Horned Promax

[Charger20sv]

Im currently building a new powerhead for my charger. Coming from a bridgeport. This time around im going with a stock promax 225 block, crank, rods/ pistons with a modified bp efi front half and 260 reeds, horn and running 16 amp electrics with digital a49 box.

Has anyone here built a motor similar to this? My goal is more power then the bridgeport and hopfully longer rebuild intervals.
Ps the bridgeport pushed my boat fastest of 89 mph at 7300 rpm turning a 28" chopper. Anyone think i will get into the 90s?

Interested on feedback

[Capt.Insane-o]

I have one built but haven't run it yet. Starting with a pro max curve in a pcu. The water is still cold here so it'll be another few weeks before I'll get to fuss with it. A stock pro max pushed my vector to 102 easily and I have some rough acceleration times to compare it to.

The 2.5 motors fair better on heavier boats, keep us posted on your numbers.

[Charger20sv]

I hear you on the cold water. Will still be a little bit for us too.

I am very interested in hearing your comparison numbers on horn vs laser. Can you or anyone else confirm weather or not a promax block is close porting wise to a 260? Im hoping the move to a 2.5 gets me a stronger motor. My boat will use it

[texasvector]

yes itll run....we got 1 running right now....currently have a 56 A6 tune on it.....pulls hard...very hard....ran into the mid 90s with a 30....havent strung it out or dialed it in yet.

should go faster than the BP

the a49 box ....if adjustable.....should be great

[tlwjkw]

I wanna here more on tha 2.4 front half goin' on tha 2.5 block half???

[texasvector]

I wanna here more on tha 2.4 front half goin' on tha 2.5 block half???

dunn and maybe others are machining the fronts to fit. ... and moving mains to line up

[tlwjkw]

how much "meat" is left at tha bolt holes after tha saddles are drilled out??.. do they align bore it or just guess on tha two mains???......... sorry, I jus wouldn't trust it myself.. jmo.

[Charger20sv]

Dunn is doing my front half. He and others say it works fine. I will be doing a close inspection before assembly either way and will let you know how it goes.

Only altervative would be find a small bearing 260 front which i could not do. And i had lots of bp stuff to play with.

[tlwjkw]

have you talked to anyone actually runnin' that front/block combination?.. or is it jus a "they say" deal?.. keepin' tha crank straight is pretty serious I think....

[Charger20sv]

yes i am not the first person to try this. This is a service that dunn provides so not sure he would risk his name on somthing he wasnt sure he could do properly? i agree 100% on the front halfs role on keeping the crank straight. And i will for sure check the match between the block and modified front when it arrives.

That said i didnt start a thread so we could argue here. I get what your saying, and not saying your wrong. I will report back with my findings.
If anyone else has ran a horn on a promax feel free to chime in

[tlwjkw]

jus something I never heard of anywhere.. on here or any other hot rod site.. will be interestin' ta say tha least.. gl with it...

[Steve Pope]

Milling new mains bolt positions and enlarging bearing saddles seems a lot of work when you could buy or trade for a 260 front half. Remember the front half takes all of the power load from the crankshaft.

[90 5.0]

Milling new mains bolt positions and enlarging bearing saddles seems a lot of work when you could buy or trade for a 260 front half. Remember the front half takes all of the power load from the crankshaft.

Thats the way I was gonna do it when I was seriously thinking about it, but small bearing 260 front half’s are getting harder to find and cost more than the seemingly tons of Bridgeport front halves from motors with bad chrome that no one wants to fix.

Ive looked into both routes, the bp front half solution seems to be working quite well for quite a few people.

[Charger20sv]

This was my problem. Next to impossible to find a good 260 front half for a decent price. was cheaper to just have a bp one modded.


I should have everything in the next couple weeks and get it dropped on and try it out.

[Charger20sv]

Just an update on this. The dunn modified front half worked flawless for the 40 hours i ran it. Over the winter i scored a very clean 260 front for 200 bucks so i swapped it out.

As far as numbers. With the bp my boat did 87-88 mph with a 28 chopper. With same prop, height and fuel load i did a 92.7 mph pass. I am confident it will do 95 with a better prop and some tinkering. Definatly more power then the bp and much better acceleration. Overall a great motor and hoping it will get more time between rebuilds then the bp.

Very happy with the horny promax