Engine will only run above 4000 RPM. Carbs or timing?

[Captain Obvious]

I'm sorry, but I've lost the pea. Can you put together a refresh of what's currently on the engine in terms of carbs and ignition?

You're running round tops, right? What about ignition... What are you currently running? Points or something electronic?

[Wade Nelson]

Any progress on this motor? I honestly think it has jumped time, the timing chain is off a tooth or three. Either that or two of the throttle butterflies are not opening, and it's attempting suck charge through a single carb. Above 4000 it has enough suck to do that.

[bartsscooterservice]

I found that the fuel regulator was having no effect when I did the fill test at different settings, 5lbs or 1 lb the I'm getting 1.5L of fuel per min. The pump only pushes with 4lbs of force but to eliminate the fuel pressure as a possible problem I disconected the power to the pump and tried starting the engine with just what fuel was in the bowls, all the symptoms are the same.

Thinking I might pull these SU's and pack them off to Ztherapy so I can start working on the car again.

I'll let you guys know what happens when I get them back, thank you very much for all the help.

Chris

Chris, you still working on it?

[madkaw]

Chris probably walked away for a while. It sucks when you get this frustrated-especially from a freak issue like this. You get to wonder about your luck. It's not like fighting a rusty bolt, which is understandably frustrating.

Hopefully he walked away long enough to get some fresh eyes on the situation .

[grannyknot]

Stanley, And the Cheeseburger Demon Squirrel Award goes to ...?

Any progress on this motor? I honestly think it has jumped time, the timing chain is off a tooth or three. Either that or two of the throttle butterflies are not opening, and it's attempting suck charge through a single carb. Above 4000 it has enough suck to do that.

Wade, the engine has not been loosened in any way, there is no way that I can see of that happening and the timing checks out. I have sent the SU's to ZTherapy with no illusions that it will solve the problem (but I hope it does)

but it will eliminate the carbs from the equation. I have parallel ground the head side of the intake manifold and cleaned up both surfaces of the SU spacers. Also thinking about a adding a smear of silicone gasket sealer. There will be fresh gaskets, yada yada

Chris, you still working on it?

Every spare hour.

Chris probably walked away for a while. It sucks when you get this frustrated-especially from a freak issue like this. You get to wonder about your luck. It's not like fighting a rusty bolt, which is understandably frustrating.

Hopefully he walked away long enough to get some fresh eyes on the situation .

You said it Steve,

It's not just your luck you wonder about, you start questioning your ability and experience and the all the other guys helping you work through the problem. I talked to Steve Eperly of ZTherapy the other night (and this guy knows an L6 engine as well as anyone) he said "sounds like a big ol vacuum leak" just like so many of you have said and as I know from my own experience. While I'm waiting for the carbs to be delivered I'm going to try and finish the rest of the car.

I WILL get this sweetheart running.

I really don't know what in the hell I would offer as the CDS Award (Cheeseburger Demon Squirrel )

Chris

[Reverend]

HAH @ CDS Award. . I'd love to see how that looks like, some evil-eyed little squirrel sitting over a burger, coated in gold over mahogany wooden box. I wish you all the best with this quest. Im considering CDS awards to anyone who fixes my Z as well.

[Zedyone_kenobi]

I have not read all of this thread, but what about a non parallel intake?

While the carbs are off, why not try a new manifold?

I can ship you my polished SU manifold? NO cracks and perfectly flat if you like.

[Zedyone_kenobi]

Okay buddy I have been thinking. I would like you to try to remove that regulator. I know you said it was putting out 1.5 liters smoothly, but that was with zero backpressure. Regulators require backpressure to work. What we do not know is how it is metering fuel with that electric pump AND that regulator. I would like you to try to run with a different regulator maybe. I am still not convinced it is not fuel related.

[madkaw]

Chris,

Have you put a straight edge across the EXHAUST manifold flange?

[bartsscooterservice]

Okay buddy I have been thinking. I would like you to try to remove that regulator. I know you said it was putting out 1.5 liters smoothly, but that was with zero backpressure. Regulators require backpressure to work. What we do not know is how it is metering fuel with that electric pump AND that regulator. I would like you to try to run with a different regulator maybe. I am still not convinced it is not fuel related.

That's why I said, go back to mechanical pump with the su's and try..

[madkaw]

Everybody wants the CDS award!

[grannyknot]

I have not read all of this thread, but what about a non parallel intake?

While the carbs are off, why not try a new manifold?

I can ship you my polished SU manifold? NO cracks and perfectly flat if you like.

I have a buddy that runs a cabinet carpentry shop and has an inline table belt sander that is 4'x8', 180 grit.

I trued up the exhaust manifold before all of these tests and since dis-assembling the SU's I have trued up the intake manifold and there were no irregular wear patterns, it came off uniformly.

Okay buddy I have been thinking. I would like you to try to remove that regulator. I know you said it was putting out 1.5 liters smoothly, but that was with zero backpressure. Regulators require backpressure to work. What we do not know is how it is metering fuel with that electric pump AND that regulator. I would like you to try to run with a different regulator maybe. I am still not convinced it is not fuel related.

I didn't know that! I haven't sent the carbs to ZTherapy yet so I'll reassemble them and try again with no regulator,

with a new regulator and with the mechanical pump.

Chris,

Have you put a straight edge across the EXHAUST manifold flange?

see above

That's why I said, go back to mechanical pump with the su's and try..

see above

Thank you gents

Chris

Edited May 18, 2013 by grannyknot