PMO Carb Float Level Adjustment Advice Needed

[RoninLB]

Originally posted by EWPurdy
The problem first arose after the carb conversion.

I don't have hard experience with carbs on the 911.. plenty around here do.. so better to bow out on that one..

if the tach takes a sharp dive at this miss, then definately ignition problem somewhere...........Ron

[pwd72s]

I'm just a neophyte, and my car is injected. But if I were to be given the job of designing a float level window in a carb? I'd think the level should be dead in the middle of the window, with everything off. Then a dead level, middle of the road level should be right. Right? Here I go again...thinking things should be logical. One needs only to observe the current and past political scene to know that isn't so...

[RoninLB]

Originally posted by pwd72s
Here I go again...thinking things should be logical.

One needs only to observe the current and past political scene to know that isn't so...

Hey Eric .. if you want to get logical I have the 3 soft covered Weber books/at least, and can scan anything you want.. the scanner is a new toy and I can't shrink it and still be legiable.. so I'll have to do a direct e-mail.. not confirming that being logical will solve the issue

Hey Paul .. Libya is now chairman of the UN Human Rights Commission.. maybe the UN figures it's about time for truth in advertising... screw the UN, that's logical.....

[1974carrera]

Eric, what are you using for a fuel pump and fuel presure regulator with the PMO's? In the pic of your engine, is that the pressure regulator immediately to the right of the pressure gauge?

[EWPurdy]

Ron,
I've got one of the Weber books myself and as each day passes I'm learning more and more. The problem is that the PMO is a little different here and there and that seems to be where it counts. I had the carbs apart yesterday and I should have taken a few pics but I was hot on the trail of those floats and didn't get any pics. Wish I had taken the main jets/emulsion tubes/air correctors out while I was at it. Just couldn't imagine they're plugged already.

More info is always appreciated but please don't slave away over the scanner to send a bunch of files. If you see something particularly insightful, I'd love to see it. I'm at:

ericnbel@2fords.net

No dip in the tach btw- that's a sure giveaway for the ignition. I only wish it was that easy.

Break...Break....

Paul, the fuel level with the floats properly adjusted and working 4.0 are dead on the sandblasted dot in the center of the view window. Mine aren't quite perfect with the internal specs of the floats pretty damn close to PMO's requirements. I may tweek some more to get them dead on.

[EWPurdy]

Bob,
Pump is stock CIS pump with a Mallory 3-20 psi bypass regulator.

[EWPurdy]

...

[pwd72s]

[QUOTE]Originally posted by RoninLB


Hey Paul .. Libya is now chairman of the UN Human Rights Commission..

You're kidding? You're NOT kidding? What's next? A Ted Kennedy school of driving????

[RoninLB]

Hey Eric .. that's the Braden book.. I have more if you need greater/maybe info on a topic..
-but I kinda think, if your coil checks out, that the miss may be a pop.. so if it's not a lean adjustment on that carb, then the external gaskets to the head may be leaking.. just a thought..
- but the air screw on #2 ????
-and do you notice the "miss" thru the carb? or thru the exhaust?
-does/did any spark plug look hot, as from a lean condition?
I bet if a 911 carbhead reads all this the prob will be over...

and Paul .. Not Kidding

[EWPurdy]

...do you notice the "miss" thru the carb? or thru the exhaust?

Not sure as I can only get this to happen under load while accelerating. If I rev the car in the garage it runs fine up to redline.

...does/did any spark plug look hot, as from a lean condition?

Plugs all looked uniform and a bit sooty. Switched up to the next hotter heat range plugs.


I bet if a 911 carbhead reads all this the prob will be over... Amen! Calling all carbheads.

Thanks to all for their interest and help.

[RoninLB]

Originally posted by EWPurdy
[B
Not sure as I can only get this to happen under load while accelerating. If I rev the car in the garage it runs fine up to redline.

Thanks to all for their interest and help. [/B]

the load info is meaningful.. if me I'd go after points and coil, then the box.. because you don't have any resistors in plug wires.. I hate Beru connectors

"Thanks to all for their interest and help".... it'll cost you on payback one of these days, LOL................Ron

[RPMClassic]

You might check that you have a good seal between the spacer blocks and the base of the intake manifold for starters. All idle screws should be relative as a baseline. As for the miss - the float bowls need to be PERFECT. Your CIS pump might be overkill, as the carbs only need 1/3 of the pressure your pump is putting out. If your floats continue to stay flooded to the top- nothing good will come of this condition. Too much gas and it will have no where to go but out onto your HOT engine= fire! Talk to Rennsport Systems,TRE,COX Motorsports etc - all their customers have race cars with these carbs - your floats need to be persuaded within range to get the fuel level to the sand dot on the inspection window of the carb.

Good luck.

[EWPurdy]

My suspicions about the veracity of the fuel pressure gauge I had seem to be founded. I turned the regulator down until the indicated pressure was 2 psi and, low and behold, the float levels droped to the proper location on the sandblasted dot. I knew from previous reading that these gauges are inherently inaccurate especially when reading near the extremes. I'd like to get an electric sender to wire a gauge into the cockpit so I can monitor it from there with no hazard of fire. Any suggestions. At any rate I'll find a replacement in the meantime.

Alas, the miss is still there and I was able to reproduce it in the garage. It's not nearly as noticible just a some popping in the exhaust (not out the stacks) when I get up to about 4K RPM and beyond. While driving the effect is much more pronounced. I'm going to go through and double check the balance on all throats at 4K RPM and above to makesure I'm not missing something easy here.

Ron,
BTW, got the PDF files - thanks mucho!

[RPMClassic]

Next step for you is to check the pump volumes with the vial that was included with your carb purchase. It is VERY important that each cylinder is the same. Do you have a carb synch tool?? Are you positive that each barrel is pulling the same amount of air? You are on the right path and most likely will be able to dial out the miss you are speaking about. Good luck.

Jim

[ttweed]

Just found out that PMO has a website now. Go to PMO site and look under "support".

When I had a "rising idle" problem with mine, it was the distributor not retarding the spark enough at idle.

Good luck,
TT

[blackbird225]

What does PMO statnd for ( yes I'm new )


Michael

[RickM]

Wonder who's muffler is on the PMO site....

[ttweed]

That looks like a Dansk.

TT

[EWPurdy]

Porsche Mail Order...PMO.

[RoninLB]

what was the answer to this mystery ?