R/B Cylinder Heads 1975 MY 440 HP

[amazinblue82]

Insights from anyone please?

I have 440 HP from a 1975 U code police car (Gran Fury).

Not one of my most well-documented acquisitions (very thin on history, related in-service documentation, unknown # of owners, etc), body was shot but it was otherwise complete.

Body was harvested for cop-car unobtanium to keep in reserve, including a running powertrain, rear axle, suspension stuff, etc.

That was a decade ago and its time to fo something with the engine. Discovered two different heads (casting #'s):

source: A Guide To Mopar V8 Cylinder Head And Block Casting Numbers

i am inclined to freshen the engine with seals and the like, put it on the stand and run it, degrease & paint.

No plans to rebuild it unless sitting indoors for 10 years has made it behave badly. Even then would be more likely to harvest it for its HP pieces.

From what little i know, these heads are close to being identical (enough) as not to make a difference. other major castings/hard parts are consistent with 1975 HP & VIN matching to the the donor where applicable.

reuse application doesn't require perfection/non-stock performance .. just a driver quality R/B. unless this head casting thing is a disaster in the making?

thoughts anyone with a viewpoint on these heads?

thanks in advance.

 

[furious70]

That engine won't know the difference in those 2 heads.
My fury had a reman engine with a 902 and 346 head I think

 

[CBODY67]

Perhaps knowing the casting date/build date on the block and heads might shed some light on the different/mis-matched casting numbers?

 

[amazinblue82]

block 3698830, cast in august 1974, the 902 head cast November 1973, the 975 head cast June 1974.

i believe it should have had 902's at factory but may have lost its original set to Father Time.

dont recall exactly when car was built but it was like January 1975.

i am thinking/hoping along lines of @furious70 said. engine couldnt give a hoot as to head "mismatch". both heads appear to be unmolested, bone stock pieces.

dating doesnt bother me, for my purposes, if this thing runs good enough (eg good compression, pressures, doesnt smoke, or make noises, etc), on test stand.

it is NOT going back in a police car or anything demanding better than stock performance of the era.

 

[amazinblue82]

Another source shedding some perspective on the head situation in general. Lotta material in this article. I took a few excerpts below. Still too long, but interesting to anyone as UNinformed as me..

902's vs. 975's, assuming heads are in good order otherwise -- summary to a layperson? Nothing to see here

https://www.motortrend.com/how-to/cylinder-heads/

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[CBODY67]

I strongly recommend reading the full article. LOTS of information in it!

Within the article, is good information as to what is what, as to actual flow numbers. It was noted in other articles that when the Mopar Perf porting templates were used, that ALL of the heads flowed the same, even the allegedly "bad" ones. As the article points out, the "bad" ones were within a 5% window from good to bad, for all of the casting numbers.

Which addresses the OP's original concern . . . verifying they are all the same as to performance.

Thanks for posting that link and article,
CBODY67

 

[70bigblockdodge]

They are basically the same, 902,346,975 are all "early" unleaded or low lead heads. The 452 are the true unleaded head with the best offering from the factory hardened seats. Can't remember which ones got which process, but 452 castings have deepest hardening. I have a 902 here with no valves, it's twin was cracked a long, long time ago. Basically it's a door stop.
If you have a valve job done on those heads the surface hardening will be gone and they are essentially 906 castings with slightly larger chambers.