# 1970 455 rocker clatter



## GKling (Jan 8, 2008)

Could someone give me the correct way to adjust valve lash on a 1970 GTO 455 engine? Please start from , let's say a fresh engine rebuild.

I bought this car and it is a little noisy at startup but not bad. After you drive it and get everything warmed up than the noisy clattery rockers come alive. I've readjusted them from static cold (loosen rockers, with that particular piston on TDC and than tighten until all vertical motion of pushrod is gone and add 3/4 turn). Than start the car, let it warm up and back off until noticeable clatter is heard. Than tighten slowly until clatter goes away and add 3/4 turn. Seems OK at first but if I drive a few miles the noise is still there. Now maybe i'm not letting it warm up long enough before the dynamic adjustment, but just seems very odd. The engine has about 4500 miles on it since rebuild I was told. So what is up--weak lifters?(hydraulic here i'm talking).

I carry about 75psi oil pressure when running and 25-30 at idle.Also the noise is from both sides of the engine not just the aft RH side as I am told is sometimes a low oil pressure area.

I have also read in a Chilton manual about just torqueing to 20ftlb on some models? Whats up with that?

Any thoughts or experiences with the pontiac motor here is appreciated. Thanks.

GKling


----------



## 05GTO (Oct 6, 2004)

Hello and welcome to the forum, here is a procedure from *Pontiac Street Performance*. Good luck and let us know how it turns out.


----------



## GKling (Jan 8, 2008)

Ordered poly locks today. Will let everyone know how it turns out.
Thanks for your help!


----------



## seamus2154 (Feb 17, 2008)

I have a 70 455 also and I'm going thru the exact problem you have. i have a new rebuild also and have even gone as far as to start w/ new cam, lifters, and pushrods. The pontiac motor stock has no adjustment like your doing. W/ the correct pushrods you torque it down to 20 ft lbs and that sets the proper preload. The problem is w/ head gasket widths, milling of the block or head it can be way off! So I borrowed a dial indicator and had to check the pre load after tightening all to 20 ft lbs and when released got my pre load on the dial indcator. I had 8 improper pre loads 4 too little which usually gives you the noise, and 4 too much which will wear the cam down. i had to order the right pushrod lengths to achieve the right pre load. A real pain in the ass! The chevy small block is as easy as pie to adjust and lock in. Good luck let me kn ow how you make out Jim


----------



## Eric Animal (Oct 28, 2007)

Are you getting enough oil to the lifters? do you have the proper length push rods? :willy:


----------



## 646904GTO (Feb 10, 2008)

05GTO said:


> Hello and welcome to the forum, here is a procedure from *Pontiac Street Performance*. Good luck and let us know how it turns out.


I just read the PSP article and can agree that is how I do my rocker adjustments. On the SBC chevy I find the 1/2 turn down from 0 lash correct/ On the Pontiac I have found that 1/4 turn down and the 'lock the nut another 1/8 works best. Sometimes I hear a murmer of a tick but, if you preload the Pontiac even a little to much you can get the engine to fall on its face and die if you decelerate it to quickly. If the push rods are in fact to short(if they aren't the stock one from the engine) they could be hitting the edge of the valve retainer and that it what you hear. Good luck


----------

