Tunnel ram or no tunnel ram...

So you would use even smaller IFR than I already have? Why is that? I'm pretty sure Im in the transfer slot when my problems occur.
I can plug the lowest hole easily as a temporary sollution. What will this cause for me? I'm trying to understand the way this works...

Yes, smaller IFR’s. When you use 2 four barrel carbs with four corner idle you are effectively doubling the IFR area. You just don’t need it. And a .003-.004 change in IFR is like making an .008-.010 change on the MAB. And like I said, once you get close at idle then you can fine tune it with MAB.

I always always start with the idle circuit and work my way up so to speak. If the idle circuit is screwed up, every tuning change you make after that will be wonky because these circuits over lap each other. So cleaning up the idle should be first.

Then I go to cruise which is what the primary main jets do. You get to your cruise speed/RPM/load and then take main jet away until you get a lean surge. Once you get that lean, you go up 1-2 sizes and leave it alone. You don’t touch the primary main jets again UNLESS and that’s big unless you get to the drag strip and you get a bit lean. Then you can add some primary main jet BUT you need to go back to your cruise main jets when are done.

Why is that? Because at the track it’s much quicker and easier to change out a main jet than it is to pull the power valve and change out the PVCR’s. If you need to add primary main jet quickly then you need to go back to what you had so your cruise tune up is where it needs to be.

Once the idle and cruise circuits tuned up, then I move on to WOT. That’s a change of PVCR’s on the primary side and main jets on the secondary side. Again, once your cruise tune up is spot on, you don’t change the primary main jets to get your WOT tune up right or you screw up your cruise tune up.


When all of that is done you can work on your transition circuit. Thats the T slots and T slot restricters. That includes getting your power valve opening time correct. An early opening PV will cause a rich condition in transition and a late open PV will cause a flat spot in transition.

The T slot restricter size changes the cruise AFR only when you are cruising on the T slot. This is when a data logger is worth 10 times its weight in gold. You can measure MAP, throttle position, AFR and graph them together and see exactly where you are in the throttle so you can easily determine exactly what circuit you are on and how far into that circuit you are.

Either way (data logger or not) the T slot restricters change the amount of fuel at cruise on the T slots.

Thats a quick run down on how I do it and why.