Yet another person that has fallen victim to improper connecting rod to camshaft clearance. After degreeing my cam in and setting it up where it needed to be, my rods contact my camshaft lobes on 1 and 6. I thought this was only a problem on the more exotic strokers (396, etc) but I guess not.

I am running a billet roller camshaft with a 3.75 stroke crankshaft in a 350 with Scat cap screw 4340 rods. Before we advanced the camshaft we noticed they were just barely hitting the cam lobes. After advancing it to where they need to be, we can no longer turn the motor over on the engine stand.

You guys think a small base circle cam will fix this or am I looking at taking material off the connecting rods too? How small is too small on base circle, and what do you guys think of having my camshaft reground on a smaller base circle?

 

I don't know how much interference you have, but grinding a bit off the head of the rod bolts is perfectly acceptable if that will do the trick. If you need a smaller base circle, it will mean a new cam (not regrinding your existing cam).

Rich

 

We got a mirror and a flashlight back in there and we believe it is hitting on the cap of the rod. We had discussed just grinding a bit off when it touched but didnt interfere, now I think I am stuck going to a smaller base circle .

 

I wouldn't touch the cap, so I think you need a new cam.

Rich

 

Yeah I guess so. I really appreciate all your help Rich .

 

The Scat I beams will hit on a 383, you just have to grind them in the top of the bolt area... not a big deal but it's almost needed on any stroker I have seen with those rods.

Bret

 

The thing is, we just built a 383 with Scat I beam rods and they didnt hit with a solid roller just as big as this one . I dont really want to touch the rods now that the rotating assembly is balanced, think I can get away with just a smaller base circle?

 

How small of a base circle do you have now?

Grinding on them after the thing has been balanced is not a huge ordeal... balancing is basically a best guess... a slight under or overblance is not going to cause issues. I would just do everyone of them the same way.

Bret

 

Not sure on the base circle, I will check it out tomorrow.

 

You just have to use the right rods. We don't do anything to most of our stuff and still always run full base circle rods on everything even 396s. You just got to get the right stuff! On the 396s we cut the rods back a small amount. After that they are still strong enough to run 8.00s at almost 3300 pounds.