Single Lean Cylinder

[HuD 91gt]

Vancouver BC. I'm slowly making my way through the tune up procedures. After installing all the ignitions points etc the car was idling very nicely. Unfortunately this seems to have changed as it sat for a week or two and is no longer the case.

I'll try a valve adjustment and see where we sit. I just ordered a Haynes manual as the FSM doesn't seem to explain how to do things, but rather how things work. I think the combination of the two should help immensely. Thanks for everyones suggestions.

[siteunseen]

Doesn't the '71 have 2 choke levers? Are they both pushing and pulling the cables completely? Here's how I learned to do the valve adjusting, PictureTrail: Online Photo Sharing, Social Network, Image Hosting, Online Photo Albums. Doing them cold will get you close enough for your 1st time. But you gotta go back and do the "fits, or doesn't fit" when the motors hot some day. That Haynes manual will make a good beer coaster while you're reading this forum.

[Sean240Z]

I ran into a similar issue where I thought number 3 cylinder was running rich (when compared to cylinders 1&2). Turns out I had a manifold gasket leak at the intake manifold for cylinders 1&2 which leaned up the mixture for those cylinders. Since tightening up the manifold nuts, I now have much more consistent plugs across the first three cylinders. The intake runners for cylinders 1&2 and 5&6 are "siamesed" so only way I could see this being your issue would be if the rearmost intake manifold bolt was loose or perhaps you had a manifold gasket leak for the #6 intake runner.

The remaining plugs do look rich. Suggest you clean the plugs and reinstall. Then check that the chokes are fully off (i.e. push up on the bottom of the carb needle housing to ensure that they are fully closed). The P.O. for my Z had installed bike cables instead of solid choke cables and the chokes would not fully close without assistence. If chokes were fully closed, suggest leaning each carb by 1/4 turn of mixture nut. That said, you really can't get an accurate reading on the plugs without driving around for a period of time, with the engine under load.

[HuD 91gt]

2 choke cables would definitely make sense. But I am missing one in the cabin, but there is a spot next to my choke(On the centre console) which looks like it could house another(I was always curious what it was for. But besides that, the single choke lever I have does indeed actuate both chokes(He must have put in a linkage from another motor?). After advice from other forum members, I had to clean up that area so the chokes would spring back up. The car ran great. Maybe they are sticking again! I didn't even think of that.

Over the next couple days i'll try and check the manifold too. Thanks for the suggestions guys! Also thanks for the valve adjustment link. I also found a video tutorial of a guy doing them on a L20, (maybe L16) so I'm thinking it will be pretty simple by following that. I will update once i'm back home, for now im on the road for the next few days.

As for doing the valve adjustment hot or cold. I don't see any harm in doing them up to temperature as the car will idle well enough to get up to temperature. But it all depends how fast I can do the adjustment if it will stay hot. Ha. How quick do you need to accomplish this task?

Edited May 7, 2014 by HuD 91gt

[siteunseen]

I've never done this but some people use an unlit propane torch to find intake manifold leaks. The RPMs will raise when it sucks in the propane at the leak. Or maybe a can of ether would work? google.com it.

Good luck.

[Mark Maras]

My 71 had a single choke lever from the factory that operated both chokes. The missing lever was for a hand throttle (20th century cruise control) & was discontinued shortly after production.