I have a 383 and for lack of money reasons, I had to buy hooker 1 5/8" shorties. I am going to invest in some high quality and more 383 compatible headers. I wanted to get 1 3/4" ceramic coated SLP's. Is this best application for a 383? Thanks.

 

yep.

 

This is one of those dangerous topics some people say that 1 5/8 headers are good up untill 500 hp... Some dont. I personally have the 1 3/ 4 headers (not installed)
You could also open up the backpressure debate with this one too...

 

That is one thing I had in mind. Since I have true dual exhaust, I questioned whether 1 5/8 with true duals (no cats) would flow as well as SLP 1 3/4 with a single tailpipe like most F bodys have. I wouldn't want to loose any backpressure.

 

Smaller pipes do not increase backpressure!!!!!!! They increase scavenging!!!

A crappy muffler increases back pressure, and back pressure is never good!!!!! Hell, even the 4.3L V6 cargo trucks that UPS uses, have a 3" single exhaust pipe. But only because they have to have a muffler.

I just recently read CHP mag, and they were building a 500+HP SB 400. The first headers they used were 1 5/8". The engine produced a nice flat low RPM torque range. But it also fell short of the 500HP mark. It was ~490HP

Then they switched to 1 7/8" headers because that's what they had laying around. With no other changes, the low RPM torque dropped like a bowling ball, but the peak TQ was at a higher RPM. Only like 12 lb.ft. more, but the best thing was they reached (IIRC) 516HP. They hit there +500HP mark. And that's what they wanted.

Although they did say since this was gonna be a street/strip car (some street car huh? ) that they wish they had a pair of 1 3/4" headers to try. To them it would have been a good balance of TQ and HP.

They summed it up by saying that the 1 5/8" headers "over scavenged" the heads. Well of course they meant that they produced more TQ downstairs than upper RPM HP, which is not what they wanted.

So I guess it all comes down to what you're gonna do with the car, what cam you're using, heads, etc., and how much HP you're looking to get out of the motor.

If you're looking for HP numbers then go 1 3/4" or maybe even 1 7/8" (if anyone makes them in shorties?????). If you're looking for streetable TQ, then use the 1 5/8"

But I say this again, BACKPRESSURE IS NOT A GOOD THING!!!!!!

AJ

 

SLP 1 3/4" headers are the best smog legal headers out there for 350 and larger engines, in my opinion. Since you're going with dual exhaust I assume you dont have smog checks, so you could also look at Hooker long tube headers.

 

They don't necessarily increase scavenging either, just lower the RPM range at which it occurs.

 

Sorry, I didn't mean to upset you, dude. BTW, good info!

Nope. No emissions worries. Gathering from the 1 5/8 to 1 7/8" result comparisons by AJ, I'll look into getting those Hooker 1 3/4 long tubes. Those aren't any harder to install are they?

 

Wrong and right.

You got the second part right. Now just understand that it IS the increased scavenging that causes that.

AJ

 

I told you it was a dangerous topic

 

you were right!