Inliners International Forums General Discussion Engines Lean running 292

I'm having an issue with my stock '69 C10. Since I've owned it it never idled right but beyond that it ran good but rich. A few weeks ago I swapped out the stock MV for a 250 MV. It runs much better but it seems to also run lean. I can leave the choke partially engaged and the engine performs better than with the choke off. I know I'm running a smaller carb but I'm surprised there would be that much of a difference. Thoughts?

The 250 carb is jetted leaner because of emissions. If you don't have a vacuum leak see what the jet size and rod size are on both carbs. Maybe some combination of the 2 would work? Jay

I'll look into that. Thanks Jay.

What other carb options have been proven effective for normal street driving?

If you don't want to change the intake manifold, a model B Rochester is possible. There are/were kits from landgons I believe that used a weber 32/36 carb. With a 292 if I were going that route I would upgrade to thr 38/38 carb. Another possibility would be a small base 2gc rochester. That carb, along with the adapter required, comes out about the same height as the Monojet. The small base 2gc also uses the same size hole for the air cleaner so the stock unit would fit on the carb. Any solution I mentioned other than the B carb would need an adapter to fit the stock manifold. Jay

What size primary am I looking for on the 2GCs?

I am not a 2gc expert by any means. This is what I know. Depending on which mono jet came on your 292 it would be either 250 or 210 cfm according to Doug Roe's book. There is supposed to be 2 sizes of the small base 2gc that has the same size hole as your stock air cleaner. One has1 3/32 Venturi and 278 cfm. One has1 7/32 venturi and is 320 cfm. I have never seen the 7/32 version, but that doesn't mean they exist. Both carbs have a 1 and 7/16 throttle blades.
There are 5 sizes of the Large Base 2gc carb. One has 1-3/32 Venturi and 1-7/16 throttle blades just like the small base carb. I didn't know such a carb existed til I measured one of the carbs in the garage.
The other 4 large base carbs have 1 11/16 throttle blades.
The Venturi sizes are 1-3/16, 1-1/4, 1-5/16 and 1-3/8.
If I were trying to run the stock air cleaner I'd go with a small base, the bigger Venturi if I could find it. This assumes that you have the stock cam. I DO NOT know if the linkage ect will clear your air cleaner might want to try a test fit before purchase. Some early small base carbs have a high mounted choke coil might not clear the carb.
If I were going with a Large Base carb on a stock 292 I'd go with a 1-1/4 or maybe a 1-5/16 Venturi model knowing that the stock air cleaner won't fit. The bigger the Venturi the more sluggish the low end will be with some improvement in top end. I hope that others that know more than me will chime in. Jay

Thanks for you advice, Jay. Hopefully I can also get better gas mileage out of my 292.

Strummin 67, please take a little time to educate me.i have heard that 292 engines are gas hogs, that guys with a 305 V8s do better on gas. Is this true? Could it be a 292 is usually in a truck with steep gears like 4.11? I have thought about putting a 292 in a 77-79 full size Chevy. I think the stock 2.41/2.56 gears would work well with the 292s low speed torque. Jay

Hi Jay.
The 292 I have is in a '69 pickup. I believe the gears are 3:73s but I'm not 100%. I get decent mileage as long as I stay off of the freeway and even then I'm usually driving about 55mph.