'76 2002 engine problems

[decoupe]

This is also posted on the 2002faq.com forum but I thought someone here might have run into this as well - not that I would wish this on anyone..

I'm struggling to get the carb set up on my '76 2002 stock engine with 38/38 downdrafts and given the similarity with the m30 and the number of e9 weber downdraft conversions, I'm hoping for advice.

You can see that plug #1 is sooty to the point of fouled, #2 is lean to the point of knocking #3 looks just about right and #4 is showing rich - and this is a new set of plugs. Using Best Lean Idle setup procedure with 45 150 185 jets, it drives but not well and within minutes it's missing and jerking at any rpm and #1 is fouled with #4 on it's way as well. Same thing happened when jetted 50 145 185. Going one range hotter to NGK BPR5ES and adjusting my float level to spec I hoped I had resolved my set up.

No luck.

So everything is new with less than 500 miles on it and the timing set with ignition at idle (900rpm) 12 BTDC. Starts like a champ and the electric choke functions just fine.

So what combination of air, fuel and spark produces over rich on #1 and 4 and lean on #2 and 3 ?? One carb feeds all 4 sparks from a common source - fuel pressure regulator in place. Coil is newish Flamethrower and points replaced with Petronix.

The same air/fuel mix is being supplied to each cylinder but with very different results so is the problem is electrical? Replaced the plugs had no effect. Replaced the dist cap with OEM had no effect. Checked for spark and all four showed good spark.

Distributor? Is it possible the distributor is so worn that there is a wobble and instead of circular it spins in an ellipse? How to test that?

Grrrrrr

 

[jmackro]

Is the compression consistent in all four cylinders?

Are the integrity of the valve stem seals and oil rings consistent in all four cylinders? In other words, is it possible that you are seeing signs of oil burning, rather than an over-rich mixture, on plugs #1 and 4?

is the problem is electrical? Replaced the plugs had no effect. Replaced the dist cap with OEM had no effect. Checked for spark and all four showed good spark. Distributor? Is it possible the distributor is so worn that there is a wobble and instead of circular it spins in an ellipse?

How new are the plug wires? Though, if the car runs well, it probably isn't the wires.

I doubt the problem is due to a worn distributor, particularly since you have a Pertronix.

 

[Stevehose]

Have you tested for vacuum leaks on each cylinder where the manifold meets the head? If you have a leak on that lean cylinder then you may be compensating by over richening the others. Do you have one or two carbs?

 

[adawil2002]

I had my distributor 'wobble', had metal filings under the dist cap. They were collecting on the plate around the Pertronix. I bought the Ireland Engineering Dizzy as a replacement. Set timing to 32 degrees at 3300rpm, that's the max of the advance curve for the IE unit.

I also had to replace my plug wires and plug caps, #2 was bad so replaced with a Beru wire set, car runs great.

How's the linkage between the carbs? Had a friend who chased his tail for a year trying to sync his webbers. His throttle linkage was old and would twist and starve #1. He rebuilt the linkage and all is good now.

 

[decoupe]

Update/replies

Jmakro - haven't done a compression test but this engine is a rebuilt with less than 10,000mi and doesn't burn or blow smoke. The valves are well seated and adjusted (and checked). Plug wires three years old but less than 500 miles on them. I'm going to swap the #1 and 2 wires as they are the two most extreme cylinders to see if there is any change.

Stevehouse - Vacuum leaks at intake/head - they are gasketed and torqued to correct value (I was hoping this would be the one but...). I'll spray with ether to check. It's a single 38/38 downdraft carb on a good Cannon intake manifold.

Adawil2002 - What were your symptoms with the dizzy wobble - how did you diagnose it? Good to know about the IE replacement and it's relatively cheap too. My wire swap will confirm the state of the ignition plug wires and caps. Already installed new rotor and dizzy cap with OEM for a 2002. Single carb as noted.

Thanks guys - still looking for the culprit. I should have also said that when I put the car away last fall it was running well but a little rich on all cylinders. Started it up this season and it's gone bi-polar.

Here's the engine when I was replacing the head gasket to stop an oil seep.

http://s54.photobucket.com/user/decoupe/library/m10 Engine?sort=6&page=1

 

[adawil2002]

Adawil2002 - What were your symptoms with the dizzy wobble - how did you diagnose it? Good to know about the IE replacement and it's relatively cheap too. My wire swap will confirm the state of the ignition plug wires and caps. Already installed new rotor and dizzy cap with OEM for a 2002. Single carb as noted.

Developed a random miss and a little buck like a random cylinder not firing. Replaced plugs and wires discovered a bad #2 wire. Mechanic found the filings on the dizzy plate. Replaced the dizzy and all has been good.

Still have to send the original dizzy to Advance Distributors for restoration and recurving. Rob Siegel, Jim Gerock & Paul Wegweiser have all had theirs redone with great results.

 

[decoupe]

The missing and bucking sounds familiar. Do you recall looking at your plugs? Was one really black? Of course that could also be the bad plug wire.

 

[adawil2002]

The missing and bucking sounds familiar. Do you recall looking at your plugs? Was one really black? Of course that could also be the bad plug wire.

Plugs all looked good when I replaced the Iridium plugs with NGK BP6RESs. They're still on my work bench. I believe the mechanic pulled the NGKs, I did not see them at the time.

The car started to exhibit the problem on my way to BavAuto Show N Shine in 2012. Started diagnosis spring of 2013 and got the IE dizzy just before leaving for The Vintage in W-S NC. A 1900 mile round trip.