[TheBlueBomber]

Originally Posted by Super73

I suggest rethinking the size of the turbos as well. I spoke to several turbo companies before I settled on twin Precision 67/68's for my 418" LS motor. My motor is 131 cubic inches bigger than yours and these turbos on my motor should make 1200rwhp all day long and carry RPM to roughly 7,000.

Here is a 427" LS with Precisions 67/66 making 1143rwhp on 19lbs boost.
http://ls1tech.com/forums/dynamomete...1040-rwtq.html

The point I am trying to make is selecting a turbo based on CFM required for your power goals and selecting the smallest one to achieve that will most likely make you much happier when it comes to spool time in a truck.

Spool is sort of like converters or cams, each person has their own interpretation of how much "lag" is acceptable.

I definitely agree with everyone 70s is a bit over kill especially for a street truck and I'm definitely open to and exploring other options like the precision turbos

And one thing I want to make sure of is to avoid being over cammed/turbo'd

Originally Posted by tinydb84

Super73-Question for you (since you probably know).

Looking at Sinister's build he has the twin 70's. Does the fact that he is running E85 make up a significant difference for lag time? I know that you have to run a larger amount of fuel but does that necessarily produce a larger gas volume?

One good thing about using turbos too large for your 4.8 is that when you blow it up (if you do) then you wont have to buy new ones for a 6.0 or 408.

A big part of his reasoning for the e85 fuel is to help keep his IAT's down so he didn't have to run an intercooler. He mentions the fact there is significant lag but when he hits boost it pulls like a train. The difference in his experience is night and day between the smaller On3 turbos and the 70's

Originally Posted by Super73

I don't believe the fuel volume will help in spool time.


If twin 67/68's move enough air to make 1200rwhp on a 418" motor, they well surely move enough air to do the same on a 4.8.

I have seen twin 66's make 1100rwhp. Again it comes down to ones goals.

Without a doubt. Speaking of goals, I never mentioned in a previous post what my goals were... originally when I thought about doing this I was thinking around 650hp... but since the truck will be running soon and I'll be building this engine outside of the truck I don't see why I can't aim for an 800+ hp build.