First off, I'd like to apologize if this is the wrong place for my question, but the lounge had way off the wall questions and my q doesn't apply to f-body's.

Here we go. I have 1.5" primary tubes that feed 2.5" collectors on my c1500 pickup. These are draining exhaust gasses from gm's 330 hp crate engine (the one with vortec heads). Well, the shop that put my 2.5" crimp-bent duals on couldn't get the 2.5" pipes to connect to my headers. So they cut up a v6 y-pipe and bolted 2" collectors to my headers and then they welded the 2.5" pipe around the 6" stick of 2" pipe.

I was a little mad. ;-)

But, they didn't fix it, and I had to pay them. So, my question is, does this really hurt my performance? The truck doesn't run nearly like it should, and I don't know if this is the problem or not. Would going from a 1.5" shorty header to 1 5/8" primary tube FULL length headers that are bottle necked down help me out?

Do you guys think there would be enough gain to warrent the extra work? And let me put that question into perspective. I think true duals of f-body's are worth the work.

This is my daily driver. It's not a raceonly truck, but I like good performance.

Some extra info (if this could help). It's fueled by a 600cfm holley and the cam specs are 212/222 on a 112.5LCA .435&.460". The engine spins a 2400 B&M that's connected to a Th375 (yes a 375. a th400, but with a 27-spline output shaft vs. 32). Then it goes to 3.43 eaton posi.

Plans are polished and cleaned vortecs that will accomodate more lift .500-ish and then more converter. 1.75's for the truck are too expensive as it won't be around that long.

Is the fix worth is?

Moderator: Move this please, if it's in the wrong spot.

Thanks so much,
Ben

 

The shop put a big cork in your power output, IMO. It really doesn't matter what's in front or behind those 2 inch restrictors.

You need to rethink almost everything from the headers back. Keep the 2.5 inch size going from the headers to two free flowing mufflers like Dynomax Ultraflows or the equivalent Magnaflows.

I'd replace/fabricate everything from headers to mufflers with mandrel bends. If you have to buy the bends, cut and fit and weld them together, do it. Once you are behind the muflers, 2.5 inch crush bends aren't all that much problem, mainly because the exhaust has lost most of it's heat and has less volume. 2-1/4 mandrel bend tailpipes wouldn't really cause much problem.

I would look for a shop that was willing to do it right. I wouldn't go back to "Muffler Bob".

IMO, it's not the shorty-vs-full length headers that are the question; it's the primary pipe diameter. 1.5 inches is a little small for a 330 hp 350. The tend to help torque in the 3000 range, where 1-5/8 tubes will help inthe 3600 range. With your 2400 TC and the 2.48 first gear, that 3000 range isn't bad for launching the 1500.

If you decide to buy new headers, go for the 1-5/8. Personally I like shortys or intermediate lengths for engines in this power range. However if you don't do the good 2.5 inch system and high flow mufflers, you won't see much, if any difference. It will be a big waste of your $.

Now, if you keep the shorty 1.5s, and free up the rest of the system as mentioned above, and throw in an h-pipe before the mufflers, you will get the torque/hp GM advertises, things won't hit the ground, and you'll be within a few hp of long tubes. Unless I had a buyer for the 1.5 inch shorties, I'd keep them!

Bottom line is your must fix the header-back problem. It's constipating your engine.

My $.02

 

edit:
misread the question to be a long tube vs shorties question.

 

Trey: It's not a long tube vs. shorties question. It's a "is this a problem question". The "this" being the 2" pipes.

As for now, I have 2.5" 50 serioes Flowmasters and a pair of Dynomax Superconverters. That's relatively free, but I'm just trying to see if I'll do better after the bottle neck's removed.

This IS NOT a shorties vs. long tubes question.

Please read my post more carefully. It's more of a primary tube size question (as the tittle implies) and a bottle neck question.

The Flow's aren't going anywhere, but the Flowtech headers are. Yes, I think I have a buyer for the shorties. He'll give me $100, and I paid like $180 plus S&H, so I'm looking alright there.

Thanks so much for the replies guys (OldSStroker).

Ben

 

i edited my post 5 min after i posted and 3 hrs before you repied. geeze, calm yourself. too many sugar pills for you

 

Yikes. No, not good. Fortunately a short piece of small pipe is not as bad as a long piece of small pipe but still a 2" pipe is about 40% smaller than a 2.5" piece of pipe as far as flow area.