308 aceleration problems

My '77 308 GTB has been running poorly and now I don't know what to do.

First a little history. I bought the car last year and have had some aceleration problems. I took it to my local mechannic to have the carbs adjusted and he discovered the problem with the manifolds. There was some corrosion and we added metal then machine them back to original specs. The carbs were adjusted and sinchornized.

When ever I acelerate there's always been a problem with the engine going over 5000 RPM. Now it's down to 4000 RPM. Tonight I ran some diagnostics on it and found the following:

The micro switch on the carburator is missing.

At 4000 RPM the spark dies out if the aceleration is quick. If I bring the RPM up slowly then it'll go to 7000 RPM.

At 4000 RPM the fuel mixture goes very lean. I know this because the exhaust get red hot, and the engine pops and sputters from both the carbs and the tail pipes.

The advance works and the distributors both advance to 32 degrees.

At idle the coils are putting out 14000 volts. At idle, 9000V seems more reasonable to me.

I get 10 volts across the fuel pump, which is a Stewart Warner 1235A-D.

I do not know the actual fuel pressure (should be 3.5 to 5.0) is to the carbs. I'll get a gauge and check that out

How should I go about to getting this fixed? I know that putting the micro switch on it is part of the solution. I don't know how to wire it up though. I do have a set of scemetics so I'll trace that out. What is the likely problem with the carburators?

Also, I put Birdman's fuse blocks in and have noticed a little inprovement in the electrics. Mostly, the instrument lights are really bright, except for the tack. Maybe I need to look at the ground on that light. The windows are just as slow as they've always been. So I have to take them apart and clean and grease, etc. Ahh, the list grows longer with each passing moment.

Lastly, the serial number is 21039. The car is red on top and black below the seam like a boxer. If anyone on the list recognizes this car give me a private email. I'd like to talk to you about the car. The dealer I got the car from said he got the car from the San Francisco Bay Area.

Thanks, in advance

Bob Wassam

 

Hey Bob,
It's tough to diagnose this way, but here are some thoughts that may or may not be helpful.

1. Replace the ignition wires and especially the extenders between the wire and the plug. They go bad after a while and arc. Even if this is not the problem, it's not that expensive and worth doing anyway to be sure you eliminated that as an issue. Unfortunately, if this IS the problem, it's very hard to diagnose other than to just replace them.

2. If you are sure you are getting a good advance on both distributors, I guess you checked that, because the hesitation thing definitely could be dizzy advance. You say the spark dies out if you accelerate hard. Are you sure about that? That really can only mean points/distributors. Sounds like you might want to rebuild the distributors and have them set up on a machine, and replace the points/capacitors. Or switch to a electronic ignition and trash all that garbage!

3. You probably need larger main jets. What are the jets you are using? Modern fuels need richer jetting than the fuels made when these cars were new. Plus, I doubt you have the original (restrictive) thermo-reactor muffler, so you are probably jetted too lean to begin with. Better to run the car a little rich than a little lean. Running lean is hard on the valves. I'm running 1.40 mains in my '77 with Ansa exhaust and the "Russ" airbox mod and it likes it a lot better than the 1.35s I had in there before. I would expect you should be running at least 1.35's with a non-stock exhaust. It's stamped right on the rop of the jets, which you can see while they are installed in the carbs. All you have to do is pull the airbox lid off (4 nuts) and peek at the tops of the carbs.

4. Forget the microswitch. All that thing did was swap out the points to another set that were retarded at idle so the car would run hotter and burn emissions better. It actually makes the car run worse, not better. It was put on there purely for emissions in the U.S. and was not put on the Euro model. Many 308s had them disabled or removed. Mine have never been on there since I bought it (PO removed them entirely). About 8-10 degrees of advance at idle makes the car run a lot better at idle. The microswitch moves the ignition to the regular set of points as soon as you touch the gas, so the microswitch would not at all effect how the car runs when driving or accelerating.

5. The dim tach may just be a bulb out. There are two or three (can't remember) bulbs in the tach and if one is out, it's a lot dimmer. Also, you should remove the dimmer rheostat from the dash light circuit. It has a tendency to heat up and melt things, not to mention it dims the instrument lights even when turned all the way up because there is a voltage drop through it.

Hope some of this helps....

Birdman

 

One more thing. Check the accelerator pumps. When you hit the gas hard, you should get a squirt of fuel right down the throat of the carbs. You can have someone pump the gas with the car off and watch down the throats of the carbs to be sure that each carb gets a squirt. The pumps are replaceable with a rebuild kit in case one of the pumps is torn. They are basically just rubber "bellows" type jobs and if they get torn they not only don't squirt, they leak air. Unfortunately, although it looks easy to replace them, two of them are hard to reach with the carbs in place. But if they are not working right, the carbs will lean out like crazy when you stomp it and the car won't rev. But the car would still rev slowly, which sounds something like what is happening to you.

Birdman

 

First things first.. carburation set up really only matters on part throttle and lower rpm.. if it wont pull at full throttle/high rpm... almost guarantee it's ignition.. unless your main jets are blocked or fuel pump is dead... both HIGHLY unlikely

what's the coil/s primary winding resistance...

whats the dwell angle, points gap... and points condition, and how are the little wires/terminals that connect the points to the dizzies?

Condensors ok?

Twin dizzy car I assume?... are both banks timed correctly.. Single dizzy car... is phasing correct?

Are the rotor arms short circuiting to the dizzy shaft? (surprisingly common on the twin dizzy cars (but not single dizzy).. right through to same part used on 308QV etc)

bottom line..

carry out proper diagnosis, step by step... it's all trade school stuff in theory...

and yeah.. forget the micro switch... get rid of spare points/switch etc

 

If the accel pump diaphragms are split.. they'll PI55 fuel out...not air in...

The other thing to look for is that the pump jet valves are seated properly... run the engine at about 1500-2000 rpm, and watch the accel pump jets.. they should not squirt or dribble AT ALL unless you move the throttle... you may get dribble from the copper washers... remove the valves/jets and flatten the seal surfaces with 1200 grit paper.

 

Looks like you are getting full advance........

As noted look to ignition/plugs/wires......sounds like one bank ignition is failing to me......

 

Sounds like a coil failing to me.....the glowing header is unburned fuel and the popping sound is the EXACT problem I've faced with mine this week!!
Unburned fuel hits the functioning side in the exhaust system.

I haven't fixed mine yet but new plugs, clean extenders and wires have not resolved it permanently. Oddly, the problem was intermittant, for some time.....

CAREFUL as I've blown headers apart, when forced to drive very far this way......

 

A glowing header "could" be unburnt fuel, it could also be cam timing or ignition timing out.

 

Hey Phil I agree in terms of the rev issue, but he said the headers were glowing which sounds like it might be running lean as hell. We all know about these somewhat fragile sodium exhaust valves, so I was thinking that not addressing that ASAP could get expensive.

The thing I don't get is.....if you can rev the car slowly but not quickly, can dizzy's cause that? Maybe the advance is sticky and it won't respond quickly, but eventually as the revs build, the weights gradually move?? This is a funky problem and I will be curious to hear what the culprit turns out to be. I do agree with Phil that the issue really seems like it would be ignition related.

Birdman

 

Once the car starts sputtering, it doesn't stop. I'm concerned about the valves too.

So, after thinking about it today, I've decided to richen up the carburators first. I plan to do this by doing two things. First I'll go to 1.40 jets since I'm not only at sea level, but the moist air here on the Oregon Coast all contributes to a lean mixture. I'd rather run a little rich anyway. The second thing I plan to do is change fuel pumps. I believe that when the stewert warner pumps go out, they begin by drawing more than normal current and output pressure starts to fall off. Also, they don't last very long.

I'll start with that, and if it doesn't work then I'll tackle the ignition system. The electonic ignition system is starting to look better all the time.

thanks to everyone. Bob Wassam