Main cap studs and a Girdle
Rod bolts replaced with ARPs
Head Oringd and studs installed.
Exhaust porting. cutting the intake off and porting out the intakes will help too but isnt necessay.
Camshaft with higher lift and duration values, matching valve springs you'll need to discuss with your grinder to get a good pattern for your application
370 injectors may or may not get you there. if you run 370's you'll be better off with the marine Ceramic coated pistons with teflon coated skirts. or the better oprion is get some EDM injectors and use domestic pistons and get them ceramic coated and teflon on the skirts. you have to remember the piston bowls need to match the injector spray pattern at those HP levels to really be efficient. marine injectors are ok but dont burn as well when matched to a domestic piston
Well Balanced engine assembly
Doing it with a Single would be a feat i think compounds would be alot more efficient at getting the job done.
I would probably start thinking about it with a S300 like the HTTB with a 60mm/12cm housing as the primary but the spool up on that may be a little too much as a primary on a 4bt the next option which i've had good success at the 450-490 hp range with a HX35/12 with the exhaust wastegate drilled out to blow off both ports. that would give you good flow and good spool up. match that to a HT3b/23 (most come with 26's) for your large compressor
I ran a large S300 as a secondary and the results were that my drive pressure ratio was off..... i thought i had it when we converted over to a S400 but cracked an oil return line on the lower turbo (because my bracket wasnt strong enough) and lost too much oil, the 4bt was a fun idea, got the motor for cheap like $600, honed it and ringed and then we did ours on a budget by passing the pistons and custom injectors. We used a marine head gasket and had blow off valves on the intake tubing..... would i do it again maybe, the thought has crossed my mind but the cost of doing it right is more than a 6bt so its hard for me to accept
that was 7 years ago so my memory is a little fuzzybut that will get you in there. tuning it is your responsibility as one combo can make 300hp running all the same parts and another with proper adjustments can clean up and make 450..... life span i know of three truck now running twins for more than 3 years and over 30k miles now on 4bts that they drive to the track and then race.......
the Ford recieved a 6BT two weeks later and used the HX35/14 with a S400 for a fantastic compound towing combo that dynod into the 567hp for 4 years and 300k miles towing GN most of its life. sold the truck last i know it just clicked 500k but is currently turning only 490hp towing a 5th wheel trailer around the country.
