Thread: Engine & Tranny & Exhaust what should I consider?

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Jerilynne. if It were me, I'd build it like the one I'm driving now except for adding a 4 speed. The combination I'm running seems to fit most of the things you want to do with the car and gets reasonable gas mileage. Keep in mind this is a total drivetrain package and EVERYTHING works together.

Engine: First I'd stay with a Pontiac engine with one possible exception and that AIN'T a Chevy. The Camaro and Firebirds are basically the same platforms so a Chevy drive train will bolt in with Camaro mounts and exhaust and Bellhousing (just me but if I wanted a Camaro I'd have bought one . ). JMO but I personally believe the Firebirds, ESPECIALLY the TAs were a lot more car than the standard Camaro due in large part to the Pontiac engines installed in them. Additionally the car is just a lot more impressive from an ascetic standpoint with a Pontiac engine in it (again JMO but a Firebird with a Chevy drive train is just a Camaro wannabe and who wants to do that (No offence meant to out Camaro owners out there).

Now before I start into the details, just a little nugget of Firebird history; In the late 70's some Firebirds built for sale in California were equipped with the 403 Oldsmobile engine (instead of the Pontiac 400) in order to meet emission requirements. It's not uncommon to still come across these cars here in the western states. The 403 Olds like the 400 Pontiac is a torque monster and seat of the pants driving feel between the two engine is almost identical (I've put a bunch of miles on firebirds equipped with both engines). Additionally, should you ever end up in a situation where you have to bring the car back into emission standards It should be doable with these engines (although a major pain) as either engine was an option through the 81 model year (at least according to some of the reference material I have come across).

If you were building the car as a real street terror with no worries about gas mileage or tire life I recommend a 455 Pontiac/Olds engine motor. Based on availability, gas mileage and the real world driving you want to do I feel that a 400 Pontiac would be the first choice and if you can't find one or just run across a "can't pass up deal" on a 403 Olds that would be my second choice. Either engine should be a bolt in swap onto your existing motor mounts. I'm not absolutely sure, but I also believe that your existing accessory brackets will be a bolt on with the Pontiac engine (the Olds brackets a just slightly different and will have to come from an olds engine if you go that route.

The key (and I can't emphasis this enough) go with an EARLIER (76 or older) 400 or 403. The latter engines with the emissions heads and slightly lower compression just do not run as well. Once you have an engine do a good basic rebuild and LEAVE IT STOCK (did I just type that???? ) . Actually I did, The 400/403 in stock form (stock cam and intake) make a gob of torque at lower rpm. They do run out of steam at around 5000 rpm but you make up for that with gears that I'll get into a little latter. If you go with an aftermarket intake or cam keep them as close to the stock configuration as possible. Many of the aftermarket pieces DO help the engines make more HP and torque but it's at the expense of bottom end torque (with the gears I'll recommend latter this is a BAD thing). Go with an earlier non-emissions Q-Jet or a 750 Edelbrock Performer carb. A stock GM HEI (pre-emissions) ignitions will be more than sufficient for the car (you can and an MSD box if you don't have anything else to spend you money on, but chances are you won't see any real improvement). If you want to go with headers, you will likely pick up a little improvement, but you should weigh this with the hassle of installing them, reduction on ground clearance, and hassle of occasionally changing gaskets when they blow out (especially if your on a cross country trip). Overall The stock 400/403 manifolds will work fine on this combination. As far as emissions (if you don't have to pass an inspection) delete everything except PVC and vacuum advance (if you have an EGR, pull the vacuum line and plug it. At this point the computer no longer has anything to do . One last item, plan on upgrading to a 4 row radiator.

As far as exhaust from the manifolds/headers back, use minimum of 2 1/4" (preferably 2 1/2") true dual exhaust with free flowing mufflers (I'm running obnoxious burner out glass-packs but that's just me re-living my misspent youth ).

Transmission: You have some choices here and what you choose will determine your final gear ratio. The easiest and cheapest (relatively speaking) would be to go with an M20/21 Muncie (while a Saginaw 4 speed would physically fit, chances are it won't take the torque of the engine very long). This would be a bolt in with no fabrication using stock Firebird clutch pieces/linkage (Camaro peddles should also work). As far as a 5 or 6 speed or add on OD they wouldn't hurt, BUT look into the costs and fabrication required to install them. The engine I've described makes enough torque over a wide RPM range they don't really need a bunch of gears.

Rear end: As Tech would point out this is really the key to the whole combination. With a high torque low rpm motor you don't want a deep rear end ratio. From my experience you likely have a 10 bolt (if your real lucky it's a posi) with 2.46 gears. Believe it or not the 10 bolt is stronger than most people will lead you to believe, and should last behind the engine and tranny (unless you decide you really like doing hole shots with the 4 speed (then you look for a 12 bolt )) . While the 2.46s would likely be OK, with a stick I'd really look for something in the 2.70 something range. REMEMBER YOUR ARE MAKING A LOT OF TORQUE AND DO NOT NEED A DEEP GEAR. The lowest I'd go with this combo would be in the 3.00 range. If you go with an OD plan on something in the 3.40-3.70 range. Believe me these ratios will be deep enough to smoke the tires at will . You will want to add a Posi if your car doesn't have one or you will be replacing 1 tire on a regular basis. The beauty of these ratios is the car will just sip gas and cruse at highway speed all day long.

Just for general info, here are the specs on my 81 TA Clone. Stock 1976 Catalina 400, cast iron manifolds, Rebuilt/Re-jetted Q-Jet (Pre Emissions), Stock HEI, functional Shaker Hood, 4 row radiator with stock fan and fan clutch. The transmission is a TH 350 and the rear end is the stock 10 bolt with 2.46 gears. Tire size is 3235/70/15.

It will light the tires up at will, and the last trip I took to Phoenix it got 22 MPG at 75-80 MPH, temp ran 190-195 degrees (it was only a cool 90-95 degree day ), and that was with the AC on and was pulling my Harley on the MC trailer that weighs about 1000 pounds.

I know some of you out there might be shaking your heads (as I would be) but this combo just flat works.