My Son Matt sold his .040 over 360 shortblock out of his Duster a couple of months ago to a Friend. Needing a set of heads for it I have been researching ways for him to get the engine assembled and into a Dart that he recently bought. Knowing the Procomps (Speedmaster) had some issues I tried to find some info on the ProMaxx small block head that Jegs sells. With springs good for up to a 575 lift cam they cost slightly over 1400.00 a set shipped, app 200 plus dollars cheaper than Edelbrocks. I told him if he bought a set I would flow test them on my bench and strip on down to check it out for free. So far I have nothing but GOOD news for these heads and they put the Edelbrock heads to shame in both quality and flow numbers. The only issue I see so far is that the exhaust port flows almost EXACTLY the same as the Edelbrock head and they both have terrible (slow) air-speed on the exhaust side. He is going to install these as delivered so I can't wait to see the results. Air-speed at .500 lift on the exhaust port maxed out at 175-180 FPS and I good exhaust port should be at least 325 FPS and needs bell-shaped to get there. Both exhaust ports maxed out around 182-185 CFM and were checked without a ex flow pipe

-----Edelbrock--------------ProMaxx
--------Intake-----------------intake
.200-----128--------------------129
.300-----182--------------------184
.400-----215--------------------235
.450-----226--------------------251
.500-----233--------------------255-260 high air-speed
.550-----236--------------------260
.600-----242--------------------264
.650-----243--------------------270
.700-----243--------------------263-270
.750----------------------------263-270

As you can see by the numbers this BOTH ports need more volume. The air speed on the ProMaxx at the pinch at .400 lift is 300 average (center) at the pinch and 370 on the pinch turn. At .400 lift 365 FPS-390 FPS on the short-turn. At .500 lift at the pinch center 340-350 FPS and 401 FPS (pegged my gauge) at the pinch turn. At .500 the short-turn is way high at 390-401 FPS (pegged).
So far 4 valves were removed and the valve guide clearance is GREAT and a very nice at least 4 angle valve job done. The stainless valves look nice and come with a 30 degree backcut. I will be buying a couple sets of these later this year. One set with stock 2.02 valves and one set bare so I can go with a 2.08 valve

thanks for posting this info!

Monte said the Promaxx guys have nice equipment and know how to use it, which really makes me tempted to get some big block Promaxx heads for a hot street build and save some cash over the Trick Flow heads.

Some pictures

More

He are some Edelbrocks that I bought last year. This is one I have preped for a 2.08 valve so the valve job is NOT from Edelbrock. Their quality control is really going down-hill

Good info John, I think by the lack of replies it shows the mopar world here is still reluctant to embrace the offshore castings even when looked at from a decent company with decent qc.

If this were 25 years ago or better most would think the top pics were the usa cast headand the lower being the china junk.

I know your all about buy usa but what can ya do when it seems edelbrock takes so much for granted or simply just dont care.


Would you trust this company and quality of parts to run every set ootb, or would you still pull them down for inspection?

Thanks. Honestly I was starting to think it wasn't worth the effort even posting results or findings anymore. Fat guys are more worried about installing aluminum bolts to go faster. Lol

I am never going to install an out of the box head on any of my builds. A good friend bought a set of AFR chevy heads that were then sent out for some cnc porting. The flow numbers provided were 20 cfm low and the air speed was out of control. 2 valve guides were so tight I know for a fact he would have had issues. I was very glad he was at my shop to witness this. Some guys think all CNC'd heads are the same but trust me they aren't. I sure hope more of today's kids take an interest or years from now I see problems. Someone's gotta get dirty

Those are some pretty good numbers as-cast. What sort of rocker gear do they take?
What size valve stem?

Do the ProMaxx heads come with heli-coil style thread inserts?

They are nice looking heads, for sure. Thanks for posting.

Vey Interesting and useful info.

What's very telling is the ~20 to 25CFM OOTB difference from .400 through .600 is going to be worth roughly 40HP or more to a combination with enough cam and compression to take advantage of it, that's a VERY SUBSTANTIAL difference.

The Story Bryce Mulvey (yes I am aware of the horror Show) told was that Procomp sent their Eddy clones to DrJ's/Airwolf for testing and they suggesting some mods to the roof and the next batch would outflow the Eddies. Full disclosure, my 414 motor has the Airwolf SBM (using Steve Dulcich's 408" shortblock) heads from the magazine article.

That's what I liked too. I'm thinking that with very little work these heads would go 280 plus and I mean very little. Bell shape the exhaust port to get some speed and let her breath.

Looks like they did a better job of the port entrance/exit than they did with the BB head.

I am a little puzzled why they cost $320 more than the BB heads though.

If you open the exhaust exit, won't it be out beyond the size of most headers?

I don't know if it's just the pics or what, but the roof of the intake port, adjacent to the guide boss, looks much more "normal" than the Edelbrock head.

The exhaust port kinda has a Herman Munster forehead on the exhaust short-side and needs widened some and shaping. Like I said on these its all free checking for a Friend to get him up and running so the grinder won't be touching these. It will be a good test. On my car I will make the exit however I deem necessary because my headers (1 7/8 hedmen) have already been modified. The headers on my Duster are W2 headers with adaptors.

What have you gotten out of an rpm head(intake port),and what was the runner volume when it was done?

I've never poured one after porting but I got 315-318 cfm with a 2.08 valve without moving the pushrod. Tubed but not moved and a lot of work. Bolt hole is also tubed but I do that on every Edelbrock head I port. K&S tubing makes it to easy not to. I won't be sonic checking the floor on this set but I'm betting they learned from Procomp (Speedmaster) to fill the floor some. From what I hear several guys approached Edelbrock about doing this and they didn't want bothered.

Some good info.


https://www.youtube.com/watch?v=hxLnEID_Xfc