Finally the test run to check AFR's

[kent olsen]

[kent olsen]

Got my AFR installed and finally made the test run. Idle, steady 2,3,4,5000rpm I'm getting 10.7. Wide open is 13.5. As typical with webers there is still a transistion stumble about 3000 I can hold but with more/less throttle opening it goes away. F3 emulsions, 50 idle jets and 160 mains with both main and idle correction jets. Modified to 42mm by Paul Abbott. It has a special cam from Dougherty and makes 245hp @ 6900 and 230 ft/lbs at 4800rpm.

This may seem a little rich but after playing with these webers, with help from Paul, for years it seems to be what the engine likes. I've autoxed and tracked the car for years (249,000 miles, about 20,000 on my rebuild).

[PeteKz]

Kent, my 1973T with 3.0 stroked to 3.2 with CIS sits about 14 at idle. I know you have carbs, but 10.7 at idle and no load seems really, excessively, rich. My high-RPM WOT is in the 12-13 range.

But if it runs well for you with whatever cams and pistons you have installed, then I guess it's good.

[Trackrash]

Too rich everywhere except WOT. You should be in the 12s except at light cruise, then 13s is ok.

What size , venturis, and idle air? 160 air correction?

My 3.0 runs ~12.5 everywhere except light cruise, then in the 13s.

I am amazed that you are in the 10s with 50 idle jets.

[3literpwr]

I have PMO 46's on my 3.0 and have good numbers in most places, but can't dial my numbers above 11:1 without a lean spot on transition...I'm here for the comments.

[Nditiz1]

My 2.4 with 40 PMOs is 11.1 everywhere else is high 12s low 13s. I'm still data logging with my 3.2 with 46 PMOs. I have a feeling it will be the same with 60 idles in it.

Paul Abbott had some great advice when I spoke to him last. He said his PMOs also run rich at idle. Paraphrase - If it's only rich at idle, rip out your AFR gauge and stop worrying about it. Sage like advice.

[Old H2S]

For carbs everyones numbers look good, it's that what it wants to run well and the main reason to add an AFR gauge in the first place. I say that the AFR shows how screwed up your CIS is too, and how it jumps around crazy being a mechanical system. I fight with the EFI guys about how long it took in software dyno changes to get it right and half of them will not show the AFR trace. Every engine is different BLA BLA BLA, but they all come out close in the end to the same wants for cold idle, hi power blast and lean best cruise.
10+ for cold start
12.8-13.8 for blasting
15+ lean best cruise

[kent olsen]

Well this is what's in there: F3 emulsions, 50 idle jets, 95 idle air corrections, 160 main jets, 170 main air corrections. Paul opened my weber's out to 42mm, he also put the dam in the float bowls to prevent sloshing. 9.5:1 pistons and Dougherty GT2-102 cam. 245hp @ 6900 and 230 ft/lbs @ 4800rpm. The car weighs 2200lbs with 1/2 tank of gas.

[1QuickS]

Kent's main venturis are 36mm. My references suggest 155 to 160 mains and his AFR reading at WOT are good with his 160 mains.

50 idle jets are fine with the 95 idle air correction jets, 60s are typically used for engines of 2.7 liters and up but idle air corrections are 110 which leans out idle/progression. The smaller idle air correction jet extends usable range of idle/progression to help transition mixture without too lean a slow speed response.

Difficult with carbs to manage mixtures at steady state to be sufficient with partial throttle acceleration, you need to choose drivability over AFR perfection.

No matter what the AFR gauge says, if engine lean stumbles then richen mixture until it is happy.

Kent has been driving & adjusting jetting with the 42mm Webers I created for him since I completed them in August2013.

[kent olsen]

Just got back from a run up into the hills behind my place. I have a couple favorite valleys and hills there. Soo, I got back there and the engine was well warmed up. Ran up to the 7000rpm redline in 2nd, 3rd and 4th a couple times. Feels good when you give her some room and let her rip.

Interesting, back down on the highway coming home, No More Stumble thru the 3000rpm transision!!! Weither I slowly accelerate thru that spot or not the transition was smooth. I guess she just didn't like sitting in the garage all winter.

Since I'm close to 80 years old I quit driving the car at track days. It probably misses those days as much as I do.

[1QuickS]

Classic Italian tune-up.