Thread: exhaust pipe diameter

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hello guys, i sold the comet, sold the torino because of lots and lots of rust, and i gave the camaro to my brother for his 21st birthday. and now i have a 64 chevy stepside. i plan on a cheap restoration this spring. this truck will be my daily driver so i want a little power and some sort of fuel efficiency. heres what i got in mind.

goodwrench 350, 260 horse with a better cam, im thinkin about a comp 268h high energy,performer eps intake, 600holley, 1 5/8 headers, stock hei

rebuilt turbo 350 with a manual/automatic valve body, cool floor shifter

3.23 gears, 255/60/15 rear tires, 245/60 front

i want duel 40 flows with x pipe. i know that 2 1/4 inch pipe is plenty, but i may put more engine in it down the road and i am wondering, if i get two and a half, will torque suffer?
feel free to comment on my other ideas too

It may suffer a little bit, not that you would notice because your putting a little more cam in which will shift the torque band up anyways. Got any pics of it...i also drive a `64 chevy fleet, 350 / 350 / 373. Hopefully soon BBC.

Not original with me – but should help

Exhaust Pipe Size Estimate: A good section of straight pipe will flow about 115 CFM per square inch of area. Here’s a quick table that shows how many CFM each common pipe size will flow, as well as the estimated max horsepower for each pipe size. NOTE: These numbers are just estimates. All pipes are assumed to be 16 gauge steel.

The table above is probably over-estimating pipe size, but you can see that a 400 hp vehicle with a dual exhaust system only needs 2 1/4 – 2 1/2 inch pipes. Anything larger is overkill.

i suppose ill go with the 2 1/2 then. hey 406 rich, ill take some pictures tommorow and put them up. ive only had the truck for about a week.
So have you upgraded the brakes or converted to power steering with your 64?

Keep your '64's 4:10 rear and use a 700R4 instead of the Turbo 350, I did that in my '65 I had, the lower first gear in the 700R4 made it launch much harder and the overdrive made it EZ on gas when cruising.With new HEI's selling for around $100 junk the stocker and get a new one with a better performance curve and higher voltage to work with your cam and intake.

You want to stay with 2.5" pipe mainly for the reason that you can buy flanges for 2.5". 2.25" is a bastard size but if you are going to run pipe that doesnt need a flange connection to the header then you should be fine.

Originally Posted by josh bichard

i suppose ill go with the 2 1/2 then. hey 406 rich, ill take some pictures tommorow and put them up. ive only had the truck for about a week.
So have you upgraded the brakes or converted to power steering with your 64?

Yes power steering and power drum, I used the REZ powering steering bracket.

so you still have drums on the front? do they work ok?

jeff, your telling me my truck has 4.10s in it? i did not know that. hmm, theres a guy in town who will sell me a rebuilt 700r4 for 650 with a new torque converter and detent cable. but its just a stock rebuild, will it hold up? I may pull a trailer every now and then.

o and i was looking at the jegs street spark hei. its got a hotter coil and its only 100 bucks. would that be a good choice?

Originally Posted by josh bichard

so you still have drums on the front? do they work ok?

jeff, your telling me my truck has 4.10s in it? i did not know that. hmm, theres a guy in town who will sell me a rebuilt 700r4 for 650 with a new torque converter and detent cable. but its just a stock rebuild, will it hold up? I may pull a trailer every now and then.

If it had a standard 3 or 4 spd trans almost all were 4:10's the PowerGlides were 3:73's either would work great with the 700R4,while you have it out I would do two mods to it,change to the Corvette servo and a Trans-Go shift kit and towing will be no problem.Try www.oregonperformancetransmissions.com put these numbers in search: NTP-K51828C and TRG-700-2-3 And yes to the Jeg's HEI.

You`ll really need to ID your gear ratio first, top right side of diff housing will have the id number, it could be 373 / 410 or 342 /331 if its original one of those four, it could even have a later 308 if someone else has changed it over the years, i`m still running stock drums, if you choose drums go with the later 67-72 6 or five lug, on all four corners they are a little larger, you`ll have less brake fade, Early classic chevy or Cpp has all the disc brake change over or just change out the complete front cross member with everything attached will bolt right up to your frame, you just have to drill two new holes, from `66 to `86 will work, you`ll also need to grab master cyl, power booster lines proportioning valve, or get a complete donor truck.

top right looking from where? behind the truck or looking to the rear from the front

If your looking at the back of the truck top right side just before the u-bolts on the axke tube. A double click on it shoud make it legible.
http://qptwaq.bay.livefilestore.com/...20Axle_ID2.jpg