Ok, '85 had the 190-HP L69 with T5, ( really 200 HP on premium unleaded ) or the 215-HP LB9 with 700R-4. Why did the LB9 drop to 190 for '86? camshaft and exhaust manifolds, but that's how, not why. '86 had a new, better engine computer. And the Players' Challenge F-twins had L69s, as did the Monte Carlo SS, so obviously it was still clean enough, why didn't non-Players, F-twins get the L69 option? Even with a 700R-4 and a 3.42:1, still would've been more fun than the '86-spec L69. Anyone have any insider facts? I have my own theories and opinions, but history is about uncovering and sharing facts, and this sub-forum is about history.

 

Because an 85 LB9 was too close to GM's flagship Corevette. So they "Detuned"

 

Corvette must always outdo all other sports cars in the lineup. Its their trophy car of sorts.

 

I'm guessing CAFE average economy standards.

 

I'm guessing customer complaints over the slightly loopy idle with the L81 cam in the 305.

 

Some yutz always has to throw in this juvenile piece of crap "explanation" (NOT) for some reason.

And of course, nothing about 350 vs 305 would happen to enter into the picture, of course.

Are you talking about actual "power", or just "ratings"?

It's known of course that the 86 had less cam than the 85, although the electonics were better. AFAIK the other parts (heads, exhaust) were pretty much the same.

As far as "why", the CAFE suggestion would be my "guess", being the uninformed outsider that I am.

 

But not all of the LB9s dropped to 190 hp in 86,some models maintained 215,I wonder why also

 

Again, they couldnt outperform the Corvettes. They of course got "peanut' cammed. And the inake on the birds were very restrictive.
I highly doubt that anybody that bought an iroc in 1985 would have "complained" about its "lopey" idle. lol
The 85 LB9 cars perform fairly well. Ive done alot of street racing in the 90's. and a stockish 85 always outpulled any 86-92 LB9 car. regardless of manual or auto, and of course peanut cammed or not (same difference).

 

Good Grief, stop it with the "can't outdo the Corvette crap"... Starting in 1986 there were new emissions standards...

 

Anybody know why they under rated the TTA so much?

J/K

 

Fail. That cam has -25 degrees of non-overlap at 0.050", that means a dead-smooth idle, barring any vacuum leaks or sensor failures. Those same cam specs continued well into the '90s, albeit in HR form. Thanks to Okfoz for trying, both at a factual answer, and for keeping it on-topic. The Corvette nonsense is easily dis-proven by the 'vette having another 45 cubes, bigger intake valves, the 4+3 manual transmission, and less weight. More curious, the Mustang 5.0 also lost power for '86, the how being the heads and restrictive intake manifold. The unknown why may confirm new emissions standards. However, every domestic V8 sporty car came back stronger than ever for '87, without any dramatic losses of static compression, which was the previous solution to emissions standards. Putting the LG4 cam in the LB9 created even higher dynamic compression under some conditions, and that's no help to emissions. Yet this continued to be offered through '92. Still seeking insider facts. Tighter regs are easily offset by the new, improved computer.

 

Yes the new emissions and fuel economy standards were the main reason that the LB9 got the LG4 camshaft in 1986. For 1985 the LB9 was rated at 215hp and 275 pound feet of torque. For 1986 the LB9 was rated at 190hp and 285 pound feet of torque.

Also for 1986 the records show that only 74 L69 engines were produced. The L69 was in between the LB9 and LG4 motors to begin with (these were the most profitable V8 motors for GM in 1986) and carbed motors were on the way out. 1987 was the last year a carbed motor was installed in a thirdgen - the LG4. L69 production ran from 1983-1986.

I like the L69 motor but I am sure it didn't stand up to well in terms of the new CAFE government fuel economy regulations and emissions regulations that were coming down. The L69 paired with the T-5 gave you 3.73 gears. If you choose the 700r4 you got 3.42's or had the option of stepping up to 3.73's. These gears are great for performance - but this is why the vast majority of F-bodies came with the 2.7x freeway gears from the factory - these non-performance gears are better for fuel economy.

Also keep in mind that GM was considering stopping production of the 350 engine all together because they were concerned that the 350 was not going to be able to meet the new government standards. TPI was designed for the 305 so that it would be able to give simular performance as an earlier (mid to late 1970's) 350 carbed motor while still meeting the government regulations. So TPI's main objective was to improve the fuel economy and emissions standards while still giving consumers compariable performance with what they were used to. The boost in power was a welcome addition but it was a by-product of meeting the new federal regulations that were being imposed at the time.

Also keep in mind that GM stepped the gearing down to 3.23's and 3.42's for many of the TPI motors that were given these more performance oriented axle ratios. TPI dosen't need a lot of rear gear for good performance but many from the 1960's-1970's muscle car era were used to cars with 4.10 gears in the rear so GM had to keep that in mind too.

We are also talking about 1985-1986 time frame so this was only roughly 15 years after the first big influx of muscle cars so this era was relatively fresher in peoples minds than when we are looking back at that muscle car hey-day 40 plus years after it happened like we are today.

The LB9 was also going to be installed in the Corvette as well. GM did testing with the TPI system and determined that they could make the TPI 350 engine meet the new federal regulations. As a consequence, however, GM placed the same TPI unit from the 305 on the 350. The only thing that was changed really was the fuel injectors. LB9's got 19 pound per hour injectors and L98's got 22 pound per hour injectors and a chip matched to those specific powertrains.

The 305 and 350 engines were technically part of the same Gen 1 small block family of engines so transfering many components from the 305 to the 350 wasn't going to take much engineering and design work as if would if GM peformned a specific TPI 350 engine program like they did with the 305 TPI motor. This way GM wasn't starting from scratch and they saved money in a less involved, lower cost research and development program for the 350 TPI motor. Also since the 305 TPI unit got transfered over this simplified the process for GM with respect to getting the TPI 350 motor certified and ready for sale so GM could get some more of their investment money back.

This is why TPI is more of a restriction on the L98 350 TPI motors compared to the LB9 305 TPI motors - TPI was orignally designed for the 305 - a motor which has 45 less cubic inches of displacement than the 350.

 

It was just a guess, and of course it could be wrong. I have no independent information that it is true or not.

I base it on the fact that mine idles pretty rough, at least compared to most modern cars I'm used to, though this could be a function of a small vacuum leak and inability to diagnose it on my part. But two mechanics have looked at the car and said everything's just fine. They thought I was crazy in fact. I don't think so but that's another story...

Anyway, this wouldn't be unprecedented. Didn't GM allegedly changed the Ram Air III and SD 455 cams for this very reason?

 

Emissions and MPG. My 86 LB9 with the 2.77s and LG4 cam had EPA ratings of 17/25...an 85 LB9 with the better cam and 3.42s standard was rated 15/24.

End of story...moving on...

 

Can't be CAFE, the L69 was good for 27 MPG with the T5, 0.73:1 fifth, 3.73:1 axle, and 215/65R15 tires. By '92 the LB9 was rated at 26 MPG with the T5, 3.42:1 axle and 245/50R16 tires. Can't be emissions, since the L69 continued in the Monte Carlo SS, carbureted, through 1988. The L69 only making 240 TQ, same as the peanut-cammed 8.6:1 LG4, proved that the better 9.5:1 compression was totally offset by the lame cam. There were 74 '86 L69 IROCs, true, but don't forget the 26 L69s in T/As, also for Players' as the total was 100. Of the possible engines for '86, the only one that was fun stock was the L69. Fixing the LB9 would have meant having to get the better exhaust and cam from an L69 plus getting an '87 chip. More cost. More tech facts can be found here: http://www.gmheritagecenter.com/gm-h...tion-kits.html with the relevant page being this one: http://www.gmheritagecenter.com/gm-h...let-Camaro.pdf

 

What's the difference between the '86 and '87 LB9? This site lists them both at 190hp. Does my car have the same motor that the '86s are always dogged for?

 

1986 was the year that GM put the LG4 cam in the LB9.

In 1987 the LB9 could finally be paired with the T-5 and the power was raised to 215hp and 290 pound feet of torque. Basically it was the 1985 LB9 with more torque and now it could be paired with the T-5 instead of just the 700r4 like it was in 1985. This power increase was thanks to the L98 style cam.

The 1987 LB9/700r4 cars got the lower lift cam. I'll post some links so that there is some information people can read. I think the LB9 cars that got the G92 option came with the L98 style cam.

I'll post some links so people can check the facts out.

This link shows the difference in the cams between the 1985 & 1985 LB9 in addition to talking about the 1986 Camaros
https://www.thirdgen.org/1986-chevy-camaro

This link has information on the 1985 Camaros and lists the cam specs for LB9 & L98 engines that were produced between 1985 - 1992
https://www.thirdgen.org/1985-chevy-camaro

This link gives info on the 1987 Camaros
https://www.thirdgen.org/1987-chevy-camaro

 

Not all the 86 LB9s got the LG4 cam,check your RPM tach for the red line.The LG4 cam,red line is at 4500 -5000 and the hotter cam is 5000 to 5500.I wonder how many of those got through the production line.

 

Early 86 cars were at 85 power levels, mid year and later were detuned down to the "offical" 1986 levels. I had friends with both the 85 and 86 models and the 85 was no joke - easy low 15 car stock...

 

My 86 was born,Feb.86,so that explains this RPM tach.

 

According to the specs for my 1986 WS6 TPI LB9, with a build date of July 86, it is supposed to have a a rated HP of 215. The tach does yellow line at 5000 RPM and Redline at 5500 RPM. So maybe it is one of those few that were built with the better camshaft? It does not sound exactly stock idling, which is just an observation and has no basis in fact. What is fact, that the car is bone stock right down to the original spark plugs. I have seen about as many sources listing all 86's as having 190 HP, as those that list the 86's as having a 215 HP rating. Figured that it is not worth starting a debate one way or the other. If I understand it correctly, the 87 LB9 has a roller camshaft, and can be identified by the center-bolt valve covers? My car being a WS6 came with the 9 bolt diff and a 3:27 ratio, which is pretty common for this package. It seems to work well with the HP, available torque, and weight of the car. It will turn low 15's in the quarter with me driving which is not saying much. The biggest problem is getting the tires to stick on launch, which may be due to crappy tires. One thing that I have not done, but believe that will be interesting to know, is to have the car dyno tested to see exactly what HP it is making. Charles

 

Well that blows the early production theory!!!! you have a July 86 model and I have a Feb.86 model.I wonder how many 86s are like this???

 

Firebird Tachometers as per the Parts Catalog

There was two designs, the 1st design has 5500 Redline and 2nd design has 5000 Red line, it does not specify when the design change happened. Same goes for the Speedometer, there was two designs, the first only reads to 85Mph and the second design reads to 140Mph.

In an unrelated side note, the parts catalog only shows the 305G (HO) being sold to Canada, as they did not offer instrument cluster for the US market...

There was 3 tachometers in 1986, (at least in construction)
25059404 was used on the LB9 & L69
25059403 Was used on the LG4 & LB9
25059402 Was used on the 2.8L

Not much help, but something

 

Canada was where the Players Challenge series was, mostly, right?

Also, as far as the power levels being down in 86 and back up in 87... in 87 they introduced the roller cams across the board in the F and Y cars. That surely got them a little more power. Also, late 86 was the first year they got rid of those awful smogger heads on the C4 Corvette 350. They came out with the first version of the aluminum heads in 86... and a better version in 87, which boosted the Corvette's power numbers and compression, which probably got it a little better gas mileage. Roller cams across the board probably increased gas mileage a tad. It was probably a combination of all of the above.