Tillotson KA7A part number needed.

[Heliarc]

I would appreciate some help. From the Mercury Mark 55H parts list, what is the part number for the 'Inlet Needle, Seat & Gasket' for the KA7A carburetor? Thanks very much in advance.

[mercguy]

I would appreciate some help. From the Mercury Mark 55H parts list, what is the part number for the 'Inlet Needle, Seat & Gasket' for the KA7A carburetor? Thanks very much in advance.

1395-9258 1 needle and seat assy (fine thread)


readily available from Mercury..........

[Heliarc]

1395-9258 1 needle and seat assy (fine thread)


readily available from Mercury..........

Thank you, Daren.

[trident]

KA7A Inlet Needle and Seat

I would agree 1395-9258--1 is the one to use... its a current production solid brass seat with a soft tipped needle that is compatible with today's fuels. This needle works well in any of the old KA / KB / KC series carbs.

However, the original Mk 55H-1 parts book listed 1399-1473, the almost universal one from back in the day, which was a neoprene seat in a brass holder, with a steel needle. I'd highly recommend against using that original neoprene seat for running motors today, as that neoprene seat swells with today's fuels, shrinking the orifice and thus messes up your float height setting... then it dries and goes back to original size, so you never know what you have for float height.

BTW, again from the original Mk55-1 parts list, a few KA7A's were equipped with a racing only solid brass seat with a screwdriver slot instead of a hex head, and a solid steel needle. Those were better, I felt, than the neoprene version, but still could give trouble, leaking. The trick was to 'set' the needle by smacking the needle lightly into the seat with a small hammer. That needle and solid brass seat assy. was part number 1399-593, listed as a 'Note' at the bottom of the parts list page, I believe. Don't have a new one in a package to verify the number to the part, however.

Hope this helps.

Jerry Wienandt
Trident Racing

[mercguy]

I would agree 1395-9258--1 is the one to use... its a current production solid brass seat with a soft tipped needle that is compatible with today's fuels. This needle works well in any of the old KA / KB / KC series carbs.

However, the original Mk 55H-1 parts book listed 1399-1473, the almost universal one from back in the day, which was a neoprene seat in a brass holder, with a steel needle. I'd highly recommend against using that original neoprene seat for running motors today, as that neoprene seat swells with today's fuels, shrinking the orifice and thus messes up your float height setting... then it dries and goes back to original size, so you never know what you have for float height.

BTW, again from the original Mk55-1 parts list, a few KA7A's were equipped with a racing only solid brass seat with a screwdriver slot instead of a hex head, and a solid steel needle. Those were better, I felt, than the neoprene version, but still could give trouble, leaking. The trick was to 'set' the needle by smacking the needle lightly into the seat with a small hammer. That needle and solid brass seat assy. was part number 1399-593, listed as a 'Note' at the bottom of the parts list page, I believe. Don't have a new one in a package to verify the number to the part, however.

Hope this helps.

Jerry Wienandt
Trident Racing

ah, I have a KA6A that has the LARGE slotted needle and seat assy. Was wondering were it came from. The threads are even larger than the standard type needle and seat assy's (fine or course thread)........don't really have a use for the carb, if anyone is in need.

[Bob Dunlap]

carb

Yes Daren I need the KA6A, I will pm you.

[Heliarc]

I would agree 1395-9258--1 is the one to use... its a current production solid brass seat with a soft tipped needle that is compatible with today's fuels. This needle works well in any of the old KA / KB / KC series carbs.

However, the original Mk 55H-1 parts book listed 1399-1473, the almost universal one from back in the day, which was a neoprene seat in a brass holder, with a steel needle. I'd highly recommend against using that original neoprene seat for running motors today, as that neoprene seat swells with today's fuels, shrinking the orifice and thus messes up your float height setting... then it dries and goes back to original size, so you never know what you have for float height.

BTW, again from the original Mk55-1 parts list, a few KA7A's were equipped with a racing only solid brass seat with a screwdriver slot instead of a hex head, and a solid steel needle. Those were better, I felt, than the neoprene version, but still could give trouble, leaking. The trick was to 'set' the needle by smacking the needle lightly into the seat with a small hammer. That needle and solid brass seat assy. was part number 1399-593, listed as a 'Note' at the bottom of the parts list page, I believe. Don't have a new one in a package to verify the number to the part, however.

Hope this helps.

Jerry Wienandt
Trident Racing

Thanks for the explanation, Jerry. Much appreciated.

[trident]

Ka7a

Interesting that you have a larger screwdriver type seat on that KA6A... maybe an oversize one for Alky?

However, that solid needle, solid brass seat with the screwdriver slot supplied OEM on some KA7A's is the same fine thread size as the 1399-1473 neoprene seat holder. Direct interchange. Its just that it has a screwdriver slot face instead of the usual 5/16" hex. Makes for easy visual inspection, without disassembly to tell one from the other.

Jerry

[sam]

Yes, the KA6A is a special alky carb The nozzle is the same size as a KC

[trident]

Ka6a

Same size as a KC what?

Actually, the KA6A was made OEM, and was supplied with instructions, to run on gas or alcohol. Simple, 5 minute job to convert them... Then, the motors were not raced as a stock class, as gas burning motors, so its kind of moot. I suspect many of the motors were converted to alky Carters, anyway...

The bottom brass plug on the KA6A is the same as a KC, as the nozzle is too large to fit through the 'regular' KA opening, but the KA6A's I had were equipped with huge main nozzles at .180" ID! Don't know what all the different KC's were, but most had a larger nozzle than a KA, with a correspondingly larger thread to install them into the carb body.

My favorite KC's, the KC16A and KC15A (modified) were the 1 1/16" throat version of the casting and those had nozzles at just .157-.159" ID. Still bigger than production KA's, however. The KC's varied some, as they were pretty sloppily machined. I had 10 brand new ones... no two were exactly alike. Sheesh!

Did some of the 1 3/16" throat KC's have bigger nozzles? I don't have any untampered ones to check... Anyone? (Help! I'm channeling Ben Stein)

Jerry

[Fast Freddie]

The 1 3/16" KC7As I found have nozzles around (rough maesurement) 0.155" ID. Is that why they may stumble once in a while?

[trident]

KC's

OK, now we're getting way afield, here from the original KA7A discussion...

Fred, I'll drop you an e-mail. This may get lengthy.

Jerry