383 running rich, using gas like crazy! Help!

[Billccm]

What I do know is that I'm pulling 20 inches of vacuum

WOW! On my 383 11.5 inches was the best I could get. I believe 14 inches was the most I ever saw on various MOPARs?

My 383 runs rich (at least the exhaust smells rich at idle), but I do not have a black soot issue. I have not checked MPG, but for what little I have driven it I think it's pretty good as my last fill up was only 2.2 gallons and that is after idling it off and on for several months during my disc conversion and then a 20 some odd mile round trip with several rounds about my neighborhood testing and bedding the brakes.

Watching this thread and good luck to you.

 

[moparnation74]

WOW! On my 383 11.5 inches was the best I could get. I believe 14 inches was the most I ever saw on various MOPARs?

My 383 runs rich (at least the exhaust smells rich at idle), but I do not have a black soot issue. I have not checked MPG, but for what little I have driven it I think it's pretty good as my last fill up was only 2.2 gallons and that is after idling it off and on for several months during my disc conversion and then a 20 some odd mile round trip with several rounds about my neighborhood testing and bedding the brakes.

Watching this thread and good luck to you.

Even though this is a 440....This is the engine just recently done for my GTX over in my build thread in the restoration section here...Look at the vacuum gauge reading....

 

[PurpleBeeper]

Hey Triple Black -
1. Fuel pressure should be about 5 psi
2. It definitely sounds like a carburetor issue - It sat for 20 yrs? That carb needs a rebuild because almost certainly the gaskets dried out. You might try some fuel injector cleaner (2 bottles of the cheap kind) to clean out fuel varnish in the tank, pump, lines, etc.
3. Tune Up
a. Put copper plugs in the engine @ 0.035" gap. I prefer Champion (original)
b. After engine is completely warmed up, connect timing light to battery +/- and #1 cylinder's plug wire (front one, driver's side).
c. disconnect & block off vacuum advance hose
d. timing light is a "strobe light" - point it at the timing marks on harmonic balancer/timing chain cover & you can see what your initial timing is. Record this value.
e. You can adjust the timing (more advanced or retarded) by slightly loosening the one bolt at the base of the distributor & turning the distributor slightly. With the engine running & the timing light pointed at your timing marks (balancer/timing cover) you can "see" the timing change as you rotate the distributor. 10-12 degrees advanced at idle is a good place to start.
f. Tighten bolt down again & record what your new timing advance is, then re-connect the vacuum advance hose.
g. Idle fuel mixture - attach a vacuum gage to the engine. There's usually a "T" near the back of the manifold where the brake booster connects that you can tap into. Turn the idle mixture screws in/out very slowly, one at a time to maximize the vacuum reading at idle. By slowly I mean, turn a 1/4-1/2 turn, wait 60 seconds, check vacuum & repeat. Again, one side at a time. The idle mixture screws are the two big screws with springs on the front of the carb right at the base.

Now.... go drive it. Floor it up-hill & check for "knock" or "ping" and overall performance. In general, you want the timing as advanced as you can get it (without "knock") on whatever fuel you're running.

 

[Triple Black 73]

Hey Triple Black -
1. Fuel pressure should be about 5 psi
2. It definitely sounds like a carburetor issue - It sat for 20 yrs? That carb needs a rebuild because almost certainly the gaskets dried out. You might try some fuel injector cleaner (2 bottles of the cheap kind) to clean out fuel varnish in the tank, pump, lines, etc.
3. Tune Up
a. Put copper plugs in the engine @ 0.035" gap. I prefer Champion (original)
b. After engine is completely warmed up, connect timing light to battery +/- and #1 cylinder's plug wire (front one, driver's side).
c. disconnect & block off vacuum advance hose
d. timing light is a "strobe light" - point it at the timing marks on harmonic balancer/timing chain cover & you can see what your initial timing is. Record this value.
e. You can adjust the timing (more advanced or retarded) by slightly loosening the one bolt at the base of the distributor & turning the distributor slightly. With the engine running & the timing light pointed at your timing marks (balancer/timing cover) you can "see" the timing change as you rotate the distributor. 10-12 degrees advanced at idle is a good place to start.
f. Tighten bolt down again & record what your new timing advance is, then re-connect the vacuum advance hose.
g. Idle fuel mixture - attach a vacuum gage to the engine. There's usually a "T" near the back of the manifold where the brake booster connects that you can tap into. Turn the idle mixture screws in/out very slowly, one at a time to maximize the vacuum reading at idle. By slowly I mean, turn a 1/4-1/2 turn, wait 60 seconds, check vacuum & repeat. Again, one side at a time. The idle mixture screws are the two big screws with springs on the front of the carb right at the base.

Now.... go drive it. Floor it up-hill & check for "knock" or "ping" and overall performance. In general, you want the timing as advanced as you can get it (without "knock") on whatever fuel you're running.

Thanks man! I'll do this. I see I made a minor mistake by leaving the vacuum advanced attached when setting the initial timing.

The carb is a reman Summit Racing Thermo-Quad with parts number showing it's for a '72 400 : https://www.summitracing.com/ga/parts/sum-210232/overview/ (Looks like I bought the last one, lol)

 

[Triple Black 73]

WOW! On my 383 11.5 inches was the best I could get. I believe 14 inches was the most I ever saw on various MOPARs?

My 383 runs rich (at least the exhaust smells rich at idle), but I do not have a black soot issue. I have not checked MPG, but for what little I have driven it I think it's pretty good as my last fill up was only 2.2 gallons and that is after idling it off and on for several months during my disc conversion and then a 20 some odd mile round trip with several rounds about my neighborhood testing and bedding the brakes.

Watching this thread and good luck to you.

It's all about the cam. I had a major issue with a CS-661 cam that didn't pull 3 inches of vacuum due to low compression, retarded timing gear set, and a wide LSA. I pulled the cam and replaced it with a CompCam XE256 along steel shims, timing gear, and springs, etc. Now the engine draws a ton of vacuum along with a TON of torque down low. The CompCam CamQuest tool estimated torque to be around 460 at 2,500, however my experienced butt would say it's closer to 375 @ 2500 right now. I know there's more in the engine once I get the carb set up right.

 

[coloradodave]

That's amazing. In over 55 years of working on cars I've never known anybody who could rate torque foot lbs. with their butt. You're to be congratulated...lol.

 

[Triple Black 73]

That's amazing. In over 55 years of working on cars I've never known anybody who could rate torque foot lbs. with their butt. You're to be congratulated...lol.

I have driven many cars and trucks of all sort of power. If you know the weight, gear, speed, and time to reach a speed one can extrapolate an very good estimate of power. LOL!

 

[Triple Black 73]

UPDATE: Thank you everyone for the help and resources. I got engine running like a top now! The idle was set too rich and the secondary bar wasn't adjusted right. I think I might have turned the cross bar set screw by accident. The timing was prefect (initial, mechanical, and vacuum advance). The exhaust smells great now, no soot, the engine idles like it should, and it revs like a beast.

I also figured where the gas is going. There is a pin hole leak in the old steel fuel line that's dumping gas onto the intake manifold evaporating it almost instantly. I found it while closely examining the fuel lines. I'm going to park it until I can get a new stainless steel line.

 

[miller]

For the heck of it, another suggestion, on your fuel lines. If they are fairly old, change each one, at the tank, and the pump, to Gates fuel injector rubber hose. The older fuel hose breaks down, with this new gas.

 

[PurpleBeeper]

UPDATE: Thank you everyone for the help and resources. I got engine running like a top now! The idle was set too rich and the secondary bar wasn't adjusted right. I think I might have turned the cross bar set screw by accident. The timing was prefect (initial, mechanical, and vacuum advance). The exhaust smells great now, no soot, the engine idles like it should, and it revs like a beast.

I also figured where the gas is going. There is a pin hole leak in the old steel fuel line that's dumping gas onto the intake manifold evaporating it almost instantly. I found it while closely examining the fuel lines. I'm going to park it until I can get a new stainless steel line.

SWEET! It feels good after all that frustration and hard work, doesn't it?

 

[Triple Black 73]

For the heck of it, another suggestion, on your fuel lines. If they are fairly old, change each one, at the tank, and the pump, to Gates fuel injector rubber hose. The older fuel hose breaks down, with this new gas.

All the rubber fuel hoses, from the tank to the carb, are new - GATES 27028 5/16". It's not fuel injection rated. In fact is says "do not use for fuel injection on it." Here's a link:

http://www.oreillyauto.com/site/c/detail/GATR/27028.oap

The steel lines are 5/16" original. The pin hole leak is in the hard line from pump to the carburetor. The hole is too small to see but drips when pressurized. I didn't replace the last last year because I wasn't sure which carb I was going to run. I've order a RPC7301S to replace it.

SWEET! It feels good after all that frustration and hard work, doesn't it?

Heck yeah it does!

...but finding a leak in the fuel system is scary as hell! If that thing caught fire.... I don't even what to think about it.

 

[miller]

All the rubber fuel hoses, from the tank to the carb, are new - GATES 27028 5/16". It's not fuel injection rated. In fact is says "do not use for fuel injection on it."

Description says for PVC.
Use what you want. Just going by what others have said, that the fuel injection hose, won't break down internally, from today's gas.

 

[Triple Black 73]

Description says for PVC.
Use what you want. Just going by what others have said, that the fuel injection hose, won't break down internally, from today's gas.

You're right. I'll pony up for Gates 27340. The hose isn't that much more and I need less than two feet of it (tank to line, line to pump, pump to carb line).

http://www.oreillyauto.com/site/c/detail/GATY/27340/N0887.oap

 

[Dragon Slayer]

I was going to say did you check for fuel leaks. 4-5mpg was too low to be just carb, without series engine running issues in my opinion. Glad you got it.

 

[moper]

I was reading the thread and all I kept thinking was the air door and step-up rod hanger need adjusting...lol. I LOVE the Thermoquads but it's a dying art to set them properly. Nice work.

 

[Triple Black 73]

UPDATE: I replaced the hard line and the rubber hose with the Gates FI hose. The line didn't exactly drop in however the hose was skookum as frig. I put 5 gallons in the tank since needle was sitting just above E. The gas needle settled just above 1/2 half. The 30 mile trip moved the needle to the other side of 1/2. That's more like it! I also increased the timing to 40 all in at 2500 and 14 at idle to correct a stumbling issue at going from cruise to WOT. Here's a video of cold start and idle: