popping through the exhaust at 4500 rpm or so.. HELP!

[Zedyone_kenobi]

That is VERY generous of you Steve!

But I cannot do that to your daily driver. I would never ask you to. Not yet anyway ! HA HA.

I would rather just buy the mikunis and webers and have those as a back up to my SU's, or have my SU's as a back up to the triples.

I wish I had an easy answer to what this was. We have picked the low hanging fruit. Now it is time to find the more obscure things that have a drastic effect. Things like the vacuum leak come to mind.

When I go more than 3 turns out the car just stumbles and dies when it tries to idle. Perhaps I should try to open up the flappers a bit more to keep her running. A wideband will tell me how lean or rich I am at idle so that should provide some insight to that issue.

[Zedyone_kenobi]

I changed out my fuel filter same thing happens. Nothing of note. Should also note my last chance filters in the SU's were very clean as well when I looked at the float bowls

I put a vacuum gage on the manifold vacuum going to the power brakes. After the engine is warmed up, it pulls 19-20 psi pretty steady at 750 rpm.

NOTE:

I checked out my exhaust slip flanges from where my 6-2-1 header goes from 6 to 2. They were a few turns loose each. The one that goes from 2 to 1 I could not get to without jacking up the car.

Edited January 4, 2012 by Zedyone_kenobi

[240260280z]

Could the popping be "knock" and you are advancing too quickly?

[Zedyone_kenobi]

Nah, when steve91tt we ran the car at essentially 1 deg BTDC with his distributor and it still did it.

It popped when I ran it at 10 deg, 14, deg and 17 degrees, and it fully advanced by 3100 rpm or so.

I got my Innovative LC-1 wideband in today. I just need to wire it up and get my exhuast drilled for the metal cupling. I was hoping it would have come with a plug AND a sensor. But it only came with a sensor. I wanted to get it installed with the cap on, then come home and install the sensor. Now I will have to do it a bit backwards.

Wire the computer up and install the gage, and then drive to a muffler shop to get the bung welded on and a hold drilled.

Edited January 5, 2012 by Zedyone_kenobi

[doradox]

We have picked the low hanging fruit.

Speaking of that, have you plugged the PCV or tried pulling the choke to artificially enrich the mixture as several others have suggested?

Steve

[240260280z]

Popping through the exhaust is usually rich and popping through the intake is usually lean (or very bad spark scatter or improper timing or plug wire mix up).

[Zedyone_kenobi]

I do not have a suitable plug for the PVC yet but plan to pick one up tomorrow along with a plug for my o2 sensor bung. I will try the choke tomorrow but I recollect doing that before with little success but let me confirm for you. No stone left unturned!

Have I mentioned you guys rock

Getting my o2 sensor hooked up must become top priority. It will remove some of the guessing

[doradox]

Popping through the exhaust is usually rich and popping through the intake is usually lean (or very bad spark scatter or improper timing or plug wire mix up).

Which is why it runs better with SM needles? And has no other symptoms of being too rich? If it's mixture related yanking the choke will either make it worse or better. I imagine that information would be useful. I can't imagine a single good reason why one wouldn't try it. As a matter of fact I can't imagine a single good reason why it wouldn't be the first thing you would try.

Steve

[Captain Obvious]

I'm having a little trouble justifying a typical vacuum leak. You said your idle is perfect, and I would expect the impact of your typical "constant" vacuum leak to decrease as you give it pedal. That's why I was trying to think of more atypical vacuum leak sources that might get worse off idle.

Well whatever you find, I'm pullin' for ya!!

[madkaw]

You need to get this off your list. A wrong setting would be most apparent at higher rpm cruise. If anything I would go rich on the setting-the worse scenerio would be a bit of fuel in the carbs. To low of a level will throw off your mixture at higher load/higher vacuum scenerios. I don't believe adjusting the mixture screws will make up for a poor setting on the floats. I know you have the factory setting in there, but tweeking the floats a couple off MM's will not hurt.

What I have witnessed is a car that I rebuilt the carbs on that it would run in all parameters, but not much power top end. It was all about the floats not being set right. Believe it or not I just tweeked the floats without a real measurement-just richened it up a bit. Car made much more power and never overflowed the bowls.

Here is what I have NOT done:

I have Herchecked fuel pressure from my brand new fuel pump, which was good, but I have not checked volume. OR pressure while the car is being driven. But I ruled that out as if I can rev to 6500 rpm at wide open throttle I am getting fuel.

I have NOT checked if the fuel level is right at the top of the jet opening in the carb body, I just assumed the float bowls being properly adjusted was okay.

Edited January 5, 2012 by madkaw

[doradox]

UPDATE:

5pm this evening I get all the carbs back together and fill them with a lighter oil. I used Marvel Mystery oil per somebodies suggestion. Car now pops and sputters at any throttle change above 2200 rpm. It is leaning out way to fast as that piston rises so much faster. Definitely a step in the wrong direction!

I will clean out the carbs again and fill them with straight 20 wt oil. I have no idea what the SU oil is that I bought. I only know the marvel mystery oil made the plunger FAR easier to push up.

Did you ever try this with 30 wt recommended by the FSM? Or maybe some 40 or 50 to bracket the results?

Steve

[Zedyone_kenobi]

Nope, but I intend to.

I will get a bottle of SAE straight 30 wt to give it a try.

I am sort of on hold until after I get my O2 sensor in. My time is very limited each day, and I try to squeeze as many ideas you guys give me as I can. But windows are small.

I will make every effort to go for a drive to day to try the choke thing again. I just do not remember the results.

I will also try today to block off the PCV and see what happens. I am going to order more SU float bowl gaskets and try to get an actual visual reading on that float level with a straight edge and a piece of clear tubing. While I do that I am going to put the SM needles back in.

You guys are worth your weight in SU oil let me tell you!