What do you think of this plug?

What does this tune up look like?

  • Total voters
    9
  • Poll closed .
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yellow rose said:
The power valves are 8.5’s but I’m changing them to 10.5’s.

If I go smaller on the main jets, it gets a lean surge at cruise.
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How is your transfer slots ? Have you checked them for proper specs? I think it's .040 if I remember
 
Are you using a wide band or just tuning by the plugs? Have you reduced the main jets to lean it out up top? What did it do to the cruise? You mentioned at one point you had a lean surge, are the carbs four corner idle? Is there another idle speed screw on the secondary's?

I highly recommend some type of recording wide band, it's a wonderful tool for carb tuning.

My advice would be to reach out to Dom.
 
justinp61 said:
Are you using a wide band or just tuning by the plugs? Have you reduced the main jets to lean it out up top? What did it do to the cruise? You mentioned at one point you had a lean surge, are the carbs four corner idle? Is there another idle speed screw on the secondary's?

I highly recommend some type of recording wide band, it's a wonderful tool for carb tuning.

My advice would be to reach out to Dom.
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Tuning with the plugs.

I only change the secondary main jets and the primary PVCR’s to change WOT. This particular plug is from a tunnel ram with 1:1 linkage and power valves in both ends, so I have the cruise pretty close. I only change the PVCR’s to change WOT on this application.

Carbs are 4 corner idle. The lean surge was from the T slot restricters being .004 too small. Opened them up and the lean surge was gone.

The one thing I didn’t do on these carbs was change the secondary linkage to an adjustable stop. Kicking myself for that. So you still have to pull the carbs to adjust secondary opening.

I’ll see if I have a decent video of it and post it here.
 
yellow rose said:
Tuning with the plugs.

I only change the secondary main jets and the primary PVCR’s to change WOT. This particular plug is from a tunnel ram with 1:1 linkage and power valves in both ends, so I have the cruise pretty close. I only change the PVCR’s to change WOT on this application.

Carbs are 4 corner idle. The lean surge was from the T slot restricters being .004 too small. Opened them up and the lean surge was gone.

The one thing I didn’t do on these carbs was change the secondary linkage to an adjustable stop. Kicking myself for that. So you still have to pull the carbs to adjust secondary opening.

I’ll see if I have a decent video of it and post it here.
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Is it still square jetted? If you're satisfied with the cruise I'd take a big swing at the PVCR's and see what the plugs look like.
 
yellow rose said:
I try to keep them at .030-.040.
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That's good then.
yellow rose said:
The power valves are 8.5’s but I’m changing them to 10.5’s.

If I go smaller on the main jets, it gets a lean surge at cruise.
Click to expand...
Jeez, i ran into this with a chev 383 I changed the secondary jets two sizes smaller. When both both 4 barrels were opened there was just too damn much fuel, the only other issue the guy had was float level too high & I mean just a mm or so. Do your carbs have removable air bleeds ?
Is this a race only engine? Or do you cruise it? 1500 cfm sounds like over carbed for street duty. What does your exhaust smell like? I'll go out on a limb and say just from the looks it's being washed a bit & the black under where the threads are is unburned fuel & carbon from exhaust reversion . It's just a guess, if I could smell your car & see it I could nail it, I'll be over in a few weeks hopefully for good. Great at idle, good at mid rpm and most likely over rich at wot that's where I think it maybe cleaning your porcelain
 
justinp61 said:
Is it still square jetted? If you're satisfied with the cruise I'd take a big swing at the PVCR's and see what the plugs look like.
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Yes. Still square jetted. I left it as is for now. I’m thinking of going back to his place on the 4th of July to play with it a bit more, but not sure if I can make it. If I can’t, then it will be September before I can get back there. He’s about 5 hours from me, but he is just a damn nice guy.
 
yellow rose said:
Here is a short video of the truck. The dog is named Tank. He is a damn good dog.
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Holy fuckin **** okay, yeah your probably not over carbed. By sound it is running perfect but that black part is probably just exhaust reversion. I couldn't hear anything that would be concerning. Whooohooo
 
You didn’t say what cylinder head is on it. It must be an open chamber and really inefficient to like 41 degrees total. Plug looks better to me than most plugs people post here. I’d like to see a close up of the ground strap at 41 degrees though. How did you settle on the total timing number?
 
TT5.9mag said:
You didn’t say what cylinder head is on it. It must be an open chamber and really inefficient to like 41 degrees total. Plug looks better to me than most plugs people post here. I’d like to see a close up of the ground strap at 41 degrees though. How did you settle on the total timing number?
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It’s a Dart Pro 1 head. I should have took a picture of the ground wire but I just forgot.

I should have mentioned that I did roll it back to 39 total. Didn’t move the mark on the ground wire.

I just did his brother’s SBC last night. It ended up at 41 total. With 3 different lights.

That’s usually where most of the chevy junk runs. A SBM has an open chamber head but only needs 35 total. It’s more about plug location and rod to stroke ratio than anything else.
 
mini said:
If you have to ask then put in a wideband :poke:
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I asked because I got sideways (went backwards actually) on Friday night. Got there Thursday afternoon and by Friday evening had it about perfect.

Then I had the brilliant idea that since I was there for the weekend I might as well make it 1:1 throttle opening, and for some reason that just kept throwing me multiple curve balls and a couple of good balls.

Took me until Sunday at noon before I pulled my head out of my arse and realized with 1:1 throttle opening it was on the transfer slots a lot longer so I put a skosh more fuel in there and BOOM...the driveablity was about as good as it gets.

It was totally worth the headache because it drives so much better with all 8 holes opening at once.
 
Nice! Yeah more than. Likely without being synced 1:1 they were on different circuits at seperate throttle positions. Hence your headache haha.

I was the carb tuning guy with all of my Chevy friends too funny
 
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yellow rose said:
Here is a short video of the truck. The dog is named Tank. He is a damn good dog.
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Boston terrier dogs are great!

I’ve had mine for over ten years.

Here she is watching tv
 
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