My Car:

305 LO3 TBI

Hooker Headers (3" Collector w/ Y-Pipe)
Catco High Flow 2.5" Cat (Keeping this)
Flowmaster 3" CB with 2.5" taper at Cat to fit 2.5" cat
Open Element
Edelbrock TBI Manifold
Full MSD Ignition

Brothers Car:

305 (Van Motor)

Hooker Headers (Old 2 1/4" collector size)
2.5" Exhaust with Flowmaster Muffler NO CAT
Edelbrock Manifold
Edelbrock 600cfm Electric Choke carb
Open Element
Mild Cam
Rebuilt top end with rockers

Our deal is that he THINKS that by having a 2.5" exhaust versus my 3" he will have more torque...but I told him with him having that 2.5" with all those mods he is actually not gaining as much as he would with a 3"

So all I ask about this topic is..whats better for TQ and HP for both cars, 2.5" on his car or 3" on my car? Who will have better power gains from their exhaust?

I have been told on here to go nothing less than 3", so by him doing 2.5" I figure he is making himself lose power instead of gain.

 

wat was the outcome??

 

assuming that before this, both cars had stock exhaust, your brother wont be losing hp with the 2.5in exhaust. he just wont be gaining as much as if he had a 3in setup. although the difference between the two wont be that much. if he was goin from a 3in like what you have to a 2.5in, then he will be losing hp. but again, the difference will be minimal.

as far as torque goes, the smaller 2.5in diameter piping creates a bit more beackpressure than 3in piping, which IIRC helps torque a little. i forget the reason why this is.

just curious, what kind of headers and y-pipe do you have?

 

Hooker 2460 Ceramic Coated with Hookers y-pipe (2.5" y-pipe)

I just wanted to know who you guys thought would make the most out of theirs.

As my car isnt coming out until spring 08. His is coming out this weekend, and were gunna go dyno it in and Ill let you guys know how it goes. Ill get video and sheets.

 

I don't think 2.5" exhaust is hurting him signifigantely. If anything, it may build better scavenenging sooner in the RPM range where the 305 is strong.

Your 3" cat back is negated by a 2.5" cat, you're flow is only as good as your tightest bottleneck. But mild cam and intake says it all, assuming he's properly tuned and geared, I'd think he'll pull on you no problem. Don't let people jerk you around think that 1406 Edelbrock carb is junk either, properly tuned the run quite well. (Stock its so lean my mild 305 was done pulling at 4000rpm, required a big secondary jet change, and some rod tweaks.)

 

im certain his setup will be better than yours... also for your info 2.5 pipe is good for 500hp or so.. so he has not bottleneck.. 3" pipe is good for 600hp.. i doubt both of you have enough power to out do yall exhausts anyway..

your cat will help your tq some, as its a nice bottleneck their... but still, i think his car will edge, he has mild cam, and rebuilt top end, with prob 1.6 rockers... also simply put his 600cfm carb will out do the tbi 500cfm or so...

 

Well it sound like you brother has more stuff done. I think he would win because his motor from what you said it is rebuilt alittle.

 

What cam/intake/heads is he running? Is it an LG4, or a TPI to carb swap? Defintely interested to see where he's at power-wise, sounds like a similar setup to mine. Of course that depends, everybodies definition of a mild cam is different...

 

Thanks for all your comments.

I know he'll beat me easy because he also has the 3.42 gears because it used to be a V6...as opposed to my 2.73's.

As for tuning not much can be said as it JUST got timed. So tuning comes next but as my brother being the non-tuning knowledge guy I dont think it will be setup for the best.

Well since I now know Im in the crapper under his ***, what would you guys suggest I get next? To ENSURE I beat him?

I was thinking along the lines of Richmond (lightweight) 4.10 gears, Trans Go Shift Kit, a 10" TC from Pro Built Automatics and Hurst V-Matic 2 Shifter. Gears are like $???, Shift kit is like $80 (tops) and the TC is $600 and the shifter is $210

Gears = Waiting for e-mail.
http://www.richmondgear.com/01pdfs/RICHLITE.pdf

Shift Kit
https://www.700r4l60e.com/store/prod...p?productid=72

TC
https://www.700r4l60e.com/store/prod...&cat=59&page=1

Shifter
http://store.summitracing.com/partde...&rsview=sku&Ns

Let me know what you guys think. Thanks ALOT...as my biggest concern is getting all this in time for spring and installed.

 

Converter and shift kit, defintely. Gears, 4.10's might be more than you want, especially if this is your daily driver. Sticking a launch with converter, a 700R4's super low first, and street tires with 4.10's is gonna be complicated. What stall speed are you looking at? Shift looks expensive for zero gains, but to each their own. I'd spend $200 on roller rockers, lcarbs, good rear tires, just about or anything other than a cosmetic part inside that car.

I don't know a lot about TBI, but I'd think I've heard there is some valuable gains to be had with adt'l tuning. Making the intake side of the motor breath easier wouldn't hurt I'm sure.

 

Around a 2600-2800 stall.

I figure since I have a 305 with no top end keep this thing bucking off the low end....would you recommend 3.73's?

Well I will go ahead and forget the shifter.

Just keep letting me know, I want the best street capable setup.

And which of these would you say would work best as I am going to in the future buy GM's FastBurn heads.

http://store.summitracing.com/Compar...KU=HUU-3838521

 

And as far as tuning goes. I think I quoted myself around $500 to start, with 2 chips, a laptop and all connectors/adapters, plus program.

I havent been in this thread for a little while now so i have lost my knowledge on tuning...but not for long.

I'd like to do tuning too but dont want to mess with emission settings until I get this thing checked.

 

If you want to beat him, you need tuning equipment, knowledge to tune, and cam it. That would actually probably do it for you (after the shift kit, tc, and gears(4.10's too much, I prefer 3.42 or 3.73 make sure you get a posi setup too). That'd make you somewhat equal to him and then if you tune it perfectly the FI will outduel the carb I think.

You say Fastburns in the future, remember that those are vortec style heads, so I wouldn't bother buying an intake manifold now if you can't use it later. Not much of a gain there anyways.

Also, somebody said up there the difference was your 500cfm TBI vs 600carb. This doesn't matter at your levels. As long as you get enough air and fuel to feed the power of the engine it doesn't matter where it comes from.

 

if you want a quick easy method to beat him throw a cheap nitrous kit on your car. its easy to install takes very little time and you dont have to learn how to tune or touch the internals of your motor.

 

He has got you with the Van 305, assuming it is a 1981-1986 build. That engine is equivalent to the L69. This is how mine ran with just a TPI setup and Tri-Y headers, in a 5,500 lbs van.

http://youtube.com/watch?v=UEeZ5ruugWA

http://youtube.com/watch?v=PX5Av4pS1RA

 

If you need a set of gears I have a set of richmond 3.42's brand new in the box that I'm trying to get rid of. let me know.

 

Fast, i have a GMC vandura 2500 350 tbi 4 bolt mains convertion van ha wat should i do to it, i have a flowmster 50 series on it, wit the stock 3 inch exhaust wit no tailpipe