Here in NY private sellers and junkyard sell used engines for 1,200 and up! OUCH

Once in a blue moon company here sells crate motors on sale for $1,200 plus core, tax, and shipping and handling!

OUT!

Is there something terribley wrong with this picture that a 383 only 205hp? I know torque is what counts...but still think it would put out better numbers.

Unless you have non ethonol fuel dream on you will never see 20 mpg. My brother has an 01 he used to see 20+ quite frequent (drives like an old man 55 max) with the shit fuel we have now hes lucky to get anywhere close to 18. My truck has gotten worse to usually 13 or so around town witch is close to about the same as it ever did stock the 383 hasnt really changed my milage.

Crazyhoe i got the 383 from gm that comes compleat except the intake i used to stock one off my l31 abd upgraded the spider. I am planing one a diffrent intake soon i want the eddalbrock pro flo and im hoping ill get better performane out of the truck no matter the engine. As far as restriction the only thing i can think of is maby spark curve or fuel i know its not exhaust because theres no cats with flowmasters on it. Im trying to figur out if i need to get more tunning done or if i need to try somthing else

Dont get a different engine, get some tuning..... You can toss all the engines you want at it but at the end of the day if the computer isnt tuned then your smoking $100 bills.

$3,500 Ht383e
$400 New spider assembly
$500 for blackbear tuning
Increased power, and mileage, Priceless!!!!!

GM makes it clear that the HT383e engine needs tuning, the stock parameters wont cut it. Blackbear Performance will send you data logging equipment you attach to the truck and drive around for a while, take it off and send it to him and he will then use that in conjunction with tuning your computer. If you are limited to a mail order tune that this the best alternative you have. I have not used Blackbear, but in reading how he does it he at least talks about going about it the right way. Tuning on just a dyno, only on the road, or based off some stock parameters isnt the way to do it. You need to use all three...

You mentioned scrapping the intake and going with a pro flow, you will need to have that tuned as well. Dont kidd your self Edeljunk is not going to be any better than your current situation.

How are you running no cats in California??? Put some cats on the thing you need some back pressure.....
TJ

98Blackss wrote:

Put some cats on the thing you need some back pressure.....
TJ

I don't subscribe to that belief.

My tuck ran strong with out cats (it was tuned for that). But I put them in anyway as the stink was ridiculous. And it was returned and ran just the same.

Agreed, Today’s catalytic converters aren’t the power robbing monstrosities they used to be. There is no good reason to not have them……

You can have too little back pressure though and that will rob you of torque in the motor if its not tuned for it... I used to hack off the mufflers and put mandrel bent pipe with free flowing mufflers in my youth. I quit that when I lost low end power in my 2000 S-10 ZR2 4.3L. It sounded nice but geez what a pig it was.

When I got my current truck it had glass packs dumped before the axle. I took that off and put on the Gibson cat back side exit and both mileage and power were seat of the pants noticabley better.

TJ

98Blackss wrote:

Agreed,
You can have too little back pressure though and that will rob you of torque in the motor if its not tuned for it... I used to hack off the mufflers and put mandrel bent pipe with free flowing mufflers in my youth. I quit that when I lost low end power in my 2000 S-10 ZR2 4.3L. It sounded nice but geez what a pig it was.


TJ

It's been a while that I've read about the effect of back pressure on a stock engine and the effect it had on the torque.

It had more to do about the effect of pressure waves inside the exhaust that played a role on scavenging and exhaust reversion.

Having back pressure, slowed down the waves IIRC, and freeing the exhaust altered the resonance in a way that was non constructive for intake and valve-train timing at low rpm, but could have been fine with different components.

I don't recall if it simply moved the power ban and/or if it was possible get back the same torque curve by timing the valves differently. Anyway, it was D.V. that wrote about this.

Here, enjoy reading this:
Hehe.

Quote:

You may be inyerested or wish to comment on the following written by a fellow MG owner

Exhaust tuning theory is actually fairly simple, it’s all about getting the negative (and, hence, scavenging) pressure pulse to arrive at the exhaust valve as it is opening. To do this we have to set the pipe lengths and diameters correctly.

The formula for Primary pipe length is:

P = [(850 x ED) / RPM] - 3

Where:
RPM is the engine speed to which the exhaust is being tuned.
ED = 180° plus the number of degrees the exhaust valve opens before BDC.
P = Primary pipe length (on a 4-1 manifold), or Primary pipe length plus Secondary pipe length (on a 4-2-1 manifold), in inches.

Generally road engines will require the manifold to be tuned to the max torque rpm whereas race engines will be tuned to work either at max bhp rpm or a speed midway between the max bhp rpm and max torque rpm.

4 -1 manifolds restrict the the power band whereas 4-2-1 manifolds give better mid-range power but reduce top end power by as much as 5-7%.

Generally speaking with a 4-2-1 manifold the starting point for Primary pipe length is 15 inches, thus Secondary pipe length is P - 15 inches. Changing the length of the Primary pipe tends to rock the power curve around the point of max torque. Shorter Primaries gives more top end power but less mid-range, and vice-versa. There is, however, little change in the peak torque or the rpm where this occurs.

Ideally the Primaries should come off the cylinder head in a straight line for around 4 inches before any turns occur.

Inside diameter of the pipe can be gained from:

ID = ? [cc / {25 x (P + 3)}] x 2.1

Where:
cc = cylinder volume in cc.
P = Primary length in inches.

In some engines it can be useful to have a 'step' between the exhaust port and the Primary (ie the Primary bore is greater than that of the exhaust port). This tends to be the case in engines with rectilinear exhaust ports.

For a 4-2-1 system then, Primary pipe diameter is calculated as above. Secondary pipe diameter is given by:

IDS = ?(ID x ID x 2) x 0.93

Where:
ID = calculated inside diameter of the primary pipes.

The pipe diameter can be used to change the peak torque rpm – a reduction in diameter of 0.125 inches will drop the peak torque rpm by 500-600 rpm in engines over 2 litres and by 650-800 rpm in smaller engives. Increasing the pipe diameter by 0.125 rpm has approximately the opposite effect.

The total length of the Collector and Tailpipe (to the front of the silencer) sould be equal to P + 3 inches (or any full multiple of P + 3 for a road car).

Tailpipe internal diameter is given by:
IDT = ?[(cc x 2) / (P + 3) x 25] x 2

Where P is calculated as above.

Collector length is given by:

CL = [(ID2 – ID3) / 2] x CotA

Where:
ID2 = diameter of Collector inlet
ID3 = diameter of Collector outlet.
CotA = Cotangent of angle of Collector taper (which ideally should be around 7-8° (certainly less than 10°).

The design of the collector should be such that the inlet pipes terminate abruptly otherwise the tuned exhaust pressure wave will carry on into the tailpipe and the calculations done to get the negative scavenging wave back to the exhaust valve on time will all be wrong.
NormPeterson (Structural)
4 Jan 07 16:21
(1) Am I to read the meaning of "?" and "x" in formulas such as

"ID = ? [ cc / {25 x (P + 3)}] x 2.1"

to read as follows when written in Excel

"= 2.1 * SQRT[ cc / {25 * (P + 3)}]"


(2) Does the "25" in the formual for IDT belong in the numerator or the denominator?

Ok, it's in the book "How to Build Max-Performance Chevy Small-Blocks on a Budget", and also: "How to Build and Modify Chevrolet Small-Block V-8 Camshafts and Valves"

So, if you alter the back pressure, the overlap has to be altered also.

Quote:

“I have found that reducing exhaust backpressure always improves power and fuel economy, providing, of course, the air/fuel ratio and ignition timing are carefully optimized both before and after exhaust system backpressure is decreased”

Last edited by CrazyHoe on Tue Jan 10, 2012 11:49 am; edited 1 time in total

Luvss wrote:

Crazyhoe i got the 383 from gm that comes compleat except the intake i used to stock one off my l31 abd upgraded the spider. I am planing one a diffrent intake soon i want the eddalbrock pro flo and im hoping ill get better performane out of the truck no matter the engine. As far as restriction the only thing i can think of is maby spark curve or fuel i know its not exhaust because theres no cats with flowmasters on it. Im trying to figur out if i need to get more tunning done or if i need to try somthing else

For street drivability, the OEM intake is going to be hard to beat.

The way i can get away with no cats aspecaly in cali is im in the army and only stationed here. Im from oregon where the is no smag laws we dont get our vehicle checked at all... Yet And the truck is tagged for oregon and my permanet address is there also.
I have had it dyno tuned once and i have bean talking to justin at blackbear but havnt had the money to get any tuning done by him yet befor i switch engines im going to let him have a shot at it first and i will see what hapenes from there but i need to get an engine back in the truck that will do better on gas than this one is right now a 1000 mile trip home cost me in gas $750 round trip i made the trip 3 times with the old 350 and it cast about 450-500 round trip.

I think i am going to change intakes just to get a better fuel system on the truck. I read somewhere that the 383 maxes out the stock intakes air flow and fule?


When i took the cats off i got more power and milage out of the 350. Could it be diffrent with the 383?

Luvss wrote:

When i took the cats off i got more power and milage out of the 350. Could it be diffrent with the 383?

No, could have been partially clogged, maybe not good flowing cats, your fuel map maybe altered.