modified 3.0 w/ carbs way down on power/ any help/ideas appreciated (kind of long)

[911pcars]

Depending on fuel storage conditions at the station and in your tank, water can be transferred/present in the fuel system. If sitting for long periods of time, even if fuel doesn't evaporate, as it will in a carb. float bowl, it may cause long term corrosion (water is heavier).

Sherwood

[ddinham]

What have you concluded?

[wachuko]

Why not just change the fuel filter and test again?? Fairly inexpensive test.

[jmz]

conclusions so far:

1. I don't have much spare time these days. ...haven't fixed the problem yet but will.

2. When I do get it fixed, I'll be inviting people to come test drive the car so I can sell the engine and make way for a 3.6 vairoram. ...love the early car stuff but I'm tired of carbs so modern fuel injection here I come.

[jmz]

Well,

The fuel filter wasn't the problem as it was changed without any effect.

Fuel volume is good with a quart being pumped in considerably less than one minute ( I read a post from Steve Weiner that at least quart under a minute is the goal).

The car is running fine at the lower RPMs, accelerator pump volume is good. The only thing I haven't checked is the float bowl level but I don't know how this could suddenly change.

It's getting full advance...

I am lost. I guess I'll take another look inside the carbs...

[myfast911]

did you check the pick up screen in the gas tank? i have a 3.3l with 46 webers. had some work done and got it back and it did the same thing. i went through everthing and found nothing wrong. when some one i know asked me if i had ckecked the pick up screen in the tank, well you know the rest. bingo, it was pluged tight. at no load it tached right up. but under load it ran like sheit. hope this helps.rgm

[jmz]

I haven't checked the pick up screen but was thinking of doing this tonight.

A question though: If I have good fuel pressure AND volume how could a bad pick up screen cause any problems?

Another question: Where is the pick up screen and how do I pull it out to inspect it?

[jmz]

...I suppose the fuel pick up screen is on the bottom of the tank where the drain plug thing is. too bad I have a full tank of gasoline...

[myfast911]

as you use the fuel pump, it draws the crud into the screen and restricts the fuel flow through it. thus load.car in 4th @ 4500rpm. in the garage not in gear there is no load. as far as the screen, you must drain the tank. put the front of the car in the air and disconect the fuel line atthe tank. their will be a nut at the base of the tank where the fuel line connects and that is where the screen is. you must break that nut loose and the screen will be on the other side of it.

[pope]

But if his pump can manage a quart in less than a minute and he tested it off the tank, then the screen cannot be the problem.

[jmz]

well we can check the pick up screen off the list. I pulled it and it was free and clear. -the one attachced with the hex fitting - there's not another one that I'm missing is there?

time to check the float levels and double check the main jet passageways.

[RoninLB]

Originally Posted by jmz

Under load it just goes flat and bogs down. I can't get the engine to let loose and scream...

It must be either starving for fuel or air is all I can guess...

goes flat and bogs sounds like a very rich condition.



if in 4th gear and rpms steady at 3.5-4k, does it bog or spit ?

under load means when you're accelerating? Or steady rpms and going up a hill?

[jmz]

in the low RPM band it performs as it should. Once I try to get the R's up and on the cam it just kind of goes flat. ...the engine doesn't sing like it should. While reving it in the garage while in neutral it screams like a banshee.

I'm out to the garage to check the float level now. The float level guage arrived yesterday. -Thanks Pelican.

JZ

[RoninLB]

if it was a kettering ignition I'd guess the coil is bad..






"Once I try to get the R's up and on the cam it just kind of goes flat. ..."

meaning you can't attain any power up there when accelerating or, lets say, it can't hold a steady 4k rpms?

[jmz]

I'll have it running again tomorrow and give you a report and the best description I can comeup with.

I don't even know what a ketering ignition is... F.W.I.W. mine has an MSD 6AL and blaster coil.

[911pcars]

JZ,
Pardon this basic question at this stage of diagnosis. Have you performed a compression test to confirm the mechanical integrity of the engine? We should get those basics out of the way, otherwise we chase our collective tails.

Is it possible to temporarily reinstall the original ignition and test? It's been known for electronics to go south, $.10 resistors and capacitors and all.

Sherwood

[jmz]

Hey Sherwood,

Good question. The compression guage is out on the bench and on the list of things to do. Of course that is my fear ...that I somehow damaged the engine. I still think it's a afr problem though. It runs right in the low RPMs has a little bit of grunt it just won't wind out.

As for the ignition, I never had any of the original 3.0 ignition stuff. The car is a '74 and when i did the transplant I just sourced an MSD for the job.

[JGalt]

Forget the carbs, pull the fuel tank. You have crap in it. It may even be corroded. Start with the basics and work your way to the engine.

[jmz]

Fuel Tank looks fine.

I pulled the float sensor off the top and peaked in and it looked new.

I pulled the screen off the bottom and it looked good with minimal debris.

This tank is fairly new as it came from an '88. I installed it about 12 years ago when the '74 tank was in questionable shape.

I didn't have a chance to check the float level on the carbs last night but will this weekend.

[justinp71]

Did you check your firing order? I had mine off on my car once and it was the same thing, revved great but drove like a 2.0... (it is a carbed 3.0)