Just replaced the heads and went from centerbolt to perimeter bolt style and the covers I purchased won't clear the GLM exhaust system. The heads are these but milled to 68cc http://www.aamidwest.com/enginequest...cylinder-head/ and the covers are these http://www.summitracing.com/parts/edl-4449/overview/. Is there a certain type of perimeter bolt covers that will fit behind the manifolds/risers? I'm feeling totally screwed right now...

Maybe some manifold spacers? Anyone know if these work on GLM manifolds?

I run those valve covers on my motors because the factory covers would not fit over full roller rockers, I also am running RHS aluminum heads(not that effect anything), but I have the emi thundermanifolds and longtail risers, so I dont have the issue you do. The edelbrock covers are just a little taller then factory covers, so my guess is you are just barely having clearance issues.

They sell aluminum "marine" manifold spacers, but they are damn near $200 for the pair. The best thing for you to do, if you dont want to spend that kind of money is, either go back to your factory covers, unless you are running roller rockers...If stock covers are not an option, my advice would be go onto summit racing and order a pair of loose header flanges. They sell just the flanges for opeople that build there own headers, they are about 3/8" thick plus gakets, you will have plenty of room then.

Here's what I'm working with, hoping adding a 3/8" header flange will work? The covers a sitting on the heads with no gasket.

2013-07-20_17-06-12_89 by hopper75, on Flickr


2013-07-20_17-07-49_847 by hopper75, on Flickr

I'm running AFR heads and AFR standard height aluminum valve covers on my 385 with no problems. they are tight but plenty of room to remove and install with manifolds and risers installed. GLM alum manifolds and Hardin Marine risers.

Are your covers centerbolt?

You can run Merc stock valve covers with full roller rockers with a few tricks. The oil breather baffle and internal support brackets need to be squeezed between the rockers during install. Once they pass the tight space between the rockers they clear everything. Use a thicker valve cover gasket so the top of the rocker bolt will clear the top of the valve cover. You only need about the thickness of a playing card to clear.

I'm not running full rollers, only roller tip and short valve covers. The rockers aren't hitting the valve covers, the valve covers are up against the manifold.

I heated my covers slightly wit a torch and "clearance" the to fit around the risers. The rockers are large bodied Comp and still clear.

I understand, but my point was the stock valve covers will clear both aftermarket rollers AND the GLM manifolds. Some taller valve covers interfere with the exhaust manifolds so I kept the stock covers to eliminate this type of fitment issue. You could install the stock covers and should be on your way. They may not be as flashy but you could get them chromed if that was important to you.

Best of luck.