[Backdraft1725]

Hi Paul.

Well, I typed up a nice response, but it got sent to the admins for review (due to the picture??) and I don’t know if there are actually any admins here. I’ll retype the description with no pics and see if it goes through. [EDIT] See pic of my setup in the post below. This is in an ERA with a 427 side oiler.

Sorry for the confusion above, I’ll stick to standardized terminology here:

• Idle Sync Screws - for front-to-back balance
• Linkage Adjustment – for left-to-right balance
• Idle Stop Screws - to set base idle speed
• Throttle – throttle cable or assembly from the accelerator pedal
• Idle Mixture Screws – lean/rich idle adjustment on each runner

My “aha moment” was that the carb balance is different when sitting on the Idle Stop Screws than it is when it is when pulled by the Throttle. Everything that I read said to sync the carbs at idle, but nothing, prior to reading the Ferrari 308 setup guide, mentioned that there is going to be some play in the carb linkage, so setting on the Idle Stop Screws (which pushes the carb linkage) is different than setting based on the Throttle (which pulls the carb linkage). Based on this, my new carb mechanical balancing procedure accounts for both a Throttle balance and an Idle Stop Screw balance.

Here’s what I did:

1. Set the Idle Mixture Screws at ¾ turn out (just a good starting point).
2. Set idle using the Throttle. I used a jig to hold the Throttle open a bit and then turned the Idle Stop Screws out to make sure that they weren’t influencing anything.
3. Front-to-Back Balancing. Balance carbs front-to-back using the Idle Sync Screws. Do this on each side and don’t worry about the carbs matching up left-to-right.
4. Throttle Balancing. Using the Linkage Adjustment, balance carbs left-to-right. Try to find a balance where the left and right linkage arms are the same length (if you have separate arms). This is your Throttle Balance.
5. Idle Stop Balancing. Set the Idle Stop Screws to where they are setting the idle speed and release the Throttle (take the Throttle jig off). Here you are going to balance left-to-right using the Idle Stop Screws. I found that the balance was a few kg/h off on the syncrometer from the Throttle Balance, so re-balanced left-to-right using the left-to-right this time using Idle Stop Screws. This is your Idle Stop Balance.

With this setup, I am balanced at idle (based on the Idle Stop balance) and I am balanced on the Throttle (based on the Throttle Balance). Previously, I was balanced at idle, but unbalanced when I got on the Throttle. It might also help to set the Throttle Balance at a few different RPM settings to make sure that it stays balanced. Balance matters less and less as you open the Throttle, so getting a good balance down in the 1000-2000 range likely is most important.

I hope that this is clearer and that it helps someone out. Here is a link to the Ferrari 308 Tuning Guide that I was learning from: Ferrari 308 Tuning. Step 5 talks about setting the balance using the Throttle.