Help B's gone Gutless

[Stewart]

Last days with my B before I head back to the god forsaken cold of the north and she's gone gutless. Runs good on the low end but once it hits around 3k rpm its like someone is pulling on the E brake and it quits accelerating beyond 3800 to 4k in first and about 3500 in second.

So far I've double and triple checked the timing. set currently at about 15 degrees. Distributor was rebuilt and new vacuum advanced installed.

Carb was checked over and a new diaphragm was installed as the old was quite flimsy. High needle was set flush with the air valve.

Only recent addition was a K&N air filter and it did run fine for a bit afterwards. Shows same symptoms with filter removed.

Also the auto choke started to leak gasoline and was replaced with another used one. It seems to be functional and works well.

It is the ZS carb

Any one have any ideas as I'm Stumped.

 

[Geo Hahn]

Knowing almost nothing about Bs... does yours have a catalytic converter? I have had old cats collapse inside with symptoms very much like you describe.

Diagnosis is to feel the amount of pressure at the tailpipe (assuming you can recall what it felt like before!) or any muffler shop can test the back pressure in front of the cat. You may even be able to hear the innards rattling around if you can give it a shake.

Pls ignore if a '75 does not have a cat converter.

 

[Dave Russell]

Hi Stewart,
I believe your 75 still has point ignition. It sounds like the point gap may have closed up. The points should be set at about .015 inches. It is an easy thing to check.
D

 

[Americanshine]

About your problem, I think looking into the cat converter would be the solution. I have had cat's go bad and they back up the air flow in the car. It really is more common than you would expect. The 75's had catalytic converters, and once plugged, nothing runs right. I remove them off any car of mine that does not require smog any more. Good luck.

 

[Steve_S]

When you installed the new air filters did you change the carb needle to a richer one? If not you may be running very lean. You may also want to check your head torque. If it's loose you could be getting a leak between cylinders at higher RPMs.

 

[Stewart]

Steve Thanks

I didn't switch the needle out. Didn't realize how much of a difference the filter would make. Returned it back to stock and Walla right back where it was before. Been a long night and I'm going to bed but a lot was done. Distributor was rebuilt and works great rear brakes were completely rebuilt and she runs good again now if I could just get the blasted steering wheel off and if it ever stops raining life would be perfect.

 

[Deleted member 3577]

DING-DING-DING...We have a winner!.......Tell Steve what he has won.

 

[Steve_S]

The prize pocket lint from a British wool sweater? /ubbthreads/images/graemlins/laugh.gif