As those of you who have seen/read/commented on my post in the $200X forum about trying to find a set of tall valve covers know, I recently figured out that the stock valve covers don't have the clearance for the new rockers/polylocks and thus I need taller ones. Since I'm using Vortec heads, I need newer, center-bolt valve covers and not the older, edge-bolt ones.
The problem is, center-bolt valve covers both come at a premium new as well as being FAR less common on the used market. A basic set of edge (or perimeter as I think the technical term they use for it...) bolt tall covers is only about $20 new from Summit. The cheapest I've found for tall center-bolt ones (on eBay) is about $75.
My primary question is this: Is there anything really stopping me from tracking down a cheap set of tall edge-bolt covers and just drilling the holes in the top to make it a center-bolt? Is the flange profile the same between them such that it will fit and seal properly on the Vortec heads? This seems like a much easier and simpler solution than making my own tall covers from several sets of stock height ones.
Thanks!
I doubt they would seal very well. The center bolt covers have reinforcements inside to prevent them warping.
As I wrote that, if you could find an old sturdy set of cast aluminum ones, you might be able to get away with it.
As I wrote that, it occurred to me that you could probably weld up some sort of exoskeleton to reinforce the stamped steel unit. Bend up some 12ga material that runs down to the gasket rail, with the bolt through the middle.
As I wrote that, it crossed my mind that I have no idea whether the gasket surface is the same shape and size.
As I wrote that, I decided to not think about it anymore.
Get another set of perimeter bolt valve covers.
Cut top up both sets and weld together. Boom done.
That was what we did for our lemons car.
What about a center-bolt to perimeter bolt conversion plate? I've seen quite a few of those floating around. Wanted to run those on the Corvette so I can use Vortec heads with my LT-1 (early, not the newer stuff) valve covers.
Mazda787b wrote:
What about a center-bolt to perimeter bolt conversion plate? I've seen quite a few of those floating around. Wanted to run those on the Corvette so I can use Vortec heads with my LT-1 (early, not the newer stuff) valve covers.
those cost more than new center bolt covers and new perimeter bolt covers combined.
i second welding 2 sets together. for your challenge budget anyway. then run better looking ones everywhere else if it bothers you.
patgizz wrote:
Mazda787b wrote:
What about a center-bolt to perimeter bolt conversion plate? I've seen quite a few of those floating around. Wanted to run those on the Corvette so I can use Vortec heads with my LT-1 (early, not the newer stuff) valve covers.
those cost more than new center bolt covers and new perimeter bolt covers combined.
i second welding 2 sets together. for your challenge budget anyway. then run better looking ones everywhere else if it bothers you.
Yup, I've looked into the adapters- they do indeed cost more than either than the cheapest center and perimeter covers combined.
I'm probably going to have to end up with fabbing my own from two stock sets- but will likely be picking up the cheapest production set I can for the mean time since I don't have welding gear in my own shop and don't know when it will be convenient to make it up to the teammate's place who does have the equipment and want to get this thing running and mobile ASAP.
One other thing I thought of. I believe they sell spacer plates to do this exact thing.
Rob R.
Rob has an idea.. can you machine up some spacers?
I can imagine using rigid valve covers like cast aluminum for this, but just bolting down stamped steel covers won't do the trick. Centerbolt covers have internal tubes and supports to handle the clamping load. Just drilling regular covers for center bolts won't do it.
You could pookie them up with silicone, but again.... the steel will relax and lose its clamp on the gasket.
i've seen where people have just drilled holes in tall cast alumimum perimeter bolt covers to use on centerbolt heads...
but that's not what i'd do..
i'd try to get ahold of a set of rocker arms and poly locs designed to clear the centerbolt covers- GM installed Crane roller rockers in Corvette LT4 engines in 1996, and they still sell them.. they passed all of GM's endurance and durability testing for installation on a factory built car, and they are the rockers that are included with the HOT cam kit.. Crane also sells them under their own brand name, and they aren't terribly expensive as far as roller rockers go.
this is what they look like installed... ignore the bent pusrods on the #1 cylinder- that was my fault for not getting a poly loc tight...
