Big Block Cylinder Heads "915 vs 906"

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69 Cuda 440

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Has anybody taken these Cylinder Heads in 'relatively' stock condition,
and performed a swap, to see just which Head performed better.

The #2780915 {regarded} as the 67' 440 'HiPo' Head.

The #2843906 {regarded} as the 'Big-Mouth' Head.
 
From what I have seen, the 915's will increase the compression almost a full point, but have port flow issues compaired to the 906's. With that said, both can have the larger valves installed and have the bowls worked to perform equally. With THAT said, after the performance mods are done, it is just a decision on what compression is needed with your combo. I hope this helps.
 
From the factory,

The #2780915 Cylinder Head {closed chamber} came though at 78.5 CC's.

The #2843906 Cylinder Head {open chamber} came though at 88.0 CC's.

If you popped on a set of #915 {closed chamber} Heads on a 1968 thru 1970
440 Engine, you would gain approximately a 'full' Compression Point.

That was with 'no' machine work.

Based upon 'general calculations', you would increase Horsepower by approximately
4% to 5% {15 to 18 Horsepower}.

In a '1968' Dick Landy article about the 'new' 440, Dick stated that the new
1968 #2843906 Cylinder Heads were designed with the 'new' Open-Chamber
"strictly to aid smog emission at lower RPM's".

The 'open-chamber' design helped cylinder flow at lower RPM's, but at maximum
RPM's there was no difference in performance with both engines running with a
10.0-1 Compression-Ratio.
 
Paul, my understand has been that essentially, they are the same head, port wise. One an open chamber version and the other closed. Of course, I could be totally off base, but I believe that's right.

Also, the 915 I think would have another advantage besides compression alone. It has the ability to create quench, whereas the 906 does not. I am like you though. I would like to see a comparison of stock VS stock......but also ported VS ported, and on a zero deck height engine with flat tops.
 
But why 906's? If we are speaking in todays world 452s would be a better replacement. Non racing application. They already have the hardened seats. Flow wise there isnt much different. That mopar muscle article is really good and does well at breaking down each head.
 
The 906 and 915 heads have similar (the best) ports, Josh. The port floors are not flat. They are rounded to help increase velocity.
 
72ScampTramp said:
But why 906's? If we are speaking in todays world 452s would be a better replacement. Non racing application. They already have the hardened seats. Flow wise there isnt much different. That mopar muscle article is really good and does well at breaking down each head.
Click to expand...


I should have 'explained' myself better.

It was the 'mind-set' in 1968, that if you 'swapped' on a set of
67' 440 'HiPo' Heads on a 68' 440, you would gain {20 to 25} Horsepower.

That was what Chrysler was 'promoting', with a gain in compression
of {+1.10}.

Bringing your 1968 '440' from 10.0 to 11.10 Compression-Ratio.
 
69 Cuda 440 said:
I should have 'explained' myself better.

It was the 'mind-set' in 1968, that if you 'swapped' on a set of
67' 440 'HiPo' Heads on a 68' 440, you would gain {20 to 25} Horsepower.

That was what Chrysler was 'promoting', with a gain in compression
of {+1.10}.

Bringing your 1968 '440' from 10.0 to 11.10 Compression-Ratio.
Click to expand...


I think alot could be taken from that. With the bump in compression but also with the 915 increase fuel combustion with proper quench.
 
In 1968 thru 1970,

It was either 'mill' your #906 Heads {.032"}, or pop on a set of stock 67' 440 'HiPo'
Heads on your {1968 thru 1970} 440 to get the same Compression.

Though some also claim that the #906 {1968 thru 1970} Heads had a slightly better Intake Flow at Higher RPM's.

Actual Results coming up,,,,,,,,,,,,,,
 
69 Cuda 440 said:
In 1968 thru 1970,

It was either 'mill' your #906 Heads {.032"}, or pop on a set of stock 67' 440 'HiPo'
Heads on your {1968 thru 1970} 440 to get the same Compression.

Though some also claim that the #906 {1968 thru 1970} Heads had a slightly better Intake Flow at Higher RPM's.

Actual Results coming up,,,,,,,,,,,,,,
Click to expand...

Can't wait to see this. When I pulled my '68 2bbl 383 apart, it had 250 castings...I just pitched them in the junk yard as I figured they weren't worth the trouble, but I am very interested for the results since I have a set of uncut 915s sitting in my storage unit, disassembled.
 
In case any 915/906 cutaway pics might enter this topic, for comparisons, I have once cut an older 516 head to get an idea of the portshape and wall thickness.

Exhaust-port;
AUT16807.jpg


Intake-port;
AUT16859.jpg


How the cuts were made;
AUT16868.jpg
 
FWIW: If I'm swapping cyl heads,going to at least bowl port,proper valve job. My .02¢.
 
I'm just following up on an old 1970 Mopar article,

With respect to the #915 and #906 Cylinder Heads.

On a 1970 'stock' 440 GTX with 3.55 Gears and Automatic.

A 'brand' new GTX with nothing more than a 'general' quick performance tune-up,
ran the 'Quarter-Mile' at Milan Dragstrip at 14.11 @ 99.19 MPH.

The #906 Cylinder Heads were pulled off and CC'd at 88.2.

Swap the #906 heads for a set of Stock #915 Heads {w/Factory CC level at 78.8}

Result............ 13.78 @ 102.34 MPH

Gain............... {-.33 ET} and {+3.15 MPH}
 
69 cuda 440 said:
i'm just following up on an old 1970 mopar article,

with respect to the #915 and #906 cylinder heads.

on a 1970 'stock' 440 gtx with 3.55 gears and automatic.

a 'brand' new gtx with nothing more than a 'general' quick performance tune-up,
ran the 'quarter-mile' at milan dragstrip at 14.11 @ 99.79 mph.

the #906 cylinder heads were pulled off and cc'd at 88.2.

swap the #906 heads for a set of stock #915 heads {w/factory cc level at 78.8}

result............ 13.78 @ 102.34 mph

gain............... {-.33 et} and {+2.55 mph}
Click to expand...

:d:d........ Some Chrysler Reps were stating that the '67 440 HiPo Heads were '40 HP' Heads.
 
.............I did that swap on my buddys duster on a 74 440 that was just re-ringed way back in the 80s.......picked up 1.5 tenths and 2 mph..............kim.........
 
nitrojunkee said:
Why bother with either, really.
Click to expand...

I'm with nitro. I did an engine with both sets. The 906's were ported with oversized valves (cost nearly what eddy rpms's cost) and ended up having to be epoxied as they leaked like a ****. Used the MPP templates. Never again...
 
I used a pair of 915's on my Race car in the 90's.
My machinist told me that they were like a early swirl port type head.
Back them, that was the big thing, swirl port heads, as this was just coming on line with the OEM manufacures.
I didn't have anything on 906's for comparison.
The engine was based off a 440-6V engine, .060 over, balanced, stock rods, stock crank, L2355F pistons, & a 620 lift Crane roller cam.
It would run 10.60's in my Super Street Duster @ 3100LBS.
The heads had the bigger valves, the bowels opened up & the int & exh ports gasket matched.
I thought it ran very well for what it was.
If I had my choice, I would pick the 915 over the 906. I like the closed chamber.
 
i did this on my nearly stock 383 RR took off a good 906, put on a set of 915 bowl blend gasket match left the stock 1.60 exhaust valve and just opened up the exhaust bowl and polished the port. nice gain!!
 
Back in 1968 or 1969,

Super Stock & Drag Illustrated or Car Craft Magazine had an article on
the 67' 440 'HiPo' Cylinder Heads, and called them the 40 Horsepower Heads.

Back then they were all the rage.

You could pick them from your local Mopar Dealership Parts Department for
a crazy low cost, something like $125 for a set.

The Heads and a 'Street Hemi' grind Hydraulic Camshaft, pretty much guaranteed
you about a '1/2 second' off your Elapsed Time.
 
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