(2)450 DP's vs (2)750 DP's

I’ll say it again. A .033 MAB is bigger than any Holley built before they crapped the bed.

As that gets bigger you will be richer sooner and leaner later.

And it doesn’t take much to make a move. You can see this easily on the dyno.

What happens is once the MAB is that big, it causes you to do other things to get the fuel curve back in shape.

As Mattax said above .028 emulsion holes is as big as I ever go. Tunnel ram stuff with small carbs OR a quality annular booster may only want one emulsion hole of .024 size.

Tuning this stuff in the car verses a dyno is two different worlds. I would never try to do another TR without it going on the dyno.

It’s so much quicker and easier to sort it out. The relationship between the booster, MAB, the T slot restricters and throttle opening and load is near impossible to control in the car.

I know a dyno is out of the question (talking engine dyno) but even a chassis dyno would make things easier.

I can’t emphasize how critical it is to get the MAB correct and then sort out the fuel curve than to just drop a MAB in there and tune around it.

I believe that most of the horrendous tune ups I see coming in some of these carbs is directly related to MAB sizing.

The other thing is guys get hung up on numbers. Like saying a .026 MAB seems too small to me.

Or, one of my favorites from my early teens trying to explain to full grown men that your dirt bike doesn’t need to and shouldn’t be pumping black goo out of the pipe and why mine didn’t.

I ran smaller jets than they’d ever heard of so they were sure I was going to stick a piston. Their fear of a number made them do bad tuning.

To that end, main jet sizing is the same. If you get the MAB sized correctly you probably will need to reduce main jet sizing by 4-6 numbers.

It looks like my carbs are going to be in the mid to low 60’s for a primary main jet. That’s on a 1.410 X 1.750 carb that SHOULD be in the low to mid 70’s.

That’s because the MAB is .026 and that’s probably a bit big. For now that’s where I’m starting.

Add to that Mark Whitener’s boosters and I can run jets that small and not be lean.

Fuel distribution is generally better with smaller jets IF YOU DONT NEED THE FUEL.

And don’t forget to get the PV open sooner when reducing MAB sizing if you need to cover a home in the fuel curve.