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Discussion Starter · #1 ·
Got the ole 383 up on the dyno. Put down peak torque of 346 ft/lb at 3800 rpm and peak hp of 322 at 5700 rpm.

It’s weird to me to be making more HP than TQ with the 200cc heads. I was honestly hoping for something in the 375hp range.

Im definitely still learning how to tune a carb. I was just going off the AFR gauge which at idle reads in the 13’s...cruise is about 14-15, and WOT is 12 or so.

The truck has always smelled super rich but it has no cats and I figured that was why. I pulled a plug today when I got home and boy, is it black. Plugs have maybe 3,000 miles on them and look super rich. I realize the AFR/wide and is only reading one side of the motor but that’s the side I pulled the plug on. I’m thinking I may be running way richer than the gauge says and that’s hurting some power. Check this out, what do y’all think?
614781
 

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AFR gauge is telling you it is rich. The plug most definately is.

WOT the AFR should typically be 12.5-13.2 range.

Idle don't even worry about gauge reading, just get it to idle nice, don't target some reading just because you think it needs to be a certain number, and at idle it is hard to get repeatable numbers due to overlap, especially if you are open headers or short exhaust.

Cruise can be much leaner than 14-15, can be as high as 17 for best mileage.
You'll hear about how 14.7:1 is "perfect"...but that is just perfect as far as the chemical reaction is concerned, 14.7 part air with 1 part fuel is scientifically perfect(stoichometric)for fewest left over emissions, ....but we aren't racing in the science lab....best cruise mileage will more often be leaner than stoichometric.

Just offhand, looking at the plug, your idle and transition circuits are rich. That is what you are running on for your idle and cruise
 

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Discussion Starter · #4 ·
AFR gauge is telling you it is rich. The plug most definately is.

WOT the AFR should typically be 12.5-13.2 range.

Idle don't even worry about gauge reading, just get it to idle nice, don't target some reading just because you think it needs to be a certain number, and at idle it is hard to get repeatable numbers due to overlap, especially if you are open headers or short exhaust.

Cruise can be much leaner than 14-15, can be as high as 17 for best mileage.
You'll hear about how 14.7:1 is "perfect"...but that is just perfect as far as the chemical reaction is concerned, 14.7 part air with 1 part fuel is scientifically perfect(stoichometric)for fewest left over emissions, ....but we aren't racing in the science lab....best cruise mileage will more often be leaner than stoichometric.

Just offhand, looking at the plug, your idle and transition circuits are rich. That is what you are running on for your idle and cruise
I’ll try leaning out the idle/transition circuits. I did order a new accelerator pump kit, it’s got a bad initial accel lean, which seems to be pretty common. Do you think that’s why the plugs look so rich? Thanks for info also.
 

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What would you recommend? Also, dumb question, what makes it a race plug?
NGK-R plugs are their racing plug series. Normally race plugs are intended for higher RPM use which helps with keeping them clean. Around town idling at lights and stop signs plus lower speed cruising can lead to deposit buildup. They are also non-resistor plugs. I would look for one of their resistor plugs in the same heat range you have as a start and of course the correct plug reach and threads. On a typical street engine today, we expect to see the plug colored in with a white-ash look using unleaded fuels. Some combustion chambers are so efficient now that a plug will hardly show any signs of coloring.
 

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I’ll try leaning out the idle/transition circuits. I did order a new accelerator pump kit, it’s got a bad initial accel lean, which seems to be pretty common. Do you think that’s why the plugs look so rich? Thanks for info also.
How about a discussion about how to lean out the idle & especially the transition circuit ?, As you point out. these are what its running on a good share of the time .
 

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IIRC OP has an Edelbrock carb. This should be interesting! I know how to do it on a Holley or Quick Fuel with replaceable IFRs and IABs. No clue on Edelbrock - never had or worked on one.

Once you figure out how to adjust the carb for all things, you can take it back to the dyno - set timing to 34 total max and first optimize mix for the best power. Then optimize timing for the best power. This is called dyno tuning! You will need more than the 3 pulls usually given. I used a half-day of dyno time and yes they expect you to pay while you are working on it. You don't have to beat your engine all the way past 6000 RPM each time. Note the air density and AFR it was tuned at, for possible modification of mix later in year when temps/humidity is different. Adjust to maintain same full throttle AFR on your gauge.

Here are mine after dyno tuning and getting the correct plugs. I was told at least 3/4 of ring around electrode should be carboned up. Center cylinders on mine are a bit richer than the 4 outside ones ( I have a Vic Jr and QF SS830).

614782
 

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Discussion Starter · #11 ·
How about a discussion about how to lean out the idle & especially the transition circuit ?, As you point out. these are what its running on a good share of the time .
I
NGK-R plugs are their racing plug series. Normally race plugs are intended for higher RPM use which helps with keeping them clean. Around town idling at lights and stop signs plus lower speed cruising can lead to deposit buildup. They are also non-resistor plugs. I would look for one of their resistor plugs in the same heat range you have as a start and of course the correct plug reach and threads. On a typical street engine today, we expect to see the plug colored in with a white-ash look using unleaded fuels. Some combustion chambers are so efficient now that a plug will hardly show any signs of coloring.
Doesnt the “R” in the NGK R stand for resistor?
 

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That is rich, pig rich if those plugs are relatively new.

We'll assume a wheel dyno. Can you fill us in on the rest of it? I.e. trans, rear, tire and wheel combo, cam, compression, timing specs? Any tuner near by that can handle a carb and dizzy?

And I'll thow in that plug choice is the least of your concerns presently. Leave them in there until you get things closer.
 
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