Starter · #13 ·
I have never ran a full turn usually a 1/3 to 1/2 and all good. My first build in the 70s I popped the V/C on my pulled 327 and counted haw many threads were protruding above the nut and tightened the ones on the new 350 with an old Hyd Crane Fireball the same. This was after trying to go a full turn and failure to start due to too tight. That old small b lock fired right up and ran great to 6000. Same motor got a .500 lift Comp Stage II hyd. a few years later.
On my other 350 in my Austin gasser I was told by Comp Cams to run 1 full turn preload. I fired the engine and did the flat tappet breakin. Then pulled the valve covers to check adjustment and saw almost no oiling on the upper end! I started the engine up with the valve covers removed and it was barely oiling! I began backing it off, and finally had to shut the engine off because I was seeing so much oil everywhere! Readjusted to 1/4 turn and no more problems.
My Howards roller cam is .530/.525 lift, and the Dart heads have high lift springs to work with this lift.
 
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