procomp speedmaster heads revisited

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moparmat2000

moparmat2000

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Hi Y'all,

I bought a pair of the procomp speedmaster SBM heads off ebay bare for $380 each. They use std length 11/32" Shivvy valves. The castings look real good. Basic machining is done on these, bronse guides installed, but not sized.

I have messed with mopar 2.2 turbo engines, and to be frankly honest with y'all those stock mopar aluminum castings were really crappy. And they were factory stuff.

These speedmasters look like an LA casting but have heart shaped combustion chambers, magnum style runners, ports, and bowls. These use 2.02 / 1.60 valves.

I am unsure of the CC on the chambers i think procomp stated 65cc. If i use these on my 318 with true KB 167 flattops even with a .050" headgasket i have a bad feeling this things gonna be at or near 11 to 1. Too much for the street. Can anybody verify this?

If i run these with the stock 318 slugs. 74 model 318, about what would i be looking at compression wise?

Eventually i would like to swsp this top end to a 360, but for now i want to run what i got. I know with a 2.02 intake i will have to unshroud and relieve the cylinder bores on the intake side, and run a 360 ,headgasket because of this.

Anybody good at engine math that can tell me? Stock bore x stroke 318, stock 318 slugs, .050" thick 4.00" bore 360 head gasket, 65 cc heads.
 
They are good castings from what I have read. They do need some tweaking under the valves. Also some unshrouding around the spark plugs. Also, have the guides replaced when you take the heads to the machine shop. All the info I have read that was posted by machinists, they all say the valve guides that come with the heads are too soft and are junk.
 
zero decked with a .040" gasket I get 10.63:1 CR
 
A cam with a Intake Closing Point of 45 degrees ABDC @ 0.050 lift will give you a dynamic cr of 8.5:1 which is probably the minimum you want to try to get away with.
 
Whoops sorry, yes these are 65cc. I transposed numbers. I will fix original post to reflect this. I plan on using an eddy performer rpm 7176 (non airgap) heads dont have heat riser, so i may fill crossover in the intake with fiberglass insulation , and put a valley baffle in the block to help w heat dpak issues. Was going to aldo make a 1/4" phenolic or plywood spacer for under the carb.
 
I used an engine calculator on the net heres what i got.

.030 overbore, and flat top KB167 and 65 cc chambers i get 9.76-1 compression and 322 C.I.


.060 overbore, kb flat tops 65 cc chambers 10.02-1 cr 327 C.I.
 
toolmanmike said:
Correct me if I'm wrong guys but 10.5/1 with aluminum heads isn't a issue.
Click to expand...

Mike, the more of a compression ratio you run, the more octane it will need. A larger cam will bleed off some compression and reduce the octane requirement to a degree. Limiting total timing will allow a higher ratio but will cause a power loss.

I myself run a 11-1 - 360 engine with aluminum heads. The cam is a fairy stout one. The smallest I have run is a Purple 292/.509. It has 248*'s of duration at .050. I have not run a smaller cam with this combo. But this runs well on 93 octane. Your results may vary with the grade of available fuel, quality and where you live. (FWIW) I'm a few feet above sea level.
 
Thanks for the advice on the guides, i will get those changed out, and take the ones from the heads and drop em in my scrap bucket.
 
All of the procomp heads i've worked on had odd sized guides . some were .505 OD , some were .507 OD, instead o the usual .502 OD. So you better remove and measure before you order new guides.
 
j par said:
Never seen this thread before when I was searching...
Click to expand...

Well ignore what I said about soft and odd size guides, at least as far as their sb mopar heads are concerned. When I posted that, all I had dealt with were sbc and sbf procomps. I have since had some sbm ones here and their guides were .545 od and did not try to mushroom from being too soft when I drove them out with the air driver.
Early on I saw all sorts of problems first hand. One sbc head had one of the the holes for the locating dowels in the wrong spot by about .100. The customer called the ebay seller he got them from , and they told him to just drill the holes bigger till they fit! I insisted he send it back. I could go on and on, but it seems that they have improved since the early years.
 
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