327 main cap size

[Joe L.]

Re: 327 main cap size

Yes, you might say that. After 38 years in manufacturing and assembly plants, it's almost humorous seeing some folks obsess over having to have "all matching headmarks" for full judging credit.

John------



I noticed that headmarking "variation", too, and I couldn't agree more that it is a perfect example of what you and I and others have been saying here for a long time. All those bolts were once in boxes with the same part number on them. That's all the guy that kept the bins stocked at the various assembly positions paid any attention to. The guys on the assembly line just grabbed the bolts from the bins and paid absolutely no attention to headmarkings. In fact, I'll bet that if, even during their working days, you asked one of these guys to describe even ONE of the various headmarkings they installed, most would not have been able to do so.

[Joe L.]

Re: 327 main cap size

Boyan,
Email me at home. tparsons6@cox.net
I MAY have a set, but I'm at work and can't check until I get home tonight.

Tom-----


I'd love to see photos of the caps if you have them and can post. If not, at least a description of any "embossments" would be nice.

[Bob J.]

Re: 327 main cap size

Bob----


What is the casting number on these caps? Any other markings besides the "N"?

Joe,
The caps look just like the ones in Tim's picture. Mine are Flint blocks not Tonowanda but the caps look the same with 7178...........I think the earlier cast iron caps have a casting number 3743951. Bob

[Joe L.]

Re: 327 main cap size

Joe,
The caps look just like the ones in Tim's picture. Mine are Flint blocks not Tonowanda but the caps look the same with 7178...........I think the earlier cast iron caps have a casting number 3743951. Bob

Bob-----

Thanks very much for the info. It's especially interesting to me that both the Flint and Tonawanda caps would be the same. Tonawanda never had an on-site nodular iron foundry. As far as I know, only gray iron was poured at Tonawanda. So, the nodular iron caps would pretty much have had to have been produced elsewhere. I believe that the nodular foundry at Defiance, OH was a source for many of the Tonawanda nodular iron castings.

For Flint-manufactured engines, I believe the nodular iron foundry at Saginaw (as distinct from the larger gray iron foundry there) was the source for most nodular iron castings.

Unfortunately, I don't think that either Saginaw Nodular Iron or Defiance Nodular Iron ever used foundry identification marks to identify their castings.

This may seem a "droll" subject to most folks, but the actual manufacturing source for Corvette components, especially if that source was an internal GM operation, is a subject of very high interest to me. So, I hope folks will indulge me when I get off on one of these "excursions".

[Boyan B.]

Re: 327 main cap size

Thanks for all the imput guys.....I hope I didnt open Pandora's box with the question! It is appreciated.

Boyan

[Tom P.]

Re: 327 main cap size

Tom-----


I'd love to see photos of the caps if you have them and can post. If not, at least a description of any "embossments" would be nice.

Joe,
I DO have a complete set of good 327 nodular caps from a FLINT engine. The block was junk and I hauled it to a scrap iron dealer here in OKC, but kept the caps. They are 100% identical to those in Tim's pictures above.
The picture will be the same as those above, and the ONLY difference that I can see is the GM mold numbers.

[Joe L.]

Re: 327 main cap size

Joe,
I DO have a complete set of good 327 nodular caps from a FLINT engine. The block was junk and I hauled it to a scrap iron dealer here in OKC, but kept the caps. They are 100% identical to those in Tim's pictures above.
The picture will be the same as those above, and the ONLY difference that I can see is the GM mold numbers.

Tom-----


Thanks. The pattern numbers would most likely be expected to be different. I'm sure there existed a lot of patterns for these caps given the volume they were once produced in.

The "N" on these caps (as well as many other GM castings) MIGHT refer to the Saginaw Nodular Iron foundry. Of course, that would also mean it's nodular iron since that's all they produced there. I've never been able to confirm this, though. So, it either denotes the nodular iron foundry (and, consequently, nodular iron material) OR it simply denotes nodular iron material cast at an "unknown" foundry.

Some castings have an "NF" suffix. That supposedly denotes "nodular ferrous". I don't know why this was used as opposed to just an "N", though----"ferrous" is just another term for iron.

Those bolts sure weren't picked out of any parts bin at Flint Engine. However, they're DEFINITELY THE ones to use if one is smart.

[Clem Z.]

Re: 327 main cap size

Tom-----


Thanks. The pattern numbers would most likely be expected to be different. I'm sure there existed a lot of patterns for these caps given the volume they were once produced in.

The "N" on these caps (as well as many other GM castings) MIGHT refer to the Saginaw Nodular Iron foundry. Of course, that would also mean it's nodular iron since that's all they produced there. I've never been able to confirm this, though. So, it either denotes the nodular iron foundry (and, consequently, nodular iron material) OR it simply denotes nodular iron material cast at an "unknown" foundry.

Some castings have an "NF" suffix. That supposedly denotes "nodular ferrous". I don't know why this was used as opposed to just an "N", though----"ferrous" is just another term for iron.

Those bolts sure weren't picked out of any parts bin at Flint Engine. However, they're DEFINITELY THE ones to use if one is smart.

i would be surprised if stock caps were nodular iron as GM sold nodular iron caps in their performance catalog as a replacement for the stock caps for 350 engines. when we raced 283 and 327 engines we used cap straps to reinforce the caps by machining the caps flat on the bottom and using a steel bar across the bottom of the cap held in place with longer studs

[Joe L.]

Re: 327 main cap size

i would be surprised if stock caps were nodular iron as GM sold nodular iron caps in their performance catalog as a replacement for the stock caps for 350 engines. when we raced 283 and 327 engines we used cap straps to reinforce the caps by machining the caps flat on the bottom and using a steel bar across the bottom of the cap held in place with longer studs

clem-----


For the large journal engines beginning in 1968, caps were made from BOTH gray iron and nodular iron. One found out which ones one had when one actually looked at the caps in one's engine. However, I believe the only ones GM ever carried in SERVICE were the nodular iron variety. So, if one had an engine with gray iron caps and you wanted to upgrade to nodular iron, you had to buy the SERVICE caps.

I agree that I was surprised that some or all 63-67 327's used nodular iron caps. I never knew that; I thought that all were gray iron. But, from the little bit of research I did to confirm it, they were, indeed, nodular iron but only from 1963 onward. 1962 327's, from 250 hp to 360 hp apparently used the gray iron caps also used for 283's

Plus, the "N" casting symbol pretty much confirms that the 63-67 caps were nodular iron.

[Tom P.]

Re: 327 main cap size

Uhhhhhhhhhhhhhh Boyan, that's what forums are for!

[Tom P.]

Re: 327 main cap size

Joe,
Those are ARP bolts that were in the caps when I pulled them off of the engine. Two bolts were missing from the whole set, and I have no clue why. The engine was junk and I just removed the caps and scrapped it (block was busted from obviously freezing from lack of antifreeze).

[Duke W.]

Re: 327 main cap size

Thanks for all the imput guys.....I hope I didnt open Pandora's box with the question! It is appreciated.

Boyan

Hey, Boyan - I see you're causing trouble again.

This thread reminds me of all those "do I need four bolt mains" discussions - maybe not so much here, but on some other forums.

For a road (or light racing) SB up to about 7000 revs I never considered them to be necessary.

This newly revealed information that the '63-up caps are nodular iron adds credibility to that argument.

Gray iron is brittle and the yield and tensile strengths are both about 25 kpsi. Nodular iron has good ductility. The yield strength is about 50 kpsi and the UTS is about 70 kpsi, so it's a much superior material for a highly loaded component.

Duke

[Timothy B.]

Re: 327 main cap size

For what it's worth, I wanted to share pictures of the main caps on my 63 300 HP engine.

I believe the crankshaft has been replaced because #4577 is not the crankshaft part # in 1963. I think the caps are original though..

When I overhauled this engine I had to go .060 and use reconditioned rods, I believe the rods are the 66-67 type.

[Duke W.]

Re: 327 main cap size

Yes, the rods do look like the late 327 type.

Duke

[Joe L.]

Re: 327 main cap size

For what it's worth, I wanted to share pictures of the main caps on my 63 300 HP engine.

I believe the crankshaft has been replaced because #4577 is not the crankshaft part # in 1963. I think the caps are original though..

When I overhauled this engine I had to go .060 and use reconditioned rods, I believe the rods are the 66-67 type.

Tim-----

Excellent. And this confirms, as I expected, that the "7178" is a derivative of the full casting number-----3817178.