What were KA11A, KA12A merc carbs used on?

[Inline Six]

I have some NOS carbs that I found digging through my stuff, they are KA11A and KA12A carbs, look like they are from a 50 or something. I have piles and piles of 4 cylinder 44ci merc stuff so thats what i assume they came from but just wondering

[Ron Hill]

D Mods are 44 cubic inch, but all the engines I have have KA-7 A carbs...I think...What numbers are needed for D Mod Motors?

[Mark75H]

The KA's were on the 22, 44 and 66 ci Mercs.

Any KA is fine for D Mod - KA7A's have the mounting holes elongated to use on studs drilled for Carter N's ... that's the only thing special about them

You might want to consider deep nozzles as released in an upgrade kit in the 60's and I prefer KA's with external shutters vs KA2A type throat mounted choke shutters

[greenmerc]

Ive been making the longer pickup nozzles for the ka,s Ive even made some for the kc,s to convert them to adjustable jets!!!

[Trident]

KA-11 was used on 1961 Merc 800, KA-12 was used on 1961-62 Merc 700.

Yes, KA-7's had elongated mounting holes to fit the Carter stud pattern.

They were also the only production KA supplied OEM with an adjustable high speed needle (all others were fixed jet). Mk 75H KA-6 weren't really 'production'...

The KA-7 also has an additional fuel passage, a sort of main jet bypass. Yogi said, "you can see a lot just by looking"

Hope this helps.

Jerry Wienandt
Trident Racing

[Ron Hill]

Yogi also said, "When you come to the fork in the road, take it..."

What is the carb or choice for a D Mod?

And while I'm asking do most people run the mags or electronic ignition???

[Trident]

Darn, I thought I answered Inline Six's question about KA11 & 12.

Calm down, Ron... no need to get sarcastic.

What do old people smell like? Depends...

Same answer on suitable D Mod carbs. Depends on what motor, 40 or 44, what you have on hand and what you're capable of building. Depends on what your motor is, where the powerband is...

Almost any can be made to run. None are 'right' as OEM. Some run better than others.

The good news is all are easy to work on, what with removable parts, rather than cast in, like the old AJ's.

Keep in mind, though, that all were engineered to run at 5500 rpm. We buzz 'em up way past that, throwing all the calibration off. Its fairly easy to get them to run at top RPM. The trick then is to get them right across the rest of the RPM range. Top end with punch. No loading up, no classic KA-7A stumble.

KA-7's are good as a starting point, due to the features I pointed out. They will run on both 40's and 44's, but I modify those, to suit.

In addition, I've had success with modified KA-9's & 19's on 40's, modified KA-2's, 9's, 18's, 19's, 21's, KC-16's, 15's, WMA-6's and 7's on 44's. Note those are all modified. None are box stock OEM.

Other builders, I'm sure could rattle off models they like. That's the beauty of Mod; there is more than one right answer.

So pick a number. Test 'em, tune'em, modify as needed...

[Ron Hill]

I've got five 44 blocks with off set heads....But don't seem to understand what Freddy Hauenstein means when he say the "BIG" top bearing...All five seem to have the same size crank....As I call it a crank from the "THREE SCREW" Port cover motors...

So, I need to get the KA carbs out of the scrap aluminum pile!!!!

Old men don't smell or die, they just can't remember where all their props are!!!!

[MTECHMARINE]

I CAN'T find my beveled Quincy crank!!

Found it Saturday, now I can get to work.