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why does my 383 suck? >> now a crack??

ashman

ashman

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I've been exploring dropping a 6.0 in my truck for quite awhile because I'm unhappy with my current engine. plus I want EFI pretty badly.

However, every time I mention that I have a 383 people react like it should be a sweet motor, but it's not. This has always puzzled me because I just haven't been impressed with it. Then, this past weekend while camping one of the guys up there mentioned that he thought my truck sounded like it needed bigger exhaust and it got me thinking... maybe I've just set this thing up all wrong. If I set it up correctly maybe I will like it after all. :dunno:

I've decided to give it a shot before I proceed with a swap, so hopefully you all can help me figure out what I'm doing wrong.

current setup:
stock exhaust manifolds, dual 2" all the way out the back.
edelbrock carb 600 I think.
HEI ignition all stock GM stuff.
I'll have to check on the heads, but I'll assume nothing fancy there.

The biggest issue I have at the moment is pinging. I've adjusted the timing all over the place and even using 91 octane gas I get pinging. I can't really put my foot in it at all because if it. Solving that issue would be first priority. Hard to get any low end torque if you can't give it any gas for fear of pinging. :confused:
 
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#1 problem is the pinging, if that's what it's doing. What's your timing set at?

#2, what carb do you actually have and has it been tuned to your engine/altitude?

Your 2" exhaust is absolutely not the problem.
 
Do you have your camshaft specs on hand? If it were me I'd say the exhaust is on the smaller side as well as the carb but that also depends on what your cam/head combo is.
 
yeah, something's not set up right... if it's pinging, it's not running right...
 
Sounds like a lean problem. Have you put a light on your timing to see what it actually is?

A 600cfm carb on that motor should make awesome low end torque. You could also have trouble with your cam-crank timing via the timing set. Who built the motor for it?
 
There are a few causes of pinging but my guess is the compression ratio is too much. Lots of people want to build an engine with more compression ratio than what is really needed because they think that will give you more power. In a heavy vehicle you want to stay as close to 9:1 as possible to prevent having detonation issues like you're having now. Also that exhaust is too small. I would recommend a single 3" exhaust with headers.
 
Agreed with a few exhaust is too small. Either a full 3" single (from headers back) or 2.5" (of course headers back) possibly with a crossover (often overlooked, but very good for even exhaust scavenging)

On to the pinging, once you've verified your timing is good, you'll need to make your AFR (air fuel ratio) correct, you could try some octane booster, if its still pinging, otherwise it'll require a drop in compression,(most likely)

But being the internets we don't know all the specifics, so it's hard to diag. I'd def start with the timing, what plugs are you running and AFR that's got to be right a good wideband AFR gauge goes a long way into knowing what's goin on in the engine.
 
I have a 383 w/ dual 2" out the rear, 8.5:1 compression, mild RV cam. I am happy with the power from this motor :D. I did have some carb problems, but it still made good power on the bottom end.

Seems like fixing the pinging would be a good place to start.
 
2" works lots of y'all have proven that but I stand by the science of physics, that although bigger isn't always better, there is a size something should be for best efficiency.

http://www.magnaflow.com/wideopen/performdata.asp
http://www.exhaustvideos.com/faq/how-to-calculate-muffler-size-pipe-diameter/

Examples.

There is something to be said for torque, but if a guy has a dual plane intake(torque maker) and long tube headers (torque maker) there should be plenty of torque W/O causing basically a restriction, maybe not noticed with factory heads, and close to factory cam specs, but drastically affects performance heads and cams.
 
TerryD said:
Sounds like a lean problem. Have you put a light on your timing to see what it actually is?

A 600cfm carb on that motor should make awesome low end torque. You could also have trouble with your cam-crank timing via the timing set. Who built the motor for it?
Click to expand...
Yeah, I put a timing light on it a few months back and set it to what the book said. 8-10 degrees I believe. I'll get out there tonight and check it for sure.

The motor was just built by some guy that was recommended to me so I guess it's possible something got screwed up. A few years back I did have a belt come off and overheat enough to warp a head. I replaced the head so maybe I screwed something up. I don't remember if I had the pinging issue before that or not.

Is there a tool I can use to test the compression ratio?
Is it possible that my timing is right at idle but that it's not advancing correctly and that is the problem?
 
myk5rox said:
2" works lots of y'all have proven that but I stand by the science of physics, that although bigger isn't always better, there is a size something should be for best efficiency.
Click to expand...
Sounds like bigger exhaust and headers is something I need to do, but not my first stop on the "fix it" path.
 
I dunno bout other's experience but I never set timing by the book unless I'm working with stock stuff. Otherwise I crank that ish up til it knocks on the starter, then dial it back, not really helpful I know, but tis what I do for power,
 
figure out your pinging problem first. Don't do anything till then.

Do you have specs for the motor????

Kind of need more information.

Whats your daily driver. I mean if you drive a Ferrari 455 (:haha:) for a daily driver you might be disappointed in your 383:haha::haha::haha:


Do a leakdown test on it. IMHO compression tests are useless
 
A gasoline IC engine is an air pump. The easier the air flow, the more efficient.
So, larger exhaust would probably help. But you get into laminar vs turbulent flow, and sometimes smaller is better.

But, there are several engines in this forum alone, that are working fine with that size exhaust, so I would tend to suspect other problems.

Which brings us to the pinging.
Remember what pinging is: Its the fuel igniting way before it should while the piston is headed up.
So, instead of suppling power to the engine, it actually acts against it.
It not only burns gas that you should be using for power, it is slowing the engine down and making it work harder to just run.

While damaging the engine at the same time.

Plus, if you have a working knock sensor, the computer will reduce power to try to eliminate the ping.

So, the result is, your engine will suck. And have a shortened lifespan.

There are so many things that could cause this, but try the timing first.
Its the most common and easiest to adjust.
 
I would get the pinging under control. Its either in the timing or carb itself. Its possible your cam vs crank timing is advanced and messing with you as well. Also your vacuum advance, or mechanical advance could be kicking in to early, or to far in total timing, causing the pinging as well.

Dont waste money on 2.5in exhaust if your running manifolds, you will probably lose power anyways because the gasses will cool and you will lose velocity. Headers will give you more power with that 2in vs manifolds and 2.5.
 
need to work out timing. Need to know if mech advance is working, and how much. setting base time is pretty useless unless you know what total timing (and curve) is going to be.
 
get the cam specs and compression ratio...

a lot of folks go with too big a cam, causes a plethora (word of the day:D) of problems.

a well built 383 is a beast of a motor...
 
blazinzuk said:
figure out your pinging problem first. Don't do anything till then.

Do you have specs for the motor????

Kind of need more information.

Whats your daily driver. I mean if you drive a Ferrari 455 (:haha:) for a daily driver you might be disappointed in your 383:haha::haha::haha:


Do a leakdown test on it. IMHO compression tests are useless
Click to expand...
Unfortunately I don't have any specs on the motor. I'll just have to get whatever information I can by testing it.
I drive an SHO which is sweet, but certainly not enough to spoil me from massive power. :haha:

I've never done a leakdown test. what is involved? can I rent the tool?
 
black dawg said:
need to work out timing. Need to know if mech advance is working, and how much. setting base time is pretty useless unless you know what total timing (and curve) is going to be.
Click to expand...


yup..... I set timing in carbed gas boats at 3200 rpm's.. all in... total is what's important.... especially if your advance is f*cked up... :haha:
 
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