Me and my buddies went to the track the other day and I thought I would share the results. Comments are welcome.

Bird #1- 1998 Trans Am WS6
LS1/6 speed
HP- 360-380??
Catback/Lid/Filter
Runs- 13.0@108, 13.0@108, 12.8@109.

Bird #2- 1988 Firebird GTA
L98/4 speed
HP-270-290??
Catback/Headers/Intake/Runners/3.70 gears
Runs- 14.1@96 14.0@96 14.0@97 13.9@97

Bird #3- 1982 Firebird
LG4/5 speed
HP-150-170?
Catback/Filter
Runs- 16.0@85 16.1@84 15.9@87

 

That L98 needs some help in the upgrade department.

 

He couldnt hook very well with the 3.70's and the tpi's torque haha.

 

The MPH is still kind of weak for the mods. Great times from the 98' though.

 

Yeah the L98's dont trap very well with tpi and the stock cam. Times look about right for the ls1. Dynoed 340 on a dyno jet but I feel that is high. 320wrh and 360 motor would probably be more accurate.

 

My high mile L98 with a carb conversion trapped 101.

 

My 91' with just free mods, a BBK 52mm TB, K&N's, MSD 6A & coil trapped 97.2 a few years back. Stock manifolds, cats, cat back, etc. I bought the car with those worthless mods, doubt it would have trapped much lower with the stock parts in place.

Now I have a fresher L98 from a 90' Corvette (50K miles), SLP Tri-Y headers, 1.6 rockers, self-ported base & plenum, SLP runners, 2800 stall. If it doesn't at least trap 102, I am going to push it off of a cliff.

A chassis dyno is good for validating mods/changes. Too many variables to consider it the gospel. I won't even tell anyone what my 2000 made on a dyno jet, it's pointless. The ET & trap speed speaks for itself. The car is a hair over 3700lbs with driver, based on the weight and track #'s... anyone could pretty much come up with a close # for what the car layed down.

 

I hate to tell you this but my FULL bolt on L98 always had a hard time breaking 99 mph. Maybe yours will do better though. I would really ditch that TPI for an HSR or maybe even an LT1 intake. On the other note I believe GM rates drivetrain loss for the m6/ls1 cars at 13%. Even though a dyno is just a tool its a good thing too work with.

 

carb>tpi anyday

 

The 86' IROC I had years ago was a heavier car than my 91', had a non-lock up converter (lost MPH), similar mods to my 91'... it trapped 102-103. It had an 87' L98 long block in that car to replace the original LB9.

As for chassis dyno's, too many variables. I have seen a variance of 20-30 RWHP between local dynos. I prefer the NHRA factoring formula.

 

Thats a really good mph. I remember my old 89 car dynoed 240-250rwh and would trap 99-100mph. I cant remember exactly but I remember running consistant mid 13's. Not too bad. Good enough for 290bhp I guess. On the other hand I love the ls1. The car never stops pulling, especially on the highway.

 

When I first got my 91' over two years ago, I went to a local dyno day... unlocked converter - 202 RWHP - 311 RWTQ. I laughed, then was surprised that it trapped 97+ a few weeks later. I haven't redyno'd, need to yank out the slipping "rebuilt" 700R4 and install another 700R4 I picked up. Before the transmission started acting up, I raced a heads/cam/bolt on fox body coupe on the street. It was a pretty even race, usually ending with me nosing him out around 100 MPH. That car ran 13.50's - 13.60's @ 102-103 MPH. We were both on street tires and spinning pretty badly from a dig on the street. His track times were achieved with regular old street radials. That's the closest gauge of how I think the car will run without taking it to the track. I'll run it once I have the transmision issues sorted out and the weather cools down. A cool day here lately has been mid 80's and humid.

 

was the 5 speed swapped in? that trans wasnt availible til mid-year 83'

 

Yeah the whole car was rebuilt. Still runs like crap haha.