SU carb clean and reset

[MSHolme13]

Hi all. Has anyone any hot tips for initial setup of HIF SU Carbs (bottom float ones)?

I put new floats into these carbs (floats were full of fuel) and had some leaky gasget issues so used some instant gasget stuff. Car started OK and was running sort of OK and was about to use the colour tune to set the mixture when the engine died.

The car will sort of re-start but sounds like it's running on 2 cylinders only. I suspect some of the blue gasget gunk has broken free and is blocking something.

Carbs are now off and I intend to strip them down and clean everything. Is it worth replacing needles and jets at same time? The ones in the carbs are not that old (5 years?) and car was running OK before the new floats went it.

Are there any tips for re-assembly, such as where to set the mixture screw? Fully backed out, or a couple of turns from where it touches the little plate, etc?

Thanks in advance for the help!

[Flying Phil]

I'm sure the needles and jets will be Ok, as you think it is most likely that a bit of "Stuff" is blocking a passage so a careful clean and rebuild should see you fine. The adjustment screw is usually closed- then back out two turns...ish.

[MSHolme13]

So, all back together and things are better, but not great. Idle is fine once warmed up but really rough and mis-firing on applying throttle. I tried the colour tune and on one carb couldn't get a blue flame no matter how far the adjustment screw was backed off. The other carb seems better.

Car will idle fine and doesn't stall at idle.

Carbs are balanced quite well and have a brand new electronic distributor, and timing is correct.
Will try the compression tester today in case it's a mis-seated valve but doubt that.

Any ideas? Thanks in advance

[MSHolme13]

So, update. Came to the conclusion that the timing was at fault. Had it set with the strobe and the timing marks matched up.
By trial and error got the car runing (rather well) by turning the dizzy clockwise. Now neither timing marks are even visible with the strobe at any rev range

What's going on here then?? When I installed the new dizzy, rotor arm was pointing to no 1 (or so I thought).

Have I installed on the wrong stroke of the engine, as I beleive TDC is reached twice??

[Flying Phil]

You are quite correct that TDC is reached twice so it is possible to be 180 degrees out. You want the No 1 cylinder tdc when both valves are closed, so rocker cover off to check. You can also check the tdc position with the plug out and a screwdriver resting on the piston, going up and down as the crank is slowly rotated. Also check that the rotor arm is actually pointing at the No1 plug lead terminal.

[MSHolme13]

So it would be possible to have the dizzy in 180 degrees out and still get the car running by rotating?
Thanks for your help, Phil

[oakdale]

If the dist was 180 deg out the car wouldn't start (unless you swap the plug leads around) but the timing mark would still align on cranking.

I think you may be barking up the wrong tree re the timing, was the dist changed at the same time as the carbs were done or was it running ok with that dist before the floats failed?

There will be a balance tube runnig across the inlet manifold, which means if one carb isn't fueling, the engine will still run on four intermittantly but with a very weak mixture (extremely so on two cylinders) which can cause a lot of confusion.

I think you're advancing the timing which is masking the weak mixture to an extent, where was the leak that caused you to use sealer?

[Flying Phil]

I suspect that you will need to go right back to basics as you have changed both ignition and fuelling systems. Now it is difficult to see the effect of any one thing. All we can really say is that timing will affect all cylinders, one carb essentially will affect one pair of cylinders.
Good Luck - you will get there!

[MSHolme13]

Problem is, I have it running really well now, but just timing by feel and sound. I guess I'll have to take the dist out and start over, make sure I look at the valves this time to get it in the right position.