All Big Six ProMAXX CNC ported big valve heads are now available.

Relates to all big sixes

Green ford f150

Active member
Supporter 2021
The last set of Scorpion 1.73 ratio rocker arms installed required longer pushrods so the stock pushrods were replaced with longer Comp 3/8' pushrods.
We have seen stock pushrods bent in stock engines so I don't know at what point they should be replaced.
I recommend stock pushrods replacement with any valvetrain upgrade.
Paul thank you !
 

Sevensecondsuv

Well-known member
At this power level an injector swap will be necessary. I have Siemens deka 80s at Decipha's recommendation so anyone serious about running this head with stock EFI should slap the 80s in and take decipha up on his offer of free dyno time. My bottom end has 240k on it so I'm gonna have to wait until I need a rebuild to order this head.

No point in paying for S-D 80s unless one is going to run E85. A set of 21 lb/hr injectors out of a 2v mod motor will support 250 HP in a 4.9L running gasoline. Beyond that Gen 1/2 coyote injectors are something like 34 lb/hr, are still plenty cheap, and would support over 400 HP in a 4.9L.
 

pmuller9

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Supporter 2021
No point in paying for S-D 80s unless one is going to run E85. A set of 21 lb/hr injectors out of a 2v mod motor will support 250 HP in a 4.9L running gasoline. Beyond that Gen 1/2 coyote injectors are something like 34 lb/hr, are still plenty cheap, and would support over 400 HP in a 4.9L.
Not even close.
Six 21 lb/hr injectors at 80% duty cycle supports 200 hp and six 34 lb/hr injectors support 325 hp on pump gas.

Edit: Sevensecondsuv reminded me that the fuel pressure is much higher than the standard pressure that injectors are rated at so the injectors will support power closer to the figures he stated.
 
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efloth

Well-known member
Numbers aside, If there is ever a hope of the community being able to offer a base tune for a 300 with this head then everyone would obviously need to settle on the same injectors. SD 80s are recommended as they are very linear and work well with the single injector slope of the speed density computer. More technical folks could then take the base tune and scale for turbos or whatever else they want to push it to the max without being limited by injector flow.
 

Sevensecondsuv

Well-known member
Not even close.
Six 21 lb/hr injectors at 80% duty cycle supports 200 hp and six 34 lb/hr injectors support 325 hp on pump gas.

At standard 39 psi fuel pressure, yes. However, the 4.9 runs about 50% more fuel pressure than other Fords, which makes the injectors act larger. Given the general relationship of pressure and flow is a square root, multiply by the square root of 1.5 (comes out to about 1.23) to get an approximate value for the injectors running at the 4.9's fuel pressure. 14 lb/hr injectors act like 17s, 21s act like 26s, and 34s act like 42s. This is why Ford used 14s in the 4.9 while nearly everything else in that era got 19s.

So multiply your HP numbers by 1.23 and you arrive at my HP numbers.

FWIW, I'm running four coyote injectors in my 2.3L turbo Ranger with a stock 4.9L fuel pressure regulator and it'll hold 11.4:1 AFR up to 20 psi boost which is about 300 HP.
 

jgavac

Active member
I'm not surprised at all. You either cannot get parts or the parts that are available have ridiculous lead times.
Add that to the long turnaround machine shop times and it is no wonder that there aren't any completed engine projects.
I think that Promaxx has done a great job of supplying their heads by comparison
So, has anyone actually ran these heads yet? I'm still curious about the results.

I'm pretty surprised it's been this long and no info yet on someone running one... I know if I want results I should just do it myself I'm just saying... This is weird considering the hype and everything else.

Pmuller is right, real long lead times on everything is killing build times. I got one of the first heads they offered, but I'm still waiting on components. 6 weeks for rods, 8-10 weeks on pistons, 4 weeks for the cam..... Granted, I'm going way off the component deep end, so YMMV

I imagine it'll be around the holidays before I have mine assembled in carbureted format for break-in, and a while longer before I get EFI going.
 
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THE FRENCHTOWN FLYER

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One of my buddies asked me if I could build him a 9" rear end. I said yes but why not get it done by a pro shop? They couldn't guarantee when it could be done so he said just sell me the parts and I'll have FTF build it. They said that is the problem - parts are not readily available to build one. Go figure.
 

wallen7

Well-known member
One of my buddies asked me if I could build him a 9" rear end. I said yes but why not get it done by a pro shop? They couldn't guarantee when it could be done so he said just sell me the parts and I'll have FTF build it. They said that is the problem - parts are not readily available to build one. Go figure.
And it's probably going to get worse - Twice I have been to Chick-fil-A for a peach milkshake and the story is we dont have any & my wife stopped at BoJangles for a steak biscuit and the story is we dont have any.
 

InlineDave87

Well-known member
I'm pretty surprised it's been this long and no info yet on someone running one... I know if I want results I should just do it myself I'm just saying... This is weird considering the hype and everything else.
I could have gotten mine running but my brothers boat got in the way and my knee decided to take a vacation… fromwhat i hear it will be back on the job in 2 weeks… im planning on ordering more parts that i need in the mean time but as soon as i get it done ill be happy to share… and as well as posting everything to youtube
 

80f150custom

Well-known member
Any reason to suspect that the CNC version of the heads could handle a higher compression ratio versus the original heads as far as detonation is concerned?

Based on the flow numbers any idea of the max NA horsepower potential of the CNC Head?
 

Green ford f150

Active member
Supporter 2021
Any reason to suspect that the CNC version of the heads could handle a higher compression ratio versus the original heads as far as detonation is concerned?

Based on the flow numbers any idea of the max NA horsepower potential of the CNC Head?
More Detonation tolerance maybe . The head definitely likes more ignition timing. power Depends on to many variables . Give Bob the builder and Arnie the assembler the same parts your not going to get the same engine . With some compression and solid cam and a 2x4 tunnel ram I'll guess a about 350 horsepower.
 

Wesman07

Famous Member
Supporter 2020
Ftf - Pro maxx un shrouded the valves enough to loose most of the swirl characteristics. On the power nation video, I think they found 36 degrees total was the sweet spot for their combo. Don’t quote me on that exact number.
 

Green ford f150

Active member
Supporter 2021
I know alot has to do with the combination of parts. Was more curious how much horsepower 218-225cfm would support.
Goes right back to the combination. More compression equals more horsepower per cfm. More rpm the more horsepower you get from your torque until the cylinder head choke point . You pick mild ,street strip, or 14.1 on methanol. Any engine has a torque limit dictated by cylinder filling cubic inches and compression. It's how far you carry the torque up the rpm band that gives you horsepower.
 

King_Kong

Active member
I guess there is a little more to it than just cfm.
Richard Holdener talks about this in the video below (but he wrote the hp potential formula wrong: it should be "potential HP=cfm x 2".....which obviously most street Ford 300s will never actually attain).

He has built and dynoed a lot of different types of engines & combinations of parts, so he knows his stuff. He also answers questions on his livestream and does have experience with inline 6's.

 
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