[mopar70]

Hi
I wouder if someone has put in Comp Cams Roller Rockers 1621 in a 383 Engine with stock heads 906 or 516
My question is how long Pushrods do you have and what size of pushrods?

My Engine 383
camshaft is CompCams XE-274
Rockers Comp Cams 1621 (1.5)
Heads are 516 with 1,74 ext and 2.14" int

But I wounder what lenght and size of Pushrod should I buy?

How much preload should I adjust is 3/4-1 turn ok

Regards Roland

[Adrian Worman]

Are the rocker arms ball stud type? So you need cup/ball pushrods?
I think they should be stock length.

Check the manufacturer's recommendations for oreload, I seem to remember the plunger should be depressed around 0.030".

Daveman or Eddie will know

[mopar70]

the pushrod must be ball/ball to fit the lifters and the rocker arms.
Stock Pushrods is to long but I do not know what lenght I need to have

[Eddie]

Hi Roland,, there are too many variables to suggest a length you can just order and put in your engine and have everything fit as intended. Has the block or heads ever been decked? (Material removed from the deck surface to ensure equal cylinder banks and material removed from the head to reduce chamber cc's or to ensure a flat surface), then there is the lifter height and cam lobe base circle,,this all will be different from stock OEM parts. The proper way is to place the rocker arm adjuster with 1 thread showing below the rocker arm,,, the cam lobe for that cylinder being measured on it's base circle(both valves closed),,then take an adjustable pushrod checker and carefully take up the slack against both the hyd lifter and the rocker arm pushrod socket,,without compressing the lifter which will be installed without oil in the lifter body,,be careful because the empty lifter will compress easily, I usually oil the epushrod tip lightly turn/spin the pushrod by hand to ensure it's fully seated without compressing the lifter. If you don't have a long travel Vernier caliper to measure your adj, pushrod you can simply tape it up to prevent movement and tell your vendor to add the pre-load which should be 1/2 to 1 full turn on the lifter,,,also this is important,,,make sure the radius in the lifter and the rocker arm adjuster matches the radius on the pushrod,,some are different but most are 5/32 radius. Hope this helps,,,Eddie

[Eddie]

Do not install the lifters filled with oil as seen on various internet boards,,this will cause the valves to remain open on start-up and may cause the valves to hit the pistons,,,breakin lube on the bottoms ONLY,,,regular motor oil on the sides! MAKE sure the new lifters ROTATE FREELY,,,this is vital!!! Carb primed and ready,,ignition good,,on start up,,rev the engine to 2000-2500 rpms changing revs frequently,,, objective: getting the lifters to spin as they are intened to do,,without this they WILL FAIL. Good Luck

[Eddie]

1 Full turn on the rocker adjuster= .036 1/2 turn=.018 anything in between this is fine

[Eddie]

Forgot to mention Roland,,with the springs you need for that cam which is a Mild Hi-Po Cam,,5/16ths hardened Comp Cams pushrods will be plenty, these are much stronger than the OEM rolled sheet steel rods which flex with even a Carburetor vacuum pod spring,,LOL

[dave-r]

I made myself an adjustable pushrod so I could set the exact length I needed. But in my case I had adjustable rockers and solid lifters as well as cut to length pushrods so in all it was a lot easier to get it exactly right.

I used just a half turn preload when I had hydraulic lifters. More and there is a chance of them pumping up at high rpm.