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Promaxx Heads
Just a PSA, I am rebuilding my Superboat's 454 and did some reading of old posts. It had some GM 990 iron heads that were going to need some attention so I decided to go to aluminum. I am no expert by any means but wanted to do the build as value minded as possible. I was worried about going with preassembled heads not designed for marine use for obvious reasons.
I called Promaxx and they do set up for several reputable marine builders. They are building me some 317's with PAC springs, Inconel exhaust valves, and appropriate clearanced guides, assembled for $2600. I went with the 317's instead of the 290's because I needed the bigger chambers and the rest of my junk is set up for rectangular ports. I know the 290's are probably the better choice for most people. I just thought I would pass this along as it seems to be an excellent value. |
I did something similar. I picked up the 290 heads and the Promaxx folks put the inconel exhaust valves and also a spring I needed based on my cam specs. They also gave me a decent deal for getting two sets at one time. Very good people to work with. Those heads have a good air flow properties for the money as well. Still working on my engine builds so still anxiously awaiting to see what the dyno shows.
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Your situation sounds just like mine did. 990 heads in bad shape and opted for Promaxx 317 heads on my mild 502 I had built.
I would ask what clearances they (Promaxx) are using for the marine application and see what the guys on here think. My builder opted for the bare heads and chose to do his own set up. Only reason I suggest this is because I have read a few posts where guys had heads come from AFR or some other head manufacturer set up for marine use and had issues. The consensus has always been never trust the product right out of the box. Verify your clearances prior to installation. Coil bind or stuck valves can be costly and prevented by inspection. Good luck with your build. |
Thanks I was concerned about the valve guide clearance. I was thinking about taking the springs off and checking the guides and maybe testing the springs as well. I’ll do this and report back. I know all it takes is someone making a small mistake to cause big problems.
What type of intake carb cam,etc. did you go with? |
Intake
https://billmitchellproducts.com/pro...ere-more-info/ Carb https://www.holley.com/products/disc...18422862e267bc Cam Comp Cams did a Crane 139021 on a Gen V/VI core. https://www.summitracing.com/int/par...39021/overview Lifters Crane 26535-16 https://www.summitracing.com/int/par...make/chevrolet Rockers Crane Gold roller rockers https://www.summitracing.com/int/par...50-16/overview Distributor MSD Billet https://www.summitracing.com/parts/MSD-8560 Exhaust CMI Fusion headers https://custommarine.com/product/e-top-header-13910/ Piston JE with Total Seal rings, rods Mercury Racing H beams (Manley), crank OEM Promaxx 317 heads with HD SS intake valves and inconel exhaust. Isky springs and retainers |
Originally Posted by MyIsland3
(Post 4919331)
I did something similar. I picked up the 290 heads and the Promaxx folks put the inconel exhaust valves and also a spring I needed based on my cam specs. They also gave me a decent deal for getting two sets at one time. Very good people to work with. Those heads have a good air flow properties for the money as well. Still working on my engine builds so still anxiously awaiting to see what the dyno shows.
Most aftermaket heads need a going over, and at least a confirmation before install. |
Originally Posted by SkiDoc
(Post 4919321)
Just a PSA, I am rebuilding my Superboat's 454 and did some reading of old posts. It had some GM 990 iron heads that were going to need some attention so I decided to go to aluminum. I am no expert by any means but wanted to do the build as value minded as possible. I was worried about going with preassembled heads not designed for marine use for obvious reasons.
I called Promaxx and they do set up for several reputable marine builders. They are building me some 317's with PAC springs, Inconel exhaust valves, and appropriate clearanced guides, assembled for $2600. I went with the 317's instead of the 290's because I needed the bigger chambers and the rest of my junk is set up for rectangular ports. I know the 290's are probably the better choice for most people. I just thought I would pass this along as it seems to be an excellent value. The 317s flow really well and have a stable port. The 290s aren't as good in that regard. Despite being a bit smaller. A well matched cam and intake will minimize the issue. |
I had Saris Performance Marine build and setup some PROMAXX for my engine build, they started with the bare casting and set them to marine spec using high quality components. Engines on the dyno this week.
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Post some photos Jim!
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Bang for the buck they are some of the best heads out there. Jason and his team at promaxx (in alabama) are also great people. They also do awesome repairs on all makes of head. I have race teams with more than one championship on promaxx heads. If you arent buying dart, brodix, or profiler, buy promaxx and be happy.
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Originally Posted by TeamSaris
(Post 4919554)
Bang for the buck they are some of the best heads out there. Jason and his team at promaxx (in alabama) are also great people. They also do awesome repairs on all makes of head. I have race teams with more than one championship on promaxx heads. If you arent buying dart, brodix, or profiler, buy promaxx and be happy.
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Originally Posted by Wildman_grafix
(Post 4919559)
I noticed AFR missing from that list?
Padraig |
Originally Posted by Wildman_grafix
(Post 4919559)
I noticed AFR missing from that list?
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Originally Posted by TeamSaris
(Post 4919570)
Not on purpose. I have AFRs on the engine in my boat, and our race boat. They're an awesome product.
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Originally Posted by Tartilla
(Post 4919425)
Not bad considering they're $1500+ bare.
The 317s flow really well and have a stable port. The 290s aren't as good in that regard. Despite being a bit smaller. A well matched cam and intake will minimize the issue. |
Originally Posted by JaniH
(Post 4920011)
flotek/promax 290cc good port is turbulent out of the box, reshaping the head bolt pump inside the port fixed the problem in flotek 290cc heads.
2 different heads... |
Originally Posted by SkiDoc
(Post 4919545)
Post some photos Jim!
https://www.offshoreonly.com/forums/...tered-gun.html https://cimg6.ibsrv.net/gimg/www.off...bbef685180.jpg |
Originally Posted by Rookie
(Post 4920036)
Please don't confuse flotek and Promaxx heads.
2 different heads... |
Jim beautiful!
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Have had great results
I had great results with my 317’s built to marine specs!
https://cimg2.ibsrv.net/gimg/www.off...b908fd357.jpeg |
Originally Posted by 87CigCafe
(Post 4920358)
I had great results with my 317’s built to marine specs!
https://cimg2.ibsrv.net/gimg/www.off...b908fd357.jpeg |
https://cimg3.ibsrv.net/gimg/www.off...9c1be98d1.jpeg
317’s made great NA power. 750 + on my 565’s. 87 on gps in a straight bottom 12 m ftn edit: BTW - That was Tks to Valako. His name should be on the valve covers! |
Originally Posted by getrdunn
(Post 4921156)
https://cimg3.ibsrv.net/gimg/www.off...9c1be98d1.jpeg
317’s made great NA power. 750 + on my 565’s. 87 on gps in a straight bottom 12 m ftn edit: BTW - That was Tks to Valako. His name should be on the valve covers! 317s really perform. The Weingartner test of 290vs317 head to head wss very revealing. They both shared higher HP as the rpm curve went up. He even dropped milled down the 317s to the 290 chamber size to make it an even test. Part throttle cruise with vacuum and less flow...will likely favor the 290s, certainly in smaller (454) BBC displacements. |
Originally Posted by Tartilla
(Post 4921162)
What are you running for a cam?
317s really perform. The Weingartner test of 290vs317 head to head wss very revealing. They both shared higher HP as the rpm curve went up. He even dropped milled down the 317s to the 290 chamber size to make it an even test. Part throttle cruise with vacuum and less flow...will likely favor the 290s, certainly in smaller (454) BBC displacements. Valako wedged my intake ports and opened up some crucial areas. I think mine wound up close to 350 cc but they outflow the 340 cnc by a substantial amount. You’d think they’d be lazy even on 565’s but definitely not. Peak hp @ 6k. Amazing how much torque and throttle response in my heavy boat but has a slippery bottom to help. the oval port 290’s be my pick up to 502 ci depending on application. Light boat vs heavy boat - hull design etc etc. My old 454 builds on roids had the dart oval ports and worked awesome. |
https://cimg3.ibsrv.net/gimg/www.off...96b727dbe.jpeg
https://cimg5.ibsrv.net/gimg/www.off...fe5852690.jpeg https://cimg8.ibsrv.net/gimg/www.off...02136adb9.jpeg https://cimg9.ibsrv.net/gimg/www.off...27156becd.jpeg https://cimg0.ibsrv.net/gimg/www.off...3402999e0.jpeg Got back from machine shop and got short block done, installed cam tonight. See shot of card. |
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Need help picking head gaskets. The block was decked and I did not have the machinist do a smooth finish. As a matter of fact it seems rough. The heads are very smooth. I purchased some cometic mls .040 gasket and now realize that a rough surface is problematic with a MLS style gasket. The short block is assembled and I don't want to go back. From the research that I have done it seems like a copper gasket with the seals seems like the best selection for the situation, a rough surface deck and very smooth head?
040 |
I always use Fel-Pro 17042. I have been using a light film Permatex 80697 copper spray with great results.
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Thanks how do you apply it? Do you tape off cylinders? Thanks
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Originally Posted by SkiDoc
(Post 4921944)
Thanks how do you apply it? Do you tape off cylinders? Thanks
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You could get some 600 grit emery cloth and a flat sanding block and go over the deck surface. Just make sure you seal the cylinders up.
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Originally Posted by SkiDoc
(Post 4921944)
Thanks how do you apply it? Do you tape off cylinders? Thanks
Originally Posted by sutphen 30
(Post 4921956)
just spray the gaskets
Shake the can up good and keep shaking. |
I ordered some of the FelPro head gaskets. I hate to waste money but it seems that everyone has had no issues with them. Assembly should be done this week just as soon as I get the head gaskets balancer and push rods. I disassembled 2 cylinders of head and all the guides were finished nicely. I should have checked them all.
i ordered some of Jegs dowels, installed them and the heads wouldn’t go down. The dowels were.007 wider than the head! I taped the whole deck and dremeled them down. Got the high volume pump installed, customized the pick up and welded it to the pump. Thanks for the help https://cimg9.ibsrv.net/gimg/www.off...a1788c368.jpeg https://cimg0.ibsrv.net/gimg/www.off...91a2badcd.jpeg https://cimg1.ibsrv.net/gimg/www.off...65b9f4c3a.jpeg https://cimg2.ibsrv.net/gimg/www.off...61352584f.jpeg https://cimg3.ibsrv.net/gimg/www.off...4b5f54186.jpeg |
Originally Posted by SkiDoc
(Post 4922285)
i ordered some of Jegs dowels, installed them and the heads wouldn’t go down. The dowels were.007 wider than the head! I taped the whole deck and dremeled them down.
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the chinese drill is a little worn out.:)
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Originally Posted by BillK
(Post 4922286)
Just so you know, that meant that the holes in the heads were too small, not the dowels too big lol. If the dowels fit in the block then they were the correct size.
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Should I do anything about the discrepancy between the water hole in the block and the head gasket. The old head gasket, the cometic, and the new FelPro are all mismatched the same way?
https://cimg5.ibsrv.net/gimg/www.off...0f7b82d3f.jpeg |
Originally Posted by SkiDoc
(Post 4922551)
Should I do anything about the discrepancy between the water hole in the block and the head gasket. The old head gasket, the cometic, and the new FelPro are all mismatched the same way?
https://cimg5.ibsrv.net/gimg/www.off...0f7b82d3f.jpeg |
Please post a picture of front and rear of gasket, gasket installed to the block.
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Those ProMaxx heads sound pretty interesting.
I have a pair of 482cid BBC NA engines in a heavy 40' Hustler Fiore. I wasn't initially intending to put that those small of a CID in my big heavy boat, They only made 510hp @5000rpm on the dyno with GM Rectangle port cast iron heads with some clean up and blending of all the ports. I also had the cylinder bores "bore notched" on both intake and exhaust sides of the cylinders to unshroud the valves for better breathing/flow for the 4.25" bore size, but the bore notching creates a drop in my compression ratio. I cannot remember if the pistons are a true Flat Top or maybe have a slight dome. I would have to wait until I would remove the GM heads and look and see what I have as far as my pistons go and see how far they sit in the hole at TDC. I think the hydraulic roller Cams may be the old Merc 502cid/HP500 cams, but I am Not exactly sure, but the engines only make peak power up to 5000rpm according to the dyno @32° with only a stock Merc Thunderbolt distributor and stock Merc/Holley 800cfm carbs. I am kinda thinking that my Comp Ratio may be as low as 8.0 to 8.6 ratio which is a bit low. So, I thought that maybe the ProMaxx heads would be a good solution to my issue especially with their 110cc combustion chamber size. I am only looking for a little more KICK in power to maybe about 580-600hp while retaining the same Cams and I thought I could accomplish this without swapping out the Cams. Also, I want to try and avoid putting to much strain on my XR Bravo drives and I thought that perhaps the ProMaxx 290cc head would be the ticket. I've been watching Eric Weingartner's videos and doing a lot of research on them. I am wondering what you guys think or would appreciate any input/feedback. Thanks 👍 🇺🇲 |
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