RD Engine Cylinder Head Casting Numbers

Can anyone share information on where the casting numbers are on an RD-engine cylinder head? Are these the same numbers used in the parts manual?

For example: I have a RD372 in my R185. There is a number stamped right above the engine number on the upper left corner of the head. This number is 215 723 R1, and there is another number both cast and stamped on the head in the top upper right front corner of the head: 132 157 2D (I think). To confuse things further, I have a head off of a 501 parts engine but it has a 2-barrel carburetor. The number stamped on it above the engine number is 858 412 C3.

In the MT-105 parts books I have, the part number for a 372 head is 131 892 R21. In this same book the head part number for the 406, 450 & 501 head is listed as 131 893 R21.

I downloaded the engine information from Gangster Mike (thanks a lot!) and it shows the same part number for all the RD engines: 132 892 R41. It looks like this manual is newer than the MT-105 I've got.

My ultimate goal is to see if the recently rebuilt head on my RD372 will work on a short-block RD450 I'm either going to buy or build. It looks like it will from Gangster Mike's information. Thanks for any and all info. I searched previous topics in this forum and came up short.

Very confused Redk5guy

"Casting" numbers are cast into the casting itself not stamped. Some do revert to service PN's,sometimes with slight changes in the suffix ie; R11 could change to R12,R21 and so on and sometimes not at all.
Did you try Googling any of the PN's? If you do,get rid of the spaces! For instance,131 892 R21 will likely not give any hits but 131892R21 is more likely to.

132 157 2D is not an IH part number,no question.

The most current parts manual Mike has that includes the RD 372 is the MT-119, cylinder head & related parts are Fig.12-77 in file G12.04.

The PN's for heads are listed 2 ways,1st is a bare head with only guides installed,the 2nd are complete heads (head w/valves (and springs)) which is the "normal" service part,the one a dealer would have ordered for a customer.

The head gasket is the same PN for all 4 engines so theheads will "fit" from one to the other,BUT in see the rocker arms,push rods & exhaust valves are different pn's for the 372.What the differences are ??? The only likely way to tell is matching them to each other. What will happen by using the "wrong" ones ????
Also I see a part listed as "tube,cylinder head seal" (key 51) that has a different pn for the 372. It's illustrated next to the head bolts and I'm not sure where it actually goes,but the head bolts are the same for all engines.
Point is,pay attention to the small parts and not just the objective one(s).

It might be better to find an engine with a head then chance destroying a freshly rebuilt one that could be sold instead.

Once again, thanks for the info - it helps clear things up. I see that I misread the cylinder head part numbers in Irish Mike's manual. The cylinder heads are not the same. The 372 is listed by itself while the 406 and 450 are the same numbers.

If I'm reading the book correctly, the P/N for a complete 372 head is 83 962 R95 while the P/N for a 406 and a 450 head with standard altitude pistons and standard compression is 258 415 C95. Can you verify that please?

With what you've posted and the different P/N's, I'm going to take your advice and try and find a long-block RD450. In case you're wondering why I would like to take out a good-running 372 and replace it with an RD450 is because whenever people talk or write about the Red Diamond series of engines, they almost always talk about the 450 and the 501; you never really hear too much about the 372. I was at a truck show a couple of years ago where a guy brought in an R-195 with a 450 - it just had a whole different sound than my 372 - more of a rumbling, throaty idle (if that makes sense).

Anyone need a good-running 372?

Thanks.
Redk5guy

I'm going off memory so don't shoot me if I am wrong.
The early (RED's) all had the same stroke but different bore's The RD series all use a common bore but different stroke.
Again the mind is going, so may be wrong, The smallest RED's (318, 360 somthing and possable the 372) might have had a short stroke as well. The reason for the different heads might be for smaller valves on the small bore engines.

Yeah, I think you might be right about the different valves for different engines depending on size. The exhaust valves for the 406, 450 & 501 might be sodium cooled since the bigger engines were generally worked harder. I know some of the heavy duty Ford V-8's (477, 534 cid) had these type of exhaust valves for better heat transfer and cooling back in the day.

I've got another complete RD372 in one of my parts trucks. I've also got a cylinder head which I believe came from a 450 (has a 2-barrel carb, Holley 852-FFG instead of the funny-looking 885-FFG on my 372), a used 450 crankshaft and a used set of rods and pistons, also from a 450. I think I'll take the 372 apart, take the block with sleeves, the crankshaft, the rods, pistons and the cylinder head to my friendly neighborhood machine shop and see what I can come up with.

Thanks for the info.

Redk5guy

Just make sure the deck height is the same on the engine you want to put the 450 liners in.

Here's the head pn's you wanted verified...

Head w/guides (bare head)
131892R41 RD372
258414C41 RD406/450 standard comp.
131893R81 RD406/450 Low comp./5,000/10,000 alt.pistons/LPG
258414C41 RD501 standard comp.
131893R81 RD501 Low comp.**

Head w/valves (complete head)
83962R95 RD372
258415C95 RD406/450 standard comp.
132170R99 RD406/450 Low comp.**/5,000/10,000 alt.pistons/LPG
258415C95 RD501 standard comp.
132170R99 Low comp.**

** FWIW,Low compression engines were export only.

I see something about internal crankcase parts mentioned? Again,better check the (service & parts) book's first! I glanced at a few things. The liner for the 372,406 & 450 are all the same pn but that's were the similarity ends,pistons etc. are different for each.
See Fig. 12-72 in the MT-119

If you have a good running 372 why change??? Just because someone else's truck "sounds better"? Could that have been due to the exhaust system? I know the 2 header pipes went into a single muffler and there was no option but...

For whatever reason the 450 was the most popular of the 4 but,they were all good reliable engines. What you have could be called "unique" and that might be worth keeping the truck stock.