Hello everyone!!!

I just wanted to say that I've learned A LOT from reading these forums and it's great that so many third gens are still out there!

So let me get straight to the point here....

I have a 1984 Trans Am with a stock 305 (not H.O.....) and a 5-speed manual transmission. I got a copy of those gearbox DVDs with the intention of rebuilding my engine (which only has 60 000 km on it but was abandoned at one point and runs like.... well.... you know... not good) but then got to thinking that since the power plant lacks, well... power, I might as well get my hands on a 350!

Basically, I wanted to know what engine I should be looking for if I wanna keep a carbed 350. I'm new to all of the more technical engine lingo but am willing to learn and get some ''oumph'' out of my T/A. Ideally, I'd still like to rebuild any engine I do end up purchasing and will be looking around scrap yards around town for a great find (hopefully).

My goal would be to have 350 - 400 hp and I'd like to avoid a transmission swap for the time being.

Any help would be greatly appreciated!!
Thanks!

 

Welcome aboard thirdgen.org.

I'd suggest looking for a '96-'99 Chevy or GMC light truck 350. It will have Vortec heads, which were about the best factory Gen I small block Chevy heads ever made. You will need a new flywheel (for '86-'92 3rd gen V8 manual transmission), intake manifold (Vortec spread bore style for your stock carb), and front timing cover and harmonic damper, but the benefits will outweigh those expenses. The engine will have roller lifters, which make replacement cams more expensive, but you don't have to replace the lifters with a cam change. The stock truck cam won't be that bad if you decide to stick with it, but you will have to replace the cam to get to your 350-400 HP.

Assuming it needs a rebuild, you don't have to do anything special. Replacement pistons, rings, and bearings will be fine.

Your 305 exhaust is really poor, even for the 305. Were you planning on headers and new exhaust on back? Without replacing all the exhaust, forget 350 HP.

You won't have to swap the transmission to do this, but you won't be able to beat on the transmission as hard as the engine will be capable of beating on it!

 

Thanks for the reply! Maybe I got carried away with the 350 - 400 hp. (for the time being anyway )
Since I don't really wanna rebuild the 305, I'd like to opt for a 350. Assuming I locate a '96 - '99 chevy or gmc truck 350, how much hp would I obtain from a very modest swap? I know that's a vague question, but I'm trying to get a better understanding of the whole process. new exhaust headers are not out of the question at all....

I plan to keep most of my 305 intact as a dummy engine anyway...

 

In the trucks, they were rated at 255 HP. Compared to your 155 HP, that's a pretty decent jump by itself.

I would expect a stock '84 carb with aftermarket intake manifold and good exhaust to do better than that, maybe 275-285. Even a modest aftermarket cam will easily take that over 300 HP.

And, those are "net" flywheel HP numbers, as installed in the vehicle and running the accessories (alternator, water pump, fuel pump, with air cleaner and exhaust). The typical quoted crate engine HP numbers are "gross" flywheel HP - velocity stack instead of an air cleaner, electric water pump and fuel pump using facility power, open headers, whatever carb/intake that gets the best HP or best torque (could be different carb and/or intake to get each of those numbers), etc. So, even the "stock" 285 net HP is more like 325 gross HP.

 

How much should a scrapyard engine like this cost? I haven't looked around yet and wanted a rough idea. I happen to live in Canada so maybe value may differ slightly.

Also, is there something I should look for to be sure that I'm not being taken for a ride by the scrap yard? What about things to avoid in picking up an engine in need of a re-build?

Thanks again!

 

Any JY motor is going to be a gamble because you can't disassemble it til you've got it home. Some indicators:

A truck/car that's been wrecked is much less likely to have arrived at it's present location due to a bad motor.

Black rockers (as opposed to semi-shiney) under the valve covers generally indicate lack of routine oil changes and/or overheating.

A motor that has had it's innards exposed to the weather/rain is probably rusted somewhere inside.

Although most yards will drain fluids, you can sometimes get an idea of the latest oil condition under the valve covers.

The L31 motor brand new can be had for around $2300 US. A local rebuild would cost me around $1400 (with core). That would be a budget, not a performance, build.

Make sure what you're buying is an L31. It should be stamped 5.7 top left rear and have cylinder head numbers that end in 062.

A you-pull-it JY engine near me runs $150-200.

 

What I am looking for right now, is to slowly put together an engine that will mainly be a Sunday driver during warmer months (lots of snow in Montreal so she hibernates in the Winter )

For the time being, I just want a little better performance than my 305....which isn't that hard to find....

I contacted a SY and they said they had an L31 for 1250$ with a 3 month warranty.....
I'm sure that I can do much better!.....

 

$1250 may not be bad with the warranty, especially if thats in Canadian $. You'll just want to make sure you can get it installed and running within three months, or that the warranty period doesn't begin until it's installed.

Shop around none the less.

 

Is there a good place to get some modest configurations for the L31's?
I'm trying to put a budget together before I dive into this thing....

 

You can start with exhaust. Since yours is a non-HO, it needs to have every piece upgraded. Headers, y-pipe (3" best), cat (3"), and cat back (3" at least).

The '86-'90 TPI single cat was one of the best systems from the factory (dual cat slightly better, but with today's high-flow replacement cats, a 3" single is fine). Look for parts made for that application. The Hooker 2055HKR shorty headers with y-pipe is one of the best off-the-shelf systems available (if you're looking for the best shorty system, PM TGO member Dyno Don - he makes custom headers for our cars). The Catco 9118 direct fit cat, or a direct-fit model like it from Magnaflow or other reliable brand, is the next piece. After that, most any cat-back for the above application from Hooker, Magnaflow, Edelbrock, take your pick, will complete the system.

Your stock computer controlled q-jet is fine for good street performance. With Vortec heads, your intake choice is a little limited, but good choices are available. If you go with other than Vortec heads, I'd still say keep the q-jet. Since you have a T5 transmission, it could be argued that a Holley double pumper would be a slightly better choice (requires changing the distributor, and isn't emissions legal), but if you don't get a Holley double pumper, keep the q-jet - no other carb choice makes sense.

With a better engine, you'll probably want better rear end gears. And posi, if you don't already have it. If you already have 3.73 gears and posi, you should be good there.

Oh, any '86-later SBC will have a one-piece rear main seal crank, meaning your '84 flywheel won't fit. Just get a replacement for the '86-'92 305 f-body manual transmission application. If you get an '85-earlier engine, your current flywheel will work.

 

Thanks again for all the help!

The Trans Am belonged to my Uncle, and he had the exhaust system changed about 8 years ago (before giving the car to me for my 18th birthday! )

He doesn't remember what specs the exhaust system has..... go figure.... Are there indicators on the muffler that would tell me the make or model? As for the exhaust pipes, I will be measuring them shortly!

Will be heading out to see if I can find my L31 this week!

 

The 906 heads are exactly as good as the 062 heads

 

I don't know what the currency exchange rate is, but in current U.S. Dollars, a Vortec 350 complete can be had for $200 at the pull-it-yourself yards, and that includes a 30-day exchange policy. At the other yards, they go for $500 with a 30 day full guarantee for the long-block. Paying more than that is silly, because you can get any '87-up 350 block, stick new Vortec heads on it, and convert to junkyard 305 roller lifters for less.

 

Look at the y-pipe. If the car still has the factory y-pipe it's the biggest restriction in the system. The y-pipe for the LG4 would have crimped bends and be roughly the size of a garden hose. Anything that's been added to the back of the factory y will only change the tone of the exhaust.

I agree that 906 heads are equivalent to the 062 although, for whatever reason, I've never seen them in the yards I go to. Perhaps its a regional thing.