Anyone know what the minimum amount of clearance is required between the big end of the rod and the camshaft for a chevy 383? I got my motor half way together just to check the clearance and so far #1,2 & 5,6 are clearing, but #2 has only .009 clearance between the rod and cam. I haven't checked the clearance on the rest yet.

Also, is it safe to grind on the rod a little to get the extra bit of clearance or should I just wait for a small base circle cam to be made?

I'm using 6" scat forged h-beam rods.

 

i usually go .050" and i pre-clearance my rods on a fixture i made just kind of go at a 45* angle on the rod where its close. also to check your clearance you can use a piece of solder and then check out the pinch on it, its soft and wont hurt anything. some of the larger zip ties work also i've seen guys put them around the cam lobes but its a bit of a bugger to get off.

 

What kind of rods were you using?

I'm using a set of feeler gauges at the moment. Would I be ok just grinding on the rods that are hitting? So far it's only #2 and #6 that I had to grind. I've checked #4 and it's clearing by quite a bit without modifying it. I'm gonna finish clearancing 2 and 6 and check a few others.
I really dont like the idea of grinding these rods, but I've seen where this is common practice since a small base circle cam is a last resort.

Thanks for the response, I appreciate the help.

 

I think careful rod selection goes a LONG ways towards avoiding this situation.

 

Well these rods were "profiled" for stroker engines and I saw a few posts where people didn't have problems with them clearing.

Maybe they used really small cams or just assumed the clearance was good because nothing made contact while spinning the motor over.

The cam specs are .530/.522 230/236 so I would have thought this was small enough to clear profiled rods.

I did what ws6 said and ground a bit on the rod at a 45 degree angle on the rod shoulder and was able to get between .45 and .51 clearance on all 4 rods that were coming too close.

 

Is it a small base circle cam?
What size is it -.900-.950- what?

 

It's a standard base circle cam, not sure the size, but it's definitely not a small base circle

 

Hind-sight's 20/20.

.050" is a good safe number to shoot for.

In the past I've knocked - make that ground - off the edge of the offending rod nut(s) to give me that. Had no problem with that "fix".

Jake

 

If ya get a .900 base circle ya won't have to do any grinding/or very little.

 

yeah, i initially ordered a small base circle cam, but after a month I was told they didn't have the right billet in stock to grind it. Since I need to have my car running for a race at the end of this month, I got a standard base circle cam instead. My rods were supposedly profiled to clear the cam and after reading about other ppl using the same rods without problems, I didnt see a reason to wait for an indefinite amount of time for the small base circle cam.

 

Ever stop to think what "profiled" or "profiling" actually means? It's just grinding off the offending area to gain the clearance you need.

The very first time I "profiled" a set of rods, many, many years ago, I was really nervous about doing it too. The 8200 rpm 1/4 mile BB never knew the difference though.

Jake

 

This is something I never quite understood. Do you check the clearance with the timing chain installed or get the rods in their closest position to the cam without the timing chain and then spin the cam around to see if it clears, and by how much?

 

Do it with the cam installed and degreed in.

Rich

 

Thanks