Correct Intake Manifold Bolts??

[Ralph E.]

I have a 1967 Corvette with a base engine, 327/300HP. The car is an early prodution car. What are the correct Intake Manifold and T-Stat bolts? The JM list, for the intake, "M, FP, or F". Some of the vendors list the "M" for 427 and "TR" for the 327. What is correct? The JM list "RSC or TR" for the T-Stat, most vendors list only "TR" bolts.

[Gene M.]

Re: Correct Intake Manifold Bolts??

Ralph, If you want to get very specific there are variations that kiss and tell the difference of reporo and original bolt markings. The TR are the closest to correct originals in appearance. Try and find originals unless you plan to use a lot of paint to cover up the repro's.

[Ralph E.]

Re: Correct Intake Manifold Bolts??

The "TR" bolts aren't listed in the JM as acceptable for intake manifolds for the small block base engine. Only the "M, FP, or F" bolts are listed. Where did you get your information that the "TR" Bolts are correct for small block base engines.
I've been searching salvage yards here in Connecticut, for old chevrolet engines, I've discovered they are hard to find. Nobody seems to know where I can find old bolts.

[Peter L.]

Re: Correct Intake Manifold Bolts??

Ralph -

Corvette engines -

Sept'66 built 300/327 - Therm: RSC(long) & TR (short); Intake: NAT

Jan '67 built 300/327 - Therm: TR(long) & T (short); Intake: TR & M

Chevelle engines -

????'66 built 283 - Intake: RSC

Apr '66 built 275/327 - Thermo: TR (long & short); Intake RSC & NAT

Hope this helps. Pete

[Ralph E.]

Re: Correct Intake Manifold Bolts??

Pete, Great information! How come the JM isn't listing the bolts as you have outlined? My intake bolts have NO markings. Is that what you mean by NAT? My car is at a shop about 40 miles from home. I can't check the bolts at this time.

[John H.]

Re: Correct Intake Manifold Bolts??

June '67-built 327/300:

Intake - "TR" Thermostat housing - "TR"

[Peter L.]

Re: Correct Intake Manifold Bolts??

Ralph - The bolt head marking is the letters NAT in caps as printed. Pete

[Ralph E.]

Re: Correct Intake Manifold Bolts??

Pete, You sound emphatic that the NAT bolts are the correct bolts. Again, why aren’t they listed in the 1967 JM?? Also where is it documented? Not being a pest, just trying to understand :-)

[Terry M.]

Re: Correct Intake Manifold Bolts?? *TL*

Ralph I can't tell you why the 1967 TIM&JG does, or doesn't, list certain bolt head markings. But when I was 1970-1972 team leader we put almost no bolt head markings in the manual because we didn't believe we knew ALL the possible marks for a given position. If we failed to list one or two marks those cars with them could have the original bolts removed to pass judging. We believed it better to not list any than risk creating the impression that an unlisted mark was not original, and lose that data or make deductions for what we later might learn were original items.
In the intervening decade we (1968-1972) have learned a lot more about headmarks, there is a different team leader, and the 1970-72 TIM&JG is currently undergoing revision with some different team members. Time will tell if this philosophy changes.
This information may, or may not, be relevant to the 1967 manual, but it might help better understand the dynamics of what does and doesn't go into a manual.
Remember when the engineers specified a fastener they did not specify the headmark. They specified performance and function details. The headmark, except for the grade lines, is that of the fastener manufacturer. The folks who purchased the fasteners likely put them out for bid and at any given time the source (and thus headmark) could have come from several manufacturers.

[Gene M.]

Re: Correct Intake Manifold Bolts??

Ralph, If I remember the manifold bolts are grade 5 (that's 3 lines).
My 67 had originally both NAT and M bolt markings.

[Ralph E.]

Re: Correct Intake Manifold Bolts??

I think Terry has a good explanation. I do not wish to debate policy. I think we can assume is was possible that the engine assembler would just reach into a bin and grab what ever bolt would fit his needs? However I would like to understand where Peter L. got his information.

[Peter L.]

Re: Correct Intake Manifold Bolts??

Ralph - Sorry I wasn't clear. The bolt head marking I listed are what's on the '66 Chevelle 283 & 327 and the '67 Corvette engines I have. I did not mean to imply in any way that those were the only head markings that are correct. In fact I was attemping to let you know that there were a number of different botl head markings for the applications you asked about. I trust Terry's explanation cleared things up. Thanks Terry. My additional comment is that although some engines might have bolts with all the same headmarkings, it is not uncommom and in fact more likely that one finds several different head marking on the intake manifold bolt heads. Again, sorry about the confusion. Pete

[Ralph E.]

Re: Correct Intake Manifold Bolts??

Pete thanks for clearing things up. When I read your post I didn’t realize you were referring to your car. Terry's explanation was very good wasn’t it:)

[Peter L.]

Re: Correct Intake Manifold Bolts??

Ralph - You're welcome and that's why he's the Editor. Pete

[John H.]

Re: Correct Intake Manifold Bolts??

Terry, excellent post/explanation! Having spent most of the last 37 years in assembly plants, I can assure you that the on-line fastener bins were filled from the aisle side by a stockchaser who poured the contents of the box full of bolts into the bin with absolutely ZERO concern over what they looked like, as long as the box had the correct part number on the label, and there were multiple sources for every fastener part number. In those days, Chevrolet built about 12,000 cars and trucks every day in 18 assembly plants and three engine plants (Flint Engine and Tonawanda built 270 engines per hour each, 5,000 per day), and that's a LOT of bolts. The issue was "does it fit?", not "what does the head look like?". I walked by stock racks 22 feet high every day loaded to overflowing with boxes of fasteners from every supplier you can imagine, and only the part number mattered, as that's how they were inventoried. Every time I hear someone talk about "matching headmarks" I feel a lecture coming on...