920 vs. 302 Heads

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I don’t have any flow numbers for either head but I do have a bit of real world experience using the 920s on differnt engines. I had a 273 2bbl motor that I rebuilt with standard low compression pistons back in the early 90s. I had a set of 920s on it with a .488 lift crower solid cam and an edelbrock LD4B. I ran it at the loca drag strip and it ran 15.60s. I built a .030 over 340 for my Dart and before I got heads for it, the 273 let go. (I regularly shifted at 7000.). I used the same cam in the 340 and installed the same 920 heads. The car ran really well with the small valve closed chamber head. I wound up back at the drag strip and ran 13.7 at 103 mph. I eventually did get a set of J heads and with the bigger valves and open combustion chambers, the car ran 13.98 at 102. This was all with a stock AFB carburetor and stock stall 904 trans. My point is there is some power potential in the heads and flow numbers don’t always mean everything. My theory was that increase in compression was more important than bigger flow numbers until you spin the motor past 5000. High rpm you will definitely need the flow.
 
ddartdude said:
I believe the 920's were used on all of the 66 273 engines - both 2 and 4 barrel. The w/CAP engines had a different intake PN and distributor. The D/Dart had the w/CAP intake, Holley, adapter, manual choke, cam, headers, mechanical advance distributor, and unique unsilenced air cleaner. The fuel line was rerouted up and over the passenger side inner fender.
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According to the Galen book, early 66's used 2536178 heads and 2658234 for late heads. 2658920's are listed for 1966 and 1967 with no information why.
 
All these long posts are like a good laxative.
 
Looking at doing a mild 318 build for my kids car. I have a stock 74 318 long block. Was wondering if the 302s will help to wake it up along with other mods I have planned. RV type cam unknown specs as of this moment, either an eddy streetmaster 318 I have currently, or an eddy performer RPM intake, 600 cfm 4 barrel carb, mopar electronic distributor with w GM HEI module, 68 340 exhaust manifolds with dual exhaust. I have access to a bunch of late 80s M bodies at my boneyard. What to look for in a pair of these as pulled from the wreckers? Any specific spots that are cracking prone? Also I dont want to pull a pair of these unless they would be better than stock open chamber castings that are on the 74 V8. Dont want to go Magnum LA hybrid either.

Thanks
Matt
 
I'm running a pair of 302s on a 360ci. Street-only engine. 11.3:1cr.
Smoothed the ports and gasketmatched everything.
CompCams XE256H.
 
Like the sound of that. Often wondered how that would work out.

Have laid the 360 head gaskets on the 302 heads . . Looks like a Go !

5000 rpm, good low end torquer.
 
Big Block
how do you make a cam that closes the intake 56 degrees ABDC @.006 work with that compression? what is your cranking compression? What heads? quench?
E85?
congrats
 
dirty white boy said:
in the small block book larry says the 302s the best factory head for a 318 all way around! no sense wasting time or money on 920s if you got 302s!
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I don't want to piss on the man BUT he was also one to perpetuate the myth of the "THIN Wall 440" of the 70s. He often was quoted as saying that no 74-78 440 should be bored more than .030.
There were no thin wall 440s.
 
That it needs less advance is a good way to make a decision for a place to start
Check out the EQ iron heads
or go aluminum
 
Those 302 heads work great on a 318... but they asphyxiate a 360 without a lot of port work, like more than most care to do on a 360 head. Lol
 
Wyrmrider said:
Big Block
how do you make a cam that closes the intake 56 degrees ABDC @.006 work with that compression? what is your cranking compression? What heads? quench?
E85?
congrats
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'302' heads are milled to 60/61cc. Stock valves. Polished chambers with a few quench grooves.
KB 107 pistons. 0.029" quench height.
Cranking-comp is 208-210 psi.
AirGap intake.
Fuel is Propane.

Normal daily operating range is 500 - 3000rpm.
Engine hardly ever sees 5k rpm, but starts to come alive from 3k and up.
But at around 4k the propane system is maxing out the supply.
 
BigBlockMopar said:
'302' heads are milled to 60/61cc. Stock valves. Polished chambers with a few quench grooves.
KB 107 pistons. 0.029" quench height.
Cranking-comp is 208-210 psi.
Fuel is Propane.
Click to expand...

Hank Hill would be pleased.
 
The stuff costs more than half of what gasoline costs overhere, AND it can cope with high compression ratios better.
I'll take a little loss of power for granted then.

Engine will be updated with a set of Streetmaster heads and a Mike Jones 268 rollercam in the future.
 
BigBlockMopar said:
The stuff costs more than half of what gasoline costs overhere, AND it can cope with high compression ratios better.
I'll take a little loss of power for granted then.

Engine will be updated with a set of Streetmaster heads and a Mike Jones 268 rollercam in the future.
Click to expand...
Just asking
so how far does it drive on say 10bucks worth of propane compared to 10bucks worth of gasoline. Just a best guess on account of I could easily pull 200 psi out of my current combo with just a cam swap, and 220 with a bit less chamber. I'm always willing to spend a little today,to save a lot tomorrow.
 
Well my car is a single fuel setup, just propane.
So I don't have any mileage numbers on what it would do on gasoline.

Just looked up some prices, and it occured the LPG is more like 1/3rd the price of gasoline (!).
Premium Gasoline (98RON) is around €1.68 p/Liter.
Propane (LPG) is around €0,51 p/Liter (used to be few cents higher until recently).

The general concensus here is that gasoline gives some 10-20% better mileage over LPG. But that's mostly based on cars with dual fuel-systems.
But mileage in my car is poor, with around 11mpg overall. That's about 4.7 km per liter.
(Given the things I've done/tried to improve it, it only resulted in a car that's much more fun to drive, but hardly no actual mileage improvements to show for.)

You probably like to do the calculations and conversions to Canadian Dollars yourself here so I won't spoil your fun. :)

I had hopes the 11.3:1cr 360ci would change the mileage for the better, but it's still roughly the same as with the 8.6:1cr 318ci I had before.
The mileage-issue is located in the drivetrain (or me).
 
Way to go Big Block
That piston design/ propane combination was first done by TMS Propane in Santa Fe Springs and Speed O Motive. R&D cams were done by nearby Bill Jenks at Potvin > later MOON cams. Sadly Jenks and Richard Bauman of SOM are gone.
Your roller choice is also spot on- none better, but let Mike pick the numbers based on everything including head flow- get a low lift flow number also if possible as piston demand is important. Mikes 256 hyd cam also works VERY well- would be tough to beat with a roller. Although it looks like seat duration is similar to your Comp at .006 it is actually much shorter at .004 and actual seat to seat while being much fatter at .200. For example it has 50% more duration than the DC 260 at .275. The DC 260 is measured at around .008 and checked as so by me and is actually about the same at .006. (It is also a better choice than the comp)
I worked on this project. Lots of dyno time mostly on BBM propane transit bus motors 413 Industrial/ 440 (for that use the 413 was much better)
I will be very interested in what you come up with next
cheers
 
Mike mentioned the cam would make more pressure than my current one, which I picked solely on the rpm-range listed at the time.
I've got a XR274 solid roller in a 496ci with longram intakes and I like it's power. The engine is a bit of a handful to have idling in drive because of the fuel distribution of the longrams, but (even being in a '60 NewYorker) just keeps pulling like a steamtrain when the pedal is mashed.

I'll take a couple of months before Mike's cam and lifters arrive overhere, but I can't wait to install it, along with the Speedmaster heads.
 
We used to fix those longrams with popsicle sticks
there were write ups on how to do it back in the day
We built a 413 with longrams for a roadster pickup
471 on each long ram
looked awesome
backfire was not helpful
BTW how about EFI for those longrams? port injection would solve lots of problems
which of mikes grinds did are you getting
Don Bass was the expert at TMS propane, genius, wrote well, I learned a lot from him
 
I flow tested a 920 head about 25 years ago....... haven’t seen one since.
I don’t have the numbers handy, and frankly...... wouldn’t know where to even look for them.
But, I do remember that they flowed better than any of the stock 318 heads I’ve tested, including 302’s.
They would have gotten re-used on an oval track build, but one got damaged beyond it being worthwhile to fix, and we couldn’t find another one....... so we went in a different direction.

If one is building a 318 “to make some power”, the 360 heads crush the 318 heads(including 302’s).

Been there/done that on some oval track motors, where both heads were legal.
Back to back on the dyno...... 596 heads were 35hp better than 302 heads.
Chamber volumes equalized for 10:1cr for both heads.

The owner was running the 302 heads because of the MP literature(propaganda).
My flow bench said the 360 heads were way better...... and on a motor that could take advantage of them...... they were.

If you’re building a mild street motor with a small cam, not much stall or gear, etc...... then the 318’s are probably a better “overall” choice........ but if you’re looking to make some upper rpm power and turn some rpm...... the bigger 360 heads will pay off.

Those oval track 318’s went from “uncompetitive” with the 302 heads(from the previous builder), to winning multiple series and track championships with the 596 heads.

These motors were run to 7000-7200rpm.
 
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When I bought my car it had a set of mild 302's on the 360 it was low comp with a 256 @ 0.050 solid cam. That engine make ridiculous torque and was still making power at 6K where it was limited with the MSD. I've since had the engine with ported 587's and various cams but none have matched the 302 headed combo for pure acceleration.

I think the 302's are a very underrated head.
 
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