im running a set of hedman shorty headers 1 5/8" primaries with 2 1/2" exhaust no cat flowmaster 40 series muffler into duals with 3" tips.

is this exhaust flow good enough for my motor?

Is there a big difference between 1 5/8" and 1 3/4" Headers??

One reason i was thinkin of SLP 1 3/4" headers is because they are coated would look beter with my engine, mine now are rusty color but also because i was told by a few people to upgrade to 1 3/4" and bigger exhaust like 3" or 3.5"

355
Edelbrock RPM Heads 170cc 64cc
Edelbrock RPM Cam w/ 1.6 Pro Mag's .520/.542
Edelbrock RPM Air Gap Intake
Edelbrock 750 CFM Carb
March Pulleys, Weiand Aluminum Water Pump.. Blah Blah

 

i asked the same question. everyone told me that it depends on what you want. if you want more low end torque, 2.5 in exhaust is the way to go. more top end would be the 3in and up. wether this is true i dont know, but thats what i was told when i bought my headers.

 

well i will be using the car until about 6000RPM or little more...doesnt start to work good until around 2500-3000RPM so it wont be for low end.

 

I'm running 1 5/8" headers and making 330rwhp with a 350. That being said with my next round of modifications I'm switching to 1 3/4" headers for max power.

 

so it is worth it...i was just wondering what kind of difference bigger primaries made, i know more flow, but is it really worth it to pay the 700$ for the SLP's

i was going to get the hooker long tubes but my clearance right now is 4" from the exhaust and long tubes would bring that down more.

and you say low end torque is good with 2.5".. should i go 3 or 3.5"? bigger the better?

 

SLPs are not long tube headers, therefore unless you're stepping up to hooker coated super comp headers I don't see a reason to swap it out. Even the headmann 1 5/8" long tubes will make more power than your shorties right now, and I believe you posted you're running true duals as well. dual 2.5" will be more than enough for your setup and then some. I still am running 1 5/8" headmanns on my camaro with 2.5" dual exhaust and run the same times uncapped as through the exhaust.

 

The thing that immediately got my attention when I read your opening post is that you're only running a 2 1/2" exhaust. That's more than likely holding you back much more than your header size.

But with the 1.6" exhaust valve and larger port in those heads, the 1 5/8" headers could also be restricting flow if they're blocking part of the port by not complete surrounding it. And if that's the case, you should prolly go with the 1 3/4" headers, which would prolly be recommended for those heads anyway.

So if you can afford to do it all, then do it all. Otherwise, I'd stick with those headers for now and upgrade that exhaust system first... 3" minimum.

Just my

 

its 2.5" y-pipe not duals.

 

I went from the Flowtech shorties with a single 2.5in exhaust to a Hedman long tube with dual 2.5's and 24in Classic Chambered mufflers; the difference was amazing on a stock bolt on TPI 350. A freind in town did the same headers, same Hedman S bends but with regular mufflers with the similar results. The 2.5 in single is definetly holding you back, go with a good 3 to 4in single, or dual 2.5s. I can't say from experience if the larger primaries will help you because both of my headers had the smaller 1 5/8 primaries, I would guess there wouldn't be a huge difference.