What spark plug are you using ?

[FLYER15015]

Well, I guess talking spark plugs is like talking engine oil, which is like talking religion, but here goes.

In a 1940 Buick series 90 (big engine) the book says to use AC-46 gapped @ .023-.028"

I know that with AC plugs the higher the number, the hotter the plug.

So is anybody out there using AC-46,7,8,'s in their engines ?

I'm thinking of moving up to 48's for low speed crusing, and short trips, to prevent fouling.

I'd welcome any other input.

Mike in Colorado

BCA#45728

AACA#994416

:confused::confused::confused:

[Guest Straight eight]

I've been using AC #C49 in both my 41 and 47. I do next to no highway driving, just back roads up to 45, and rarely 50 mph.

[Guest BigDogDaddy]

I have the AC 46s in my car now. They have been fine. No problems, and I do plenty of driving.

[Dodge1934]

I have a dodge rather than a buick... I use AC 48 in it but I find the best fix for fowling and other similar problems is to take the car on long drives.

I took my 34 dodge on a 2 week vacation a few years back and it never ran so well and it stayed that way for several years... I need to take another vacation with it now... it isn`t running like it did.

FYI

[FLYER15015]

I've been using AC #C49 in both my 41 and 47. I do next to no highway driving, just back roads up to 45, and rarely 50 mph.

Strt 8,

Per my local Carquest, the C-49 is a "commercial" plug still in their inventory, and is @ the top of the heat range. Might be just what I'm looking for.

They don't have one in stock but can order them for me.

Can you tell me how it matches up w/ the C-46 plug ? Overall length, reach diameter, will it fit under the tin plug cover on my '40 ?

I'd hate to order a set and find they don't fit.

Best Regards,

Mike in Colorado

:confused::confused::confused:

[60FlatTop]

I have been using AC 45's in all my Buicks for years. 44's just are not hot enough. Keep the choke in good working order.

I have used an NGK plug in a '50 super and it was just fine. I do not remember the number, I carried in an AC and matched it up.

Bernie

[FLYER15015]

I have been using AC 45's in all my Buicks for years. 44's just are not hot enough. Keep the choke in good working order.

I have used an NGK plug in a '50 super and it was just fine. I do not remember the number, I carried in an AC and matched it up.

Bernie

Flat Top,

I think the NGK plug you are referring to is the "BR6S", a resister plug my local Carquest guys said was an equivalent to the AC 46.

I can tell you IT'S NOT ! Besides being way to cold, the NGK plug is just shy of 1/8" longer, and the threads don't go all the way down the barrel. A good way to strip threads in the cylinder head.

Up on the top side, the extra 1/8" makes putting the tin plug cover on an issue, unless you replace the stock studs w/ longer ones. Then it rattles. This comes from personal experience, w/ my '40 LTD.

But thanks to my 20 year old Black and Decker 12 vold plug cleaner, and some new silica sand, the old AC 46's are back in and running well. Still waiting for the AC 48's I bought last week on E-Bay,(set of 8 NOS) for $30.00.

I still would like to see an AC C49 just to check the demensions against my 46's and satisfy my curiosity.

Mike in Colorado

[Jolly_John]

Greetings, Mike. I hope all is well with you. With today's gas and oil technology, you can easily increase the plug gap to .30 without any problems. That will reduce the possibility of fouling. The problem with going to a hotter plug than the AC 46 in your straight eight is that bad things (like igniting built-up carbon and piston top hot spot creation) can occur, IF you take the car for longer, higher speed trips....i.e. highway driving. I'm not saying that putting 48's in your car will cause a problem immediately. But, why worry about it, if you suddenly decide to take a road trip?

In 45 years of straight eight driving, including lots of local and extended highway trips, I've never had to go with any plug hotter than the AC 46. Happy motoring! John

[FLYER15015]

Hi John,

Took the Buick out cruzin yesterday. 100+ miles. The 46's are cleaned and back in, and running well.

Speaking of carbon build up, now i'll try to really muddy up this thread:

Has anyone ever "decarboned" their head, by getting her really hot, winding her up pretty good and slowly pouring cold water down the carb ? It's an old trick from many years ago.

When you do it, the black crap really flys out the tail pipe, so be sure and point the exhaust pipe out in the yard....

Supposedly it cleans out the combustion chamber and piston tops of their carbon build up.

Last time I did it, it was to an old ford F-150.

Any one ever tried it w/ their Buick ?

Mike

Edited September 4, 2011 by FLYER15015
spelling (see edit history)

[60FlatTop]

On the NGK's, I remember not wanting the catalog replacement plug. I had the AC45 with me and we opened boxes until I found one I liked the look of.

As to the de-carboning, there are a lot of things I would do with a Ford that I would NEVER do with a Buick.

Bernie

[FLYER15015]

High Guys,

Well it's October 28th and the day was spent cleaning the old AC 46-5 spark plugs, and test driving of course.

The plugs were a "bit" black around the inside, but the ceramic was a nice "butterscotch" brown, and NOT wet. Both the center and ground electrodes are still in great shape, with only a minor regap, and ground wire straightening called for.

The black probably comes from too much toodling around town, and not enough highway cruising.

My method of cleaning is somewhat old school, but for those interested, I'll post it here ........ and wait for the howels from the purists.

1 drill 8 holes in a 2x4 to load the plugs upside down.

2 spray all 8 with carb cleaner, and light it off.

3 when it burns down and goes out, do it again.

4 use a spark plug cleaner. Mine is an old Black and Decker you run off the cigarette lighter.

5 drop all 8 plugs in a glass jar with MEK in it and swish around a bit.

6 remove plugs one at a time, hold right side up and spray carb cleaner up on the ceramic cavity.

7 let dry, then regap as required, and straighten ground wire as needed. I gapped mine at a tight .030".

8 dab a bit of neverseize on the threads, add washer, and reinstall in head.

This is how I was taught to do it in 1959 when I started work at the local Jag/ Morris Minor/Sunbeam dealer.

Mike in Colorado

PS She ran great this afternoon, all the way up to 65MPH on the dial.

[Guest Grant Magrath]

I usually sandblast them myself, although I do like burning off the carb cleaner. I'm glad it's the 28th somewhere in the world. It means I've got another shot at remembering our wedding anniversary!

Cheers

Grant

[FLYER15015]

Grant,

Happy annivsary !!!

So tell us which one it is... We will of course want pictures of the occasion.

We just had our 49th in September. Next year the warranty runs out, and Ruth wants to know if I want to sign up for "extended coverage". I told her I would consider it............

Best Regards,

Mike in Colorado

[Guest Grant Magrath]

Ha ha!

I'm a "noob" compared to you! Only 13 years, but we've been together for 20. Had a big party for the folk's 50th 3 years ago. My mother had her wedding dress and a bridesmaids dress on display on a couple of manikins. It was a good night! They just celebrated their 53rd last week.

I have to say I love that avatar of yours. looks so much like NZ. About time you paid us a visit! Cruising the South Island would make a nice anniversary gift, and since it's your golden anniversary, you could pan for some gold while you're down there!

Cheers

Grant