C2 Intake manifold bolt headmarkings

[Jim V.]

Any C2 folks out there with TR, CP, or NAT grade 5 head markings on intake manifold bolts. My original 65 L75 has NAT markings.

Dobbins and Newton both reference them as a known GM suppliers. Newton (Corv Resto Guide, 1999 pg87) refers to intake bolt head markings of M, TR, CP & NAT. The 65 TIM&JG for L75 only refers to M, FP, or F only.

Also curious as to why the TIM&JG calls for different head markings between iron and aluminum intakes....hmmm.... Wouldn't Flint be utilizing the same bins for production of all SB motors?

thanks

[Rick S.]

Re: C2 Intake manifold bolt headmarkings

Jim,
I looked at some old photos on my 67 L-79 and was able to see, by zooming in, 2 bolt head markings,one was TR and the other one was NAT.

Rick

[Jim V.]

Re: C2 Intake manifold bolt headmarkings

Thanks Rick. Does the 67 TIM@JG call out NAT as a know intake marking?

[Rich P.]

Re: C2 Intake manifold bolt headmarkings

Jim,

I have removed many NAT Intake manifold bolts from C2. The reason the bolts were different is that aluminum intake bolts were cad plated and iron intake bolts were black.

Rich

[Jim V.]

Re: C2 Intake manifold bolt headmarkings

Jim,

I have removed many NAT Intake manifold bolts from C2. The reason the bolts were different is that aluminum intake bolts were cad plated and iron intake bolts were black.

Rich

Rich...makes sense. Is there any year specific application, or pretty much all c2s?

[Rich P.]

Re: C2 Intake manifold bolt headmarkings

Jim,

I have seen them frequintly on 65-66 and 67. I'm sure 63 and 64 could also have them. Remember that is just my experiance.

Rich

[John H.]

Re: C2 Intake manifold bolt headmarkings

The '67 JG calls for black phosphate bolts on small-block aluminum intakes, with "A", "NAT", "UR", or "FP" headmarks, and notes that they may be painted silver during the intake painting process. For iron intakes, it calls for "M", "FP", or "F" in a circle, painted engine color; my 300hp (iron) shows "M" headmarks.

[Gregory G.]

Re: C2 Intake manifold bolt headmarkings

Has anyone seen RBW headbolts used on any C2 years?

[Jim V.]

Re: C2 Intake manifold bolt headmarkings

The '67 JG calls for black phosphate bolts on small-block aluminum intakes, with "A", "NAT", "UR", or "FP" headmarks, and notes that they may be painted silver during the intake painting process. For iron intakes, it calls for "M", "FP", or "F" in a circle, painted engine color; my 300hp (iron) shows "M" headmarks.

Thanks John for the reference. Curious though, why do you suppose the overlap with the "FP" used on both iron and alum intakes? What about the theory of phosphate for iron, and cad for alum?

The TIM@JG terminology of "know orig. cars use..." is easily misinterpreted to mean "know orig. cars use ONLY...".

[John H.]

Re: C2 Intake manifold bolt headmarkings

Thanks John for the reference. Curious though, why do you suppose the overlap with the "FP" used on both iron and alum intakes?

Jim -

I think it's simply a matter of who observed what on which car and wrote it down, and it made its way into the JG over the years. They were all the same part number, and the line-side bins the operators grabbed them from were filled by part number, not by headmark; NOBODY paid any attention to headmarks at 300 engines per hour.

[Gregory G.]

Re: C2 Intake manifold bolt headmarkings

John,

So let's say in '64 they could have had a mixture of TR and RBW intake bolts?

Greg

[John H.]

Re: C2 Intake manifold bolt headmarkings

John,

So let's say in '64 they could have had a mixture of TR and RBW intake bolts?

Greg

Greg -

I don't judge 64's very often, but the '63-'64 JG notes "UR", "TR", "M", and "AP" as headmarks observed on known-original '64 cars. Any mixture of those would fly for me.