It seems that my currrent set-up is not putting out the numbers I was thinking it should. I am listing my mods with hopes of getting some guidance on what I might do differently. Please comment only if you have experience as I only want to do this one more time. Please be gentle.

90 L98 Auto Vert with 52,000 miles on engine
Stock Bottom End

Reworked 113 Heads - 2.02"int/1.57"exh, 65.5cc Combustion Chambers, 168cc Intake Runners, 61cc Exhaust Runners, Flowed 179.3/.300, 215.2/.400, 231.0/.500, 242.3/.600

Comp Cam #12-404-4 Flat Tappet, Lift .464 Int/.464 Exh, Duration @ .050 222 Int/226 Exh, Lobe Separation 114.0

Harland & Sharpe 1.6 Roller Rockers, Hardened Push Rods/Guides

SuperRam Plenum/Runners/Intake

FoMoCo 30# Injectors -- Match Flowed

Headman Elite 1 5/8" Full Tube Headers

Random Technology High Flow Main Cat -- No Pre-cats

Flowmaster II Cat Back Mufflers

Crane Fireball CDI

Blowerworks Gaseous Intercooling

Walbro SS340 Main Fuel Pump, Bosch External Fuel Pump

TCI Torque Converter 2200 Stall

ProCharger P600B -- 8 psi

ProCharger FMU

Dyno Tune Results -- 326RWHP 348RWTQ

AFR during pull was a steady 11.9/1.

Tune was performed by Corey at Henderson Performance on a Dynojet.
I will say that Corey said the fuel pressure was not as high as he would have liked. This was due to too many vacuum lines pulling from only two vacuum ports. I have since corrected this by adding another port and have seen my fuel pressure go to 55 psi under boost.

So there it is. Where am I going wrong? Cam too big? Heads not flowing enough? Fuel pressure too low? Combination of things?

90Indy

 

lets see a graph, i need more to base my hypothesis off. Is the ignition timing way low? what valvesprings are in there? seat pressure?

by all rights it should have 75+ more hp on a dynojet.

 

I don't know how to post the dyno sheet. Point me in a direction and I will try to post it. Thanks for the reply.

90Indy

 

Stock chip?

 

IMHO--I think you're about 100 rwhp low but I don't know the l98 setups that well. On my stock LT1 with 6psi boost (the basic procharger kit) I was making 385 rwhp.
CT

 

No. The chip was retuned by Corey @ Henderson Performance. The first dyno pass yielded 266 RWHP. He was able to get it up to 326 RWHP after several runs and chip adjustments.

90Indy

 

Outside of the bottom end, there is nothing left of the L98 setup. What I am looking at is a SB 350 with approximately 9:1 compression. Everything else is aftermarket or reworked. Very little "stock" in the setup.

I was thinking it should put down around 380RWHP and 420 RWTQ. I was quite surprised by the results.

90Indy

 

I would first change to a roler cam. They have faster ramps and the valves will be at higher lift longer during the duration.

Your cam is specs are not aggressive (not to big) and since it is a solid/flat, I think you are hurting there.

You may have better performance with the stock roller cam than the flat you have now.

Lots of guys running street roler cams in the 530/ 550 lift range with a 1:6

Good luck

BLWN BUX

 

A couple of other questions - how much timing are you running? and, is the 8 psi of boost measured at the manifold with a boost gauge or are you assuming it from the procharger pulley you're using?

 

As far as the timing is concerned I do not know what Corey programed. The base timing is set at 6 BTDC. I told Corey this was what I had it set too and he said that it did not matter.

When it comes to the boost pressure, I have a gage installed in a pod pillar along with a fuel pressure gage. I saw the boost gage register between 7 and 8 psi during the dyno runs.

90Indy

 

I think I've commented to you before but we have similar setups and I'm only getting a few more HP - 343 rwhp & 406 rwtq

Here are specs:

Fresh rings at 80k miles, reused rod/main bearings as they were still perfect. New cam bearings.

stock roller cam but H.Sharp 1.6 rockers

113 heads have cleaned up chambers, polished exhaust & minor clean & port match on the intake. New springs & guide plates. Machined for seals. 5 angle valve job.

Intake is a TPIS Big mouth w/ matched runners & opened up plenum to match. 52mm TPIS throttle body.

42 lb injectors from Greg & my chip is slightly moded for them. No EGR codes and cooling fan temps are about the only other mods to my current chip.

TPIS long tube headers, stock cat (at the time of dyno) and power effects exhaust in the open mode.

Last thing is the head gaskets are the thin version from corteco which is supposed to be good for 1/2 a point of compression. A stock L98 I've heard is around 10/1 so perhaps 10.5/1 now? I wasn't going the blown route when I assembled the engine.

ATI D1 w/ gaseous intercooling from Greg. I did a custom F-body runner from Vortec to feed direct from the procharger into the throttle body. 8 psi boost on the dyno as well which is about max for the compression if I want this thing to last.

ATI FMU jacks my pressure all the way to 110 psi at max boost but most of the time I see 60-80 psi on the street. The gauges set I have records max fuel & boost.

Walbro SS340 Main Fuel Pump, procharger External Fuel Pump as well

Accel 300+ ignition box (CDI) & 300+ wires as well

Bosche platinum plugs in a slightly cooler range per Greg as well.

Stock timing, heated O2 & a wide band on the other bank which read a nice fat 13 to 15 at WOT on the dyno.

I still get 25 mpg on the hiway if I baby it but 20 is about it around town.

I prob. forgot something but ask if you want.

 

Stock L98s are 9:1 CR.....