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Used the base gasket that came in the rebuild kit for a year or so before it started leaking. I made a new one with thicker material, now I'm having some trouble getting it to idle. It used to idle at around a turn and a half out on the mixture screw, but now it wants the screw to be at least three turns out, and even then it isn't happy: very lean. Everywhere but idle, it runs like it used to. I'm thinking I blocked off the fuel feed to the mixture screw somehow? I sprayed around with some carb cleaner and it didn't appear to make a difference anywhere.
I didn't copy all of the holes because some of them seemed unnecessary, and this is where I think I made a mistake or two. The carb is decently modified (mechanical secondaries, extended accel linkage, etc.,) and it ran great before I changed the gasket, so I assume it must be something I changed.
In this pic, the holes marked with a blue dot are important holes that obviously needed to be copied (bolt holes, throat bores,) and the red ones are others that seemed important based on where they led.
If anyone recognizes any holes that need to be added, I would appreciate the advice. Thanks!
Well, I copied all of the holes over and it doesn't seem to change anything. Still really lean at idle.
Something interesting I noticed is that once the engine is warm and you restart the engine with no throttle inputs, it'll catch and run for a second or two before it leans out and dies.
Didn't realize I had some old vacuum line for the brake booster still, maybe that's given up, finally.
I noticed the rear float level sits quite a bit higher than it should while running (like 1/8th to a 1/4 inch above the middle of the sight glass,) which is strange since they're physically set to carb manual specs. Maybe it's been off for a while. Probably not my idle issue, but I'll give it a look.
Sounds like a vac leak somehwere. Your car should be able to idle even with the booster line open , my car would idle but incredibly rough , but it idles none the less. I suggest tightning everything down by hand , checking all your vaccume lines/ replacin gany lines that feel hard , they may be cracked or simly not holding a good sealany more even when tightened , they tend to crack inside and air passes through. Any generic vac lines work . .
For what it's worth, all of the holes you originally did not copy over (red dots) are for the idle/transition circuits if memory serves me right. Also the baseline fuel mixture setting is ~3.5 full turns out from lightly seated, so that puts you right in the ballpark where it is now. Then again the setting can vary quite a lot depending on modifications, specifically changes to the primary venturis and no.2 air bleeds.
Edit: I think I misunderstood your markings as to which were actually punched out, but regardless, the information is still there.
Last edited by Benjamin4456; 01-28-22 at 01:55 AM.
If you are running a full rats nest, get some 3mm silicone vacuum hose and replace each line, one by one (so you don't miss connect them). Pro tip, use a color other than black so you can easily see which ones have been changed.
To clarify the car does idle, but it idles at a way richer mixture screw setting for the same AFRs compared to before I changed the gasket. Also, the AFR fluctuates almost a whole point, instead of just tenths. Probably the high float level causing that.
Yay, I think I fixed it. I believe, with the old gasket, there were just enough things wrong that it still worked and idled haha. I think the float level being too high on the one side caused extra fuel to be delivered, which is why I had to lean the mixture screw out a lot to get a decent AFR previously.
I checked the floats using calipers, plenty within spec for the carb manual, but the rear float level was still high when running. I adjusted the tab to close the float a little earlier. I also swapped in a set of 120 primary slow air bleed no. 2s, since I do not have a choke. Within 20 seconds of starting it, it was idling at less than 600 rpms doing just fine with no throttle. Got it warmed up, idle tuned in great (at around 1.75 turns out now for a mid 12s AFR) Fuel levels are centered in both float bowls. Nailed it first try, awesome.
01-14-22, 03:41 PM
Carb Gasket Between Throttle Body and Main Body
