I have a set of cast aluminum centerbolt valve covers that I bought for my brand new 383 with new Promaxx cast iron heads. The heads are drilled for perimeter or centerbolt valve covers. Not wanting to go through the misery of getting the perimeter ones just right so they don't leak, I opted for these finned centerbolt covers. The holes in the top for the studs are way off center, due I think to the aluminum fins on top. Hard to measure on my heads, but the stud holes are nearly centered between the valve cover seating surface on the heads, within a quarter inch or so. When I put these on, the valve covers are not at all centered on the head's seating surface and on the outboard sides I don't think there's good contact as I'm getting oil leaks there onto my brand new headers.

Is this something that centerbolt valve covers have (an offset) or did I get a messed up pair? Or are my heads messed up with where the studs screw into them? Thanks,

 

yes they are offset. do they fit?

 

Most people don't notice or pay attention but yes, they are all offset.

 

They do not fit very well. As I snug them down, they pull off center and the gasket sealing area on the head becomes minimal on the bottom (the cover is pulled towards the center of the engine). I know the stud is offset a little bit, but not to the extreme that this set of valve covers is. They just don't sit evenly on the heads.

I may just go with a set of perimeter bolt valve covers (heads are drilled for both types) and some load spreaders I already have and be done with it.

 

Are those the promaxx 2151 vortec heads?

 

Not vortec heads. Just Gen 1 SBC heads.

 

I got a set of cheap Summit stamped steel center bolt valve covers and they are not as offset as the cast aluminum ones in the pics above. They sit right on the head evenly. Only problem was they had ribs on the inside that interfered with my roller rockers. I cut those out and hope the covers are strong enough now to not deform when I snug them down. If not, I destroyed a perfectly good set of new valve covers and will just go with perimeter bolt covers if that's the case.

 

How are you putting them on?

 

The original covers with the extra offset? Lined them up the best I could (with the offset matching the head), put em over the studs, and snugged them down with the centerbolt kit that came with them. The hole is just offset too much and the cover does not line up with the sealing surface on the head.

The Summit covers seem to be working just fine. I have a set of ARP centerbolt fasteners that I used with a neoprene washer under a 1.25" stainless steel washer to spread the load out over the top of the cover. As I snugged it down, I did not notice any distortion of the covers. I tightened them hand tight then 1/2 turn with a ratchet, which I'm hoping is plenty tight. They're certainly not sliding around on the head. Time will tell.

 

It is possible the covers were drilled wrong, it is hard for us to tell without trying them out. But centerbolt covers only fit one way on a head unlike perimeter bolt covers. See my picture below. The centerbolt covers fit on either head, but there is a up and down to them.

 

Those look like the exact covers I have now, except mine are black. I had to cut the ribs out on the inside. I did put washers under the bolt heads to spread the load, and they fit right in between the ridges on the top. Actually looks pretty nice. If you look at the cast aluminum one in my original post, you can tell the offset is way more than the ones you have.

 

Even the stock LT1/LT4 and Vortec heads have the valve cover bolt pattern slighty skewed to the valve side.