'62 Ranchero - 250 - Aluminum Head update

Bill,

I’m using Joe Gibbs oil (BR-1 now and HR-1 after break-in).

I’m using the same carb that you set up for me with the Quick Fuel metering block. I want to see how that runs with the cam and head changes before I upgrade.

Currently, the idle AFR is good after it warms up and the part throttle AFR is good, but it’s very lean (16+) at cruise. I have #71 jets and a .032 idle jet. What do you think would correct the lean cruise?

Thanks
Bob
 
Bob, cruise AFR at over 50 mph should be close to 14.5. Go up to 72-73 main jets. Then do the next test.
If your AF is in the 13.5-13.8 cruising around the neighborhood at 15-25 mph that ok. If its leaner go with a larger idle jet. I would go with a .034 idle jet. Bill
 
Bill,

On my short drive, I was cruising at 20 - 40 mph (20 in neighborhood, 40 on four lane road), and never got up to 50 yet. At moderately higher RPM (as you would have just before shifting to a higher gear), AFR was OK. At lower RPM AFR was 16+.

One small correction to a previous post - I forgot I had changed my jets out to #71 before the "recent" dyno (just before Thanksgiving). My current settings are:

.032" idle jets
#71 main jets
.049" PVCRs
.031" Accel Pump Nozzle
Emulsion Bleed Blank - Removed

Also, I must have had a leak in my vacuum hoses, after some re-routing I'm showing 7" at a low idle (if allowed to idle naturally when first started) and 8" after warmup. That's a little lower than expected, but I expected vacuum to be lower than the 11" I had with the 274/274/108 cam.

Thanks
Bob
 
Bill,

I went to #72 jets and drove around the neighborhood. AFR is a bit lower than before but still 16+at low RPM, for example 1750 RPM @ 30 mph in third gear. At higher RPM (like 30 mph in second gear) AFR is ok.

Time for #34 idle jet? #73 main jets?

Thanks
Bob
 
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