Since I am rebuilding the Holley 1945 on my car (74 Duster, 225,auto,2.76 rear) I am trying to make up my mind whether or not to go with the factory jets in my carb or richen them up a little bit. I am trying to gain a little more performance. Does this carb have metering rods, and do I need to change them instead of the jets? I was thinking of richening it up one step but I need some advice from some carb experts out there.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Is the carb still on the engine? What do your plugs look like now? How long can you tolerate having the car down? 1945s use Holley jets. How does the car run? What specifically do you want a carb modification to do? Have you rebuilt a carb before?

Mitch

First, I would do a careful rebuild on the carb and take note of the jet size that is in it now. (I write the jet size right on the carb body with a "sharpee" marking pen)
You can take a small counter-sink and carefully chamfer the main jet's thru hole, this will increase it's flow rate a small amount. (richer) Don't get carried away, just a slight edge break at the entry and exit of the thru hole.

Run the carb for a while and "read" the plugs, if you still want to go richer, you now know your current jet size and can get the next size up. Truth is, I would go up 2 jet sizes because one size up does not make much difference.
DD

The carb is still on the engine and it does'nt matter how long the car is down. I use it mainly for car shows, cruise nights, etc.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

The idle, main and power circuits were all calibrated lean on the 1945s, the later years more so than the earlier. If you can do a few checks to provide me with more information and send me one plug representative of all, then I can recalibrate your carb. You would have to send me the carb. If you are interested, send me an email at: m5black@aol.com.

With regard to main jetting, to get this right, you really need to do testing on the car. Reading plugs, by itself, is imprecise and you need to gather more information other ways. The best way to determine if a jet change is beneficial is to use a vacuum gauge. Holding a steady cruise at between 50 and 60, does a jet change raise or lower your manifold vacuum? If your manifold vacuum increases, then you are making the same power with less throttle and the jet change was beneficial. Looking at the plugs alone does not necessarily give a good picture of what is going on because unless the heat range is absolutely correct, thier color cannot be used as an indicator for jetting.

If you want to improve performance, recurving your distributor would actually give you a more noticable affect. The earlier electronic distributors had a lot of timing built into them - requiring little initial timing. This gives poor low speed throttle response. What initial timing does your car call for from the factory? Where do you have it now?

Anyway, if you are interested, contact me. Otherwise, if you want to do a simple rebuild, look at your plugs. If possible, post a picture. Depending on what you find, a jet change up will probably be a move in the right direction.

Mitch

What is intial timing? Is that the timing you set with a timing light? In that case, the fender tag says TDC. I was hoping that with a richer mixture I would be able to advance my timing higher. Which gives me more low end torque, advancing or retarding the timing. I have a feeling that I am runnig into a performance dead end with this little Holley. Here is what it does. It pulls strongly through first gear but acts like it is running out of breath as it nears the end of second gear.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Slants love more timing. Try advancing it to 8BTDC or so and see what happens. Try runing a #61 jet in the 1945. They seem to like it. Mine does anyway (when it decides to run).

Yes. Your distributor has too much mechanical advance. You cannot start out with much more than the factory TDC because you'll end up with too much timing at higher engine speeds. So... you need to reduce the amount of advance in the distributor. This will allow you to advance your initial timing and you'll gain low speed throttle response and part throttle torque. The advance governor in the distributor controls this and it can either be swapped out with a different one or modified.
I would try getting more out of what you have before changing components. The way you go about tuning is to get your jetting as close as you can to where it should be and then work on your timing/spark advance. Your car should easily tolerate 10 - 12 initial spark with 28 total.

Mitch