I'm goin to rebuild my 12v cummins for power and reliability shooting for 500 to 600hp and as much torque as I can get because I tow often and dd it. I don't go to the track or pull events either but it would be nice to play w some quick cars . I will be swapping all my good parts from my current engine, including studs, towing cam, and pushrods. I'm gonna compound in the future after rebuild with my he351ve and hoping to go with a s472 for instant spool. I'll prob bore my cyls .020 but would like .040 if that's not gonna hurt reliability
Question
1 marine or standard bowl pistons and y
2 my injectors are 5x12 145 sac will that mess up w marine pistons or different compression ratio pistons
2 should I change compression ratio and to what
3 any other suggestions for building
4 should I fire ring, o ring or are studs fine for that level (no one local does fire or o ring) but I arty blew one cummins head gasket with studs.
My old cyl head had some cracks around the exhaust ports that u can't feel and or see but my machinist didn't want to touch it after finding those and said the head was bad Iv head that's very common and as long as there's no pressure loss it's fine, I talked to another local shop that does alot of cummins heads and said thats fine and they can put bigger seats in or bigger valves and seats with great success
The cly head I'm running now was a new ebay head and am thinking id like to go back to oe cummins head since it's prob a better casting
Any suggestions on what to do for the cyl head and either run the one I'm running now or rebuild the original head
My truck is a 08 f250, 12v cummins swap, zf6 with duel disk clutch, built 13mm inj pump, he351, Hamilton cam, studs and all the other go fast parts ect. truck currently runs good but very unhappy with the torque output feels like it's running 350 to 400 hp and 400 torque. Also when accelerating the engine doesnt feel the most balanced and i have blowby and recently replace my valve guide seals so I'm beting on I have a cyl or 2 with not the best compression and want to rebuild this engine the right way since I cut corners the first time and didn't bore or replace my pistons
Also I have a kid on the way so any way I can save, the better . Thanks

 

I would at least get some compression numbers and or do a leakdown before you bother to go that far. If power is what your looking for, a little blowby is more than likely not whats holding you back. keep in mind if all goes well these engines can run strong well past 500k even turned up. check compression and post your results!

 

thanks for the responce. I did do a compression test a few months back and had all my numbers for each cyl but lost them. but if I remember right i Wana say all were around 380 and within 25 psi difference between all cyls. I couldnt find a compression spec since ​​I guess cummins goes off the blow by test but was told what I have was good for a cummins but again every time I park I do get a few drops out the breather tube that leaves a oil spot the size of a quarter even if I park for 5 mins so I know my engine isn' in the best of health. when I rebuilt it previously I got new bearings and rings and used a **** y hone and honed the cylinders, reused the old pistons and slapped it back together. iv learned this engine isnt very forgiving cutting corners when making more hp.