The base circle on my cam is 1.450" compared to the stock measurement of 1.550". This is a difference of .050" on the radius, so one would choose 7.450" pushrods to retain the current lifter preload. But, to help combat lifter pump up, should I run the preload a little looser and go with 7.425" pushrods?



If anything, the engine is quiet now so with 7.450" pushrods it should be the same. It would probably increase the preload by .005" over what it is now. I dont want to get technical with the actual stock pushrod measurement of 7.395 and stuff.....005" is not a big deal.....025" is a big deal.



So, which would you choose and why? 7.425" or 7.450"?


I am leaning towards 7.425 as a happy median.

 

pushrod calculator
Stock base circle - New base circle = XX
1.55 - 1.45 = 0.10

> 0.10 / 2 = .050

my stock pushrods were 7.375. yours should be the same. so you really need 7.425 BUT. i ran 7.4's in my car and my dads and both of them run perfect. contrary to what people say we have absolutely no valvetrain noise. sounds like stock and should be a little easier on the lifters

 

"searches for a cam with base circle 1.450" Mike, hop on AIM.....

 

lol....black z is freakin columbo.

hahaha...

 

I use 7.425's on 1.45x base circles
To void any arguments, measure your preload. It shouldn't be lower than .060 on OEM lifters.

 

how can you measure pre-load?

 

2 methods:
>Super accurate is to use a dial indicator
>and the old school (mark the p-rod) method

 

Put in new cam and measure it's preload then decide what preload you want to run and buy pushrods based off that decision.

I just installed a cam (ZLP #51013) with a base circle of 1.479". Lifter preload with this cam was around 0.130". Decided I wanted 0.080" preload. Bought 7.350" pushrods (0.050" shorter than stock). Put then in last night and preload was about 0.080". Exactly what I wanted.

 

where can i find a how to on checking preload with a dial indicator? i wanna check my preload but i've never done it before so i'm not sure what kind of dial indicator to buy and how to go about checking it correctly. It's probably easy to do, i've just never done it so a how to would help out. Unless one of you guys can just desribe to me how to do it.