TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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I'm trying to set my long term goals for my 1990 t/a (speed density lb9, t5, 3.08 ls) and at this point in time Im thinking I may as well keep the 305. Planned mods are heads (vortec heads if I can afford the base manifold), carb approved shorty 'tubular exaust manifold', catback, fpr, chip burn and possibly injectors and an lt1 cam (keeping in mind colorado is a smog testing state).
While considering a camshaft, Ive ran into some misinformation on the factory cam that might be in my car. It is not a g92 car but it is a factory t5 and it's a 5k redline tach. According to the camshaft tech article on the site here, this engine should have the same cam as the l98 (.415/.430 lift) and everything Ive read in posts has people under that impression yet people seem to believe the g92 cars had more cam than non g92 cars (and it seems to be reflected by the 500 rpm higher redline I hear about but cant seem to verify).
I figured my best bet to be certain was to check my factory pontiac 1990 firebird service manual. According to the service manual, the only camshaft in the lb9 is the peanut cam also found in the lo3 (.350/.385) and the l98 being the only engine with the hotter cam.
So I guess the point of this post is to find out where some of this alternate camshaft information may be coming from (since it is missing from the most official source of info I have) as far as 90-92 305 tpis are concerned. I would be almost positive though that my car does have the peanut cam (regardless of other info I have found here) and that an lt1 cam would really wake it up along with some heads (since its a smoke puffer and heads need to be redone anyway, why not upgrade ) and bolt ons.
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I think not all T5 lb9s came with the l98 cam. Only the T5s equipped with the 3.42 performance gear ratio and dual cats came with the hotter cam, the way I understand it. Mine definitely did, but I upgraded the cam anyway. It made a big difference. If you are going to upgrade the heads and cam, you might as well get a hotter cam than the LT1, which is insignificantly bigger than the L98 cam. Many people have had good results with comp's xr264hr12 and the vortec heads.
It will need a tune for sure after the upgrades, but it will pay you major dividends after that.
I think not all T5 lb9s came with the l98 cam. Only the T5s equipped with the 3.42 performance gear ratio and dual cats came with the hotter cam, the way I understand it. Mine definitely did, but I upgraded the cam anyway. It made a big difference. If you are going to upgrade the heads and cam, you might as well get a hotter cam than the LT1, which is insignificantly bigger than the L98 cam. Many people have had good results with comp's xr264hr12 and the vortec heads.
It will need a tune for sure after the upgrades, but it will pay you major dividends after that.
Im not completely set on a cam yet so I do appreciate suggestions. Right now my main focus is on cracking this factory cam argument.
I keep reading in older posts here that a lot of people are convinced that all lb9s 90-92 had the larger cam. Everybody keep saying stuff like a friend of a friend pulled one out of his a4 car or napa part numbers this and that and firebird book part numbers this and that but I am having a hard time finding concrete evidence of it and Im still more tempted to trust what a factory service manual says over hearsay. Then again I wouldnt put it past gm to be lazy on keeping accurate information and it is odd that the service manual doesnt acknowledge any larger cam in the lb9 even though it seems to be pretty accepted that g92 cars DID have the l98 cam. Argh.
If you're that unsure about it, it would be easy enough to pull a valve cover and check the lift. Then you can find out for yourself what everyone has been saying about it. The tech data on this site is wrong, and the posts from numerous very well informed members is right. okfoz, Fast 355, Glenn91GTA aka Grim Reaper, Kevin 91Z, etc.
Please do not use your tach for reference. I have a previously peanut cammed 86 LB9 car with the original cluster (verified by the IP sticker right on it, dated same as the rest of the car) and the tach clearly redlines at 5500RPM. Vader owns a virutally identical car to mine, made much later in the year, and his redlines at 5000RPM. We both had the same cam.
If you're that unsure about it, it would be easy enough to pull a valve cover and check the lift. Then you can find out for yourself what everyone has been saying about it. The tech data on this site is wrong, and the posts from numerous very well informed members is right. okfoz, Fast 355, Glenn91GTA aka Grim Reaper, Kevin 91Z, etc.
Please do not use your tach for reference. I have a previously peanut cammed 86 LB9 car with the original cluster (verified by the IP sticker right on it, dated same as the rest of the car) and the tach clearly redlines at 5500RPM. Vader owns a virutally identical car to mine, made much later in the year, and his redlines at 5000RPM. We both had the same cam.
Im not basing my assumptions off of the tech data on the site or my tach, Im basing it off of GMs factory printed service manual for 1990 which seems a little more accurate a resource than some of the 'replacement part' numbers that some people have referenced on this topic in the past. What Im looking for is a little more info on what cams people have physically pulled from 90-92speed density lb9 motors, which is something I was unable to find while scouring post after post.
It just seems like its been the type of debate that's been sparsely covered over enough years that everybody just kind of settled into accepting that all sd cars have l98 cams.
Even having someone chime in with data from a '91 or '92 service manual would be very helpful. Its totally feasible that gm wasnt totally accurate on the '90 manual when they first switched these to speed density.
The cam in my 91 LB9 non G92 was the L98 cam. The motor came from the original owner of the car, and the motor was never was opened up before I got there. Honestly this issue has been beat to death and there isnt a single shred of verified physical evidence (read:checking the cam in an untouched block) that they came WITH the peanut cam. So go check yours.
That was true in most of the maf years but the belief (outside of people who think all sd cars got the l98 cam) about the sd cars was that autos had the peanut cam and 5 speeds did as well unless the car was ordered with g92.
Somebody pulled an l98 cam out of a seemingly untouched 1991 lb9 a4 car at some point which at least to some extent disproved the auto/manual theory on sd cars.
The two possibilities that people are overlooking a little I think are that a)gm may have been just using up a surplus of l98 cams in lb9s, causing there to be no complete truth about what cams were in what cars and b)that 1990 could be a different situation than 91-92. Keep in mind 1990 was a very low production year with not a lot of documentation.
1990 being a unique year (both in production numbers and the fact that it was an in between child of the 1989 and 1991 models) is one of the reasons Im debating the belief that ALL sd cars had the l98 cam. The fact that somebody pulled an l98 cam out of a 1991 car is far less effective evidence of what cam may be in a 1990 car than the evidence found in my 1990 factory service manual, with neither source being totally conclusive.
No way an extra cat gives 20 hp.....except on the Fast and The Furious.
I was told that the 20 hp difference was from the duel cats that the 5 spd had compared to the single cat the autos had with the so called y-pipe that was more of a t-pipe.
ALL SPEED DENSITY CARS GOT THE L98 CAM!!! Just like Dyno Don, my 1991 single cat 2-1/4 exhaust auto Lb9 T/A put down 187whp/ 270wtq bone stock. With a 20% DT loss thats right around 230hp. Don't see that happening with a peanut cam. Dynos don't lie.
85: big cam
86: peanut cam
87-89: L98/5spd Lb9 - big cam
90-92: ALL GOT THE BIG CAM!!!
__________________ 1989 Red GTA: 350TPI / auto / 3.27
ALL 1990-1992 LB9 engines had the L98 camshaft. The 20 HP difference on the non-G92 cars is the EXHAUST, PERIOD. The LG4/L03 exhaust chokes the hell out of those motors, much less a more powerful TPI engine.
) and bolt ons. 
