4.3L Upgrade Questions

[BlazerBoyLT98]

Originally Posted by Blazerboy1287

oh yeah, and here's the sound clip from mine... file link only lasts 14 days tho, i will try to find another hosting service

http://www.sendmefile.com/00077129

Not to go too far off topic but did you get your qoute from "The Boondock Saints"??

[04 Intimidator]

I've seen this pop up on many a performance board and you might be able to do these in a different order as you can with many other vehicles.

First point though: BlazerLT - I've seen a lot of your posts and you are a smart individual on many subject so I don't want to step on your toes on this. Nothing but respect here. There is a possible order change here though as I haven't seen any scientific data on other posts so far... It might have been covered but I haven't seen it.

It might be best to do: Intake, Chip, Muffler.

As everyone knows, the engine is nothing but an overglorified air pump. We need to find where the restrictions are to improve it. Does anyone have any dyno results on what happens when you pull the exhaust off, or the intake seperately? It has been found out on my 2004 Monte Carlo, that the exhaust doesn't really need to be changed until you hit generate more than 300 HP as it isn't that big of a restriction... the restriction is getting air into the engine. This is also on the 3.8 and 3.8 Supercharged version which is a dynamically different engine.

Does anyone know the volume of exhaust that goes out the stock mufflers compared to when you run strait pipe? Also if you pull the air box off and run stock mufflers if it changes in case the intake is choking the engine?

If we don't know these numbers, you always have to start with the intake then exhaust, then chip. If the stock exhuast is great, then you can change the chip as in the case of the Monte Carlo.

Another way of looking at it is air pump example. 1 inch intake tube to pump to 3 inch outgoing tube... doesn't make sense. Flip them around and you still draw the same as the air is not being forced into the engine, it's being sucked by the downward stroke of the piston. The best we can do is make sure the intake is good first, then worry about what is being squirted out the back. Especially if you go the low cost (which I don't recommend) method of cheap parts - Ebay intake $30, exhaust $120.

Hope this helps people.

Originally Posted by BlazerLT

1.) Muffler
2.) Intake
3.) Chip

TB Spacers are a waste on a 4.3L.

[herkyhawki]

Originally Posted by 04 Intimidator

Does anyone know the volume of exhaust that goes out the stock mufflers compared to when you run strait pipe?

The volume of exhaust going out, through a muffler or through a straight pipe will be exactly the same. The difference is in the amount of pressure required to push the exhaust through whatever restriction is connected to the exhaust manifold.
Mathmatically(simplified) PRESSURE multiplied by VOLUME = POWER. If volume is constant , but pressure increases, power(loss) increases.

[BlazerLT]

04 Intimidator,

Thanks for your input.

The thing is, there is not as much restriction in the short intake when compared to the 6 or so feet of exhaust running out to the rear of the truck.

Add in the fact that the huge stock muffler is a huge restriction and you get an overall bottleneck happening more in the exhaust that you will ever see in the intake.

There is no point in upgrading anything on the engine whether intake or chip until you have gone after the biggest power reducing in the 4.3L's path.

[04 Intimidator]

Originally Posted by herkyhawki

The volume of exhaust going out, through a muffler or through a straight pipe will be exactly the same. The difference is in the amount of pressure required to push the exhaust through whatever restriction is connected to the exhaust manifold.
Mathmatically(simplified) PRESSURE multiplied by VOLUME = POWER. If volume is constant , but pressure increases, power(loss) increases.

Whoops!! My bad on the terminology. herkyhawki is correct, we would want to measure the pressure and see how much restriction there is.

I'm also going to assume the BlazerLT knows from life experiance that the muffler is the bottle neck. Like I said looking at his previous posts in other topics I can trust him. In this case and the engine will gain HP by simply removing what is wasted by the piston trying to push the exhaust out.

BlazerLT - I don't want to word this in a negative way as it's not my intent. Do you happen to have some numbers on how much HP is gained by just removing the exhaust and running straight pipe?

[Macgyver007]

I am in process of trying to do some power mods to mine. I found the ECU programmer on e-bay for $100 so I got it, needless to say I have done ECU first, nice because it gives you the ability to return to stock with just a plug and 5 mins. i was going to try the intake first because of the $$ involved in the exhaust. However you all have brought up a good point obout the exhaust being done first. Do you think incrasing the size to 3inch from the cat back is enough? Would you not still have restriction in the manifolds and upto the cat?

[ZL1power69]

2.5 inch is as big as u wanna go with the exhaust. any bigger and you will lose power.

[black wall st]

The best and most efficient upgrade, somewhat affordable is called an LS1. But yes, it's called a scavaging effect, you want a certian amount of back pressure.

1. Cold air intake
2. Cat-back exhaust
3. Headers
4. Chip
5. TB Spacer
6. Thermost

before i upgraded to an LS1, i had an 00 4.3 vortec, .030 bore, forged pistons, stock crank, comp cam, 1.7 rockers, Stock ported heads, 5 angle valve job, fitted with oversized valves, 160* thermo, Headers, Catback exhaust, upgraded computer, corvette radiator.

[jackpot5283]

ive been wanting to build a 250 inline so bad for my s-blazer seems like the tbi is an easy swap to the inline plus inlines are soo hard to hurt. any previous experience would be helpful though ill update as i make progress. right now just bolted holley tbi on my stocker ill update after i put it through its paces

[ZL1power69]

thread is over 2 years old. your question does not relate to the topic so feel free to make a new thread about the 250.