Turbo head questions!

[BoroBrown]

I am building a N42 block trying to keep it simple and was looking for a P90 head also wondered if a P79 would work to run a turbo as well and is there any difference besides the square and round exhaust ports. Also if anyone has a P90 for sale please let me know.

[evildky]

the P79 has the same internal volume and same vavle diameter, but the intake runners are round becasue of the sleaves they have inserted intot hem, these sleaves are the restriction, as well as coming with a cam suited to n/a, if you wanted to run a different head the N42 would eb choice, but you'd want to run a 2mm headgasket, this brings you to a 7.8:1 CR which is still boost friendly

[BoroBrown]

Well I do have a N42 head at the machine shop getting cleaned but when they took it apart and pressure tested it it didn't leak but there were a few small cracks between the intake and exhaust valves. So i think it would be fine for N/A but i am afraid about running a Turbo and take the chance of dropping a seat and tearing everything up. Can the head be repaired? or should i just break down and buy a P90? Also i have heard some say that the N42 BLOCK is trualy siamesed and that it is stronger than the F54. What are your thoughts oin this? Thanks,Chris

[evildky]

the head can be repaired, they have to heat it open the crack, fill with weld, then mill it back to shape, it would likely be cheaper to buy a P90, as for block strength, the F54 is siameased every other bore, #1&2, 3&4, 5&6, the N42 has all 6 siameased together, there are arguments boths ways as to which is better but my personal opinion is that it doesn't matter, there have been a large number of each bored .120 and turbo'd without issue, thats not to say there were not some failures, the castings on these things are not as precise as we would all like so sometimes you get one where the walls are a bit thin on one side as the bores aren't as centered as they should be, these are made of high nickel steel, and much stronger than most domestic castings

I say keep an eye out for a P90, and it's always easier if you have a complete donor car

[BoroBrown]

OK so I found a guy w/ a P90 and an AFM and I am just kinda price checking. Is $275 for both shipped good??

[evildky]

theAAFM goes for $50-75, and a mechanical P90 will bring $200, $250 fro a hudraulic P90, and thats without shipping, so if it's mechanical it's a deal if it's hydraulic it's about par save for the shipping discount