Could anybody tell me what the performance difference is between a single 3inch cat back systm on a 2001 4.2 and putting the same muffler on the stock stainless steel 2.25 exaust system,I have a modified air box and kn filter. I would love to see some actual no.s on a dyno, I just wondered if it is enough gain to justify the extra 300 hundred bucks.

 

It doesn't matter what size the outlet is. Will sound different, that's about it. Just depends on what look you want.

 

Thanks for the reply tony, but I was more interested in the peformance difference than the sound.

 

I'd say that if the stock pipe is only 2.25", then going to a 3" will just kill your low end power. You'll probably see gains in the high end. Some backpressure is actually needed to keep the low end power up.

I'd think you should just replace the muffler with an aftermarket one that'll let it flow better, but keep enough backpressure to get you moving from a stop. Keep the 2.25" tail pipe and just get a bigger tip.

 

thanks for the reply, thats what I was thinking ,I talked to a tech at gibbson exaust and he said that if I wanted all the available low end tork I would have to stay with a single exaust. Because I was first interrested in dual's. He told me that new fuel injected moters require a certain amount of back pressure. That duel exaust would not be as good as a single 3 inch exaust. With that being said, he sold me on the idea of sigle exaust. Which brings me back to my original question of wether the 3 inch cat back or just adding the same hi performance muffler to my 2.25 stock systm, the tech at gibbson said it would better to go with the 3 inch cat back systm, but would not say by how much or give out any dyno no.s on both systms. If there be a tech or engineer of one of performance muffler companys willing to sheed some additionall light on the subject, please post.

 

Gibson has dyno results on their web site. Or just call the tech dept. They faxed them right over to me. Descent increase!!!1

 

Mr2X75, I went through the same learning curve....

What I found was that you can get a little less restrictive exhaust and some great sounds by using a non-resrictive "Y" pipe from 2-1/4" to 3" into a 3" inlet on your choice of single mufflers. From there on you can choose either a single 3" outlet pipe or, if you're like me and you want those wonderful dual tips sticking out from under your rig, then you can choose a dual 2-1/4" outlet muffler with two pipes.

I chose the 3" inlet, dual 2-1/4" outlets MagnaFlow muffler, which is by Banks Exhaust Systems, and you can buy it in either Stainless or Aluminumized Steel that is guaranteed for the life of your vehicle. It's a straight through Glass-Packed muffler. Part #12278

This way, you decrease the back pressure some, retain your low-end torque and get dual exhausts with some great sounds!!!

And that's the stuff that turns heads and makes life worth living.

BillVoyles
'99 Bright Red Regular Cab Flareside with 4.6 V8/ Auto 3.08 Sleeper

 

Thanks for the replys, I talked to gibson again today after getting the reply to look on there web sight for no.s. And all that is there is for the 5.4 and the 4.6 nothing on the 4.2 . So I called them again , this time the tech recomened part no. 619-608 for stainless and part no. 319-608 for aluminized this is for the 4.2 v6 specifically the diff between it and the v8 systems is that the v6 uses 2.5 pipe and the v8 uses 3.0 , these part no.s are for a complete cat back system. He said it would gain 8 to 10 horses and 25ft.pounds of tork. I asked for dyno results and he could not find any. I asked if he could check around for some, he said he would. I told him I would call back in a few days. The stainless retails for 546.00 and can be bought at several national retailers for about 420.00 on avg. I also talked to borla and they only make a system for the 4.6 and 5.4 , which is 3 inch pipe. Both companys where polite and curtious in are conversations.

 

mr2x75

I have been looking at the same Gibson system that you mentioned. The part numbers you cited are for the single side exhaust with 3" pipe. This is the same system they recommend for the 4.2L. 4.6L, and 5.4L Ford F-150s.

I am just curious about the 2.5 inch pipe. Did they tell you that they substitute a 2.5" pipe if you order this system for a 4.2L? They have contended before that there is no significant loss of bottom end with the 3" provided that the pipe exits at the stock position and is not shortened. (at least that's what I thought I heard)

 

Roundboy, I did not check to see if the part no.s where diff. the tech said on the phone that gibson had a catback system for the 4.2 I asked what size pipe was it, and he said 2.5 so i took for granted when I asked for the part no. it was diff than the identical 3inch system, maybe the tech gave bad info? or the wrong part no. either way sounds like i need to get it clear with them Im supposed to call back this week. If there is no2.5 system then borla would be just as good a call because it comes in 3 inch also. Oh while im on here the stock exaust is 2.5 inches not 2.25 like I stated earlier.