The Stovebolt Site Forums The Shop Area Engine Shop Rebuilt Carb now Spark Plugs Keep Fouling

PastorMatt - looking at your post concerning the 45 minutes of idling:

(1) Changing the main jet will have ZERO bearing on the idle calibration; only on the main metering circuit calibration. At this point, DO not change to a smaller jet! You should have received the correct main metering jet in the kit you used to rebuild the carburetor.

(2) Your last post indicated the engine was running fine. Nothing wrong with having someone with the tach, timing light, and vacuum gauge to check things; but at this point in time, I would suggest taking the truck for a drive. Close to home at first, to develop confidence in the reliability; but if no issues, a 20~30 mile trip at highway speed should tell you a lot.

(3) The comment about checking for carbon fouling after 20 minutes at sustained speed is true; PROVIDED THAT YOU SWITCH OFF THE ENGINE AT SPEED, COAST TO A STOP, THEN CHECK THE PLUGS.....NO IDLING!

Not to attempt to muddy the waters further, but a comment hopefully for understanding:

In "carburetion 101" one learns there are three major methods of improving the fuel/air atomization: (1) add heat, (2) add air velocity in the carburetor, and (3) add fuel.

What stands out in the above statement is that if the heat is constant, then adding air speed will allow reduction of fuel in the fuel/air mixture. So the fuel calibration will be more concentrated at idle (low air speed) than at higher engine RPM's (greater air speed). Not at all uncommon for 5 minutes at idle on a properly tuned engine to show some carbon on the plugs.

Stay with it!

Jon

Someone mentioned spark plug cleaner. Depending on who you listening to, they are either complete garbage or totally adequate. For $7 on clearance…..I might give one a shot. Nicer versions are available at different price points for various vendors.

https://www.harborfreight.com/pneumatic-spark-plug-cleaner-32860.html

Just spray the spark plug with carburetor and choke cleaner wipe it off and you can use a little brass bristle brush to clean up any gunked on crud. No need for any sort of special equipment

On TV, I saw Allen Millyard use a propane torch to clean a spark plug. Just play the flame on the end.

Back to the octane discussion. Never spent much time thinking about the downsides of higher octane. For E-free gas around here, all we have is 91 octane, and that is what I mostly run.

For the ethanol blend locally, we have 87 octane. Sounds like the latter is more aligned with what these trucks were designed to use….at least from an octane standpoint.

Which is the lesser of evils? The higher octane e free? Or the 87 with the ethanol?

Jon (carbking),

Thank you! That is very insightful and helpful. The carb rebuild kit that I bought from Mike's did not even come with a metering jet. I even added the extra add-on to get a new idle mixture screw, float, etc.. but no metering jet. I didn't realize it at the time of order but you have to pick the metering jet out by itself and add it as they have several dozen sizes.

JW51, Otto, and Gord

That is a really cheap price for the spark plug cleaner. I watched a guy on youtube (probably same guy as Gord) demonstrate how to clean them with a blow torch. Never thought of that before but I had been just using carb cleaner, bristle brush and a little sandpaper to clean them up pretty easy. I have used the blowtorch method too which works well but takes a little longer and you have to wait on them to cool down too!

JW51,

You ask a good question about the lesser of two evils. I wonder what someone more knowledgeable would have to say.

Jon,

I didn't realize you run the Carburetor Shop. I'll have to go through you next time for my carburetor parts.

Matt, I'm certainly no expert. I can only speak from experience.

I only drive antique cars. I do not own and never have owned a modern vehicle (cars built after '72 and trucks built after '79). The 1995 F 150 is my mom's truck.

Anyway, I've never purchased premium fuel with the idea that it's "better" for your engine as the advertising suggests. I only use premium fuel if the engine knocks using regular 87 octane. That's the only legitimate reason to use premium, in my opinion.

Ethanol, at least here in Atlanta, hasn't caused major havoc with my vehicles with the exception previously noted. I just got home driving Ol' Roy about 100 miles today. It runs great on 87 ethanol and gets 13.5 mpg. I've owned the '56 Coupe de Ville for 23 years and it's probably gotten ethanol free gas about twice in that whole time.

I've never experienced problems from lack of lead in fuel, either. I don't run out and install hardened valve seats in my cars. Unless you're racing them, the exhaust valves will be fine without lead or lead additives.

All this talk about sooty plugs makes me feel like pulling one of mine out and seeing what it looks like. I think the truck definitely idles a bit rich. On startup itdoes blow out sooty condensation.

"Cleaning" spark plugs without some sort of bead blaster to get the abrasive up into the area where the porcelain insulator meets the steel plug shell accomplishes one of two results- - - -"Slim" and "None". At least that's been my experience for 65+ years. Go ahead and try if it makes you feel better.
Jerry

Are the Carter yf 2100s carburetor for the 235 engine that Great. If they are I will be on the hunt for one

If a Carter carb calibrated to fit the engine doesn't work right, you need to go find a big mirror somewhere. The reason for the problem will be looking back at you.
Jerry

Sounds like I will be on hunt.

Much better than the Rochester. For me, anyway.

My Rochester works fine. Just wanted a spare backup for the Future. will be looking for a Carter yf 2100

Be sure it's one from the 1950s or 60s. The offshore made Carter "clones" that "sorta-kinda" look like YFs are pretty good for paperweights- - - -but only before somebody puts gasoline into them. After that, they become stinky paperweights!
Jerry

Hey guys!

For the last 4 years I've had my grandfather's truck after his passing in January 2020. It is a 1952 Chevy 3100 and he always told me that it had a 1954 235 engine. Well... I never really checked that out I could tell it was a 235 engine for sure. But last night I took pictures of the casting numbers, serial numbers, and block numbers and found that it is actually a 1956 235 cast in Flint, Michigan. I don't know if that makes any difference at all or not. Maybe you guys could chime in on that! I did read somewhere that the 56 235 is better than the 54 because 54 was one of the earlier ones.

The 56 engine will have the water pump mounted about 2 inches lower on the block than the 54 engine- - - -which creates fan and radiator clearance problems in the 1952 engine compartment. If it's been running that way, those problems were probably addressed some time ago. The water pump shaft had to be shortened or the radiator moved forward, to avoid radiator clearance problems, and a smaller diameter fan is usually fitted to clear the crankshaft pulley and lower radiator hose. The 56 engine should have a cylinder head casting number ending in "848" which is slightly higher compression than the 54 head would have been. Otherwise, the engines are very similar from 54 and 56.
Jerry

Read this link, go find the block casting code on your engine, and then post it here. That will help identify which year engine you have.

http://www.1954advance-design.com/Web%20images/casting-code-photos/codes-ser-nums.html

I used one like that for many years. It cleans them like new in a few seconds.
That is a fantastic price for it. It seems like I paid $25 for it many years ago.

George

Hotrod Lincoln,

The head casting numbers are 3836848. The engine serial number is F0419JC. The block date casting code is D171. I believe that last one means it was cast on April 17, 1956 (the 1 standing for the first year of that particular line of 56-62).

I couldn't see the block casting code very well last night. I'll attempt to locate and read that today. With all that info, can we say it is a 1956 235?

***Update*** So... the engine casting numbers are 3769716. I'm a little confused now! Based upon all the numbers I have and following the website below I am thinking I have a 1958 235. I am not sure what the last 1 stands for in the block date casting code. Any help would be appreciated.

http://devestechnet.com/Home/CastingNumbers

I'd be real surprised if that "1" was for 1956.

Bill,

I am not certain of that now either. My engine casting numbers are 3769716 which seems to indicate 58-62 235. Any ideas what that last 1 stands for in the block date casting code of D171?

Can you post a picture of the D171 ?

Many (all?) casting date codes have what looks like a slotted screw head on either end of the code.

Replacement block, cast in April 1961 ???

It is a 1961 235 that went in a 1/2 or 1 ton truck. Head numbers indicate 58-62 for a 235 and the date casting code on the block is D 17 1. This would be April 17, 1961. It was cast in Flint, Michigan.

Bill,
I will get a picture post sometime but the ones I have are very hard to make out because of oil buildup and position of the starter. There are definitely what looks like a slotted screw head on each side of the D 17 1.

Don't need a picture of the casting date now that it has been decided that it is a '61 block.