I have a 355 engine, 2-bbl, stock heads (whatever they put on the '71 SS), TH350 with stock stall converter, and an open 2.56 differential. The 355 has flattop pistons with the two little valleys in the boss (don't know what they're called), stock crank, Crane Energizer 272 cam, and my machinist said the heads have a 76cc combustion chamber. Accel's HEI distributor in there as well as far as ignition goes. The combo, even though vague...obviously really needs something to liven it up. I'm estimating it's only 250 HP, even though I've been told the bigger cam might hurt the engine with the small 2-bbl (only 390 CFM). I know things like 4-bbl carb and new heads will help, but what kind of things? I know I could probably easily make this engine have a lot more power..just unsure how to exactly go about it. Besides the engine, what stall convertor/gears would help most, but still be useful if I convert this engine or add a different 383 in the car? Any suggestions would be very appreciated. I'm not sure if anything more specific needs to be told in my combo to receive help but I'm sure I'll know if someone asks. Thanks again.

Do you have headers - or stock manifolds?

Remember, an IC engine is just an air pump. You wanna get the correct air in, the corect compresion, and then the air out as effeciently as possible.

A good base combo for your engine would be some small tube headers, a mild stret cam, aluminum intake (performer or the like) and a 650 carb would really wake it up.

Your heads are fine for now - if you are on a budget.

If you are not on a budget then I would get some smaller CC heads too, to bump the compression.

What is your existing trans/stall/rear gear combo?

Joe

I have dynomax headers...not sure the size of the tube though. I currently have a TH-350 with stock converter..I think 1800 stall? The differential is an open 2.56. Also, any reccomended headwork that I can do to these heads to get something out of them?

Taylor

I am by no means the expert here, but...

I would, with your existing engine, upgrade-

1. intake/carb (performer/650 edel or holley vac)
2. Camshaft - I would call Harold at Lunati for recommendations
3. stall - 2400
3a. trans shift kit/performance rebuild
4. rear gear - 3.55 posi

5. head work

what did your machinist say your compression ratio is.

Possibly you could mill the heads for compression and some slight porting, but I think the other 4 items would make your car move pretty good...


Then you could build a 383 with monster heads and reuse these parts on it graemlins/hurray.gif

Joe

Thanks, your suggestion makes sense. Does anyone know what kind of power I'd get if I switched from stock heads to just some non-machined Vortecs and added the proper 4-bbl carb and intake? How much boost from 245 hp would this get me over stock heads and caburetion setup?

Is this engine for the street? the strip? both?

I think that cam would be fine for the street. It's not a very aggressive profile, so it would last a while, and as long as your compression matches it your low end shouldn't be bad at all.
I was running a XE268 cam in my 350+.060" and I couldn't keep the tires from spinning... and that was with stock heads. So I think the slightly larger profile would be very well fitting.

Definately get a new carb and manifold. If this is primarily for the street I would think a RPM manifold and a 650 holley vacuum secondary carb would suite your combo well.

The headers are great, they're what I used on my 350 and what I'll be using on my 406. How's the rest of your exhaust? Some 2-1/2 pipes, an x-pipe, and some summit brand turbo mufflers would help a LOT over stock pipes.

Some vortec heads would be a nice improvement over stock, as long as it's not revved too high. I also woudn't use them on a performance 383 for example... great for the street, but they would choke out a bigger displacement engine in the upper RPM range. Otherwise youd need to port your stock heads, add larger valves, guides, seales, etc. You'll save money and get just as much performance out of vortecs.

A 2400 stall would be good for the street, as well as a transgo/b&m shift kit for your tranny. And you'd feel a big improvement with some 3.55s in the rear.

Thanks for the help, that helps give me a good idea on things too. Are there any non-Vortec stock castings to look for to machine then replace my current heads with, or if I'm going to get any new head is Vortec the way to go?

If you're going to get new heads there are a few things to consider.

I don't know about any good stock replacements. From what's said on this board, aftermarket heads beat the performance of a worked over OEM head and are less expensive all in all.

1. How much money can you spend?
2. What RPM range are you going to spending most of your time in?

If you don't have a budget, then I'd say AFR, street or strip. If you want low end torque I'd go with vortec. If you want HP on a budget, I'd go Dart IE or Toplines.

Vortec's and a good 4-barrel would probably add 75-100hp. IMO it would still be hurt alot by the 2.56 gear and lack of converter. Remember the vortec heads and stock type heads use a different bolt pattern (incase you decide to put a intake on the current heads). I would still consider installing a 4-barrel intake and a 3.55 gear, it would be a different car.

I'm with Mike. Gears and intake/carb.

Thanks for your help. Gears and carb seem to be the most logical thing right now. New gearing won't be affect by lack of a different stall will it? Also do you need to get stall converter ratings by what your engine will be doing or how the trans behind it will react? I'm just wondering if I'd need a different speed with my current gears compared to different gears, or if it all counts to what the motor is doing.

You should match your converter RPM to your max torque RPM in racing applications. The rules bend with a street application... Yes, the closer to your max torque your torque converter is will get you to launch quicker. But it could cause excessive transmission fluid heat from the possible slippage it causes (when you're at an RPM under your stall speed) and that will quickly ruin your tranny. Also, it wouldn't drive very "streetable" with a high stall. It might not move at all at an idle and you would have to give it some gas... and I don't think up a steep hill at idle in traffic would be too fun :rolleyes:

Converter stall is affected by lots of things like engine torque, car weight, gearing, tire size, etc. Best is to finalize the engine combo you're going to actually use and the gear ratio and then call a company like PTC in Alabama(Good Prices). They'll ask you all the specs on your car so be ready. Weight, tire size, gearing, header size, compression, cam duration, etc. They'll then hook you up with a proper converter to match your combo. It'll be some of the best money you'll ever invest.
If you build a new motor later, you can send the converter back and have it re-stalled for the new combo.

Randy