madam

Here's the deal, dropped my newly rebuilt L48 to 383 Stroker in last fall.

Went with a Comp cam #12-210-2[49] grind #268H. Comp flat hyd tappets, Comp high strength push rods, 1.5 Comp roller rockers in Flow-Tek Alum heads w 64cc Combustion chambers. I set the valve lash on the engine stand per the Comp instructions. (lifter on base circle rocker adjustment to zero clearance add 1/2 turn and lock). I ran Comp break in oil for the first 500 miles and changed to Mobil 1 high zinc 15-50 (per CF recommendation).

When I cold start the engine I hear some predominate ''Clacking" which I believe is coming from the valve train (checked with stethescope). As the engine temp rises up to operating temp (165deg), the ''Clacking gradually diminishes to zero.

IS THIS NORMAL for my set up or should I pull valve covers and re adjust (have not had them off since engine fire up)??

Thanks much guys.

DucatiDon

I beleive with aluminum heads you want one full turn of preload.
However, if it goes away when warm, it should be ok.

madam

madam

CanadaGrant

Which Comp lifters did you use? High Energy or Pro Magnum? The Pro Magnum have a higher bleed down rate so they perform better at higher rpm but are a bit noisy at idle, sometimes more than a bit... The High Energy are closer to stock and are fairly quiet.

keithinspace

I'm running aluminum heads with solid rollers, so I figure mine would be much more susceptible to valvetrain noise because of dimensional changes when cold than any hydraulic setup. Alas...mine runs like a sewing machine cold or hot.

Given that the motor has been stroked, and without knowing what all was done to the block, rods, rod ends, or checks on the piston-to-cylinder clearance, what is the chance that you are actually hearing piston slap?

There are some clips you can buy to reduce oil splash so you can actually adjust the rockers while the engine is running...perhaps running the car with the valve covers off would/could allow you to isolate one particular part that is giving you trouble.

If the valvetrain checks out, then you can look for some issue with the stroke kit...some close tolerance that is JUST fixing itself when hot...

madam

Actually I looked them up and the lifters I used where Sealed Power stock replacements #HT-817.

madam

Thanks for chiming in, here's some specs on the build:

Scat stroker crank (3.75'' total throw).
Block clearenced for rotating ***'y.
Stock rods reconditioned and re-used (5.7'').
Stock wrist pins (press in rod, float in pstn).
Sealed Power flat top hyperutectic pistons w/skirt coating.
Entire rotating ***'y externally balanced
Block bored to new piston specs.
.040 quench.
10.24 Static CR.

TedH

If the clacking is pretty light AND it goes away say after first 60 seconds, I wouldn't worry. As others have suggested, setting preload to 1 full turn is always an option with alum heads to see if it helps.

I run 1/2 turn after zero lash on my cast iron heads and get a bit of clack on start-up (since it sits alot) but it clears and, thankfully, is in now way approaching 'knocking' noises. I run high energy rollers and figure they need some time to get pumped up as the car sits a lot.

ajrothm

I wouldn't worry about it if it gets quiet when hot.. Worry about it when it never gets quiet.

A bit more preload may help but...it's not really a problem as long as they get quiet. XE series cams are notoriously noisy anyway.

Just keep an open ear on it and make sure it doesn't get worse. If it does continue to get worse over time, it could be wiping a lobe and there is no good way to verify this without pulling the intake and visually looking at the lobes. Lifters bleed down when it's not running so measuring lift at the valve isn't accurate.

jb78L-82

I was told 1 full turn on the rockers for pre load with my AFR heads by the builder who did my short block and that is exactly what I did. FWIW-I also followed the engine builder's recommendation on breakin after I installed the top end and cam to run Driven Breakin oil for 30 minutes with the new roller cam (yes, you should breakin roller cams just like flat tappet cams) keeping the RPM's up between 1,800-2,500 RPM and then I drained the Breakin oil and filter and replaced with Driven conventional oil 15W-50 for the first 500 miles. I will be changing that oil this spring and replacing with Mobil 1 0W-40 European Formula (1,000 PPM ZDDP) moving forward which is the oil that I run in all my cars and power equipment.

hugie82

I agree, I wouldn't worry about it, if it goes away.
Do you have forged Pistons? Forged Pistons will rattle in a cold engine until it warms up. GM had a bunch of people worried when the LS motors were doing it, so they had to put a memo out stating its normal.

REELAV8R

This is what I was thinking it sounds like also.