flat tappet to roller cam swap question

[trbojo]

im in the process of replacing a comp cams flat tappet hydraulic cam with a roller set up. I know theres a difference in the length of the pushrods needed due to the difference in lifter height. I believe the roller lifters are taller which means you would need a shorter pushrod. has any one done this swap and know the difference in pushrod length? im going to run a pattern anyway but just trying to get a ballpark....

 

[earlbrown]

You need to measure your exact setup after you get the heads and rockers on. There's no magic number.

 

[psycho6cyl]

I dont think theres a set length. Has your heads been shaved block surface decked etc. Im pretty sure these all play a viral role in pushrod length. I think best way is get an adjustable pushrod and measure length that way and order proper set/length

 

[earlbrown]

^That's the only way. There are too many variables between engines to have a 'one size fits all' part. Block height, cam height, lifter height, head gasket thickness, head thickness, rockers, and cam base circle to name a couple.

I think there's .050" or .075" difference between the Morels and the Crap Cams roller lifters alone.

You could guess, but you'd be wrong.

 

[Roc87]

My GNs getting this swap, you really need to measure. Cottons wouldn't sell em until I had measurements. In my case I needed 8.050" with nondecked block, worked heads, morel lifters and a comp cam.

 

[psycho6cyl]

Cottons came a long way. When I did my swap they sold me a "kit" and had nothing but lifter noise and binding. But this was at beginning of the roller cam craze andi also went thru 3-4 sets of comps diesel sounding lifter those were the days lol

 

[earlbrown]

Yep. Jack knows there's no off the shelf part to do it right. For example, my pushrods are 7.944 with Morels. I also had to clearance the head for pushrod clearance. Make sure to check that as well. You'll drive yourself crazy trying to adjust out the noise with shims with it's the pushrods hitting the casting making the noises.

 

[psycho6cyl]

Earl were you running champ irons or stockers?

 

[earlbrown]

8445 castings. I did lower the rocker shaft saddles .045" 0r .050" since I'm running a large cam. That will cause a need for even shorter pushrods too.

 

[trbojo]

i know theres variances in everything....but that aside I figured if you changed nothing but the cam and lifters your pushrod length would go from A to B.....im going to measure anyway...