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Holden Red exhaust manifolds - How to identify the correct manifold?
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Crusty49 Offline
#1 Posted : Tuesday, 1 August 2023 10:05:04 AM(UTC)
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Hi all, newbie here so be gentle..

I note this has been touched on in a few threads, but nothing that I have seen ties it down.

According to the parts book, there are several different exhaust manifolds fitted to red motors. e.g. the part number for a standard HR is 7429514.

Is there a way to positively identify which manifold is which? There seem to be bucket loads of manifolds around with a casting number of 7429475, but I have yet to see a 7429514.

Reason for asking is I am trying to bolt up a new exhaust engine pipe to the old HR, but the exhaust exit angle seems to be a bit skew-wiff, to the point that I get leakage at the flange.

Is it possible I have the wrong manifold? Or do I just get the pipe tweaked to make it fit?

Thanks all.
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Dr Terry Offline
#2 Posted : Tuesday, 1 August 2023 12:36:33 PM(UTC)
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GM-H used the same exhaust manifold on all 161/186/173/202 Red motors (except 161S/173S/186S) from HR to HJ, including LC, LJ, LH & early LX.

I think you might be getting caught in the trap where the casting no. & part no. are 2 different things.

If your engine has a 7429475 (casting no.) exhaust manifold & the engine pipe is at the "wrong" angle, the pipe is at fault.

Dr Terry
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Crusty49 Offline
#3 Posted : Tuesday, 1 August 2023 6:23:18 PM(UTC)
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Thanks Dr Terry,

I suspect it will come down to a somewhat malformed engine pipe as you suggest.

It does have me somewhat intrigued tho. It seems that the "casting number" is something of a misnomer.

I scraped the following two pics from the web today, both show the 7429475 casting number, but are clearly different in some respects.

Mine is the type shown in this pic...

https://photos.app.goo.gl/LdyzKCKzK1opHcvu5

And another type..

https://photos.app.goo.gl/BtYfWQ3HeTL5U2vVA

So neither of these is typically HR? Either will do the job?

Thanks again,

Crusty

Edited by user Tuesday, 1 August 2023 6:24:05 PM(UTC)  | Reason: Not specified
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HK1837 Offline
#4 Posted : Tuesday, 1 August 2023 7:03:47 PM(UTC)
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Casting number is exactly what it says. The number of the casting. Part number is a different thing as it is normally a complete item.

I'll give you an larger example:

For 1968 model year for SBC heads. There is a part number for a standard pair of "fuelie" heads as used on 275hp 327 and 295hp 350. I'm not sure what the part number is, but I could look it up. These are 64cc chambers with 1.94/1.5" valves. Standard press in studs.

For that part number there are two casting numbers: 3947040 and 3917291. 3947040 is a casting number for those cast at Tonawanda Foundry, machined at the Tonawanda engine plant. 3917291 are heads cast for the Flint V8 plant, normally cast at Saginaw but sometimes at Tonawanda. These were machined at the Flint V8 plant. They have different casting marks on the ends, the 291 heads have double humps and the 040 heads have a triangle. They are identical mechanical spec when machined with 1.94/1.5 valves, and share the same part number. 3917291 can also be machined with 2.02/1.6" valves for 302 290hp and 327 300/325hp and 350hp.

Casting numbers like part numbers can also change along the way to suit newer applications. Items with different part numbers can also have the same casting numbers - think a low comp 202 engine and a high comp engine. They are different part numbers for the assembly but share the same block casting number. Same as early Aussie 4spd and M15 3spd, same case with same casting number but different applications.

Dr Terry will know the difference between those exhaust manifolds, I never took any notice, just scrapped anything 6cyl when installing a V8!

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Crusty49 on 1/08/2023(UTC)
Smitty2 Offline
#5 Posted : Tuesday, 1 August 2023 10:03:26 PM(UTC)
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Originally Posted by: HK1837 Go to Quoted Post
Casting number is exactly what it says. The number of the casting. Part number is a different thing as it is normally a complete item.

I'll give you an larger example:

.................................

Casting numbers like part numbers can also change along the way to suit newer applications. Items with different part numbers can also have the same casting numbers - think a low comp 202 engine and a high comp engine. They are different part numbers for the assembly but share the same block casting number. Same as early Aussie 4spd and M15 3spd, same case with same casting number but different applications.




GMH Mechanical Assembly production when I worked at the Bend (and eventually ended up the finance group Costing Manager for that) used a BOM (Bill of materials) system based around the part engineering drawings (what we call blueprints these days as they were all coloured blue) in each of the plants.

The foundry would cast a part which had a cast number on it for ID purposes.. in the foundry, in fettling and then in what ever engine plant it was needed. Where it was (probably) machined and then further modified (fitment of exhaust studs in an exhaust manifold as an example)

So any complete engine assembled (in an engine plant) would have a parent complete part number.. it would have a number of parts/components in the BOM each with its own part number.
Any L6 family engine would always have for example in its BOM - 6 piston and pin assemblies, 1 complete cylinder head, 1 machined engine block (with welch plugs etc) and 1 (maybe 2 depending on the engine) exhaust manifolds. .. etc.

The complete exhaust manifold assembly part number 7429514 might have a BOM comprising 2 x studs 7414906, 2 x nuts 3829086 and 1 x cast body 7429475

If you look at the GMP&A/NASCO parts catalogues you will see ONE part number for the manifold. In the factory as complete it will be one but actually comprises 3 parts with separate numbers
and any of those parts can be used/are used as HK1837 describes with gearbox cases on other exhaust manifolds

Edited by user Tuesday, 1 August 2023 10:12:56 PM(UTC)  | Reason: Not specified

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Crusty49 on 2/08/2023(UTC)
Dr Terry Offline
#6 Posted : Wednesday, 2 August 2023 7:44:08 AM(UTC)
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Those 2 manifolds will interchange. The first one is the early HR one.

Somewhere along the line Holden must have been planning to run an automatic choke on the plain Jane 6-cyl engine, because that later pic shows the auto choke stove housing, which became the more common item.

The auto choke never eventuated but the casting remained.

The outlet however is at the same angle so the engine pipe was unchanged.

Dr Terry
If at first you don't succeed, just call it Version 1.0
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Smitty2 on 2/08/2023(UTC), Crusty49 on 2/08/2023(UTC)
Crusty49 Offline
#7 Posted : Wednesday, 2 August 2023 2:03:52 PM(UTC)
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Thanks all,

Nice to know the background and good to know the manifold I have is ok to go. Thanks Dr Terry.

Next move, back to the shed and see if I can get that pipe sorted.

Crusty
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