Idle problem

[Cliff Ruggles]

With 15" vacuum at idle any PP spring will be down.  The stronger ones lift the rods earlier, and can improve throttle response slightly with some set-ups.

The orange spring should be fine for what you are doing, but you may be able to make improvements tuning in that area.....Cliff

[dlphil10]

So I shaved the deck down 0.020" and went to an 0.040" over bore, but same heads and cam. It should be around 8.8:1 - 9.0:1 SCR. I know thats still a large cam for the setup, but I would have expected different results.

I am now getting around 11inHg in park and if I put it in gear it dies. If I put my hand over the carb it picks up rpms and will make ~15inHg. Sounds like I should replace idle tubes again with larger ones and drill out DCRs? Can DCRs and idle tubes be englarged while they're installed? Would the carb sitting for a year and a half cause issues?

[Cliff Ruggles]

They make long precision bits to drill idle tubes in place.  Dcr's are easily accessed to no problem opening them up a tad in place.

Sitting shouldn't be an issue unless a mud-dabber crawl into it and muddied it up some......

[dlphil10]

Alright so I went through the carb and changed the idle tubes to the 0.037" ones you sent (thanks!)

It idles so much better at around 12-13inHg, but we took it for a drive and it will NOT accelerate... Heavy and medium throttle makes it slow down. It only wants to speed up with light throttle and very slowly at that. Do you have any ideas on whats wrong?

Air horn idle bleeds are ~ 0.050"
Air horn main bleeds are ~ 0.070"
Lower air bleeds are ~0.070"
DCRs are ~0.050"
Mixture screw holes are ~.100" (They were like this already)
Accelerated pump hole ~0.027"
Orange power piston
42 rods and 72 jets
Float ~0.25"

[Cliff Ruggles]

Power piston stuck or hanger bent down to keep the rods from coming up out of the jets high enough??

[dlphil10]

I changed distributor springs and it's much better but I'm still thinking carb issues. The power piston moved freely when I installed it and the rods seemed to be at the right height. After tweaking the dist. springs it will bog under moderate load and when I back off it a little it speeds up and I can give it more throttle. It's consistently around 12inhg in park amd 8-9 inhg in gear.

[dlphil10]

I looked at the carb and the primaries are open well into the vertical transfer slots and and past the horizontal transfer slot. I can open up the idle bypass air and close the primaries more, correct? Would having the primaries closed further bring up idle vacuum?

[Cliff Ruggles]

Are you seeing any nozzle drip at idle, if not it doesn't need any more bypass air?

Makes no sense why the engine would not accelerate the carb has plenty of jet in it, and metering rods are 4 sizes richer than what it came with.

Maybe a fuel flow or delivery issue, filter in backwards or something odd going on?......Cliff

[dlphil10]

Is nozzle drip very noticeable? I've looked down at the nozzles with a flashlight several time and haven't seen anything...

The acceleration is a lot better. I have it idling around 700 in gear and I noticed it runs much better with the mixture screws turned out at least 1 turn from highest vacuum.

I don't have good off the line acceleration and I'm wondering if that could be from having the primaries open too far. I'm trying to maintain the idle speed, but see if regaining transition slot could help. If I give it gas it chokes then picks back up. The accelerator pump shot is strong and healthy. A vacuum gauge shows when the throttle is cracked vacuum plummets to 5inHg.

Maybe it's just the highway gears and automatic that I'm fighting?

[dlphil10]

Plugs look good creamy tan color.

[Cliff Ruggles]

Is your problem coming off idle at very light throttle openings or going quickly to heavy throttle?

Two different scenarios as "normal" driving doesn't use the accl pump or PP for enrichment.

More bypass air would simply add more air to lower the throttle angle but not add any more fuel anyplace......Cliff

[Cliff Ruggles]

Something that just came to mind was that carb every commercially "remanufactured"?.....

[dlphil10]

I don't belive it was ever commercially remanufacturered. What would be something to look for to indicate that?

The problem is a bog at practically all off idle. I think it's worse at light throttle. There's a slight grade to climb as I back around in the drive way. When I go to put it in drive to go up the hill it stumbles and I have to give it gas to pick rpms back up.

On the idle bypass I was wondering if I don't have enough off idle enrichment from being far into the transfer slot.

[Cliff Ruggles]

Most commercially "remanufactured" carburetors are mixed/matched parts and all the finish typically gone from them.

The mixing/matching is what gets you into troubles.

If and when EVERYTHING inside is correct for what you are doing, and there are still issues, time to look for fundamental problems like the wrong power piston (very common with anything commercially remanufactured).  Not using the original top and bottom will also cause running issues.

Arms bent on the power piston causing the metering rods to be too deep in the jets, etc......Cliff

[dlphil10]

Do you have a list that shows what number air horn and throttle plate should be with the 7029262 to verify?

I tweaked valve timing and ignition timing and now it idles in drive at 14.5inhg. The plugs are only faintly tan as shown in the attached. This is too light isn't it? This was with the mixture screws out 4 turns. I was thinking maybe I should open the DCRs to 0.055 if that would help.

I also was thinking of changing to the light blue power piston spring to get more gas off idle. What do you think?