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I completed my my header install last week. I'm not sure if the headers improve the performance. Using Dragy I got a 15.44 before and a 15.12 after the headers install. There's also a 31 degree temperature difference too. Using some on line calculators I gained nothing.
I'm thinking the y-pipe is a restriction.
So I'm thinking dual exhaust with dual cats. This a stock 350 Crossfire engine. If I look at some of the exhaust system pipe sizing charts it shows 2.25" would be the correct size up to 250HP. However I believe those charts are for gross horsepower, not net. So what would be the best size, 2.25" or 2.5"? I'm going to fabricate my own exhaust with the left bank crossing over to the right. After this I have no other performance plans for this car.
The 'Y' pipe is definitely a restriction. But just putting [better flowing] headers & pipes on your engine won't improve much if the heads & cam aren't providing more flow that the headers/pipes can accept. For HP improvement, cam and heads are the FIRST step to take, if you want significant improvement in engine power.
I should have been more specific. Looking at those times it seems that the bottom end is better than the top end. So I'm guessing that a 2.5 piping would be a better choice than 2.25 piping. Is my thinking correct?
I'm not looking to set the world on fire with this car. If I was the first thing to go would be the Crossfire intake. A stock TBI intake from a 5.7 truck is probably better than a crossfire intake.
Duals of 2.5" is what I consider a minimum, and your car will love it. I've built my own exhaust for the last 43 yrs. Buy aluminized pipe and mandrel bends at Summit, add an "H-pipe" if you have the room (Summit brand works great).
You are not sure the headers improved anything?
You went from mid 15s and are ready to break into the 14s. I would say that is a win-win.
Some people spend thousands to cut one tenth of a second.
But like others said, why use headers only to "choke" it down to a single outlet?
Its kind of like installing a nice Holley four barrel but locking-out the secondary.
Last edited by HeadsU.P.; Nov 5, 2021 at 05:19 PM.
Duals of 2.5" is what I consider a minimum, and your car will love it. I've built my own exhaust for the last 43 yrs. Buy aluminized pipe and mandrel bends at Summit, add an "H-pipe" if you have the room (Summit brand works great).
Thank you, I'm going to do exactly that.
Originally Posted by HeadsU.P.
You are not sure the headers improved anything?
You went from mid 15s and are ready to break into the 14s. I would say that is a win-win.
Some people spend thousands to cut one tenth of a second.
But like others said, why use headers only to "choke" it down to a single outlet?
Its kind of like installing a nice Holley four barrel but locking-out the secondary.
Well yes and no. There was a difference in the weather so I really don't know how much is due weather. To answer your question here was my thinking at the time. I was concerned about the additional noise from a dual exhaust system along with the headers. So I figured keeping it with the 2 into 1 into 2 would be the way to go. In David Vizard's book he stated that headers into a single cat is still beneficial. The car still sounds the same with the headers except when I get on it, has a nice throaty sound. So I'm ready to move on to dual exhaust.
Last edited by Fly skids up!; Nov 5, 2021 at 07:24 PM.
And do yourself another favor, ( it may already be in your plans, ) get a transmission crossmember that has pathways for true dual exhaust. With that auto trans, it will bolt right in.
if you must use a cat ... use two ... both with large ID inlets & outlets.
if ya don't have to use cat; don't. Also, as 60shark suggests, swap X-member.
Perhaps you can buy a ready-made system for C3 w/ headers; one that's true-dual but without so many connectors (restrictions)?
If it were mine, I'd have the local tailpipe expert bend up a smooth, unrestrictive system to suit mine.
The plan is to build a 2.5 inch exhaust system using mandrel bent tubing from Summit. Melting metal together is good therapy. I'm keeping the stock crossmember running both pipes down the right side into a pair of MagnaFlow 53956 cats. I want to be able to go anywhere in the US without the popo sticking a mirror underneath the car and then having to hear "boy you're in a heap of trouble". The air pump is gone, the thermac is gone, my timing table ain't doing anything for nox, so I'm not going to push it. As far as the mufflers go I'm going to reuse the my original mufflers and see how it sounds.
Last edited by Fly skids up!; Nov 8, 2021 at 11:18 AM.
I'm going to fabricate my own exhaust with the left bank crossing over to the right. After this I have no other performance plans for this car.
If you EVER had a REMOTE idea of doing any upgrades to your engine in the future, I would strongly suggest doing 3" exhaust NOW! It will save you cash and your labor now, and won't hurt anything now.
If you EVER had a REMOTE idea of doing any upgrades to your engine in the future, I would strongly suggest doing 3" exhaust NOW! It will save you cash and your labor now, and won't hurt anything now.
BUT,,,,,if your done, then leave it as is,,IMHO
Thanks, I have absolutely no intentions to build any engine that would require anything more than a 2.5 inch exhaust. All I want is a cruiser with 14 second ability.
Edit: the only thing down the road I think about is a LT-1 swap from a 92-96 Corvette. I'm constantly looking at fparts on evil bay. A easy peasy 300 horse. Has the right look too.
Last edited by Fly skids up!; Nov 8, 2021 at 01:47 PM.
Crossfire and headers
