Friend of mine is looking to buy an '87 Trans Am, LG4 automatic. I've never dealt with one of these before, is there anythign odd or special or strange about the LG4 that he or I should know before purchasing on it? What's the design history of this motor and what sort of 'performance' are we looking at here? It's bone-stock right now, save for a manual fan switch (tasefully done) and the missing spoiler (also tasefuly done). I know if he were to hop it up, he would want a carbed 350 in it's place, that or some headers if he decides to keep the stock motor - the stock manifolds don't look too free-flowing to me.

 

There's not much to tell about it, it's a small-cammed, low performance 305 with a CCC Qjet. From the factory it should have made about 145 HP or so.

 

I think in 1987 they were all the way up at a tire-blistering 155-160HP!!! Gasp!

The basic computer controlled carburetor system is VERY adaptable to a modest street-performance 350 setup, keeping all the computer controlled parts (mainly carb and distributor). Making all the the basic parts work on a larger/heavier-breathing engine up to about 350HP (real HP, not magazine hype numbers) is very do-able.

The entire exhaust on the LG-4 is restrictive- manifolds, y-pipe, cat and cat-back. The most typical upgrade is to headers and a complete 3" exhaust- like an aftermarket system for a same-year L-69 305 HO motor would take. The exhaust is the BIG expense as far as "performance" parts go, other than the cost of a complete strong performing 350 engine. Almost everything else is re-usable and perfectly adequate for strong street performance use.

 

Also keep in mind that the 305 has smaller bores than the 350's also. Externally everything is interchangeble, it is the internals that are smaller. They can be built up with some decent HP, Chevy High Performance has been doing a series of stories on a Camaro buildup. My car was an original 305, 140 HP motor.

 

So was mine, before I changed out the heads, cam, intake, carb, exhaust, pistons, rods, crank and block.

 

Sure, he could hop it up, but then there's the whole 305 v. 350 argument, which I tend to sway towards. Bang for the buck, and all that. I'll have him build a few paper tigers before he goes and empties his wallet, though, just so he knows what the many options are.

They were roller-cammed in 87, right? Pre-87 was solid lifters, and they switched to hydraulic rollers in 87, if my memory serves correctly. (Which it doesn't, half the time.)

 

They were always hydraulic. Before 1987 they were flat hydraulic, and hydraulic roller after.

 

'87 would have roller lifters, just like the TPI engines had. In '87, the LG4 also had 9.5:1 compression (early LG4 was around 8.5:1) and should have an aluminum intake manifold as well.

 

Oh, okay. Thanks for clearing that up. So, basically, the LG4 in '87 was as good as it got (for a low-output 305) for factory parts. Then it was replaced. The car in question has 150k, runs pretty good despite the mileage. I couldn't hear much of any abnormal engine noises.

 

The 87 LG4 was as good as an LG4 ever got, anyway. An L69 of any year is still better as far as carbureted 305s go.

 

Yeah, I figured that much. I was hoping it was an LB9 car at least, but then it would've been worth more, too. An L98 car would've been almost too much to hope for. I'll see what my frined thinks, but I'm leaning towards getting it as the body is really good.

 

'87 was not only the start of roller lifters, but also the slight dish in "flat top" pistons to yield 9.3:1 compression. However, with the roller cam, HP was 165-170. The exhaust and single snorkel air cleaner still held it back.

It would be a good base to build upon. 350 with decent heads, cam, and a complete exhaust job would do nicely. In fact, the LG4 heads with 1.94" intake valves and some porting work would do a 350 nicely.

 

Did all LG4s have those heads? Even in 1983?

 

Only when both are dead stock.

 

Seller went and sold it before he gave my frined a chance to put so much as a deposit on it, last night. We had agreed to meet up tonight to discuss the price. Guess the seller just couldn't wait, that or somebody else offered a lot more then we were willing to. My friend was all bummed out, he really wants a I guess the fact I own two sirt of steered him towards that.

But, I saw an '86 T/A for sale, looks beat up, VIN revealed it's also an LG4. Not as good a motor, from what I'm hearing from you guys (not roller-cammed). Hopefully, it's still running (I glanced over it once six months ago, hasn't moved much since, still for sale) or I'll just not bother taking my friend down to look at it.

Another friend of mine just bought a new Civic, but he kept his '91 RS. I knwo the RS is an LO3 car, and I know the history on it a bit. It has some issues, but nothing glaring that screams "Stay away!" so I may ask him how much he thinks it's worth.

I'm correct in assuming that the LO3 is just an LG4 with TBI on top, essentially? I know the LO3 was the low-end V8 engine choice after the LG4 went away, which was what the LG4 was. L69 roughly equalled the LB9, in terms of High Output 305 V8.

 

If they're not stock then they're not really an LG4 and an L69 anymore.

 

Yeah, that's what I thought - Once you start dumping a bunch of aftermarket parts and other goodies, the only thing it is then is a 305. A 383 L98 isn't really an L98 anymore.

 

Earlier LG4's had 416 heads. Basically the same, but with perimeter valve cover bolts and all of the intake mount bolts are the same 90 degrees.

I'm afraid the news isn't that good. LO3's got about the worst heads made for anything above factory power. The rated 170 HP is about all you're going to get, while the 190 HP of the L69 was just the beginning.

 

Ah, I see. So, if I woke up one day and found that my L98 in my GTA had been replaced by some whackos and it ws now an LO3, I would want to change the heads as well as a whole bunch of other stuff. (like the whole engine after I beat the whackos brainless...)

 

I have a strong roller H.O 305 with the computer carb(carb froz upfrom sitting) from a 1987 formula.

however I am on the main land

later

rick

 

No such thing.

 

The only H.O. with a carb was the L69. In 1987 the "H.O." was the LO3, which just proves the old adage that there's no truth in advertising.

If it's a carbed 305 in 87 it's an LG4.

 

I don't know what they call these (those ) motors, but the formula was a 305 ho motor for what it is worth-- it is also a roller 305 as for what it is and the advertising I don't know or really care it is what it is

later

and
GB

rk

 

forgot to ask where is good info to find out what this motors are called so I know what you guy/gals are talking about.

I need to get a clue on this as I am fimular with the old school motor names

thanks

rk

 

https://www.thirdgen.org/newdesign/tech/techdb.shtml

If it is an '87 with a carb, it is not an "HO". Period.

 

Those are some of the RPO codes for the engines that were installed in thirdgens. More details are here:

https://www.thirdgen.org/newdesign/tech/techdb.shtml

 

That's what I get for typing slow. :P

 

They're right, unless soemone did some work to it... The L69 was discontinuedin '86, and essentially replaced with the LB9 TPI, as the H.O. motor, although both the L69 and the LB9 could be had in '85 and '86. Counting the 50 L98's that were made in '86, there are FOUR V8 choices for a 1986 car - just enough to make your head spin, but don't count on seeing any '86 with a 350 from the factory anytime soon.

Look at your VIN, I betcha the 8th digit is an 'H'. If it's a 'G', then someone did a TPI-to-carb swap.

Sorry if this is redundant information. I've carried the 8th and 10th VIN digit 'Secret Agent Decoder Card' in my wallet for over a year. It pays to have that little bugger when looking at a car... I can't trust my memory right.

EDIT: I kant spel

 

thank youy no maybe I can learn more about the 3rd gen the right way

later and

GB

rk