Tommykat, One thing Michael brought up…
Uncle Joe 'Curto" always marks the front of the carb with the needle used.
So do this…
try a new condensor
again what spark plug wires did you use ,look in center , copper original which are fine for your set up
or carbon for more electric, long shot stab in the dark.
if you remove base of air cleaner bolted to carbs he uses a black marker to label needle size.
But unless your bleeding from the eyes with fumes?
For awhile Uncle Joe did bump up the needles for ethanol but its soooooo slight.
Good luck
needle sizes last time we checked UM stock UE middle UO richest for a stock engine set up
I talked to Joe about this within the past month, and he told me that by default (unless specifically requested) they do 100% of their rebuilds with UE to compensate for ethanol gas being so extensive nowadays.
My 2 cents
The car was running fine so everything in the car was fine something has changed
The car idles fine
You have three carbs all doing the same maybe one could act up not three
You have 6 fouled plugs maybe one bad not six soooo something common
Advance spring broken , mixture enrichment stuck on ,cable fowl
Fuel pressure do you have a aftermarket pump
Vacuum leak. Manifold loose would surge
Does it develop power
Are you pushing oil into carbs unlikely
Unlikely
rotor, cap , point gap ,( condenser maybe )
burned points from bad condenser. Not that quick and it would miss and buck
Damper oil low not fouled plugs just hesitation
Something common to all cylinders has failed or gone out of adjustment
Think the timing is 9-10 depending on compression
I am probably the least mechanically inclined person here so take this FWIW, but only a hundred miles suggests to me that maybe it just needs to be driven a bit more before taking drastic measures. I had a similar issue during my first few tanks of gas where every so often when in the canyons everything just sort of went dead. Not completely, but like a stall.
Casually, it felt like all of a sudden the engine was lugging from being in too high a gear, but this was much more severe… almost like a vacuum had sucked out whatever power existed, and it occurred while driving at an acceptable rev for the gear I was in.
Being the lug that I am, I just downshifted twice and hammered the gas to sort of blow whatever it was out. I’m sure there are more technically accurate descriptions for whatever the issue was, but since I got the car back on the road in June, it only happened during those first few tankfuls.
If the plugs are fouling as quick as you mention have you checked the choke is actually returning to the normal position on each carb?
Its can be quite difficult connecting the choke cable when you install the carbs and ensuring the clamps and screws are tight enough. its a visual check and with a decent flashlight is quick to check.
The choke mechanism is fine. We adjusted that after installing the carbs in June.
Note the engine starts easily when cold after a week.
Using a standard SU fuel pump.
We cleaned the plugs, and they fouled up again after a few minutes drive around the block.
We checked for vacuum leaks using @Wiggles brilliant technique with an unlit propane torch. In fact, that’s the first thing we did.
The easiest thing to do next is throw a new condenser at it. I have an NOS one that I will loan to him for a short time, LOL!
Next is the needles. @Michael_Frank your analysis sounds correct. My buddy started out with ethanol, and switched to no-ethanol premium and a sip of racing fuel all within a hundred miles of break-in. Since, as you say, all the needle variations act the same at idle, it makes sense that the carbs sound perfectly in tune at idle, but would be rich as the revs pick up.
Tom why don’t you pull the suction chambers off and measure the amount the jet “drop” in each carb. (the amount each movable inner part of the jet is below the outer stationary outer part)
They should all be around all be in the same depth. Use vernier calipers and don’t push down too hard.
Maybe one isn’t returning from its enrichment position. But I’d bet spark just to be safely on both sides of the fence.
Another cent
It would have to be real Rich to foul the plugs that quick should run like crap
are the plugs fouled and missing or just dry black
Accurate plug reading is done at load
You may not be running at a high enough load and the plugs maybe to cold should still run
A sign not the problem
What rpm are you running?
Changes in the damper oil viscosity affects the tune on these carbs (throttle response)
Transmission fluid 5 w
Right up to gear oil
Thin oil causes hesitation
most of the above is just fluff
What have you changed
You changed fuel and the car started running bad …hmmm
Back up switch back to ethanol fuel
Also
Vacuum leaks may only show up when the car is hot
Smooth changes are usually fuel … supply fading in and out
Sudden erratic …electrical I have test equipment for spark etc
Put the timing lite on and see what the advance is doing
Fuel pressure high unlikely but can cause it to run rich …test it
If you can swap parts with known good ones that really helps known good ones not just new
Like a buddies car
So, after all this speculation, unless I missed something we still don’t know what needles are in the carbs. This is basic information. Michael is right on here - typical for a too rich needle. I recently sold my tricarb but otherwise stock 68 ots to a friend, but ran it for years on UO needles with no issues. This past year, it started fouling plugs. The only explanation I can think of was change in fuel although I was using the same premium no alcohol I’d always used. We think of the fuel that comes from an outlet as being unvaried, but I think that is not true. Anyways, the needles were changed to UM and proved too lean, subsequently running great on UBs. If you have UM needles already, pay attention to the other ideas, otherwise change the needles as they are likely too rich for the fuel you are using.
There’s lots of good ideas on this thread make a list start with the easy ones and Eliminate them
You can ck the needles in 5 min and while your at it the bridge height too ,don’t start throwing parts at it till you’ve gone through the list
no shotgunning isolate the problem
I had a marque specialist rebuild my 3.8 engine. I picked it up and refitted it at home. He insisted that he come by and check the carb tune and general set up. I was instructed not to drive prior as “rich settings and poor float levels will wash the rings out of a new rebuild in no time”. I had one float level wrong and he didn’t charge me for the visit.
Try and sort this out on the bench. If no one above has mentioned float levels and integrity of the needle/seat set up I would look at that as well. FWIW Paul.
One way to tell if the mixture is about right, is if it bogs or carb backfires if the choke is fully pushed in within the first mile on a cool day. (60F). If you can drive the car without problems (I am not counting idle stalling here), without the choke, within 30 seconds of starting a cold engine, then it’s too rich. I should add IMHO.
Need to know what needles are in the carbs. If Joe Curto did them and is currently using UE, I think they are too rich. I tried UE, UB, UM, UO. UE was way too rich off idle. UM way lean on mid to high range. UO way too rich everywhere. UB just right. I have a stock cam, 9:1, stock points
Nobody’s had this problem with an ignition coil before? Idles fine until you close the bonnet and the under hood temp increases and the coil starts to break down . They can fail in dozens of ways that mimic carb or fuel problems.
