SBM Promaxx Flow Numbers

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Earlie A

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There's been a little talk about the Promaxx vs Speedmaster heads lately. I got my hands on a Promaxx as cast SBM head for the first time yesterday. Thought it would be interesting to compare the Promaxx vs Speedmaster vs Edelbrock stock castings. I flow tested all 3 back to back to back this morning using the same Speedmaster 30/45 valve and the same radiused entry plate for all 3 tests.
I've tested the SM vs the Edelbrock before and the slight edge usually goes to the SM. Not today. The Edelbrock head is the same as I tested about a year ago but the SM is a different head.

IMG_3302.jpg


IMG_3303.jpg
 
Not a lot of difference between the three heads, pretty much a horse a piece. Just to clarify, that is the ProMaxx 171 aluminum head correct? I have a set I'll be putting to use soon. This is the flow data from their website. Little bit of difference form your results through the range but I imagine that can be from the bench used or maybe the valve you supplied.

Flow Data @ 28″ water
lift100200300400500600
Int71133191236251254
Ext66111145173185193
 
Could be the bench, could be the valve, could be the valve job. Could also be that they cleaned up the ports a little before testing. All 3 of these heads are rough to the touch, mostly where the valve job meets the chamber and the bowl. A few minutes with a bur or sanding roll would pick up 5-10 cfm.
 
Need to get mine out. I don't remember them being rough at all, but they are used and the previous owner may have breathed on them a bit. Appreciate your efforts on the testing.
 
Earlie A said:
There's been a little talk about the Promaxx vs Speedmaster heads lately. I got my hands on a Promaxx as cast SBM head for the first time yesterday. Thought it would be interesting to compare the Promaxx vs Speedmaster vs Edelbrock stock castings. I flow tested all 3 back to back to back this morning using the same Speedmaster 30/45 valve and the same radiused entry plate for all 3 tests.
I've tested the SM vs the Edelbrock before and the slight edge usually goes to the SM. Not today. The Edelbrock head is the same as I tested about a year ago but the SM is a different head.

View attachment 1716341623

View attachment 1716341624
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Doin damn fine work over there. Thanks.
 
The promaxx as cast but complete heads are supposed to have a 5 angle valve job and hand blending in the bowls.

Is this flow test the as cast heads without the promaxx vj and blending?
 
cookietruck said:
The promaxx as cast but complete heads are supposed to have a 5 angle valve job and hand blending in the bowls.

Is this flow test the as cast heads without the promaxx vj and blending?
Click to expand...
This is an as cast head. It has a five angle valve job but there is no hand blending. I saw one of the CNC 185cc Shocker heads fully loaded at the PRI show. It was not hand blended either.

IMG_3307.jpg
 
Does your Ede head have the radius for the bottom angle on the intake seat?

That’s how the assembled heads come, but not sure what they look like when bought bare.

FWIW, I think it’s pretty rare to find the “hi volume”(TF, AFR, PM, etc) cnc’d heads to be hand blended.
 
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Just thinking about this hand blending while I was doing other stuff. We're getting these heads from China because they are cheap. Cheap stuff means cheap labor. I don't want hand blending around the valve seat and throat done by cheap labor. That area is too critical.
 
“in theory”, the guide and VJ work on the PM heads is done over here…….so it would be reasonable to assume any blending would be done here as well.

There use to be video from PM showing that stuff being done in-house.

I just looked at the website, and for the “Maxx series”
171 Mopar head, it does claim hand blending……and unshrouded chamber-
• 171cc Intake runners
• Ultra-smooth 356-T6 Aluminum casting
• Precision CNC machining
• 5 angle valve job
• Hand Bowl blended
• Unshrouded chamber
• Diamond honed Bronze guides
• Multiple chamber options
• Large spring pockets
• Multiple spring options
• Professional assembly
• Assemblies include 21-4N 1 pc stainless swirl polished back cut valves
• Machined and Assembled in the USA
Click to expand...
 
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Earlie A said:
Maybe I am mistaken.
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At 1 minute and 4 seconds I couldn't take the buzz'n anymore... LOL. Sounds like a swarm of mosquitos with a couple of bees in the mix. Not knocking their work or anything, but I'd need my own room with a shut door to do that all day.. LOL
 
318willrun said:
At 1 minute and 4 seconds I couldn't take the buzz'n anymore... LOL. Sounds like a swarm of mosquitos with a couple of bees in the mix. Not knocking their work or anything, but I'd need my own room with a shut door to do that all day.. LOL
Click to expand...
No hearing protection in view, but it looks like they are wearing safety glasses, so I don't think we can call it a sweat shop.
 
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