My 1970 Chevelle with LSx power

[1fast70]

Hey all, I have decided to start a new thread on my car as the original one was deleted.

I am eventually planning on adding exhaust dumps to the Chevelle hopefully before race season, as I believe that my small 2 1/4 pipe size is probably not helping even the baby 5.3. I figure I'll come out of the headers with three inch pipe, do the dumps, then connect to my exhaust system's smaller pipe again.

I also plan on buying a fiberglass cowl induction hood to shave a bit of weight off the front of the car!

[1fast70]

Here are the current specs on the car :

Engine: 2007 5.3 with 27000 miles
Custom ground roller cam for carb application
Patriot Gold dual valve springs
Edelbrock Performer RPM intake w Holley 650cfm double pumper
Edelbrock A-body LS swap headers / full 2.25" exhaust
MSD 6010 standalone ignition system
Edelbrock conversion mounts / custom built frame mounts
JZ Motorworks LSx oil pan with low profile sump
Kwik Performance alternator bracket
custom aluminum valley cover / custom PCV system

Trans: TCI Streetfighter TH-350
Allstar Performance 3000rpm converter
Cast aluminum pan / large aftermarket cooler

Rear: Quick Performance A-body 9" Ford housing
Ford 3.88 gears w Detroit True-trac
UMI Performance upper / lower tubular contol arms
New Ford 11" drum brakes

Misc: B&M front line lock controlled by steering wheel horn buttons
Column shift for that sleeper effect
Aftermarket tach / gauges
Aluminum 4-core radiator w dual Flexalite e-fans
Converted to manual steering
Carter 100GPH electric fuel pump mounted by tank
Bolt-in driveshaft loop

[96gtdan]

HMMMMMMMMMMM lazy no! Motivation maybe sometimes lacking lol. I know the feeling though im in that boat to. Lookin forward to seeing that grocery getter run 12s.

[Jake]

You may not be able to but if you can try and merge the exhaust into a single 3in then put a cutout on it. I ran the duel 2 1/4in on my truck and went the open single 3in and picked up boat loads of low and mid range torque..

[John]

LOL

[1fast70]

Jan 17, 2011 23:18:26 GMT -5 Jake said:

You may not be able to but if you can try and merge the exhaust into a single 3in then put a cutout on it. I ran the duel 2 1/4in on my truck and went the open single 3in and picked up boat loads of low and mid range torque..

Interesting. I wish I would have went right to LSx power in this car when I first bought it, as I wouldn't be stuck with my currently restrictive exhaust system....I could have done something like that. With what the exhaust cost me though, it will have to stay.

Any suggestions on how far away my dumps should be from the header collectors?

[CHRIS]

Honestly exhaust should be fine. 2 1/4" exhaust will handle more then what your making right now.

[1fast70]

Jan 21, 2011 8:51:55 GMT -5 CHRIS said:

Honestly exhaust should be fine. 2 1/4" exhaust will handle more then what your making right now.

You really don't think 2 1/4" inch full exhaust that isn't mandrel bent (see pics) is restricting the 5.3? Interesting. Do you think dumps would do anything for me.....like maybe turn my 13.1 into a 12.9 on a good night?

I guess I'm just going off of Dan's experiences with how his car slowed down after he put his exhaust on, even though it is a 3" monster.

Al if you see this, does your Camaro pick up any time with the exhuast opened up?

[CHRIS]

All you'd have to do it run it open header one time at the track back to back with full exhaust and see. Ive never liked running open header. Its just my opinion though. Ive always had full exhaust. 2 1/2" duals will support over 500rwhp so I dont think the 2 1/4" is really going to hurt that much.

[Jared]

I think you will see a gain with cutouts. My brothers truck cam only 5.3 has dual 2 1/2 and he has ran through his mufflers, then opened his cutouts and picked up almost 2 tenths and over a full mph. He has his located around 1 foot behind the manifolds.

[Alan]

I would 2nd the tubing size upgrade. Mine slows down .3 between cutout on/off. I noticed it between racing Friday nights and then turning around and racing street class Saturday's, this was taking D/A into account. BUT, i'm running through a stock, known restrictive WS6 Muffler.

Dan's is a good comparison in a way, but he's got high flowing aftermarket heads. However, his did suffer significantly in MPH from adding the small mufflers he did.

the best two back to back comparison's i've seen are J's truck and Jared's SS. Both got around .1-.3 on the same night just opening up the cutouts. Not having mandrel bent exhaust and being smaller diameter definately isn't helping the situation like you said.

I wouldn't expect a huge gain, maybe .1 or so unless we have a severe restriction/flow problem due the exhaust design.

If you're going to do stuff to it later, no reason not to go bigger, even if it may seem to much at the time being.

[Jake]

I think the duel 2.25in pipe is big enuf for what the engine is making as long as it was just flowing throw a staight pipe. Now all the bends you have plus the mufflers it is hurting you on power. I too gained .1 with my 5.3 with the cut out. From what we have seen its mostly mid range torque you gain with open exhaust. But you also need a 3600-3800 stall for that cam..

[John]

Alot of people are always telling me "so and so will support so and so much horepower...", BUT that doesn't mean you wont gain any if you upgrade anyway... An example, people say, "a stock MAF will support 500+HP", but, I've heard anywhere from 5-20 hp gained by removing it all together, on a dyno with a 350-450 hp engine... Hmmm..... Just sayin...

But, too big can hurt too, I'd recommend either dual mandrel bent 2.5" (thats what a stock 5.3 has up until the Y-pipe in a truck), or a single 3-3.5" exhaust, and YES, cut-outs help! My bro gained .1 sec in his truck, ant the only thing after the cut-out was about 6" of same diameter (3") pipe, 3" SI/SO Flowmaster and a mandrel bent turn-down.

[Jared]

I agree and disagree at the same time. I believe to big will never hurt. If you know how engines work there really isn't a horsepower number it's based off of torque. You will never lose torque from exhaust, it just moves the power band up or down, so If you have 2 1/4 it will feel much faster off the line and midrange, but if you have dual 3'', if will feel a little sluggish off the line but scream up high. And since ED you have a converter who needs low end torque. I think dan proved this to you all. He had 3 1/2 open header and slowed down quite a bit with dual 3'' with mufflers. Just look at it this way. Having huge exhaust after the headers isn't any different then just having open headers. An engine is a pump get air in faster and out faster= more power. Hope this helps ED.

[John]

Too big of a pipe causes turbulence and slows air velocity down, therfore creating backpressure and decreasing the scavenging effect, something you DONT want in an exhaust system. I had a personal experience with this. I had an 03 Dodge Ram Hemi with full boltons. I had the Headman LT's with the 3" Y-pipe and cut-out, well I figured, bigger is better! so I brought it to an exhaust shop and had them build me a 3" dual exhaust with dual Flowmaster 40's. I had a G-tech that I ran consistent 14.2-14.4's on and with the duals the best I EVER did in the couple weeks I had it on was a 14.6, and consitently between 14.7-14.9. It was also very noticeable that it was slower when compared to other vehicles I raced. Well, you could try to blame it on weather, DA, etc. but after a couple of weeks I bought a new Y-pipe and and put it back on with a single Flowmaster and gained my power back.

However, I do agree that the big exhaust doesn't hurt you IF you only have a short amount of pipe. If you want to run a full length exhaust (like I did on the Hemi), you can DEFINITELY go too big. If too big, then the longer the pipe, the more turbulence. IMO, with open headers, there's not enough pipe there to create enough turbulence to cause any backpressure, thats why most of the time your faster with open headers.

I also had a 3" Y-pipe with a single cut-out on my 6.0 in my Silverado, and that thing ran damn good! Not saying that it couldn't have been faster with a different exhaust, but rather that it obviously performed very well with only a single 3".

I've got LOTS and LOTS and LOTS (LOL) of research behind me, since back in the day when I used to drag race 4-wheelers, I've been constantly researching anything and everything I can about exhaust. This is why I stand firm in my argument.

Dam, that was alot of work LOL I hope someone finds it useful Mabe I'm full of shit but from the 7-8 years of research I've done, thats what I've learned. ;D