Valve Cover Casting Flaw - 7 fin

[Mark P.]

I have seen this "crack" on 2 valve covers on the inside of a 3767493. It seems like a casting flaw and goes completely across the valve cover. This valve cover does not have the flaw on the top running through the "o" in Corvette.

Is this normal ? Any issues with using the valve cover ? When I hold it with 1 finger in a vertical position and tap it rings like a bell so I am thinking it is structurally sound.

[Mike E.]

Re: Valve Cover Casting Flaw - 7 fin

Mark--
ever since mid-66 (as I recall--it's in the JM for that vintage) the covers have come with that casting flaw. As a result, any 60-up, to that point, with aluminum manifold, needs a pair without casting flaws. Those go for quite a bit more. And watch out for "NOS"--they invariably have the flaws.

[Mark P.]

Re: Valve Cover Casting Flaw - 7 fin

Mike - I heard the casting flaw through the "o" started 3/66.

Any idea when the casting flaw on the inside started ? This flaw is in the center of the cover while the casting flaw through the "o" is more to the left.

Mark

[Mike M.]

Re: Valve Cover Casting Flaw - 7 fin

mark: i just checked out a pair of early 56 al valve covers--no inside casting flaws as you describe. mike

[Dan H.]

Re: Valve Cover Casting Flaw - 7 fin

Mike - I heard the casting flaw through the "o" started 3/66.

Any idea when the casting flaw on the inside started ? This flaw is in the center of the cover while the casting flaw through the "o" is more to the left.

Mark

Mark, checked my March 64 covers and no inside flaw FWIW!
Dan

[Bill S.]

Re: Valve Cover Casting Flaw - 7 fin

i have a pair of no flaws. no line inside

[Tracy C.]

Re: Valve Cover Casting Flaw - 7 fin

I've seen this feature on MANY of the covers I've had. I'm not sure when the flaw on the inside began to appear, but you have nothing to worry about. The cover is 100% sound.

tc

[Mike M.]

Re: Valve Cover Casting Flaw - 7 fin

Yes, Mark.
The JG confirms the external flaw was first observed in March '66, approximately with VIN 17,000.
HaND

[John D.]

Re: Valve Cover Casting Flaw - 7 fin

I have seen this "crack" on 2 valve covers on the inside of a 3767493. It seems like a casting flaw and goes completely across the valve cover. This valve cover does not have the flaw on the top running through the "o" in Corvette.

Is this normal ? Any issues with using the valve cover ? When I hold it with 1 finger in a vertical position and tap it rings like a bell so I am thinking it is structurally sound.

Mark, I have been looking at many 100's of our aluminum script valve covers. The 60 to 66 valve covers are an education in themselves. Recently I saw a pair of 64 valve covers that supposedly were on the car since it was new. Engine build date of Jan 64 I believe. No signs of the cracks inside the covers. But between that time and March 66 the crack appeared on the inside and finally the mold let go and the crack or seam appeared on the outside. Now the outside flaw appears to have gotten progressively worse to the point that some of those over the counter replacement VC's are downright rough and the crack is quite prominent. Now this crack was in the mold and doesn't mean anything as far as being functional. March 66 is just a rule of thumb. One a few cars in that time period in 66 Corvette SB could have a mixture of the two covers. No seam and seam. John D

[Stewart A.]

Re: Valve Cover Casting Flaw - 7 fin

Mark you have put a 58 60 year model up on the thread so i suppose your car falls in those dates. 58 models have low script on the top .030 to be exact. 1959 and 60 has the high script .125. What I can gather late 1959 covers with the holes none staggered have the casting flaw through the ''O'' on them. The 58 has the staggered holes and they have no casting flaw. The casting flaw ran up to 1967 in small block Corvette Chevs.
I'm sure someone knows better than me so feel free to step in.
If it's cracking severely and you are worried about there longevity you should maybe epoxy the crack. Stewy

[J O.]

Re: Valve Cover Casting Flaw - 7 fin

Mark.
For added info... I've just checked 2 set's of my VC..neither have the cracks or casting flaws you mentioned.
one set is the 7 fin low script ( .030 high) staggard hole pattern set for very late 57 to mid '58 ( i believe)..
the other set is an original NOS set-(in the box-) 7 fin, high script (.125 high) staggard hole pattern set for mid '58 to mid-'59. ( late May '59 i believe). afterwhich they went to the straight across bolt pattern -high script thru Mar-April '66 when the casting flaw appeared thru the "O"...
hope this helps.
john