i was at 9.0:1, and i was running 20psi, I was told that 9.0 was a lil on the high side, the truck is going to play on the street more than the track but i do want to hit the 1000rwhp mark and run in the mid 10s with the big tank. what do yall think about 8.5:1 and do you think i will notce the loss out of boost on the street,(even tho im in boost all the time) and it hard to spoole the 88mm so will it be that much worse than the 9.0:1 motor?



thanks Josh

 

i wouldn't be scared of a 9:1. i have seen guys lower those cr's on those engines and it made it a little harder with a turbo to make very good driveable power. you will definetely notice a longer spool time. i know its an old argument but i think higher cr engines run quite nice with turbos. less spool time, more driveable power

 

Alot of guys are running that and then some on the comp end.. Just need to keep a eye on timing, use alot of meth... Even with it being 408 inches, with a 8.5 comp ratio it is going to be a dog untill you get into boost.. imo I would stay about where you are at

 

lol so 8.8:1

 

I'm at 8.65:1 for 20-22psi. I think Parish was about that as well.

It just depends on whether you want to run lots of boost and lots of timing on pump gas or not. 8.8:1 is safe IMO.

 

Maybe this will help:
I run 8.5 on my lil truck, but it's light, power is great all around and plan on running 20psi.
The 408 we just did was low 9:1 compression, maybe the owner will chime in.
One of the 408's for a customer I built had 10.6 cr, daily driving was great! Held 12psi and made 821hp, but i would push it any higher, well maybe a couple psi.

I think 9:1 will get you there, so will anything less, cr wise.

 

sooo a lil over 8.5 will be good? ill just have to see how low he can get it, i think 8.5 or.6 is all. but will see. im just ready to get it back in the truck. my new 4l80 has about 80miles on it and 4 track passes...lol, hell have not even tuned the TCI box yet.

farmtruc:: what kind of boost contr. do yall use? i have a greddy p.s.2 and dont know how to run it. i think that took the head and block out last week. just thing. when it goes into 3rd and locks up the cov. it puts a lot of load and boost justs like 5psi or more. i know i need to play with the gane or what ever the japs call it..

 

I run 9.5-1 Alot of guys on ls1tech are running anywhere from 9-1 to 10-1. You can make alot of power with less boost. Just run good gas at the track. I've run my best pass at only 12 psi with plenty still left in it.

 

You should use good fuel this time so you have a better chance of keeping a motor in it.

 

im not sure what to use.. i mean i put in the thread what i was using at the track. i ran over 5 gals of c16, VP racing, and meth...not sure what you mean about "use good fuel this time" what do you use. i guess i could run C23 or maybe Nitro....??