Help identify aluminum heads

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From personal experience with having 4.30, 4.10, and 3.91 in my car, and seeing no performance difference, I would be more conservative with the gear choice. A 500 shouldn't need more than a 3.73, and 3.91 is as low as I would go.
No problem with the 950, as long as it's not a 750 venturi carb with a 950 label slapped on it (holley has done that).
A cam swap would do wonders.
You could run a compression check to get a vague idea of compression ratio.
 
33IMP said:
From personal experience with having 4.30, 4.10, and 3.91 in my car, and seeing no performance difference, I would be more conservative with the gear choice. A 500 shouldn't need more than a 3.73, and 3.91 is as low as I would go.
No problem with the 950, as long as it's not a 750 venturi carb with a 950 label slapped on it (holley has done that).
A cam swap would do wonders.
You could run a compression check to get a vague idea of compression ratio.
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Ok, hopefully by the end of today I'll have more particulars on the build. I was told it has 3.23s & approx. 3400 stall . Thanks for the advice
 
I have come to the conclusion that the more torque an engine has , the less gear it needs. You might like the 3.23s. Bet you might not like the 4.10s.
3.50s in my opels 9", with a 454 in front. Gonna keep em.
 
427shark said:
I'm still working on finding out what is actually in the motor , but would you agree with a 950 carb & 4.10s ?
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The gears are probably the last thing I’d change.
And if it’ll see regular street duty, I’d run the tallest gear that would still let me reach my ET goal.

I’d be looking for a carb with a Venturi diameter of 1.400 or 1.450.
Pick your favorite brand.
 
Just got off with mahle, which BTW has one of the best customer service support departments I've ever dealt with. If the heads are the speed masters 78cc the CR is approx. 11.8 to 1. We know the piston & the rod is a 7.1, I do t have any info on the crank though. Assuming it's a 4.375 the engine would be 520ci
 
Also (hopefully) the combustion chamber is cnc'ed to reduce the cr. . . Plot twist speedmaster just got back to me and said the numbers on the heads don't match anything they have . . .maybe the engine builder did his own work and put his own number on them . . .
 
It’s more likely a “serial number”, or something along those lines(lot number, batch number, etc).
As I recall, the current version of those heads have the relevant numbers etched on the exhaust side somewhere.

I have an early set here that don’t have any “part numbers” there.

The numbers on these heads, that look like the numbers on your heads are 0902-0257 on one head and 0902-0424 on the other.
 
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427shark said:
Just got off with mahle, which BTW has one of the best customer service support departments I've ever dealt with. If the heads are the speed masters 78cc the CR is approx. 11.8 to 1. We know the piston & the rod is a 7.1, I do t have any info on the crank though. Assuming it's a 4.375 the engine would be 520ci
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You are assuming flat tops? I think I would get a cheap inspection camera that plugs into a phone, and look through a plug hole. 11.8 with a 220-something at .050 will be a full-on race gas only engine. (If it IS that high, the first thing I would do is convert to E85 if it's available where you are. )
 
33IMP said:
You are assuming flat tops? I think I would get a cheap inspection camera that plugs into a phone, and look through a plug hole. 11.8 with a 220-something at .050 will be a full-on race gas only engine. (If it IS that high, the first thing I would do is convert to E85 if it's available where you are. )
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I actually spoke to the owner this afternoon who had the motor built and was able to get some particulars. He told me it's 500ci, 10 or 10.5 -1 compression, & originally was built with a 950 but he changed it to the 750 for better fuel mileage. Also the heads are promaxx. . .I'm still going to remove the oil pan and see if I can figure out what crank is in it. . . Also he told me the one valve seal needs to be changed which I'm not thrilled about but I guess it's no big deal
 
Piston set with 7.1 chevy rods

20211121_205257.jpg
 
It looks like promaxx and speedmaster use the same chinese casting then.
That's okay, I trust promaxx part selection and prep much more.
With those pistons, 493" with a 4.150 crank, 505 with a 4.25 crank.
Does it say what the compression height of the piston is?
 
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I don’t think promaxx does a victor copy. Maybe the PO meant procomp.

I think those piston part numbers are for mahle pistons. Supposed to be nice with a good ring pack.
 
Took a minute but i found that part number (mahle changed their part numbers a while back and yr pic has the old one)
I dont see how they got 500ci or 10-10.5:1 compression. Mahle pistons arent dished, they have large valve pockets. maybe the motor does have a 4.375” stroke and its actually a 520??!!

B29520C4-CF74-495C-9025-378E6CD140AB.png
3372DA29-7D90-46B3-B800-5B2D9C2415C7.png
 
Procomp & Speedmaster are the same company. I suspect the change to SM was made when PC started to 'smell'.
 
cookietruck said:
Took a minute but i found that part number (mahle changed their part numbers a while back and yr pic has the old one)
I dont see how they got 500ci or 10-10.5:1 compression. Mahle pistons arent dished, they have large valve pockets. maybe the motor does have a 4.375” stroke and its actually a 520??!!

View attachment 1715828452 View attachment 1715828453
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Yeah, I'm really at a loss for how they are coming up with 500ci & 10 / 10 1/2 - 1 compression. . .the only stroke that would make sense would be 4.375 & with the .051 head gasket the cr would be 11.8 with a 78cc head. With an 85cc head the cr would be 11.3 which still seems to high. Maybe the timing is very retarded for pump gas ? I'm going to check timing and pull the oil pan soon. Hopefully I can find some marking on the crank that will help out. . .talk about detective work. . .& at the end of the day I don't see it making the claimed HP with such a small cam & 750dp. . Plus I have to change a valve seal
 
cookietruck said:
I don’t think promaxx does a victor copy. Maybe the PO meant procomp.

I think those piston part numbers are for mahle pistons. Supposed to be nice with a good ring pack.
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I think your right. The po told me "pro tech" so I assumed promaxx but more likely they are procomp. . .I was hoping they are promaxx because it seems like promaxx has larger CC
 
If the piston were used with a 4.25 crank & 7.100 rod, in a block that was decked to 10.700”.......it would be a 505 with the pistons down the hole .063”.
With a 78cc head and all the usual other stuff...... it would end up at 10.2:1.

Obviously, without a detailed build sheet it’s all speculation until someone takes a head off.
 
PRH said:
If the piston were used with a 4.25 crank & 7.100 rod, in a block that was decked to 10.700”.......it would be a 505 with the pistons down the hole .063”.
With a 78cc head and all the usual other stuff...... it would end up at 10.2:1.

Obviously, without a detailed build sheet it’s all speculation until someone takes a head off.
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oh yeah, i figured there was some combo that would've worked. i was on my phone last night and didn't have an excel spreadsheet handy to run the numbers. i wouldn't shoot for a piston .060 down but i guess it's a possibility...
 
427shark said:
I think your right. The po told me "pro tech" so I assumed promaxx but more likely they are procomp. . .I was hoping they are promaxx because it seems like promaxx has larger CC
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the promaxx has the larger combustion chamber because it's a copy of the edelbrock RPM head which is the 84cc chamber.
the heads you have are the smaller heart shaped chamber that's either 74 or 78cc, the ledge on the intake manifold mating surface of the head indicates it's the Victor head copy, not the RPM head.
 
PRH said:
It’s more likely a “serial number”, or something along those lines(lot number, batch number, etc).
As I recall, the current version of those heads have the relevant numbers etched on the exhaust side somewhere.

I have an early set here that don’t have any “part numbers” there.

The numbers on these heads, that look like the numbers on your heads are 0902-0257 on one head and 0902-0424 on the other.
Click to expand...
Your right I think it's just the casting number
 
Thanks for all the good info and help trying to figure out the engine combo. . . Assuming it is a 505 with 10.5-1 what kind of power is realistic the way it sits now with the 750 & smallish cam? . . Also is it common for a valve seal to need replacement on a setup that's approx 10yrs old with about 4k miles of easy street use ? . . Sorry for all the academic questions BTW
 
A compression test would be revealing. Also as mentioned pulling a valve cover would help you understand what that camshaft upgrade would entail based on the quality of the valvetrain parts.

I also agree that 3.23's should be the last thing to go.
 
The plan is to only change the one bad valve seal. Using the air compressor method is it a relatively easy job for a 1st timer ?
 
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