Currently have a set of TSP 1 3/4 long tubes on my 10psi Procharged lq9 with a torquer v2 cam, 3600 stall, 4.10's etc. Long story short, one of my headers needs replacing, and I am considering going with Speed Engineering 1 7/8 vs the 1 3/4 I have now. The rest of the exhaust consists of single 3", 14" magnaflow and exits at the bumper. Would the 1 7/8 be of any benefit vs the 1 3/4?

 

Your single 3" is hurting you more then the primaries. Yes 1 7/8 is better but keep that 3" on your radar for some updating.

 

I am of the opinion that even a boosted 5.3 will benefit from 1 7/8" unless its very low boost like 6 lbs. or so. It seems there is not much downside from the larger header either. Wont be a whole ton of difference but it will help a few ponies. Definitely worth it.

 

So as far as the exhaust is concerned, what would be a better option for diameter? 4" or 3.5"? Also, since they go from dual 3 to a single 3" y, assuming say I went to 4" after the y, will that 3" merge be an issue as well?

 

Dual 3 or do a dual 3" into 4" merge with a 4" tail.

 

I'd go single exhaust if I was going to do it all over again. Simpler, cost less, Use existing mounting points. Not as loud too. Dual 3" is overkill and will do 680 ponies.

 

Here is the deal when talking about exhaust set ups for blower combinations:

It can't be too big......period

 

I agree with travis to a certain extent.

Your combo will like both the larger primaries and tail pipe.

However, a properly sized exhaust and well designed camshaft can take advantage of exhaust scavenging much better than something thats too large.

 

Taking this back up, I will be getting the exhaust done next week. So how should I go about this? Do I go dual 3" or single 4" with a new y that is actually 4" merge? Truck is 4/7, and even my single 3 over the axel has a ding in it from my axel housing hitting, so keep that in mind. Although I do recall the exhaust shop saying that can ovalize it to go over the axel

 

If your builder is decent they can overcome the over the axle issue. I build my own dual 3" exhaust in my garage. Over the axle in SUV platform and no bangs to this date. I used my Magnaflow kit as a model and modified from there. Plenty of room for 3" duals my friend. No worries!

BTW I believe Spintech sells oval parts to all you home gamers out there.