Bell Housing Bolts

[Rick R.]

Hey Guys
Im looking for some direction on a restoration I have going.
I have a 1966 427ci 425hp L72 . January car.
Im having trouble with what bolts are recognized by NCRS
In the 1966 Judging manual it only calls out the 4 inspection cover
bolts.
Nothing about the 5 bolts that hold bell to block.
Currently I have markings on the hex head three bars with F & P.
Zip & Corvette Central and others say head mark should be an M marking .
Is their a reason these are not called out in the manual or is it that
they are just to hard to hard to confirm what is used?
Any direction will be appreciated. Thank You..

[Joe L.]

Re: Bell Housing Bolts

Hey Guys
Im looking for some direction on a restoration I have going.
I have a 1966 427ci 425hp L72 . January car.
Im having trouble with what bolts are recognized by NCRS
In the 1966 Judging manual it only calls out the 4 inspection cover
bolts.
Nothing about the 5 bolts that hold bell to block.
Currently I have markings on the hex head three bars with F & P.
Zip & Corvette Central and others say head mark should be an M marking .
Is their a reason these are not called out in the manual or is it that
they are just to hard to hard to confirm what is used?
Any direction will be appreciated. Thank You..

Rick-----

These bolts were likely supplied to GM by multiple manufacturers. Thus, more than one headmarking were probably used. I know that "M" was a common headmarking. "F&P" is a period-correct headmarking and I would not be surprised if yours are original. All of the bolts should be GM 280M material grade (SAE grade 5 with 3 radial lines).

Also, be advised that reproduction sources do not supply bolts with every headmarking originally used. Usually, only 1 or, more rarely, 2 are available.

Tip: as I recall one or more of these bellhousing bolts may have been of a different length than the others (e.g. at position(s) which also retained some sort of bracket). Bolts of different lengths but otherwise of the same size/configuration rarely have the same headmarking.

By the way, I'm personally opposed to reproduction sources using original manufacturers' headmarkings unless those manufacturers actually produce the reproductions. A headmarking is like a signature. Someone using someone elses's signature is forgery. I don't like forgers. In most cases, the original manufacturers are out of business and could not manufacture the reproductions or, even, give authorization that their headmarking be used. Even if such authorization could be obtained, it would still amount to forgery in my book. I don't go for it even in the interest of restoration. Some things are just sacred-----signatures (or headmarking) are one of them.

[Larry M.]

Re: Bell Housing Bolts

Rick:

The 1967 Judging Manual does specify typical bolt head marks for the SB and BB cars. They are "9/16 grade 5 recessed head flanged bolts with known head marks of RBW and/or encircled AP." The inspection cover bolts are "7/16 recessed hex-head bolts with captured serrated washers with typical head marks of E or L logo."

The 1965 and 1966 Judging Manuals I have to not have some of this information, so I cannot help you specifically for 1966.........but the 1967 head marks may well be suitable for your year as well. I do not see why not.

No mention of M or F&P head marks in the JMs for this bell housing area, although I know M head marks are frequently used throughout the C2 build period for others areas of the car.

Maybe others with original 1966 cars will comment.

Larry

[John D.]

Re: Bell Housing Bolts

Rick, Ask Richard Fortier about the proper bolts. He has a ton of ads in the Driveline. Your bolts might even be listed in one his ads.
Or email him at: richfortier@chartermi.net
810-750-1472

Then find out if the bolts are blackened or zincad. Maybe that's in the manual. John D.

[Russ S.]

Re: Bell Housing Bolts

Bell hsg bolts aren't 9/16. They are 3/8. Manual trans to bell hsg are 9/16.

Rick:

The 1967 Judging Manual does specify typical bolt head marks for the SB and BB cars. They are "9/16 grade 5 recessed head flanged bolts with known head marks of RBW and/or encircled AP." The inspection cover bolts are "7/16 recessed hex-head bolts with captured serrated washers with typical head marks of E or L logo."

The 1965 and 1966 Judging Manuals I have to not have some of this information, so I cannot help you specifically for 1966.........but the 1967 head marks may well be suitable for your year as well. I do not see why not.

No mention of M or F&P head marks in the JMs for this bell housing area, although I know M head marks are frequently used throughout the C2 build period for others areas of the car.

Maybe others with original 1966 cars will comment.

Larry

[Larry M.]

Re: Bell Housing Bolts

Bell hsg bolts aren't 9/16. They are 3/8. Manual trans to bell hsg are 9/16.

Russ:

Good observation............but I quoted directly from the 1967 Judging Manual....5th edition.....so they should have caught any significant errors by this time .

The JM is referring to the hex size of the bolt and not the thread size of the bolt.

Larry

[Russ S.]

Re: Bell Housing Bolts

Gotcha Larry but that is a weird way to reference a bolt size unless they explicitly let it be know that the head of the bolt is being referenced.

[Keith B.]

Re: Bell Housing Bolts

don't they have the same part number as intake bolts?

[Joe L.]

Re: Bell Housing Bolts

don't they have the same part number as intake bolts?

Keith------


I believe they are the same as most big block intake manifold bolts. Not small blocks, though.