cejay825

I would like to do some slight mods, just enough to wake it up. Can anyone tell why the 1990 LB9 is rated at 230hp ? what does it have the others don't? I would like to make these mods and thats about it. thanks

LB9GTA

iTrader: (1)

it had a speed density set-up and a better exhaust.

cejay825

wow! I would not have though those two things could make such a difference, but i'm no TPI expert either.

Fast355

iTrader: (2)

Not to mention that it has the L98 camshaft that is MUCH hotter than the PEANUT wanna-be.

Drac0nic

Don't forget that the G92 cars also used the L98 cam versus the peanut cam. He's right that you should be able to make a significant difference with just some exhaust and intake mods if you go as far as a cam it's probably best to port the whole intake while you're at it. A lot of people do reccomend working the plenum as it's not that hard to take off and gains a few HP.

Fast355

iTrader: (2)

Every LB9 that I have opened up from 1990-1992, G92 or not had the L98 cam. I have not seen .BIN files to show otherwise either. The Peanut cam and the L98 cam alot different in fuel requirements and less so in spark timing.

cejay825

I did some searching on this and found some things. If I put the L98 cam in my LB9, how will the idle be? I want a smooth idle.Can I leave everthing else in the engine the stock? if so which cam should I ask for when I go to purchase? I also have my cat removed, and new 19# venom injectors.

mnorton

Oh, I didn't notice that it's an Auto, so in fact it does have the "peanut" cam which gets you to 195 HP I believe.

If you want to replace the cam go with an aftermarket cam. Do a search and you will find lots of info on 305 TPI cam swaps. The bigger cams require some PROM tuning, but there are also ones that just swap right in.

D's89IROCZ

It wasn;t just G-92 cars that got the L-98 cam ...all 5 speed TPI's got it . in 1989 it had 220 hp .... then 230 with the dual cat option ... that was a MAF car.

Steve89GTA

D's correct, my 5speed 89 GTA has the L98 cam as well

Mcdamit

yeah but this guy has an 88 305 with a 700R4.. so yeah he's got the 190hp boat...

Comp Cams makes a tpi cam comparable to the L98 cam.. Just make sure you get a hydraulic roller cam and not the hydrualic flat tappet!.. Depending upon the condition of your engine you may be able to reuse your stock lifters. but its always better the replace them.. Then obviously do an exhaust and an intake setup..

I believe that I remeber hearing that all TPI's got the same bin files when they switched to the newer computer setup post 1987-88? I know the 305's and 350's ran the same prom.

Oh you don't need speed density to go faster, Mass Air flow is actually a more expensive/finely tuned setup.. Nowadays most cars run a mix of SD and Maf.

Damon

If you want an L-98 cam you can probably buy one used off the internet for almost nothing. The stock LT-1 cam is almost exactly the same as the L-98, but with a little more lift. Either will slide right in and work with your existing stock lifters.

MAF cars seem to be a fair bit more forgiving of modest changes in cam since they have a device that actually measures the amount of incoming air, while speed density cars dont- do a cam change in one of them and a reprogram is pretty much mandatory.

I will agree that 90-92 305 TPI cars probably all got the L-98 cam, even though GM never really told anyone and never changed the published HP specs. I went a few rounds with Fast355 on that one and came away convinced by the evidence he (and others) presented to prove that point. But in this case we're talking about an 88 so I'd think it still has the peanut cam if it came with an automatic.

Mcdamit

umm not sure if it has the distributor lobe on the cam since the LT1 is opti spark or Distributorless! Just buy one from comp cams!

Fast355

iTrader: (2)

It DEFINATELY DOES have a distributer drive gear. It turns the oil pump through an abreviated oil pump drive shaft that fits where the conventional distributer goes, just ends in the lifter valley.

The ONLY thing you have to do with the LTx cam is drive in or cut down the pin on the front. It hangs out about 2x as far to drive the optispark on the LT1.

D's89IROCZ

Nope , the 350 / 305 bins are different . Well the 5 speed ones are. Mine was APYS for my car ( 305 TPI 5 speed 3.08 LSD hardtop)


Also Damon .....


Not just 1990-1992 ...it was also in 1989 I know for sure ..that got the Bigger L-98 cam ( which changed a few times over production) 1989 being the biggest cam . I am guessing also 1987 and 1988 ... the 305 5 speeds got the L-98 cam .

Fast92RS

iTrader: (2)

I was looking at the GM parts catalog for 82 - 92 Camaros and I looked up the part numbers for the cams of the 90 - 92 L98, LB9 and LO3. According to this the L98 cam was the only part number listed for the LB9 there was no option for G92. The LO3 is the one with the penut cam. It seems that all LB9 engines from 90 - 92 got the L98 cam either Auto or Manual G92. I also found the heads from the LO3 and LB9 are different. I also found that GM used three different L98 cams from 87 - 92. One cam for 87, one for 88 and 89 and one for 90 - 92. The 88/89 L98 cam was biggest out of all the years. I wonder why they down graded.

mnorton

I think that the LB9 with Auto Trans got the peanut cam. It has 25HP less than the LB9 with Man Trans, and I think that's why.

Fast92RS

iTrader: (2)

But it does not list a cam for auto or a cam for manual. It only lists the part number of the L98 cam for the LB9. I dont know why the auto is less horespower. If you compare the bin from a 305 TPI auto to a manual. There is no difference in the spark tables and VE tables.

mnorton

It's interesting that the spark tables are the same. The published horse power peak is 400 RPM lower for the Auto than for the Manual, which would go along well with the smaller cam theory. I'm still thinking it's because of the peanut. Whomever wrote the 1987 Camaro tech info on our home page seems to think it's the case too.

BigWhiteGTP

All 1986-1989 auto/Lb9s (& only 1986 5spd) got the peanut cam.
All 1987-89 5spds got the L98 cam regardless of G92.
ALL 1990-1992 TPIs got the same L98 cam.

It's been documented by many members with cam swaps. Including my present 1991 auto/Lb9 Trans Am. It dynoed 187whp and 270wtq bone stock with 84K miles in April 2005. It was done on a dynojet at a reputable shop. SD 5spd Lb9s dyno closer to 205whp.

So again, only the 86-89 auto/lb9 and maybe the 86 5spd Lb9s, got the peanut cam. All else got the L98 cam.

Fast92RS

iTrader: (2)

So it bascially comes down the Manual has less power loss than automatics do and that would be the difference in HP numbers.

Kevin91Z

iTrader: (1)

The automatic's and 5-speeds without G92 got the smaller 2 1/4" TBI exhaust with a single cat. The 5-speeds with G92 got the larger 2 3/4" 350 exhaust with dual cats. That is the reason for 25 more HP.
The HP and TQ numbers from GM are rated at the back of the engine, not at the rear wheels. It doesnt matter what tranny the engine comes with.

3.8TransAM

Tear the exhaust off of a non G92 305 TPI car from 90-92 and proceed to bust out into tears laughing.

Pathetically small compared to the 350 cars of the same era.

Defintely lots to be gained from an exhaust on the non G92 305 SD cars

later
Jeremy

mnorton

My 215 HP (published HP) 1987 5-Speed LB9 has G92 and the better exhaust, but it is a single cat. I don't believe that the poor non G92 exhaust was the only thing responsible for the 25 HP difference. I believe the cam was different too. The later year dual Cats LB9's had 220 HP.

fireball451

There is tech data on the main page here to show what the HP numbers for each year are and which engine got which cam.

I put a LT1 cam in my '91 LB9, 5sp, G92 car without any broblems whatsoever!
Idles fine and runs great.
The LT1 vs L98 cam is not that great of a difference to cause any problems.

I'm pretty sure my LB9 W/auto '91 has the p-nut cam....

BigWhiteGTP

Either you are wrong ( 100% chance ) or your 1991 SD Lb9 car was the only car that left the GM plant with the retired as of 2 years before Peanut cam ( 0% chance ).

My car is a 1991 auto lb9 and it dynoed 187whp and 270wtq. Peanut cam cars dyno 20-30whp less. When GM switched to Speed Density in 1990, they just decided to make 3 TPI motors; 2 L98s ( 1 with aluminum heads, the other with iron heads ) and only 1 Lb9. Saves GM some money by only using 1 cam instead of 2 plus the advantages of a 1 cam use. No more line splitting "this peanut cam goes into these 5.0s. While this bigger one goes into these 5.0's". And they can now run the same computers with less variations.

Kevin91Z

iTrader: (1)

You can believe what you want, but its been proven on this board that the 90-92 305 TPI's all have the same cam, the L98 one.
The 88-89 got a larger cam than the 87, which is the reason for 5 more hp to make 220. The 89-92 G92's have the dual cats, which is the reason for 10 more hp to make 230.
You would be surprised what poor exhaust can do to choke an engine. A friend of my dad's had a customer back in the early 90's buy a complete Edelbrock engine package for his car, including headers. The y-pipe was more like a t-pipe, with the passenger exhaust dumping straight into the side of the driver's exhaust. It dynoed at 160 HP at the wheels. The friend sent the guy to my dad to have the exhaust y-pipe fixed. My dad made it a true y-pipe with both exhausts feeding side by side into one pipe. After another dyno test, it made 210 HP to the wheels. That's a 50 HP gain by only fixing the poor y-pipe.
So, I can easily see how a small y-pipe and exhaust would cost the lo-po 305 TPI 25 hp over the G92 305 TPI, and I hope now you can see that, too.

Fast355

iTrader: (2)

ALL Speed Density LB9s had the L98 roller cam just as Kevin said and I mentioned earlier.

I also know what a poorly designed Y pipe will do to power.

This is the one that a local muffler shop built for my G20 to get me back on the road after a header change.



I ended up re-doing the setup with a proper merge style Y (Image attached below, part #169B from Brzezinski Racing Products) below from and 2 1/2" pre-y pipes. I moved the converter farther toward the rear of the Van and put about 2 1/2 feet of 3 1/2" pipe after the Y and before the cat for a smooth transition.

The power increased by 19 RWHP/15 RWTQ.

I then changed to a true dual setup with a X-pipe and gained an additional 16 RWHP/8 RWTQ for a grand total of 35 RWHP/23 RWTQ over the above poor flowing piece.

mnorton

OK, so exhaust is a bigger deal than I had thought.... My Hooker 2055's arrived today! From what you have stated, I should see a substantial gain in power over my stock exhaust (gasket matched) "Logs" even with the MAC Y-Pipe.

The 2055's have a very nice looking Y-Pipe. Still I'm guessing this upgrade will be a 10 HP gain, and I'm sure they will change the power band some. Maybe I'll be surprised and get twice that much power. It will be impossible to tell without a Dyno pull or a track run to compare to...

Thanks for the insight!

fireball451

See, thats cute..............

205hp vs 230hp.
Has to be more to it than the exhaust.
I don't really care.
Guess I'll know for sure when the LB9 has to come out of my red '91 for rebuild.
Hopefully, that won't have to be for several more years.
So far, with all the third gens I've had, been around, worked on, and from all the information I have gathered, there were two different cams for the 305 tpi in '91.
And most of what I've owned has been '91 models.
Heck, at one time everyone thought I was going to have a monopoly on all the '91 Z28's around.
All of the non-G92 LB9s that I have driven or rode in have definitely been lacking in power (no offense to anyone on here that has a non-G92, I have one and will not be losing any sleep on the subject).
I don't care what kind of third-gen you own.
As far as I'm concerned, they are the best car I've ever had.
All need to be saved.

BigWhiteGTP

Fireball451, I'm not being sarcastic, but exhaust isn't the whole picture for performance. Most non-g92 auto cars got the crappy 2.73 rearend. Mine came stock with those horrible gears. Most G92/N10 cars got the better 3.23/3.42 gears which made a ton of difference in acceleration. .5 or so faster in the 1/4. I roast the tires from a stop now with the 3.42s, whereas before I could maybe get a chirp and I would then slug away with the 2.73s. Just something to think about.

fireball451

I realize the gear thing.
I'm even thinking of some that has had a gear swap and just didn't have it either.
I don't think there are definitive answers on the subject.
Like the hp rating of the non- G92 cars.
If you look around you find ratings from 205, 210, 215, 220, ??.
I agree it doesnt make sense for there to be two different LB9s (some with p-nut and some not) for the same model year.
Just considering the information I have seen over the years and from what I have dealt with and experienced.
Heck, here is practically the same arguement from just a couple of months ago:
http://www.z28.com/forum/showthread.php?t=81512
Its also an arguement on what is G92!
Arguing about it is silly.
Just restore these cars and make them look like something other than the piece of crap that many have unfortunately become.

Damon

Let's see if we can logic our way to a reasonable answer here.....

I think we are (mostly) in agreement that all 305 TPIs from about 90-92 (maybe 89 as well) got the bigger L-98 cam. I certainly believe that.

But in that same era they also started putting the "pea shooter" 2-1/4" single cat exhaust on any non-G92 305. (Until recently I was not aware of this myself, but I beleive if from the vast experience and observation of other board members)

It might be a resonable conclusion that GM simply changed the area of restriction on the entry-level 305 TPI package from the cam to the exhaust. Nothing more. Both are very restrictive to performance. Either could easily account for a 20-30HP drop by itself, even if GM didn't pull the HP numbers out of thin air (which they might have done anyway).

91_5.7_TPI

iTrader: (2)

I say call up the local dealers and see if you could get the stock cam specs for a 90 (or 91-92, whatever) non-G92 and a G-92 car and see how they compare. That would finish the arguement conclusivly. I wonder if they still have that info.....?

Fast355

iTrader: (2)

I have. The G92 and Non G92 have been superceeded to the same part number and that is as far as it went.

Napaonline also gives the same part number for ALL 1990-1992 F code LB9 305 TPI engines.

Here are the specs (from Napaonline) of the cam used in ALL FACTORY 1990-1992 LB9/L98 TPI engines.

Advertised Duration (Exhaust):278 Deg
Advertised Duration (Intake):273 Deg
Cam Lift (Exhaust):.287"
Cam Lift (Intake):.276"
Cam Timing at .050" Lobe Lift (Exhaust Close):10 Deg BTC
Cam Timing at .050" Lobe Lift (Exhaust Open):44 Deg BBC
Cam Timing at .050" Lobe Lift (Intake Close):40 Deg ABC
Cam Timing at .050" Lobe Lift (Intake Open):13 Deg ATC
Degrees Overlap:40 Deg
Duration at .050" Lobe Lift (Exhaust):214 Deg
Duration at .050" Lobe Lift (Intake):207 Deg
Lobe Centerline (Exhaust):118 Deg
Lobe Centerline (Intake):116 Deg
Valve Lash (Exhaust):Hyd.
Valve Lash (Intake):Hyd.
Valve Lift (Exhaust):.431"
Valve Lift (Intake):.414"

fireball451

Looking up a replacement cam is not going to get you the right answer.
Even a replacement cam through GM might not be the same grind.

Fast355

iTrader: (2)

Maybe so, but from what I have seen, the "773" was used exclusively from 1990 to 1992 and was used in 1993 as well on the TBI 305/350 police cars.

91_5.7_TPI

iTrader: (2)

That's not a bad sized cam.
Ok.. another option....pull the cam from your auto 91 and compare it to the cam from the 5-speed. At least we'll know if there is a difference between the auto and man cams. If the one from the manual is bigger, put it the auto.

Kevin91Z

iTrader: (1)

Fast355, that cam you listed looks almost exactly like the 88-89 cam on this site. The 90-92 cam listed on here is 202/207, .413/.428" lift. I'm not disagreeing, just adding my two cents.

91_5.7_TPI, several people have pulled their 90-92 automatic 305 camshaft out and measured it. That's how we got this info about the cams in the first place.

91_5.7_TPI

iTrader: (2)

Oh. I'll be quiet now.

Fast355

iTrader: (2)

I know that must be the "Generic" parts store grind that NAPA sells for the 90-92 TPI 305/350 engines.

They also have the peanut cam as well.

Advertised Duration (Exhaust):262 Deg
Advertised Duration (Intake):252 Deg
Cam Lift (Exhaust):.257"
Cam Lift (Intake):.234"
Cam Timing at .050" Lobe Lift (Exhaust Close):14 Deg BTC
Cam Timing at .050" Lobe Lift (Exhaust Open):29 Deg BBC
Cam Timing at .050" Lobe Lift (Intake Close):16 Deg ABC
Cam Timing at .050" Lobe Lift (Intake Open):17 Deg ATC
Degrees Overlap:41 Deg
Duration at .050" Lobe Lift (Exhaust):195 Deg
Duration at .050" Lobe Lift (Intake):179 Deg
Lobe Centerline (Exhaust):112 Deg
Lobe Centerline (Intake):106 Deg
Valve Lash (Exhaust):Hyd.
Valve Lash (Intake):Hyd.
Valve Lift (Exhaust):.386"
Valve Lift (Intake):.351"


This is the replacement for the COP CAR 350. The same 773 that I mentioned earlier.

Advertised Duration (Exhaust):278 Deg
Advertised Duration (Intake):273 Deg
Cam Lift (Exhaust):.287"
Cam Lift (Intake):.276"
Cam Timing at .050" Lobe Lift (Exhaust Close):10 Deg BTC
Cam Timing at .050" Lobe Lift (Exhaust Open):44 Deg BBC
Cam Timing at .050" Lobe Lift (Intake Close):40 Deg ABC
Cam Timing at .050" Lobe Lift (Intake Open):13 Deg ATC
Degrees Overlap:40 Deg
Duration at .050" Lobe Lift (Exhaust):214 Deg
Duration at .050" Lobe Lift (Intake):207 Deg
Lobe Centerline (Exhaust):118 Deg
Lobe Centerline (Intake):116 Deg
Valve Lash (Exhaust):Hyd.
Valve Lash (Intake):Hyd.
Valve Lift (Exhaust):.431"
Valve Lift (Intake):.414"

fireball451

That would not be a bad idea except the reason I put the LT1 cam in the manual car was that the original cam had a chunk missing from one of the lobes.
When I got the car, the previous owner threw a ton of part at it to try to get it running right.
It had a pecking type valve-train noise.
Adjusted the rockers only for the noise to return.
The car fell flat on its face at 3k rpm.
With as many mile that it had on it, I thought maybe the lifters are collapsing under a load.
While I was in there, might as well replace the cam with a little bigger one right?
Been reading how well the LB9 likes the LT1 cam.
So, I pull the old cam and here is the pics on another post:
https://www.thirdgen.org/forums/tpi/...9-lt1-cam.html

BigWhiteGTP

Well, I was dead wrong in that thread. Well, at least saying the cam wasn't worth any hassle, but obviously you needed a cam. Funny.