Forged Iron 370 / AFR 225's / Truck Manifolds / PT88 by 98Z28CobraKiller

By diyauto
( 2 )

5 minute(s) of a 128 minute read


Forged Iron 370 / AFR 225's / Truck Manifolds / PT88 

Compliments of 98Z28CobraKiller @


I was waiting until it was close to completion in order to start the build thread. This build is really just part 2 of my original stock longblock Lq9 build. All the fabrication is in the other thread.

Here are details on what the build will consist of:

LQ9 370 ci Iron block (.030 over)
Stock Crank
Childs & Albert Forged 6.125 rods
Wiseco K392X3 Forged 25cc dish
Livernois Stage 2 Cam (232/232 .595/595 114)
AFR 225 CNC ported w/ some additional bowl work by Mamo
FAST 90 Intake
Forward facing 6.0 Truck Manifolds
2.5" mandrel bent hot "Y" into T4 flange
Precision PT88 Turbo with .96 A/R T4 Exh Housing
4" Mandrel Exhaust into 4" Magnaflow bullet
24"X12"X6" Bellcore A2A Intercooler

Fueling is handled by:
80# High Imp Inj
Aeromotive BRFPR
MagnaFuel 4301 Fuel Pump
-10 feed and stock feed line as return

Engine Management:
Stock 98 PCM w/ HPTuners 2 Bar Custom OS in Speed Density

PT88 Turbo



I had to have 4 valves replaced in the AFR heads and have them milled after my nitrous assisted 408 came apart. The ringland broke on the piston and really gave the quench area of the head a beating. Engine builder assured me that the small amount of pitting left in the quench area would'nt cause any problems. This was the #7 hole. I am moving it to #2 so that I can keep a close eye on it.

Great question and my answer is, I'm not sure. They were purchased at 65cc. Then they got cut to 63cc when they went back to AFR for the valve recall, upgraded springs, and the bowl work. This time around, they milled them as little as possible to make them perfectly flat per my request. I'm thinking 61-62cc which should put me just under 9:1.

Launch control comes from:
TH350 w/ RMVB and TBrake (I've been [email protected] on this trans with my 408 nitrous motor so its seasoned and strong)
FTI 4500 stall
LNC-002 2 step
AMS-500 Boost controller (may add CO2)

Makes me feel better. Thanks for all the help over the last few years!

I ran it on the bone stock LQ9 long block for a while. Most of that time, I had the short runner carbon fiber intake on it. It would full spool by 5K RPM which wasn't horrible as my converter was stalling to about that at full (14-15 psi) boost. At some point during the time that I was boosting it, I developed a hairline crack that almost drove me insane trying to find. I ended up glueing my FAST together and throwing it on. Dropped the full spool RPM almost a full 1K RPM. That was then with stock 317 heads and the stock LQ9 cam. I would think that with the new cam and heads, it'll be even easier to spool and make close to 200 hp more at the same 15 psi boost level.

I managed to peel off a 6.32 @ 109.5 in the 1/8 with stock everything the night that I blew it up. 

I think I need a 5.70 to go 8.90. We will see.

Should be at about 3700 lbs. After I get everything working solid, I'll start seeing if I can get some weight out. 

I didn't want to get into a custom piston setup plus you guys wouldn't believe what I paid for these pistons and rings. I basically had to go "off-the-shelf" to get the deal. Next step up would have put me too high and I want to be able to run 93 oct for consistant 9.50's.

9.50's on 93 oct with about an 8.8:1 SCR ? Doesn't seem difficult. I ran a bunch of 10.0's @ 14 psi with 10:1 compression stock longblock. Detonation didn't kill it. Stretched rod bolt killed it.

I'll need 116 to run the 20+ psi required for the 8.90 pass.