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

[madkaw]

Wow-400+ posts and we haven't solved the mystery yet!

I feel for you man, this is got to be extremely frustrating.

I was breezing thru the 400+ posts and searching what was done as far as the fuel pump. I know you replaced your pump and checked pressure, did you also check for volume?

Have you checked all vent lines pertaining to the fuel tank and system?

Looking at your last post regarding AFR numbers, it is hard to imagine you go lean starting in the 10's at idle(which is PIG rich). Even 12 at cruise is very rich, but the tip in on the throttle looks fairly normal, another words a momemtary rise in the AFR is what you will see during tip in due to no excelerator pump. So am I going anywhere with this? It seems that the fuel pump is not keeping up during a prolonged rpm session? Would this be a different than a WOT situation?-not sure, but you would think it would show up there also.

Just thinking out loud and hoping to have the million dollar answer

[Zedyone_kenobi]

madkaw, your thoughts are always welcome and appreciated. As are everybodies. I have not checked the fuel pump volume solely based on the fact that at WOT, it does not do this. Keep in mind I replaced my fuel pump thinking that was the problem. Alas, it was not. My old fuel pump was a psi below allowable than this new one, but the problem is exactly the same. I am now putting out correct pressure. I admit I have not checked volume.

But I have news! I ran a leak down test...

Just performed my leak down test...Here is how.

Ran the car for 30 minutes to get her up to temp.

Pulled the plugs and valve cover.

Hooked up my remote starter trigger

spun the engine around until both cam lobes were up on number 1

reached in the car and yanked up the E-brake and put her in 4th gear

Filled the cylinder with 90 psi. I did this same thing on each and every cylinder.

Here are my results

Cylinder #1.....90 psi input.....88 psi output

Cylinder #2.....90 psi input.....86 psi output

Cylinder #3.....90 psi input.....86 psi output

Cylinder #4.....90 psi input.....87 psi output

Cylinder #5.....90 psi input.....87 psi output

Cylinder #6.....90 psi input.....88 psi output

You could hear the air rushing through the engine, and you could hear it coming from the depths of the timing chain somewhere. It was just barely blowing past the rings I suppose. Nothing was seen with the radiator cap off, nothing was felt coming through the carbs or the exhaust.

It would seem on the outside, I have a VERY healthy 71500 mile L24.

Anybody want to loan me a set of SU's! HAAAH

Edited March 18, 2012 by Zedyone_kenobi

[240260280z]

Wanna check fuel pump again?

[Zedyone_kenobi]

I can try to see what I am getting while it is being driven, can't hurt.

I am also going to try rig up more engine grounds

[madkaw]

Being that you already changed it out, I would say the pump itself is not the problem. The AFR numbers are still strange, but I will say that I have seen 16+ on my car with no popping.

After doing my own searching everywhere on the web, I would have to guess that you have a exhaust valve problem. either a wiped lobe, or a bad guide, failed spring that is restricting the valve or tightening up and causing the valve to hang up. IMHO

I had problems with my previous 1970 with the valves getting hung up by the valves, but it got bad enough that it showed up at idle.

The only time the car ran perfect is when I would feed the motor AVGAS. The heavy lead content would free things up and the motor ran better.

Best of luck!

Edited March 18, 2012 by madkaw

[steve91tt]

Would a sticky valve or wiped lobe only show up in a narrow rpm band? The car pulls hard to 4500 pops and then pulls hard to red line. I've driven the car. It drives like a well tuned l24 except at 4500rpm. I've got a spare e88 sitting under my work bench if you want to get adventurous. As always my parts bin is at your disposal.

[madkaw]

Your Probably right Steve. My next question was going to be for you and you already answered it by saying you drive the car and it had good power.

Such a narrow band would be more ignition or fuel.

Will the car excellerate out of this narrow band easily?

It only does this during a slow exceleration ?

[Captain Obvious]

Anybody want to loan me a set of SU's! HAAAH

Yes. steve91tt made that offer weeks ago. Take him up on it. :laugh:

Steve, go to his place, lock him in his house, and put your carbs on his car. And if you've got a few extra minutes, put his carbs on your car and see what happens.

[steve91tt]

Yes the car accelerates out of the stumble nicely. I'll break into his house and swap carbs later this week. Don't tell him, I want it to be a surprise.

[Zedyone_kenobi]

I could not hear you, I was laminating my NRA card..

HAHA

[doradox]

I could not hear you, I was laminating my NRA card..

HAHA

Don't call 911, call 1911.

Steve

[240260280z]

Popping at .4500 calibre