working with a afr headed 408, forged everything and a pt88 turbo. i will be running LOTS of boost. probably max out the pt88, i would say 20-30psi but with the afr heads it may max out before it gets that high. i have been seeing 20+psi on stock 6.0 heads.

the heads are just now going on. i would like to have the option to spin this thing up to 6500+ if it wants to go that high. my cam is a 234/232 595/590 115+1.

are the std springs on the afr's good enough? remember lots of boost pushing on that valve.

if i was to upgrade to some 921's, are stock lifters ok? i have the springs here and was going to put them on but now i am not sure because of my next question.

are comp r lifters any good at all? i have a set in the motor and they are freeking loud, sounds like a big solid lifter cam. i talked to my motor guy and he is 99% sure it is set up correct. he put the preload around .020. i talked to comp today and they say to set it at .002-.004 and the reason it is loud is because of the extra preload but i did a ton of reading and it seems there are lots of people that set them in the .020-.040 range and most people report that they are way loud no matter what but especialy loud at the recomened .002-004. to even try the .002-.004 i would need to get adjustable rockers and that is another chunk of change. i did pull my valve covers and there is 0 lash, didn't verify preload but there is some preload on all lifters.

so my options are.

stock lifters, std afr springs(patriot golds?), stock rockers. measure for pushrods.

or, same as above but with 921's.

or, 921's and comp r lifters.

or 921's and comp r lifters and adjustable rockers.

is there any benifit to running the low preload that comp sugests? if there is i may just get the rockers and let it rattle but it really is loud.

 

The PP golds should be fine, I would think, they are a stout spring. As far as your other questions, 921s can be run with stock lifters, no need for Comp "R"s.

Shawn

 

Just remember that there is approx. 3.5 sq. inches of backside valve area on a 2.08 valve. For every # of boost, you effectively reduce spring pressure by this amount. At 25 psi, you have decreased seat pressure by about 80#'s. If you have 135#'s on the seat, you now have 55#. If you really plan on these boost levels, consider a solid roller.

 

I was thinking the same thing... solid roller. That cam of yours seems a little on the wimpy side for the ci and boost you're going to be running. If your bottom end is pretty stout, I'd go with a larger solid roller. With a solid roller the sky is the limit on rpm and will make a good deal more power across the board.

BTW, toss the stock AFR springs... I certainly wouldn't chance it running that much boost.

 

i know nothing about solid roller set up's. can someone lay out the benifits of a solid roller for my set up along with the downsides.

this is a dialy driver, i put 10,000+miles on it a year even with it being down for upgrades a good portion of the time. i think the cam is ideal right now for what i do with it, maybe even a hair on the large side. my bigest gripe right now is excessive valve train noise, wouldn't a solid roller be loud no matter what? would it need adjusted often? i am about to go on a 2000mile road trip(drag week) and i want to keep it running and sounding like a mostly stock truck.

 

You need to put together an adjustable valvetrain and use the correct length pushrods for your application. I put a set of 62cc 205 AFR heads on vette two weeks ago with an .040 cometic and ended up with a 7.325 pushrod, now quieter, it seems than stock. Solid roller can be noisy, but you will be able to run sufficient spring pressures to overcome backside pressure on valves with 25# boost. Solid rollers do require periodic lash adjustments, but no big hassle.

 

Parish8 Your best bet would be to go solid roller. Tuning a friends 500ci BB with F-2 running 28# boost. He is running a crane solid roller, periodic lash adjustments are necessary. Good luck, impressive truck.