Stock Improvement Suggestions Please

[fresnoindian]

What would you do next? Cam? Rear gears? I have a stock 75 formula 400 with a 4bl Rochester. the only addition i've made is headers. I want to do as little as possible for now ($ reasons) to improve power. Especially since it doesnt burn or leak oil and I just had the heads done for big bucks cause I didnt do my homework. What max cam lift and duration can I put in it as is? Better suggestion? Thanks.

[super]

How often do you drive the car? Do you do a lot of highway driving?

What rear axle ratio do you currently have? posi unit?

What primary tube is your headers? What type of exhaust system (diameter) is your Poncho breathing through?

Thanks

[Larry]

You don't mention if you are using an automatic or a stick transmission.

Also, are you interested in just raw power, or improving take-off and performance from a stand still. With the cost of gas today, it might be wise to look at what you can do to better harness what you presently have.

I have found that after a lot of engine work, the rear end gears and torque converter can make more difference that a lot of additional engine work. If you wish to keep the gears on the high side (better road mpg), then try a 2500-3000 rpm stall converter. That can really make a difference.

Keep us posted.

[fresnoindian]

It has a TH350 and 10 bolt 2:56 rear gears (Stock for that year)
Headman headers 1 5/8 primary and 2.5 single exhaust w/cat that I am going to change to dual 2.5. through dual mufflers. If you check the specs for my year on Gary Lisk's website www.2gta.com you can get an idea of what I've got to work with. The BAR has a dont ask dont tell attitudeon the smog stuff for pre-76's here in Calif.
I would like to make it a weekend and maybe once a week to work driver. I would like to be able to drive it to out of town car shows.
My dream would be to put 3:42 rear gears and a beefed up 4spd automatic and give the motor to Bruce Fulper at pontiacpower.com and let him work his magic but thats many dollars down the road.

[Larry]

You are correct, it would be nice to have Bruce work some magic on your engine, but for the meantime, there are still things you can do.

The 2.56 gears are handy now that gas prices are going through the roof, but now so impressive, I'll bet, off the line. The 3.42 gears would make a real diference without eating you out of house and home gas-wise.

I have a '69 Lemans that I put a 400 tri-power in and did just about everything I could think of (on a budget) to get to move out better: headers, switched to Edlebrock hi-rise and Holley, nice mild cam, even bigger valve heads (valves so huge, that small children must be carefull around!). Still it was like a herd of turtles off the line. I couldn't break the tires loose, even with the 3.23 non-posi gears! Talk about disappointed.

Finally it dawned on me. I had put in an engine from a full-sized station wagon. Guess what? That car was designed for pulling boats, house trailers, etc. so consequently had a torque converter the size of a steamboat paddle wheel.

I had a 2300 stall converter put in and what a difference. This thing will flat move from a dead stop and smoke 'em as long as you wish. Don't go much higher that 2300 or so for the street. The guys who put in the 9" Vega converters sound like they're peddling a bike with their gas pedal just to drive slowly through town (trying to keep up the rpms).

I'm not trying to sound like I'm stuck on just the torque converter angle, but I know from experience what a difference it can make. For the money, it is one of the biggest changes you will make to the operation of an automatic trans car. It's almost like being able to pop the clutch on a stick car,as your engine will scream up a lot more rpms before the converter locks to the wheels. Try it, you'll like it!

[super]

Changing your gear ratio in bird would make a vast improvement in performance. A 3.23 or 3.42 axle would work great for highway cruising. Your tire and wheel combination should be another factor considered. Going from a 2.56 to a 3.42 would give your Pontiac a wake up call.

Larry's suggestion of a mild stall converter is a good idea as well. From personal experience, it was one of the best investments I made on my '74 T/A. I picked up over a half second in the 1/4-mile in my car changing converters. Went from a stock converter to a 3000 stall from Doug Herbert performance. From a 13.16 to 12.50's. It helped my heavy T/A tremendously. Great results for a $200 investment.

A 2200 or 2500 stall might work well in your ride. A guy does not want too much stall if constantly driving it on the streets. A transmission cooler would be a good thing to add as well with the converter swap.

I would leave the engine alone for now as you stated. Enjoy it for a while. Bruce would be a good choice to build you an engine in the future. The guy knows his Pontiacs and can build you an impressive low-compression engine for the street.

[fresnoindian]

Thanks guys for taking the time to respond. I do have one final question. Does anyone know what the max is on a cam swap for the motor I have. It has 1.5 rockers and had 7.6:1 compression but I don't know how much it gained 8 after the heads were milled. I know a Ram IV would be out of the question but there should be an alternative. Thanks again.

Here's my car. I removed the vinyl top and intend to leave it off. Its rust free and no missing parts. Just needs interior re-done and paint. I want to modify the lower valance to look a little sleeker and paint the bumpers the same color as the car. I'm goint to put some T/A flares on it as a final touch.

[super]

Great looking Formula. Looks great just as it is.

When you start dealing with camshafts, you obviously have several factors to consider. Getting your valvatrain geometry is key to your engines success.

I take it your heads have screw in studs. The proper valve spring needs to be looked in to. Your valve springs may do the job for a mild hydraulic cam, but I would at least test them.

The Ram Air III camshaft seems to be a popular choice. With the aftermarket constantly growing though, there are probably several better choices out there. I believe Bruce Fulper probably has several camshafts available for sale and could give you a great recommendation for your car. There are tons of factors to consider with the cam change. We have already covered a few.

Tire size

gear ratio

transmission

weight of the car

These are all key things to look at with a camshaft change.

[super]

Pontiac Purest,

What types of times did your T/A run in the 1/4 or 1/8-mile before you did any modifications and what kind of performance does it yield now that you have done all your modifications?

Rhoades lifters are a good addition if you want to pick up a little more low-end.

[super]

You don't have any numbers you can post for your T/A? Just about any Pontiac engine will do well with small performance increases. It is a great base to start with.

Numbers generally put things in perspective for others, especially when you are trying to explain to them what combination to run. I would personally want to try things first that would produce better numbers and performance for me. Get the best bang for the buck.

I am not concerned about telling you how to "correct" your set up. Sounds like you are very happy with the results. Numbers speak for themselves though. It would be nice to give those numbers so the gentlemen with the Formula could put things in perspective for his cool Pontiac ride.

[super]

Were those runs with slicks or drag radials? Open exhaust?

[super]

What does your '78 weigh Pontiac Purest?

[super]

I know my '74 tips the scales at over 4000lb with a half tank of fuel. Add another 260 with me behind the wheel.

Curious to what the '78 weighs.