Original versus repro 7 fin Aluminum valve covers

[Anthony P.]

I removed some 62 valve covers and upon inspection I found an interior crack that is across the cover (short dimension) from edge to edge that is very fine. This does not go completely through and can not be seen on the exterior side.

I am debating on getting this repaired and reskinned versus picking up a repro one, since mine are rough looking.

So my question is, are the repro covers (without the flaw), an accurate reproduction of the original?

Thanks,

Tony

[Tracy C.]

Re: Original versus repro 7 fin Aluminum valve covers

Anthony,

Before you do anything else, look to see if the same "crack" is present in your other cover. There is a typical flaw inside most every "493" cover that appears to be a crack. The "crack" was in the mold and it transfered to the cover casting. This is not be be confused with, but it similar to a "crack" that began to appear on the outside of the covers in about the March 65 time frame. This one went down through the "o" in the Corvette lettering.

You can also feel the "crack" with your fingernail. If it is raised above the surface, your valve cover is fine.

tc

[John H.]

Re: Original versus repro 7 fin Aluminum valve covers

So my question is, are the repro covers (without the flaw), an accurate reproduction of the original?

Thanks,

Tony

Tony -

As far as I know, there are no "reproduction" covers without the flaw. The covers you can buy are made by Paragon, and are die-cast in the same original GM mold (with the crack through the "o") that was used for '66-up production parts and later Service replacements. Paragon offers an optional finishing service to remove the crack through the "o".

[Bruce B.]

Re: Original versus repro 7 fin Aluminum valve covers

GM made the casting flaw aluminum valve covers from late in 1966 when the mold cracked until they sold the tooling to Paragon probably from 5 to 10 years ago.
From a judging standpoint late 1966 and 1967 Corvettes used the valve covers with the "casting flaw" through the "o" in Corvette.
No need to fix them, they will not leak.

[Paul J.]

Re: Original versus repro 7 fin Aluminum valve covers

John and Bruce, that's not the crack he is talking about.

"I removed some 62 valve covers and upon inspection I found an interior crack that is across the cover (short dimension) from edge to edge that is very fine. This does not go completely through and can not be seen on the exterior side."

[Anthony P.]

Re: Original versus repro 7 fin Aluminum valve covers

The crack I am referring to is on the inside of the cover and is almost in the center (lengthwise) and goes across the small width, so it is not even near where the 'o' flaw would be if it had one. It actually looks like at some point they were tightened too much causing a fracture that did not go all the way through.

Thanks, for the feedback.

[Bruce B.]

Re: Original versus repro 7 fin Aluminum valve covers

Attached are some pictures of valve covers of different vintages.
Basically they are made from the same tooling.
The first is a typical crack on the inside , no crack on outside. The crack is on the surface not in the valve cover.
The second and third pictures are from a valve cover bought from GM a while back and the box is dated 11-12-83. Poor inside surface finish but no distinct crack. It has the casting flaw on outside but the mold was cracked not the valve cover, therefore you see a raised crack on the surface.
The 4th picture is of a nice valve cover off a 62 corvette. No defects.

Paragon has the tooling that made these valve covers. They will remove the casting flaw as a service. They recommend calling them if you are doing a NCRS car for judging.

In my opinion once you disturb the surface of a diecast aluminum part you can never recreate that finish exactly.

[Michael F.]

Re: Original versus repro 7 fin Aluminum valve covers

I removed some 62 valve covers and upon inspection I found an interior crack that is across the cover (short dimension) from edge to edge that is very fine. This does not go completely through and can not be seen on the exterior side.

I am debating on getting this repaired and reskinned versus picking up a repro one, since mine are rough looking.

So my question is, are the repro covers (without the flaw), an accurate reproduction of the original?

Thanks,

Tony

I would look on ebay for a used original unit. Before I would buy a repro. Thats where I got mine. No casting flaw, like new lester unit.

[Tracy C.]

Re: Original versus repro 7 fin Aluminum valve covers

Attached are some pictures of valve covers of different vintages.
............

Nice pics Bruce. Your second picture showing the "crack" beside the LESTER trademark is what I was trying to describe in my eariler post. This transfered into the casting from the mold and is not a crack in the valve cover.

tc

[Patrick N.]

Re: Original versus repro 7 fin Aluminum valve covers

Having seen the pics, I would speculate that the crack appears to be what is referred to as "knit line". This happens when material enters the cavity in the tooling or casting from different locations and has the opportunity to cool a little before joining. Some knit lines are dark lines, some can have depth to them. Plastic parts have the same issues and is very easy to see if the plastic part has any metallic added-these are a huge PITA to totally avoid!

The pics don't show it, is there evidence of two round rings on the underside of the cover on opposite ends where the material comes in?

If Paragon has the original tooling, then they would have to introduce the material in the same location and end up with a consistent knit line per original.

just my 2 cents

[Bruce B.]

Re: Original versus repro 7 fin Aluminum valve covers

Patrick,
The valve covers appear to be end gated at both ends using a slot shaped gate. Some grind marks are present on some of the covers to indicate this.
The only round marks are from numerous extractor pins along the sides and the ends. There are 2 on each end and 5 along each side.
As I previously mentioned the quality of the die cast valve covers deteriorated over the years. Not much mold maintenence if any.
I am not sure how good the new Paragon parts look since they are using the original tooling.
Paragon will clean up the valve covers if desired, but as I stated previously "once you disturb the original finish it is gone forever".

[Tracy C.]

Re: Original versus repro 7 fin Aluminum valve covers

Having seen the pics, I would speculate that the crack appears to be what is referred to as "knit line". .......

Pat, I've seen this interior crack line with identical features, shape and location in 30-40 "493" covers over the years. It was in the mold and not a knit line. A knit line would have some varation between parts and I would also expect to see a corresponding line on the top side.

tc

[Bruce B.]

Re: Original versus repro 7 fin Aluminum valve covers

Woops, my pictures are mixed up in the previous post.

#1 is a nice original with a light polish on top of script and fins.
#2 is the typical inside crack which is from a crack in the tooling not in the valve cover.
#3 + 4 are NOS GM valve covers in boxes dated 11-12-83. Worn out tooling and very poor quality inside and out. Very distinct defect running through the "O" in Corvette.

[Anthony P.]

Re: Original versus repro 7 fin Aluminum valve covers

Folks,

That picture showing the cast transfer, and not a crack, is exactly what I have. What is weird is it is only on one cover, but I feel better.

Thanks for helping me clarify this, and have a great holiday.

Tony