my current project

[Arne]

I tried ATF in my carbs, got that same backfire on quick throttle openings. I suspect that the slides are opening too far, too fast. I plan to go to 20wt. in mine, as recommended by my FSM. ATF is typically about 5wt. IIRC.

[Mat M]

I tried ATF in my carbs, got that same backfire on quick throttle openings. I suspect that the slides are opening too far, too fast. I plan to go to 20wt. in mine, as recommended by my FSM. ATF is typically about 5wt. IIRC.

Hey, all!

Clutchdust...

I just had some nightmare probs with my carbs. I had the same stall out at 55-60 MPH, no matter what gear the tranny was in. At first I thought it was the fuel filter. After swapping out 4 in 3 days, I decided it must NOT be the filter!

I was running Marvel Mystery Oil in the domes, which, apparently was far too light. I tried 10w-40 weight to see the opposite end of the spectrum, and what a difference!!! I think the slower raising of the pistons atomizes the intake air/fuel mix better. I also read in a manual on SUs that one needs to make sure the float level is correct in order to maintain a proper fuel delivery. In order to check for correct float settings, take the cap off the float bowl, invert, and measure the top (now bottom) of the float, which should be at 10.1mm above the lid at the front and rear of the float. I then re-adjusted the mixture screws to 2 1/2 turns from all the way up.

The car runs fine now. Even gets better fuel economy.

[clutchdust]

i forgot to mention in yesterdays post that i cleaned the ATF from my dampers and put in 30 straight weight instead. i think i just need to bump my idle up a touch to get over that spot. problem is, i don't know what my idle currently is. like i said, since i installed the pertronix, the tach doesn't work. i will still recheck my float levels although i figure i'm pretty much there as the engine seems to run pretty well as long as the RPMs don't drop below 1200-1500.

[kenz240z]

Hi Gary, glad to hear you're making progress!

If the engine runs well above 1200 rpm, but poorly below that, then I'd suspect the carbs are out of balance, with one carb perhaps not flowing any air at idle and low rpms.

Here's a quick test: Remove the air cleaner cover. Start the car. Momentarily place your palm over the front carb mouth, you should feel suction, and the engine rpm should drop like it's going to stall. Repeat this process on the rear carb, you should get the same results. If putting your palm over the mouth of one of the carbs doesn't cause any change in idle speed and you don't feel any suction, then you've found the culprit.

At one time there was an excellent how-to tech article posted by a former member; however, I searched for it and it seems that it has been removed. Perhaps folks who have installed a Pertronix unit can help out with this one.

[clutchdust]

hey ken, i don't think that's the case. i've done the vacuum hose in the venturi and used the balance meter and both are pulling very similar at idle. it almost seems like the damper is still opening too fast, even after switching to straight 30 weight. it's like the same problem i had before but not nearly as bad, just still there. i'll play with it some more this weekend and we'll see. got some plug wires to put on it too. i still have to clean up that crank pulley and mark those timing marks better. so there's plenty of things to keep me busy.

[kenz240z]

Gary, do you have a stock distributor for the engine? If so, you may consider temporarily re-installing it. The tach will work again, and it may help pinpoint the trouble. Keep us posted!