62 3269s AFB Metering rod help

[Bill O.]

My freshly rebuilt 62 340 horse engine is currently sitting on the dyno. It is bone stock except for the LT1 cam. The carb was just rebuilt by Bob Kunz and set to stock specs. The problem is the engine is running very lean, up over 14 to 1. The jets are stock and the metering rods in the carb have no number but measure .055 on the first step and .068 on the second. Can anyone steer me in the right direction on size and where to get them. Not sure if the newer Edelbrock stuff will work or not. Thanks guys,Bill

[Duke W.]

Re: 62 3269s AFB Metering rod help

The first guy you should talk to is Kunz. I don't know off the top of my head what "stock jet (and rod) sizes" are in a 3269S. It's probably buried in some file, but it would help it you would state such.

Also, what is the A/F across the rev range. I'm assuming the engine is mounted on a lab dyno. Pulls should be made from 1000 revs to determine the entire torque/power curves and the A/F ratio across the range. Typically it will lean out as revs increase, and it should not be greater than 13.5 at peak revs. Pulls should also be made with simulated cruise load and the A/F should be about 14.5:1.

Do you have tabular or graphical data you can post? What you've presented is really too vague to make any specific recommendations.

Duke

[Timothy B.]

Re: 62 3269s AFB Metering rod help

Bill

I agree with Duke, at what RPM is the A/F ratio 14:1, I assume it's a WOT pull so the power step wants more fuel. I think the Edelbrock rods will work in your carburetor, on a Carter AFB 3461 (1963 car) the rods are .069x.060 and the jet size is .104" for comparison.

[Bill O.]

Re: 62 3269s AFB Metering rod help

Tim and Duke, thanks for chiming in. Duke don't know if you remember talking to me on the phone last spring about this engine. Anyway, I am, unfortunately 90 miles from the engine and playing phone tag with the guy dynoing it. I will try to get him to send me the table. I do know that the main is indeed a .104 and the metering rod sizes are stock size per Mr. Kunz. I did call Bob and am waiting for him to get back to me, but just wanted to throw his out there. Was curious at what point do you have to start changing jets or can you usually get there playing with the rods. I guess the LT1 cam demands a little more fuel. For Duke, it did make 315hp @ 6100 and ran great other than our little lean problem, so without a doubt there is more there. Thanks again,Bill

[Duke W.]

Re: 62 3269s AFB Metering rod help

The LT-1 cam has a later closing inlet valve than the Duntov cam. This causes more low speed reversion, which might lean it out a bit on the low end, but it's more of a part throttle than full throttle issue because reversion at any given engine speed increases with manifold vacuum.

IIRC the 3269S had very different jets and rods than the 3461S. Can you provide the calibration data from ST-12 or other service information for your '62?

BTW I have a lab dyno sheet for a "stock rebuilt" 327/340, and it made 295 gross HP at 5500, which is in line with simulations, so your additional power and revs are most likely due to the difference between the LT-1 and Duntov cams. Another point of reference is Mike McCagh's "cheater" 283/250FI written up in the Fall 2010 Corvette Restorer. This .060"-over 3.48" stroke (337 CID) engine with massaged OE heads and the McCagh Special camshaft made 315 gross HP at 5100, and it idles butter smooth in Drive at 450, just like an original 283/250FI Powerglide should.

Head massaging would have gotten your engine up to the 350 ballpark at about 6500.

Most dynos manufactured in the last 20 years are controlled by a PC that produces tabular and, maybe graphical output. It should be just a matter of your guy attaching the reports to an email. Then you can copy and paste the data here.

Duke

[Bill O.]

Re: 62 3269s AFB Metering rod help

Geez, I totally forgot that the carb stuff is in the ST-12. Let me go dig it up and see what it says.