Lifter Preload...OH WOWWW!!!!...I should have checked earlier!!!

[pmoore4321]

Some may have read my post a while back concerning the problems with the work by a local machine shop.

http://www.turbobuick.com/forums/en...e-block-back-shop-check-out-cam-bearings.html

I basically replaced the damaged cam bearings myself and assembled the engine with my fingers crossed. A year later and about 2500 miles, it's still running fine...or so I thought. The engine always seemed to take a "little" longer to fire when starting. I watched countless youtube videos of people "bumping" the key and their engines immediately firing. Mine never did this and always made what sounded like two or three revolutions before kicking off. Along with a slow start, I had a *slight* rough idle which I thought was the norm with these engines. I checked and double checked everything when I put the engine together EXCEPT lifter preload. I simply ordered the suggested pushrods for my combo(Champion irons and a roller cam) and assembled. Bad move!

I always felt that the preload was tight and I ordered a Crane Cams shim kit from Summit. I spent about an hour or so tonight adding .030 shims to the rocker shaft. It took me longer to wrestle the valve covers off than it did to install the shims. Well, long story short...the engine now idles absolutely perfect and my vacuum went from 15in to 18in at idle. The car starts by bumping the starter and the "power band" of the engine seems to roll on a LOT more smooth. I cannot believe how much difference .030 made!

I'm going to order an adjustable pushrod next week to really nail down the correct preload.

For the curious here are my mods:
Grand National mods - pmoore4321

The pushrods I am using are 8.050"

I forgot to mention that I was previously fighting low BLMs. After a short cruise tonight, without an ECM reset, the ScanMaster did not drop below 126.

 

[Jerryl]

........... I cannot believe how much difference .030 made! ......... I'm going to order an adjustable pushrod next week to really nail down the correct preload. The pushrods I am using are 8.050" . . . . .

I measured about a 0.070” variation on the lifter preload from tolerance stack-ups, and installed adjustable pushrods from Smith Brothers. I posted my findings in the Morrel lifter thread somewhere.
There has been LOTS of neg. feedback from adjustable pushrods but I have never had an issue in any of my set-up(s).

 

[pmoore4321]

I measured about a 0.070” variation on the lifter preload from tolerance stack-ups, and installed adjustable pushrods from Smith Brothers. I posted my findings in the Morrel lifter thread somewhere.
There has been LOTS of neg. feedback from adjustable pushrods but I have never had an issue in any of my set-up(s).

Cool...thanks Jerryl, I will check out your post. I drove the car to work today and it just feels like a whole new animal.

 

[turbofabricator]

I have NEVER had an issue with adjustable push rods. I have been using them off and on for more than 20 years on these engines. Just used a set when the customer supplied ported heads had stem highth variations of over .080" Had to use adjustable push rods or roller rockers. Adjustable push rods are MUCH cheaper.

 

[pmoore4321]

Ok...I am going to try them. What is a good brand/model number?

 

[pmoore4321]

Ok...I am going to try them. What is a good brand/model number?

EDIT: Nevermind, I guess I should read more carefully. Smith Bros!

 

[BuickMike]

So, did you have too much preload before? I've used TA Performance adjustables without issues for 15 years on my old big block Buick. I have them on my GN now too.