Dual B&B's yet again

[Suddensix]

Well I give up! All of your suggestions of things to check to discover why my dual carbs run so rich have been tried and have not solved the problem. To re-cap, I have a rebuilt 218 with an Edgy head and cam, electronic ignition etc. etc. The fuel system has been cleaned so that the fuel to the carbs is spotless. To-day I checked to see how much pressure the new mechanical fuel pump was putting out, it was 3 p.s.i. Also did a compression test that showed 3 cylinders at 145 lbs. and 3 at 150 lbs. I run large air cleaners, my vaccuum guage shows no vaccuum leaks and the carbs have been checked and re-checked to make sure that they are OK. I have lowered the float level. So unless anyone has any bright ideas as to what's going on to-morrow I'm going back to 1 carb which is really going to screw up my great looking engine bay but at least I'll be able to drive the d--- thing.

Have a great weekend all,

Gary

[Normspeed]

I'm not convinced that running rich is your problem, especially if the duals were running ok then suddenly the motor developed a problem. Did you ever get around to checking the vacuum advance?

Anyway, sorry to nag, just tossing out opinions, of which there are many:D I won't bring it up again.

If you do go back to a single carb, at least that will eliminate one possibility. Good luck!

[claybill]

i predict....when you go back to the single carb..it will run rich also!!!

you might get one size hotter plug...thats one number lower..

also...when do you check your plugs for the plug reading...?

probably while you tool up the driveway and back it into the garage etc...

you should check plugs imediately after a hot run....in fact on the same straightaway where you went 60 mph.....stop the car , get out and check plugs..

my dual carbs run a bit rich too.

look at my aircleanrs.. darn..dont know your email and i am off to dinner and late...claybill@netexpress.net.

bill

[greg g]

What are your plugs gapped at? Are you running resister plugs? What plugs are you running. The stock plugs are not long enough to run with the aluminum head.

This has been discussed before. Try doing a search for spark plugs and see what you can uncover. You need a plug with a longer threaded portion so the electrode is exposed into the combustion chamber. If your plugs are shrouded up in the head, they will never get to the correct operating temp surrounded by all the aluminum and its corresponding coolant flow in the head. And may read rich when they are really just to cool to purn off the carbon from ignition.

[Don Coatney]

Sudensix;

Post a picture of your air cleaner

[greg g]

stock plug and extended reach.

[Suddensix]

Norm, I did check the vac advance and it was OK. Forgot to mention it in my original post. Bill and Greg, I'm running Autolite #306 plugs with a gap of 35 thou. They are resistor plugs and I have checked them after a long run. They show the engine is running rich. Do you have a part # for the longer reach plug cuz that is something I would definately try. Don, posting photos is not my strong point. The filters I'm using are open paper elements that are 4" tall and 6" wide with spun aluminium tops and bottoms. Thanks guys for the input, keep it coming.

Gary

[martybose]

If memory serves, the Autolite part number for a 1/2" reach plug is AP425. Actually, any Autolite plug with 425 will work; the AP is a more expensive variant. This is a relatively cold plug, slightly colder than a 306.

You might check with Edgy about what plug length his head requires, I know that my original Edmunds and Fentons take a 1/2" plug, Edgy could be 1/2" or even 3/4" for all I know.

BTW, you will want to do something to chase the threads before you put in a longer plug; if they are carbon fouled, you could damaged the threads when you install a plug. If you are careful, a good tap with grease in between cutters to catch the crud will work.

Marty

[p10plymouth]

If its not too late ... check or recheck the timing chain marks or at least put it on top dead center and look at the firing marks .. .. you can also try running it with the fuel lines disconneted or (pluged) .. to see how it operated till u run out of gas... If you can put it on a old Scope that would take a lot of guess work out of your problem ! If u like the dauls there is no reason for them .."not to work" good luck..

[greg g]

A good counter guy will be able to tell you what plug is the longer reach equivelent of the one's you are using. I think that may address your situation. You might also get a set one heat range higher. You can also go to the Autolite wesite and see what compares.

[martybose]

A good counter guy will be able to tell you what plug is the longer reach equivelent of the one's you are using. I think that may address your situation. You might also get a set one heat range higher. You can also go to the Autolite wesite and see what compares.

I had actually called the Autolite tech line (number found on their website) and asked them. It took them a while to find an equivalent with similar characteristics to a 306 but with 1/2" reach. They recommended the 425.

Marty

[Don Coatney]

BTW, you will want to do something to chase the threads before you put in a longer plug; if they are carbon fouled, you could damaged the threads when you install a plug. If you are careful, a good tap with grease in between cutters to catch the crud will work.

Marty

Remember that the plug threads are metric. Get the correct tap.

[hkestes41]

Norm, I did check the vac advance and it was OK. Forgot to mention it in my original post. Bill and Greg, I'm running Autolite #306 plugs with a gap of 35 thou. They are resistor plugs and I have checked them after a long run. They show the engine is running rich. Do you have a part # for the longer reach plug cuz that is something I would definately try. Don, posting photos is not my strong point. The filters I'm using are open paper elements that are 4" tall and 6" wide with spun aluminium tops and bottoms. Thanks guys for the input, keep it coming.

Gary

Suddensix,

Don't know who's HEI you are using but you might want to try about doubling your plug gap into the .060 to .070 range. The HEI will operate with a much wider gap than the stock disty.

[martybose]

Suddensix,

Don't know who's HEI you are using but you might want to try about doubling your plug gap into the .060 to .070 range. The HEI will operate with a much wider gap than the stock disty.

That's a good point. When I installed my HEI it didn't run real well with the plug at 32 thou, but perked right up when I opened them up to 60 thou.

Marty

[Suddensix]

Suddensix,

Don't know who's HEI you are using but you might want to try about doubling your plug gap into the .060 to .070 range. The HEI will operate with a much wider gap than the stock disty.

I'm running a Pertronix and according to them you leave the gap stock.

[Plymouthy Adams]

odd are when you installed the Pertronix unit you are still utlizes the stock coil so the output voltage does not change..just the manner in which the coil is fired..the HEI uses a internal coil of greater output voltage..this allows the spark gap to be larger as it now can jumped the opened gap and give you a larger hotter spark to ignite the flame..

[Bodacious]

odd are when you installed the Pertronix unit you are still utlizes the stock coil so the output voltage does not change..just the manner in which the coil is fired..the HEI uses a internal coil of greater output voltage..this allows the spark gap to be larger as it now can jumped the opened gap and give you a larger hotter spark to ignite the flame..

And speaking of coils, I've seen weak ones mimic a rich condition causing black smoke and plug fouling.

[Suddensix]

odd are when you installed the Pertronix unit you are still utlizes the stock coil so the output voltage does not change..just the manner in which the coil is fired..the HEI uses a internal coil of greater output voltage..this allows the spark gap to be larger as it now can jumped the opened gap and give you a larger hotter spark to ignite the flame..

When I installed the Pertronix set up I used their coil and ignition wires as per their suggestion and it seems to work well. I just returned from NAPA with a new set of longer reach and hotter spark plugs, maybe they will do the trick.

[Plymouthy Adams]

watch the longer reach..by this are you referring to the length of the electrode out of the tip or the metal threaded portion of the plug...the hotter plug whuld have a difference in the length of the ceramic but not in the threaded section...

[Suddensix]

watch the longer reach..by this are you referring to the length of the electrode out of the tip or the metal threaded portion of the plug...the hotter plug whuld have a difference in the length of the ceramic but not in the threaded section...

The length of the thread is what I'm talking about. The original is 3/8" I measured the thread depth on my head and found it was 7/16" so bought plugs accordingly after much research on the net. Also moved up two heat ranges. Wish me luck.

[Plymouthy Adams]

you sound like you good to go...luck to you..I just always get nervous when I hear of people changing the length of plugs...have seen lots of damage in my lifetime...

[Suddensix]

you sound like you good to go...luck to you..I just always get nervous when I hear of people changing the length of plugs...have seen lots of damage in my lifetime...

Ya, so have I and it usually ain't pretty. Thanks for your input Tim.