Anyone Speak Fluent SU HD8? (That would be the carb on the Healey 3000)

I am working on getting the engine for a Healy 3000 ready to drop in a restored shell. So far, it is driiving me nuts. Runs like a bag of rocks.

The engine was rebuilt. The cam was reground. The engine is currently mounted on a stand to pre-run and debug. Good thing since it has been a long road and it still runs poorly.

Here is what I have checked so far:

Engine has been compression and leak tested. 175 psi across the board and 10% is highest leakdown reading. Distributor is in good shape, new points and timing set to 16 BTDC. Total advance about 35 degrees based on dial-back testing light. Intake centerline 110 degrees verified with degree wheel and dial indicator on lifter. Valve lash set a 0.012" hot (works out to about 0.015" hot". Have searched and not found any vacuum leaks in the intake other than the ones on the bottom corner of the intake manifold; the ones with the long tube and what I think is a calibrated orifice (whats with those anyways?)

This leaves me at the carbs. Front carb in particular is where I am looking. The engine runs, but the vacuun signal is bouncy around 14 inches of mercury. The exhaust on these cars is split into two 3 cylinder manifolds, and while the exhaust representing the rear cylinders has a smooth pulse, the one representing the front 3 has a snarly popping irregular sound that makes me think this has to do with the front carb?

All plugs seem a healty mocha brown color.

The carb that is on the engine was rebuilt. Not by me. I am not familiar with the HD8 version of the SU, but I do speak fluent SUese as it pertains to HS4 for the MGBs and H1s for the Bugeyes.

The carbs were rebuilt by the owner with the help of a machinist who did the throttle shafts. Is there anything that commonly goes wrong whith re-building these carbs that I can start looking for? The diaphragm assembly in particular is a deviation that I am not familiar with. Any way the owner could have screwed this up? What to look for?

I checked the float levels because it sure sounded like low floats, but they were the correct 7/16 setting.

Been at this for a few months so am running out of ideas. Any and all suggestions are welcome.

Peter

Have you done the "brake cleaner" test for vacuum leaks around the front carb?

not brake cleaner, but propane from a torch has been waved around to a great extent.

I am pretty sure that whoever assembled this carb when it was re-built, did something wrong. It is NOT worn shafts; they were just done and I inspected the work.

I am looking for something that the owner might have screwed up when he assembled. He is not a SU master (quite the opposite)

All the fuel lines where cleared before reinstall , fuel filter ect ? Call Joe Curto dot com ............ Any new progress ?

Karl:

Have not been back to work on it as of yet. All indications are that it is the front carb and that it is a lean condition. Since both jets are adjusted the same I have to figure it is something assembled wrong in the front carb when it went together.

Most likely wont get to it until thursday after work.

Karl:

Since youve been following:

It was indeed the float. Turns out the hinged bit that closes the valve was loose on the pivot pin and doing something weird. Now that fuel is at the same level in both carbs, it runs much better.

Still a few things to learn on these carbs and the manuals are not helping.

Peter -

I just saw your post, it sounds like you may have figured the big problem out. I vintage race a big Healey with triple 2" SU HD8's. Make sure you have the same needle in all 3 carbs, I even mic mine because not only are the makings near impossible to see, I have found differences between the same marked size needles. Also, it's critical that you get the tri-carb linkage adjusted and sinked properly so all three are opening at the same rate.

Good luck

Dougie

Team Healey PDX

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