Figure this one Out

johnalfa1976 · #1 (**permalink**) 09-14-2004, 02:14 PM

OK Alfa Experts - did you ever run into this?????

Driving to work last week, my Weber equiped 76 Spider started to backfire slightly between gear shifts. Doing what any "Expert" would do - did an Italian tune up - drove it real hard for the next 3 or 4 miles - problem went away. On the way home - ran great. Decided To buy some new plugs on the way home (NGK ***- 7). Installed them - started it up- sounds great. Did not test drive.

The car sat for 3 days. When I tried to drive it - lots of backfiring - low power. Pulled the plugs. #2 gap was .000001 (approx) All the others where at .025. I know I am getting old but could not believe I was that Stupid.
Regapped the plugs - drove to work - ran great. On the way home (approx 15 miles) it started to backfireing and low power. Pulled the plugs. #2 is at .00001. This baby is regapping itself!!!!!

Any Ideas???

Ciao,
John

Farace · #2 (**permalink**) 09-14-2004, 02:21 PM

Seems to me the only way the gap gets closed is if something is hitting it. The only thing there to hit it would be the piston. But why aren't the other three hitting? It makes me wonder 1) might an extended-tip plug have been in the wrong box? Check to make sure it's the right plug; 2) is it missing its gasket, allowing it to protrude farther into the cylinder?

If it's the right plug and has its gasket, it might be interesting to swap that plug with the one from one of the other cylinders and see if the problem travels with the plug or stays with the cylinder. (Not that you want to keep whacking the plug with your piston . . .)

**John M** · #3 (**permalink**) 09-14-2004, 02:24 PM

I agree with Bob:

Something wrong with this happening. Most likely the wrong size plug. I would add another compression washer as a quick and easy fix.

Best Regards,
John M

**Roadtrip** · #4 (**permalink**) 09-14-2004, 03:03 PM

Recheck the plug number. For NGKs it should be BP7ES or BP6ES. Unless you have some sort of radical pistons and shaved head or severe rod bearing disintegration, I can't believe that the piston is doing the damage. Have you looked through the spark plug hole and looked at the edge of the valve to see if there's any witness marks there? The valve would have to be pretty loose to get the plug. Look at the top of the piston as well for witness marks.

Also, try indexing the plug to be away from the valves when installed.

MrT · #5 (**permalink**) 09-15-2004, 12:55 PM

I didn't know what "indexing" was until I read the term explained some time ago. I currently think it means using additional or thicker plug washers to change the plug insertion into its mounting threads. This allows the electrode position to rotate away from a "bad" orientation, facing the piston surface.

DaveC · #6 (**permalink**) 09-15-2004, 01:39 PM

Indexing also means ordering a case of plugs. (96 in a case) Then sitting with the customer while we screwed each plug into a 14mm hole to find out where the electrode faced and sorting each by electrode position. Sometimes racers can be a pain!!!

Dave

turbolarespider · #7 (**permalink**) 09-15-2004, 01:46 PM

You could always replace them with the Golden Lodge plugs... No gap to worry about. It's what Alfa intended, even with the Carb'ed engines.

E-

Ianc · #8 (**permalink**) 09-15-2004, 01:56 PM

I wouldn't use any quick fix for this. If it's not the plug, it's got to be in the cylinder. I had a customer with the same problem on a Jag way back when I was doing OHC tune-ups on a free lance basis for dealerships, and it turned out to be a carbon build-up on the piston - just enough to let the crud touch the plug tip and close the gap. It was a weird problem, as the carbon was quite thick in a small area of the crown. Get the piston up to TDC and have a look. There are fairly cheap scopes that hook up to a computer and will allow you to look inside.

P.Webb · #9 (**permalink**) 09-15-2004, 02:34 PM

You used BP7ES which are protruded electrode (the 'P' in the part #) and can cause valve contact. Go get yourself some B7ES and the problem is solved. I use the coldest possible plug I can start it on, B9ES in the Verde.

Indexing is pointing the electrode at the exhaust valves. Draw a line on the plug with a marker where the electrode is. You can sometimes switch the plugs around between cylinders to get them to index, otherwise as suggested use additional spring washers. Don't over or undertorgue to set index.

-Peter

MrT · #10 (**permalink**) 09-15-2004, 02:37 PM

DaveC: I had been (mis?)informed that plug washers of various thickness were available, and that this is the proper way to index the plugs. None of this is from first-hand experience. I haven't personally done any of this.

And the Lodge plug suggestion is good. That's what I _usually_ do and it seems hard to go wrong.

Michael

DaveC · #11 (**permalink**) 09-15-2004, 02:55 PM

MrT You can use washers. This guy simply did not want washers. He wanted the plugs to protrude and index the same. Every little bit helps he said. Some cars have tapered plugs and indexing by matching is the only way to go.

Put Golden Lodge in. Best plug in my opinion. Pulled my Bosch crap out and installed my Old Golden Lodge. Runs smoother and quieter.

Dave

**John M** · #12 (**permalink**) 09-15-2004, 05:01 PM

I agree with Peter's definition of indexing. Not so much for avoiding contact with a valve or the piston, but for exposing more of the spark to the intake side for performance. I am not a big Golden Lodge fan...as I used to foul those guys all the time before adding the upgraded ignition. I bet they would work great now. Most likely cause of this is that someone sold the wrong plugs...too long... to John. You also won't hurt anything adding an additional compression washer to a plug going into the cylinder in question. Personally, I run bosch plats x 2 or x 4. I like the electrode open design and have not had either contact a valve or piston...and not foul.

Best Regards,
John M

johnalfa1976 · #13 (**permalink**) 09-16-2004, 07:13 AM

Thanks for all the suggestions. Will give it a try over the next couple of days.

Question. If one had high lift cams and oversize valves and the plug was indexed to face the valve - would this accentuate the problem?????

Ciao,
John

alfajim · #14 (**permalink**) 09-17-2004, 08:20 PM

Oversize valves can hit the electrode on the "P" series plugs, replace them with non "p's" as P.Webb said and you will be fine.

johnalfa1976 · #15 (**permalink**) 09-20-2004, 12:48 PM

Thanks to everyone for their help!!!

I rotated the plugs so that each where in a different cylinder. Since I could not index them from front to back - stuck an extra washer under each plug. Drove to work and back (30 miles) - Ran Great. As soon as the engine cools down, I'll pull the plugsand check on the gap.

I will change spark plugs as soon as I decide which one of you experts is right - Bosch Plat4, NGK or Lodge - the winner gets a prize- ya right!!!!!!

Thanks again,
John