CV8Z

Hi All,

I'm rebuilding a 83 Trans Am that has a L69 305 long block with LG4 everything else. The engine is in decent shape, but the valley, head and valve cover gaskets are all shot to hell pretty much leaking all over the place.

Initially I was planning on swapping in another motor, but decided to upgrade the components on the engine due to lack of funds as well as looming possibilities of lay offs. Though I wanted to get parts that are not only 350 friendly but CARB friendly visually/funtionally.

I'm fairly familiar with the parts I want to replace on the exhaust side of things... New high flow 3" cat, a decent sounding/sized cat back exhaust as well as CARB headers to suit an eventual upgrade to a 350. Since I need to pull the top portion of the engine off and replace the gaskets what other things can I do while I'm in there to get some decent gains that will benefit the 305 and eventually a 350 when the time comes?

Would a mild cam be worthwhile as well as compatible when I swap to a 350?

Admittedly I'm sort a newb when it comes to the swappability of GM SBC, but not totally unfamiliar. I know there are so many options available, that I figured I'd ask around for opinions to optimize the car.

I have done several searches and learned several things, but nothing specific to what I'm planning to do.

Any help, tips, suggestions, comments welcome!

Regards,

five7kid

iTrader: (14)

Port & gasket match the heads, have 1.94/1.60" valves installed.

A computer-compatible cam upgrade would make a big difference without compromising emissions. An EGR spreadbore intake like the Edelbrock Performer, Weiand Action +, or GMPP (ZZ4 - often show up on eBay and racingjunk) would also help.

To the best of my knowledge, Edelbrock TES are the only C.A.R.B certified L69 headers.

Atilla the Fun

The old, now-discontinued GM ZZ3 conversion KIT, (not just the engine), is CARB approved for your application, if you use every single piece specified. The result is 308 hp @ 5250 rpm, and 367 ft-lbs at 3500 rpm. This will get you into the 13s. But it'll cost you more than finding a '98-'02 Z28.

CV8Z

Port & Gasket the existing heads?

Thanks for the info Five7kid... I'm going to be ordering some parts soon. Probably going to go with the Weiand Action + intake manifold, but still deciding on the other pieces.

CV8Z

I found a page that had pictures and most of the parts listed for that engine swap. Pretty involved from what it looks like:

http://www.camarotech.com/engine-ZZ3.html

So despite the "kit" being discontinued, individual pieces are still available? I like the dual cat option versus the dinky one I have now.

Atilla the Fun

Most of the parts in the kit can be found used, then it becomes affordable. I've been through a few L69 builds, and if you go that route, I agree with the Edelbrock headers, and the larger valves. I'd add a Magnaflow cat, the Weiand 8000 intake only because it has the E.O. cast right onto the front of it, ans COMP's 12-388-4 cam if you want amazing torque fron idle through 5000 rpm. If you would like a racy sound and a stronger pull through 5500 rpm, I'd say COMP's DualEnergy 265 is the best I've tried. Both of these have E.O. numbers.

CV8Z

Thanks for great feedback Atilla...

Going this route, are there specific options on how I can optimize the carburator? I'm pretty sure it's still LG4 tuned (I read that the carburators are tuned differently between L69s and LG4s). I'm also assuming when the time comes when I pull the block and put in a 350 I'd probably have to have it tuned again.

My Trans Am is has the "H" VIN, so all the pieces except for the block are LG4 stuff. I got the car from my brother and the engine was supposedly replaced with a L69 by the previous owner. In a worse case scenario engine turns out to be a LG4 would these parts be incompatible? Or rather just won't make much power with the lower compression 305?

Regards,

naf

iTrader: (7)

G vin should have had the L69 originally. LG4's are H vin. Hopefully you've got the better L69 ECM along with the stouter rods/hangers in the carb. I'd guess you've either still got the original L69 or an LG4 was swapped in.

The short blocks between the L69 and LG4 should be the same except for the pistons for earlier years. If it's a later year LG4 it may have the higher compression pistons-a knock sensor was added in '85. You'll know when the heads are off.

CV8Z

The car is originally a H code, not G my mistake... Looking into the engine bay, it doesn't have the dual electric fans, or twin snorkel like the L69s. Also, the rear differential is open and not limited slip. Everything looks like it's a LG4. Only the previous owner saying that it has a L69 is the only claim that it isn't a LG4. Supposedly it's a L69 from an 84 F-Body.

The top portion of the engine is going to be disassembled to replace all the gaskets (massive oil leaks all over), but I guess I'll find out for sure if it is indeed a L69 internally or not.

Atilla the Fun

The 12-388-4 works well with 9:1-9.5:1 compression, and milling the heads could push you from 8.6:1 to 9.1:1. If you have 2.73:1 gears and want to drive them forever, then let's hope you have dished pistons, and use a Summit Racing K1101 cam kit.

five7kid

iTrader: (14)

Like anything else different between LG4's and L69's, the carb can be tuned to L69 specs easily, if it is LG4. Rods & hanger are the big items, although primary jets may also be different. My LG4 carb does fine on my 350, so I don't think you can be too far off yourself.

Until 1985, the only internal difference between LG4's and L69's were the cam and dished vs. flat top pistons. In 1985, the LG4's got flat top pistons as well.

I didn't have any problems with 9.7:1 and 2.93 gears, although I did have higher stall. Higher stall makes a big difference with performance mods such as a cam upgrade. I also have the knock sensor, which an '83 LG4 would not have.

Your link to the ZZ3 kit (was ZZ4 by the time I became aware of it) doesn't work. I printed out the parts list back when it was still available, and still refer to it from time to time. The last I checked, the PROM and ECM were no longer available. The fan switch is still available, and I found one at a local dealer (but you probably don't have electric radiator fan).

Dual cats wouldn't be legal for an L69. But, a Magnaflow L69 cat with the TES headers would be.

CV8Z

That's pretty much what I plan on doing in the long run, swapping out the 305 block for a 350 while using pieces from the LG4. I've seen some posts regarding updating the PROM chip for the carburator? Is that something I would need to do as well to get the most out of it?

2.93 gears were standard for automatic equipped cars right? My car has a T-5, though I'm not sure what gearing is in the differential. Since it's an open diff, I'm assuming it's probably the 3.23 and unlikely the 3.73

They must've recently took down that link. It had a parts list of the pieces that made up the ZZ3 kit as well as some pictures, though the car it was installed into was a Camaro being the only difference.

My car has the mechanical fan w/ a clutch. Though it does have the functional hood cowl which I guess was also available for LG4s as well as L69s?

Bummer about the dual cat setup... That would've nice to have setup opposed to the stock single one. I currently have the Magnaflow cat, and will be placing an order for other pieces you and Atilla had recommended earlier in the thread.

Thanks for all the great information guys! I learned a lot on this thread, but know there's much more to learn!

Regards,

Atilla the Fun

The link worked for me. The dual cat can still be found new, but it's around $900. But it's no performance advantage over the single Y from MAC Performance, which will also actually run cleaner.

five7kid

iTrader: (14)

2.73 were more like the "standard" for automatics. 2.93 was a one-year-only ratio.

No functional cowl hood for Camaros or LG4's.

I agree with Atilla. A high-flow (which is what you're going to get) 3" will flow just as well as the factory dual cats.

Atilla the Fun

My '84 Trans Am was built with both the LG4 and the functional cowl hood.

CV8Z

I placed an order for the highflow cat, but it appears that some of the other parts I'm looking to get are on back order. :-( Oh well, best things come to those who wait I suppose.

Thanks guys!

Kevin84Z28

iTrader: (3)

It's only certified for the automatic, not the T-5. I would do a set of Edelbrock heads and intake manifold with the Edelbrock TES headers. That will set you back about $1600. I even think they sell it as a sort of matched set specifically for the L69. The cam might be included in it, I don't remember.

CV8Z

Thanks for the heads up Kevin. I plan on definitely getting the Edelbrock TES headers and intake manifold, and have the high flow cat on order. I'm also considering the comp cam 256 as well.