switching from 1 5/8 edelbrock TES headers, dual hollow cats, 2.5" dynocrap cat back on my 383. Mods are in signature... Wondering what I would gain from 1 5/8 headers with dual cats to 1 3/4 headers to single 3" in 3" out 3" magnaflow cat back on my car....my power numbers in signature are with a slipping transmission and non lockup converter and of course the current exhaust on my car.

 

i'd think you'd gain ALOT.... i gained alot goin from stock manifolds and 2.5 inch exhaust to a flowmaster 3inch catback. gained even more with 1 5/8 shorty headers.

on that 383, it could use big 3 inch single system over that 2.5. also could use a 1 3/4 tube. i think my HSR Stock long block L98 could use 1 3/4 lol

 

well i heard that for 305's use 1 5/8, for 350 use 1 3/4.....but what for 383??? hmmmmmmmmm?

 

I think the single cat would negate any gains that would have been made by the 1 3/4" headers.

You need the 1 3/4 inch headers, 2 1/2" to the dual cats, 2 1/2 inch to the wye pipe and for best performance 3 1/2 on back otherwise 3 inch on back.

I agree that your present exhaust system is killing you. Get the transmission squared away and a good exhaust system and you will see big time improvements.

 

tranny is already rebuilt with new lockup converter....no dyno since the tranny rebuilt or converter.....I know i wouldve been more improvement if I would've gone 3.5" catback but running low on budget $ right now. I am getting ready to order the Dynomax 3" intermediate pipes from summit and ordered a 3" n two 2.5" outlet Magnaflow muffler from a Magnaflow dealer in town. Other than the 3.5" catback, was wondering if there was anything I couldve done to see bigger gains other than what I have now.
BTW I got rid of the dual cats because the cats inlet was only 2.25" inlet and same outlet....too much $ to get TWO aftermarket converters to get an exhaust pipe to channel into a single intermediate pipe, besides, I have emission laws where I love and according to the local muffler shops, I cannot have dual exhaust. I wouldve liked to have done trual duals....but if i wouldve done trual dual, I would gone LT style (hedman) to two hollow 2.5" cats and to two dynomax race mufflers. granted every cop in town wouldve followed my butt but o well....

 

Are 1 3/4 headers bent differently than 1 5/8 or are they the same with just larger diameter primaries?

 

i dont think they are bent much differently. there is only so much room for headers in our cars and they all seem to follow a basic design layout.

I'd go 1 3/4 primaries to atleast 2.5 inch pipes connecting into a y pipe with 3.5 inches on back. 2.5 inch y pipe connecting to a single 3inch catback is what i basically have now and its nice, plenty of flow for a mild 350 but 3.5 inch is where its at for a single system.

 

where can i get 3.5"? no muffler shop here has the ability to even bend 3" much less 3.5

 

mufflex....else your outta luck.

most muffler shops dont bend 3inch pipe so they buy prebent pieces like the ones you can get from summit or jegs. thats how my axle back was fabbed up, with just pieces of prebent 3inch.

 

$500+ dollars for exhaust?????? no sir....besides....would 3.5 vs 3" give me like 30 more ponies??? even if it was 30 rwhp thats kinda alot of $ for 30 rwhp

 

i assume that youre looking at long tubes either way, because they dont make 1 3/4 in shorties

if you go with something like hookers 1 5/8th with a 2 1/2 inch collector, dual 2 1/2 inch into a 3" y pipe you would make a crapload of torque, but it is going to seriously rob you of top end power

you have big cubes with big heads, youre shooting for all the horsepower money can buy, youre not so concerned with power at 2000 rpms, more so at 4000+ rpms.

hooker long tube 1 3/4 headers pn# 2210 is pretty clear cut what you need

your call on wether to run a 3" or 3.5" after the Y probably doesnt make much difference

 

SLP makes 1 3/4 shorties. I have them on my car.

 

SLP headers are the ones I just bought off a member on here and they are 1.75"

 

oh ya i remember those now

regardless youre still shooting for horsepower man, nothing wrong with making it scream from 4000 and above from the line.

youre going to want to run a 1 3/4 header on that motor regardless, the slp's have a 3" collector, back into whatever size Y pipe you feel like, i dont think youd gain much power over a 3" pipe all the way back

 

I bought the mufflex Y pipe and 3.5" exhaust for my car, quality is great, too bad its not stainless. but It's definitely worth the money.

 

yes, i think the mufflex is a great deal for a nice exhaust system...especially if you can find it used lol

as far as gains from 3 inch to 3.5...i dont think its all that much more but then again, i'm not sure. i would figure it would give up torque for more topend but i dont think you need that as the cam isnt that big for a 383.

a great flowing 3inch muffler on a 3inch setup should be adequate.

 

well there is a member on here that replaced his 2.5" dynomax exhaust (same one I am using) on his pretty stout 350 and went from 12.8ish to 12.4. he ran trual duals though. dual 2.5 and single 3 inch.....ive heard not ALOT of difference in power. At least not in the power level he and I are at.