I am currently building an 87 firebird. It's a V6 car right now but I am swapping in a 383 stroker. The motor will probably make about 400 hp. Can the stock trans and rearend be upgraded successfully to handle the power or should I just look for new or better quality rebuilt units. I have a TH400 tranny that I could use but I'd really like to have the 700 r4. I realize that the trans and rear end must be upgraded but should I just get rid of the stock pieces all together and not even bother with them. I am also looking for some info on the L98 vette alum head. I'm looking to port them and wonder if anybody has done this or knows anything about them. I'd like to instll larger valves but have heard the intake valve cannot be larger than 2.00. Would it be worth it. I paid $350 for the heads and can get them done(bigger valves, porting...) for $1000. Worth it? Also Eagle forged engine parts Anybody got any feedback. I am also wondering how to pass an emissions test with a 383 carbed motor. I'm going to use catalytic's but will that be enough? Please help

 

Hi 87_BIRD,

I have a 89 Firebird that I've been doing a v6 to v8 swap on. I put in a ZZ4 crate motor but I'm now swapping to a 468 supercharged big block. The fun never ends

You're tranny is fine but you should consider a basic performance build up with new clutches, etc.

As far as cylinder heads go, you'd have $1300 wrapped up in those Vette heads and they will flow 240 cfm AT BEST. If you're spending that kind of money get some AFR 195 heads and they'll flow an easy 270 cfm and work like a charm on your 383. Those will make your engine an animal and you will have room to expand if you choose to do so in the future.

Your rear axle assembly is a non-posi and if you ever did hook up don't expect it to last long. If you add up the cost for various options you will notice that the best deal for your application is probably a Borg Warner 9-bolt that came in 350 equipped cars with rear disk brakes. You will need to beef it up a bit with new gears and a heavy cover plate. Even with those changes it's effective limit is around 400 Hp. But you won't have any problems if you only use street tires. It's also cool because you will get to convert to rear disk brakes too!

You will have to change your passenger side front brake line to a V8 line because your present one travels right where your new v8 motor mounts will be oriented.

Remove your v6 motor mounts and get some v8 motor mounts. You can get the old ones off without dropping the suspension but you will likely need to drop off the front control arms to install the new ones.

Everything in the engine bay is opposite that of the v8 cars. Your battery is on the wrong side, purge canister on the wrong side, air conditioner, and alternator. No big deal though. You will need to round up some accessory brackets that allow you to keep your accessories in the same location. You will also have to reroute some of your wiring and extend a wire or two (namely alternator wiring).

You can fuel your carb by using your factory fuel pump. It actually pumps more fuel than any mechanical pump could. ACCEL makes some TPI fuel line adapters that adapt your factory style fittings to -06 AN fittings. Then use a high pressure 3-port adjustable regulator (Mallory makes one) to regulate fuel pressure to your carb. The neat thing is that the 3-port regulator has a return line and you can return excess fuel back to the tank and not over work your fuel pump. The fittings on your fuel system are double flaired o-ring style... otherwise known as power steering fittings. Took me a long time to figure that one out . The only trick you're going to have to figure out is how you're going to trip the fuel pump relay and make it shut off if you're in an accident. You can do it by having your fuel pump run only if it sees engine rpms, oil pressure or by using an inertia switch. I never got that far because I eventually went for a Holley 4Di fuel injection system. It controls the fuel pump by looking at engine rpm.

The other major issue you need to work out is fuel tank purge. It's not only an emissions issue but a safety issue too. You don't want fuel vapors building up in your tank or you could blow up... literally. Without your computer and original emission system you have eliminated the usual means of purging fuel from your fuel tank. In the old days they just used to have vented gas caps. This allowed fuel vapors to escape through the gas cap but was an environmental nightmare. Then they started venting the fuel vapors to the engine and burning the vapors through the motor. The charcoal canister was added to filter out particles and inject fresh air to help burn the gas. By the time your car rolled off the factory floor the computer knew which gear you were in and they would purge the system after you were rolling into second gear. You're main task is to figure out how you're going to purge your system. The easiest thing to do is scavenge a system off an old car that was completely vacuum operated and install it on your car. If all else fails you could use a vented gas cap but that's irresponsible and you may end up spilling gas all over the side of your car if you corner hard.

As far as passing emissions, I seriously doubt you have a chance. I would suspect you're better off to start with a Formula 350. The only reason I started with a v6 is because I ended up replacing every last mechanical item on the car anyway. It's kind of necessary when you're running 600 Hp in street trim.

[This message has been edited by 89V6toV8 (edited March 10, 2001).]

 

Good luck using the stock trans. sorry about what he said but the bellhousing is different, the engine mounts can be changed without dropping a arms, need a few extensions, swivels, and pack the socket with grease first to keep the bolt in, you do need to change the pass front brake line and i definetly would not recommend trying to use the stock fuel pump the pressure is too high and volume is not high enough, maybe consider putting a cell in and run new lines, if you have any other questions email me at zracer28@hotmail.com

 

Z28Racer is right on the tranny part, The V-6 trans won't bolt up. As for the fuel pump, I'm going to disagree on that part. You can get an adjustable 3 port regulator and plumb that into the fuel system and be just fine. They're several people here who have dne just that, including me.

 

Are my cheeks blushing yet? Sorry, I was lost in wonderland with the tranny. Totally forgot about the bellhousing bolt pattern. Thanks for catching that, Z28racer!

I'm not confused about the fuel pump though . Whereas the stock fuel pump does not supply suffient fuel flow for a typical 350 at operating pressures associated with a TPI system, it will flow an over abundance of fuel at low pressure for a carburetor. It flows so much fuel that a return line is a must so you don't burn out the pump dead-heading it agaist the carb.

 

Check the magazine articles (Stroke in the Dessert) on passing emmissions with a carb'd 383. Of course, he started out with a factory CC carb setup, which I assume you won't have. But, if you don't have a strict visual inspection and the standards aren't too high, you might get it to pass with a mechanical carb/distributor w/cat (as a point of reference, my '84 van w/mechanical carb 350 passed w/new cat well enough to meet the CC requirements of my Camaro).

As for battery location, my '86 V8 donor car had the battery on the passenger side, just like the '82 V6 car originally. It's still sitting on the passenger side.

You should be changing the front springs as well as the radiator and a bunch of other attaching stuff. If possible, remove the front springs while the V6 is still in the car, remove the engine, change the motor mounts while the A-arms are still down, put in the V8, and put in the V8 springs. That may not work if you need to be able to roll the car back & forth while removing/installing the engine (my garage is too short, anyway), but if you can, that will make the motor mount change much easier.

I just rebent my front brake line into the V8 position. The '86 lines are metric, so I would have had to change out the entire brake system just to use one V8 line? I don't think so...!

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, TBD heads ported & polished, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.