Strange power loss

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gwittman

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My 2800 CS is close to being stock but does have the JAM Engineering Weber Carb kit and Pertronics ignition. The engine is original and has about 60,000 miles on a rebuild. I rebuilt the carbs about 9 months ago and it has been running strong right up to redline until about a week ago.

I was cruising down the freeway early Sunday morning and decided to let it run free for a bit. At around 90 to 95 it just acted like I let up on the pedal but it was still to the floor. It did not act like it was misfiring because it did not jerk. I let up and after slowing just a little it ran fine again. I could stay just below that cut off point and it would run fine. It was acting like the rev limiter in the distributor rotor was activating.

I took it for a test drive last night to check out the symptoms. I could rev to redline in 2nd gear with no problem. In third gear it would shut down at around 6,000 rpm. In fourth it would shut down again at 90 to 95 mph. I didn't look at the tach but I am guessing that was between 5,000 and 5,500 rpm.

I thought it might be starving for fuel due to my old mechanical fuel pump. I have a secondary electric fuel pump that I use to prime the carbs after setting for a while. I turned it on and ran it up in 3rd gear and got the same shut down at 6,000 rpm.

I does not seem like a normal Pertronics failure but I will next try reinstalling the points to see if that makes any difference. I think my coil is still the original and it may be failing. However, it is not acting like any coil failure I have encountered.

Does anyone have other ideas as to the cause of this strange power loss?
 
Fuel filter ok?

Coil failure also tends to show itself at high revs.

Float levels in carbs to spec?

Timing ok?
 
Swap your rotor and go for spin with a volt meter
Connected to your battery also.
 
New fuel filter installed new 9 months ago. Float levels were set to spec when rebuilt. Timing to factory specs.

I think I have a spare rotor from my original distributor. I installed a new European distributor about 25 years ago. I will look for my old distributor all borrow the rotor.

My tires are closer to 24" tall but that would still make it less than 5000 rpm. I wish solving my problem was as easy as calculating rpm vs. speed with an equation.
 
Checked all your throttle linkage from accelerator to shaft cogs on each carb? All the collars that tighten on shafts with allen screws?
 
Worthwhile

To check your float level for full opening. There is a measurement depending upon plastic or brass.

But it could be possible that the engine is just leaning out at speed due to the float not opening far enough and being fuel starved yet not pump related.
 
If it has just started to do this and your coil is original, it's probably time for a new one anyway.
 
Tech Talk

Stevehose said:
If it has just started to do this and your coil is original, it's probably time for a new one anyway.
Click to expand...

I read in the Roundel that it might be the wire connecting to the coil and you could snip off the female end, expose some fresh wire, crimp on new ends and the problem is gone
 
All the linkage is good. I tried a different rotor and got no change. I have ordered a new coil to see if that works. I will be gone for about a week. The coil should be here by then and I can give that a try.

The next thing I will look at is the possibility of some kind of restriction in the gas line or gas line intake that may be starving the engine at high flow. I don't think it has anything to do with the floats as it came on all of a sudden. It has been running flawlessly until recently.

The wire connections are not very old. I installed the Pertronix ignition about 3 years ago.
 
Condiiton of ballast resistor ok?

gwittman said:
All the linkage is good. I tried a different rotor and got no change. I have ordered a new coil to see if that works. I will be gone for about a week. The coil should be here by then and I can give that a try.

The next thing I will look at is the possibility of some kind of restriction in the gas line or gas line intake that may be starving the engine at high flow. I don't think it has anything to do with the floats as it came on all of a sudden. It has been running flawlessly until recently.

The wire connections are not very old. I installed the Pertronix ignition about 3 years ago.
Click to expand...
 
Problem solved. A new coil let it run free again. I was able to run it up to 6300 rpm in 3rd and well over 100 mph in 4th without even the slightest hiccup.

I guess the old coil was saturating during sustained high rpm and stopped firing or was giving a weak spark.
 
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