I have seen that there was two differant HP ratings for 305 TPI in Z-28s in 91 205 & 230 the higher HP was manual the lower auto. The question is what is the differance in the engines? Thanks JC

I think the manual version had a hotter cam, and maybe dual converter (N10) exhaust. The earlier LB9s (87-90) had different horsepower ratings in the automatic and manual versions as well.

There have been guys on this board who have pulled L98 camshafts from their 90-92 SD 305 TPI's (verified by PN). So who knows what they actually made for power; I dont think the numbers were all that accurate. The dual cat option as mentioned above would make a difference in power.

Was the chip differant, thats what I was once told it was the exhaust and the ecm prom.
JC

All 90-92 LB9 & L98 F-body engines used the same cam...

The differences I have found so far:
FIREBIRD ONLY
LB9/A4 had 2.73 axel and a single cat.
LB9/M5 had 3.42 axel, Dual cats - Standard on Formula and GTA, (possibly optional on Trans Am)
L98/A4 had 3.23 axel dual cats - Standard on T/A, Formula and GTA when equiped with 350. I was suposed to be this way, but there may be some exceptions, nothing verified as of yet.

John

Called the chevy dealer part# 10111773 used in 5.7 (L89) and 5.0 (LB9) with manual trany. part# 10088155 used in 5.7 & 5.0 auto tany in many gm cars. Didn't get any specs will try later.
JC

According to the FIREBIRD Parts catalog the LO3 got the 10088155 cam, but the LB9 & L98 got the 10111773 cam. It does not distinguish Auto/Manual like it does for 87-90.

John

got this from the tech forum

1990-1992
305 5spd / 305 AT 10088155* .350 .384 179 194 109.0
305 G92 5spd / 350 AT 10111773* .413 .428 202 207 114.5 (116/-116)
JC

Checked a GM Service manual all LB9 had the same cam as L89, lo3 had smaller cam
JC

Far as I know, if you had the T5 you got the hotter cam in the 305 TPI. I know my 88 did!

From 1987-1989 this was definately true. When they went to SD they went to one cam for the LB9 & L98.

John

I was told that if the tach in the car Redlined at 5000rpm lower hp if the car redlined at 5500 230hp. No difference auto or stick.

If you had the:

305 TPI auto 5000rpm redline: 210hp
305 TPI 5 speed 5500rpm redline : 220hp
350 TPI auto (no stick offered) : 230hp


...least pre-speed density. Not sure about the cams after that.

Actually from 1990 - 1992 All of the LB9 engines were basically the same internally, they all used the same Cam, and they used the same heads & pistons. Similarly the L98 used the same cam.

Aaron7 has it correct for 1987. Starting in 1988 & thru 1989 the Tach & speedomoeters were a mess, it was not determined solely on the Engine & trans but also the final rear axel ratio. Starting in 1990 it was a little less messy but you could have gotten an LB9/M5 car with the 5000 redline tach, but there were no LB9/A4 cars with the 5500 redline.

Its spelled out on my website www.3rdgenformula.com on the LH side look for Speedometer & tachomoter combinations it has the info your looking for there.

John