I ran into quite a snag today when assembling my 383. The short block (without the cam/timing set installed) rotates fine. Install cam, timing set.. The engine will turn about 1 1/4 turns all the way around in either direction and then "hits." Something is hitting the cam and locking things up solid.

It's hard (impossible) to tell exactly what is hitting because of the already tight clearances of the 383.

Anyone had this issue before? What have I missed?

The cam is a Comp Cams XR276HR-10.

 

Sounds like you are going to have to get a small base circle cam. This does seem to be fairly comon with 383 depending on the rods used. What type of rods are you using and are the clearanced for a stroker combo?? If you look with the oil pan of from the bottom you should beable to see the rod contact part of the cam. You may beable to get enough clearance with a small base circle cam depending on how much clearance you need. Hope this helps some?/

 

The rods are Scat 6" forged I-Beam rods and the pistons are SRP. The short block was assembled by T&L engines. The pistons are SRP 138103.

 

You need a small based circle cam .900 That will fix the problem.

 

*sigh*.. Figures. Are all small base circle cams a custom grind or do they exist off the shelf from summit, etc?

 

I just called up Comp Cam's tech line. They were quite helpful. Even though I bought the cam off of EBay they offered to "swap it out" and grind one on a smaller base circle for me.

 

Very nice. Yeah, they are usually custom grinds, but some race shops such as Doug Herbert and Comp Cams have them in stock ready to rock!!

I just pulled my 355 apart and found out the #3 on my cam was starting to go flat on me as well. Good thing I pulled it apart instead of pushing it 1 more season. It's a Solid Roller Comp Cams as well, but I am just gonna order the same one again, maybe in billet this time though?

 

My cam is on its way to Comp for replacement. I'll update this thread when I get the new one.

 

Still waiting on the new cam, but I had another question...

I contacted T&L Engines to ask them about my cam situation and they seemed a bit surprised that I was having a problem. Apparently they use the same cams in their long block assemblies. They told me to make sure the timing set was installed correctly.. (It is..)

That made me think though.. What is the difference between the timing sets for factory roller blocks and non-roller blocks?

 

Without knowing exactly where the interference is, it's hard to give suggestions. It's possible a single rod bolt is hitting the cam but I'd doubt it. There has been times with other engines that it's simply some sort of bolt installed in the engine that's just a little too long through a non blind hole and something hits it. I've seen it happen with a bolt on the front of the engine beside the fuel pump. The bolt goes in too far and pushes on the fuel pump pushrod. If the rod can't move, the lobe can't rotate to push against it.

One of the plugs behind the timing gear not in far enough?
Pull the distributor if it's in and see if something still hits. That will eliminate the distributor and oil pump as the cause. Since you mentioned it was a short block, I have to assume the heads and intake are not on.

 

The above post is good advice.

 

Extremely helpful, thank you! I got my new cam from Comp Cams today but it will be this weekend before I have a chance to try it out. The only components installed are the crank and pistons/rods. When you add the cam and timing gears things stop moving. There's only so much it can be. Nothing else in there yet. I wish there was some easy way to see where the interference is (or was) occurring.

 

Well That's a little more information and can eliminate a lot of other potential problems. Maybe you do have a rod bolt hitting the cam.

Something else to try. Take the timing chain off. Cam and crank assembly are in the block. See if the crank will rotate all the way around even if you have to slightly turn the cam to do it. If that works, see if the cam will turn all the way around. Both should turn separately with no problems. Line the timing marks back up on the crank and cam gear and reinstall the chain. If there's still interference then you can assume something on the crank is hitting the cam.

 

Got the new cam installed today. Perfect! No clearance issues. After a few convincing blows with a hammer, the oil pan cooperated as well. I'm going to use a different oil pan gasket though. I don't like the one that came with my gasket set. I'm opting for a one-piece gasket.

Moving on to the top end next weekend!