I am building a 383 for my 86 IROC. When I put the cam in the bearing surfaces hit the rod cap studs, no big deal I turned the crank. Then I noticed the the cam lobs are the almost the same height as the bearing surfaces. The cam lobs can diffenately hit the studs, but will this occur when the timing chain is on. That's my question, will the timing set up never allow the cam lob to be down when the piston is at it's lowest point? Do I have to trim the tops of the studs?

 

That's one of the reasons when you're building an engine to put the cam, crank and timing set in first and install each rod and piston individually to check clearance between the rods and cam.

It might still happen when the timing chain is on, or it might not. If it does, you'll need to create additional clearance. The best way would be to use a different rod with more clearance, or to use a cam ground on a smaller base circle.

 

Is it the rod cap creating the interference, or the studs?

 

To be more pecise it is the Thru-bolt on the Rod cap that is hitting.

 

Put the timing set on and rotate the crank by hand through two full rotations checking for clearance on each lobe.

 

To be more pecise it is the Thru-bolt on the Rod cap that is hitting.

 

Cylinders #2, 4, 6, 8 should be the biggest problem as shown in this old GM drawing. It was made back whenn people were "stroking" a 327 into a 350. Times sure have changed huh? You should be able to "touch-up" the top of the rod bolt without affecting the strength or balance with a dremel tool if you are carefull, depending on the cam.

 

The picture is great help, but how do I measure the clearance, to know if I have taken off enough? Sorry it's taken so long to get back to this, work keeps getting in the way of my fun.

 

Slip a flat feeler gauge in while you rotate it.

 

That would have to be done from below, and I am not sure my hands will fit. But I will try.

 

You'll have to install each rod and piston individually while you do it.

 

If you want to sort out which ones you won't even have to worry about, you can use the "play-dough" method. Put a strip over the top of the rod bolt, turn it thru 2 revolutions to see which ones aren't even close. Then tell everybody which ones are the closest.
p.s. This works great for checking air cleaner to hood clearance too.