Are C2 side exhaust pipes restrictive?

[L88 crazy]

Has anyone one seen cfm flow tests on 2 1/2 inch SBC/BBC 65 to 67 side pipes? I was at the 06 Vettes at Carlisle and saw a restoration parts display. They had a cutaway of I believe an original 65 to 67 side pipe and the inside diameter was not 2 1/2 inches when it goes through the chamber crimps. That left me with the impression that they are restrictive. I help judging what I saw.

 

[JohnZ]

Yes, the factory GM sidepipes are only 1-7/8" I.D. and are very restrictive; the stock under-car exhaust is 2-1/2", and flows much more freely than the GM sidepipes. Larger-I.D. aftermarket sidepipes (Sweet Thunder, etc.) are a better idea if power is what you're after, although they're much louder.

 

[Kid_Again]

Search this forum on the topic and it's been discussed at the "other" place.

From my take on what's been said, the stock pipes ARE restrictive for a big block. You're right, they do neck down quite a bite. A number of us have put sweet thunder sp's on our bb cars and would not trade them for anything. Check out their website.

I think the stock SP's are OK for even a worked small block. JMHO.


JohnZ has spoken ;worship

 

[BLACK MOON]

Yes, the factory GM sidepipes are only 1-7/8" I.D. and are very restrictive; the stock under-car exhaust is 2-1/2", and flows much more freely than the GM sidepipes. Larger-I.D. aftermarket sidepipes (Sweet Thunder, etc.) are a better idea if power is what you're after, although they're much louder.

Actually, I'd like to keep the sidepipe look but install something quieter. Mine are really loud. Any suggestions John?
Thanks,
Sal

 

[firstgear]

I had regular exhaust out the back of my 327/365. Went with side pipes from Corvette America...WOW what a difference....they were 2.5 inch and the motor really came alive.....it really did drive like a different car....the regular exhaust was really choking it, I would have never guessed but a huge difference on start up and just plain acceleration....and of course...got to love the rumble of the 365hp cam at idle....just plain sweet!!!

good luck!

 

[JohnZ]

Actually, I'd like to keep the sidepipe look but install something quieter. Mine are really loud. Any suggestions John?
Thanks,
Sal

The words "sidepipe" and "quieter" are mutually exclusive.

 

[BLACK MOON]

The words "sidepipe" and "quieter" are mutually exclusive.

That's what I was afraid of. I thought someone made a semi-quieter pipe.

 

[firstgear]

The words "sidepipe" and "quieter" are mutually exclusive.

AMEN!

 

[midyearroadster427]

ah

HUH....WHAT DID YOU SAY????????????????????////VRRRROOOOOOOOOOOM

 

[Kid_Again]

Awright JohnZ, maybe a little explanation from you...i understand that the 2.5" internal exhaust is less restrictive...but are you saying that was measured for the length of each respective system?

...the sp's are more restictive but shorter overall (and i admit that the ugly 90* bend to go sideways looks AWFULLY restrictive), but it appears counterintuitive

 

[JohnZ]

The total system length really doesn't matter much, as the gases cool rapidly (relatively speaking) as they travel toward the low-pressure area at the exit and don't need a large diameter as they cool in order to maintain flow. It wouldn't matter if the 1-7/8" I.D. was only for one inch - that's a fixed restriction point for the total system, regardless of its length, which results in backpressure upstream of the restriction.

 

[Kid_Again]

quote=JohnZ;762300]The total system length really doesn't matter much, as the gases cool rapidly (relatively speaking) as they travel toward the low-pressure area at the exit and don't need a large diameter as they cool in order to maintain flow. It wouldn't matter if the 1-7/8" I.D. was only for one inch - that's a fixed restriction point for the total system, regardless of its length, which results in backpressure upstream of the restriction.

[/quote]


;worship

thanks!

 

[Viet Nam Vett]

The other thing that gets me about the BB Motors was the Exhaust Manifolds. They were very restrictive. And when combined with the teeny weeny stock side pipes there must be a dramatic loss in power.

What were they thinking..?? Couldn't the General come up with a better BB exhaust manifold..??:confused

 

[BLee]

I wonder how much power could be gained by extrudehoning a set.

BL

The other thing that gets me about the BB Motors was the Exhaust Manifolds. They were very restrictive. And when combined with the teeny weeny stock side pipes there must be a dramatic loss in power.

What were they thinking..?? Couldn't the General come up with a better BB exhaust manifold..??:confused

 

[Viet Nam Vett]

I wonder how much power could be gained by extrudehoning a set.

BL

Good point...I guess SWC Duke Or John Z could comment on that one.

 

[Tom Bryant]

Street racers that want to look like they don't have much Extrude hone their iron manifolds and get good results. Still less than good headers but much better than stock. Have you ever priced Extrude honing exhaust manifolds? Be setting down before you open this.

 

[BLee]

Wow, never knew it was this expensive. $675 to start, add $100 for a little additional gasket matching work. I figured a couple hundred. I wonder how expensive the machine and supplies are.

I'm in the wrong business.

BL

 

[Gerry]

Street racers that want to look like they don't have much Extrude hone their iron manifolds and get good results. Still less than good headers but much better than stock. Have you ever priced Extrude honing exhaust manifolds? Be setting down before you open this.

These guys must think everyone drives ferraris!

Gerry

 

[Viet Nam Vett]

These guys must think everyone drives ferraris!

Gerry

:L ......Or can Afford $13,000.00 Motors....

 

[Gerry]

:L ......Or can Afford $13,000.00 Motors....

That was my 52nd birthday present to myself. When you get that old I'm sure you will pleasure yourself likewise. Besides it is longer lasting than a hooker.

Gerry