[PontiacDanny]

Hi Guys!

What would be the cheapest way to have about 320 - 350 horsepower in a 100% stock 1978 Trans Am. Car has a 400 pontiac motor that came with 220hp and a 350 TH Transmission. Car runs strong and has factory original exhaust. My max budget would be approx $1800 and I dont want to pull the motor out of the car. The motor has approx 150K miles and does not smoke or anything.

[PontiacDanny]

Hi Guys!

What would be the cheapest way to have about 320 - 350 horsepower in a 100% stock 1978 Trans Am. Car has a 400 pontiac motor that came with 220hp and a 350 TH Transmission. Car runs strong and has factory original exhaust. My max budget would be approx $1800 and I dont want to pull the motor out of the car. The motor has approx 150K miles and does not smoke or anything.

[Tim Swain]

Think, exhust, carb, and distributor. Then think intake and cam. Jim Hand has a lot of Pontiac info on stock go fast stuff. Check his posts and website.

[Ken K]

Don't tell Larry I told you this but put a set of 72 cc big valve D port heads on it and a set of headers and change the intake to a Edelbrock performer or a 68-71 cast iron Quadrajet intake.

[78 GHOST]

Danny: I've got a 78 T/A which I like very much and am fighting the same basic problem you have: GM's low compression engines in response to smog emission regulations.

Unfortunately, they corked the exhaust pretty good with the low flow cats and poor overall exhaust design. $500 for a new set of duals with good mufflers.

A properly dialed in carb and dist. will go a long way to making more power. $50-100 for a GOOD distributor curve. $50 for both a carb. rebuild kit and the Q-Jet book available thru PY written by Roe.

You won't get too far down the road until you realize that the low compression is going to be a hard hurdle to overcome.

I did some minor work to the carb. on my car and say major improvements in throttle response and power that can be felt.

I'm doubtful you can do much to boosting the power to your desired levels without changing heads (at least) to a tighter combustion chamber to bump the compression. You would then want to match the cam to the new compression ratio and match the carb and dist. to that combo. I would guess around $350-700 for a good set of closed chamber heads depending on what you have done to them.

So far, you theoretically have $1350 max into things without buying a timing set, gaskets, or a cam and lifter set. I would budget around $350 for that as a ballpark. So, for around $1700 you can put a new exhaust on, new heads, cam, timing set, dist. curve, good carb. rebuild.

You probably could stand to use 3:42 gears and maybe a really small shot of gas to round things out, but that puts you over budget.

You didn't really mention how the car is to be used, only a HP level. Further info. on usage would certainly help nail things down.

Your engine has pistons which have beveled edges to help lower the compression. Eventually, you might change to true flattops.

Good luck and keep us posted, -Matt

[Will]

I agree with what everyone has already said, but let me elaborate some.

Compression is NOT as big a handicap as some will lead you to believe. At least not when shooting for relatively modest power levels like you're doing, so don't worry about the heads for now.

Free up the exhaust. 1-5/8" primary tube headers and a minimum 2.5" exhaust, preferably mandrel bent. Going too big on the header primary tubes will kill bottom end torque which you are already hurting for with the low compression anyway, so don't get 1-3/4" headers.

Better intake manifold. Pre '72 factory intakes will leak at the exhaust crossover with your heads, so if you can't find a '72 intake, then get a regular Performer. They can often be picked up used. Don't waste your money on the old P4B, it's not as good as the performer and won't accept your Q-jet.

Speaking of Q-jets, some tuning there would be in order. Richen up the secondaries with richer rods and play around with the opening rate until it opens as quickly as possible without creating a bog. Further modifications can wait 'til you've done everything else as the carb tuning will be most dependent on the rest of the combo.

Distributor recurve is a must. Without track or dyno tuning you won't know what's optimum, but you can get close. For the mechanical advance, start with a 22 degree curve that starts 100 RPM above your normal idle speed and is all in by 2400-2600 RPM. Set the initial timing to 14 - 16 degrees. Use a ported vacuum source and a 10-degree can, or better yet an adjustable vacuum can and play around with it until you get maximum part-throttle advance with no pinging under load.

To really make all the above stuff sing, change the cam, valvesprings, and that worn out timing chain. This can all be done without removing the heads. Install stock replacement style springs that can handle a little more lift. Install a very conservative cam along the lines of the Summit K2800/Edelbrock Performer cam. That cam shold work well with your low compression.

Doing all of the above should put you over 300 horses easily, and close to if not within your goals. Save the head swap 'til you get the shortblock rebuilt. If you have 6X-4 heads, you don't need different heads as you can get up to 9.3:1 with those at rebuild time.

Good luck!

[Half-Inch Stud]

...turn the key, start, run, mash the throttle.

Are you there yet?

H.I.