The Stovebolt Site Forums The Shop Area Engine Shop 235 , Good compression, black sooty plugs, runs good

Finally getting around to doing some troubleshooting / verification on the 1954 3604, 235 with 216 Intake/exhaust manifold and Rochester B Carburetor. It starts and runs fine , I think. The idle does not drop from fast idle without bumping the accelerator pedal . Seems to throttle up nicely without any bogging. The tailpipe is black and sooty and so are the plugs. Here's the compression check info and pics of the spark plugs. Is it running rich? What's the recommended solution. Timing is set at 3-4 degrees advanced, mixture screw set using best vacuum method. Running non-ethanol 91 octane fuel. Advice/ suggestions requested.
1. 135 psi
2. 145 psi
3. 145 psi
4. 145 psi
5. 147 psi
6. 149 psi
Checks done with Engine at operating temp, using screw in type Compression Tester, throttle at WOT. All plugs removed. No oil added.
Plugs are pictured 6,5,4,3,2,1

No solution for a non problem. Drive and enjoy.

Post the spark plug part number and brand. Look at Rockauto to see the plug choices.

From Champion Spark Plug Co.
Soft, black, sooty dry deposits on plug indicate carbon fouling. Carbon fouling is an indication of a rich air-fuel mixture, weak ignition, or improper heat range (too cold). Carbon deposits are conductive and can create a path for spark plug misfire.

Don't know if motor is smoking out tail pipe or not....or spitting...or ?...blow by?

Your 216 carb will run rich on a 235. Were those pulled out after a period of idling?

Is a Rochester B just for a 216? Why will it run rich on a 235?

A 216 carburetor on a 235 engine will run slightly rich. Higher air velocity for any specific RPM. If the Rochester B fits the 216 intake manifold, its a 216 carburetor. 235 carbs won't bolt on. Unless you swap to the right intake/exhaust manifold assembly and a properly calibrated carb, there's not much else you can do about the situation.
Jerry

AC Delco R43 spark plugs , not smoking or spitting anything that I can see.

No, I didn't let it idle. Drove it around the town for about a half an hour , bought it home, shut it off and pulled plugs.

Thanks Jerry, appreciate the feedback. ( the horror, the horror, Col. Walter E. Kurtz )

I think a more common recommendation is the R45 plug. Someone can jump in and correct me if need be.

Rockauto shows R43.

Thanks everyone....looks like I'm rich, not particularly the good kind, but I'll deal with it.

Thanks for the information Otto! Appreciated, as always.

Ron

You can still buy R45 plugs. And RockAuto lists them for a 235.

I have a question. Early 235s had the same intake as the 216s ( D-shaped cross section). Did they use the same carburetor as the 216?

JW51, Clean those glasses. That's a 3, not a 5 on the RockAuto listing. AC Delco R43

Ok guys I followed Otto's advice, did some digging and the R43 is heat range of 3, the R45 is a 5 . I found the AC Delco R45 in stock at O'rielly Auto Parts. Thanks !!

52 Carl - that's a good question.

Dusty, You are much better off than lean. I don't think your plugs look all that bad. Wire wheel them, gap them and put back in.

Extended tip plugs (R45S or R43S) work much better in an o-head valve engine.

George

You can get a rebate on those plugs, too! $3 for 6 plugs!

https://www.rockauto.com/Images/Cur...e_form_e-version_sparkplugs_fillable.pdf

The insulator nose/insulator tip (white ceramic) is not fouled. Which is what fouling is mainly. Still white or off white. Both electrodes are maintaining crisp shape. No burn away. You have no problem to solve. Running rich was your word. You have no symptoms while driving/idling.
As the Shakespeare play says: Much ado over dodo.

It would depend on how long the plugs have been in there/mileage. 5 weeks or 5 years as far as normal tune up. If you change to R45 watch for running hot on temp gauge. All the FLAPS say R43.

1954 factory spec for plug is:
"Thriftmaster AC, 44-5 com" *
"Loadmaster AC, 43-5 com" *

gap .035

* According to NGK, heat ranges are NOT universal between manufacturers.

Fuel has changed since 1954. Octane, leaded, unleaded, ethanol..........compression ratios....emissions...factory knowledge in 1954....Possible factors that caused a change in what heat range plug is best now-a-days. Mileage and performance is a good measure.

AC R43 plugs are pretty cold. I'd switch to R45 plugs like JW51 suggested.

Note the comment from Bartamos above "From Champion Spark Plug Co. Soft, black, sooty dry deposits on plug indicate carbon fouling. Carbon fouling is an indication of a rich air-fuel mixture, weak ignition, or improper heat range (too cold)."

The engine is going to run a little rich, by definition. Who knows if it will run rich enough to carbon foul plugs᠁but a little hotter plug (R45) might be cheap insurance in that regard.

As for the RockAuto confusion, I ran it for a 1962 235 (my engine). It recommends the R45. For all other years of truck 235, RockAuto lists the R43. Weird. I don’t think it means anything, just an oddity in the parts listings.

The plugs shown have less than 500 miles on them. Other than the annoying fast idle issue it runs good, plenty of get up and go. All said and done, leaving it alone for now may be best. Thanks again everyone, its been a positive learning experience for me. I think I'll get in the truck and go for a ride...put some more miles on it this month, review the plug condition and go from there. You guys have given me the information needed to work through this.

Ron

Concerning the fast idle issue your talking about:
* Is it when you start it up or all the time?
* Do you have a manual choke or auto choke?
* Do you have a throttle attached?
* What carb are you running?

Phil - fast idle (?) all the time.. You can tap the throttle at a stop sign and it'll drop back down to the idle setting
Has a manual choke
Yes, the throttle cable is attached and operates great. I made sure that the throttle cable is not keeping the throttle open.
Running a Rochester B

Back in the day (I’m old) the rule of thumb was R45 around town low speed driving and R43 were for highway running.

My truck used to do that same thing. Had to bump throttle to get it to idle down.

Things to look for:

* Inspect the entire throttle linkage for wear᠁grooves, egged-out holes, etc. Something could be hanging. I recently added bushings and a ball linkage at the end᠁to smooth it out.

* If you leave too long of a “tag end” on the hand throttle cable, it can hang up on the top of the manifold in certain positions.

* Might need a slightly stronger throttle spring.

That good to know, thanks .

I have the same setup as you and have no issues with fast idling. I would start by disconnecting the throttle cable from the carb so you can rule it out. Then proceed with JW51’s advice. Good Luck🍀

JW51 I thought I read where no one was smart enough to understand heat range !! My FLAPS could sure handle it !! They just don't have control over off-shore junkie tune-up parts.

In regards to your fast idle issue, when you adjust the idle mixture screw, does it change the idle speed at all?
If not, you may have a significant vacuum leak somewhere.
If you ever want to demonstrate an extreme vacuum leak, pull the the vacuum wiper hose of of the intake. The engine will go up to around 1200 RPM.

52Carl - yes, it changes when I adjust the idle mixture screw. When doing my latest "tune-up" , I adjusted the mixture screw to obtain the best vacuum on my vacuum gauge. The vacuum was in the green zone at roughly 18/19 in-hg. You think that's good?

Dusty53,
My 1957 235 runs great at just over 18in hg. See picture. Sounds like you have it running good.
Drive it, Enjoy it!

R45 is a hotter plug than the R43. R44 used to be a good choice, but I've heard those are no longer available. If you have HEI, Champion RJ18YC6 (18 and 19 are hot plugs in the Champion scheme) works pretty well...or it has for me and for what it is worth, Mr. Tom Langdon agrees on this. A colder plug is designed to transfer heat from the plug to the head faster (which keeps the tip cooler--hence doesn't burn off deposits as well). A hotter plug transfers heat more slowly back to the head so the tip and the ceramic region above it up to where the conductivity zone is located remains hotter (which in this case might be better). Good luck.

Right. I was wrong earlier about R45 being discontinued. I confused the R44 with the R45. So, disregard that post or I should just go back and delete it.

It was the R44 that the Toronado and Cadillac were originally spec'd with. The R43 is now the recommended plug.

Otto , that AC Delco R45 is not available and is shown as discontinued by my local parts store, at O'Rielly's, and on the AC Delco website. The R44 is available as is the R45S. I bought 6 of the R45S but need to make sure the extended tip is not going to be an issue. Scratch that - Wrenchbender says they will work, so in they will go.

Now I'm even more confused. R44 is shown as discontinued but really isn't? Or is it just left over stock on the shelves? R45 is also shown as discontinued but can be found?

Otto , yep its all confusing - R45 ,our local parts Store which is associated with Orielly's Autoparts does not have them and when they check the "system" it shows they are discontinued.

R44- they checked and there are plenty of R44 at their warehouse/distributor. May be old stock, like you said.

The R45S ( has an extended tip ) is readily available.

Amazon does list the R45 as available . As a test I placed some in my "basket" and they were going to let me purchase them . So ho is that possible, right?

Back in the dark ages when Delco and AC were still made in America, AC 45 plugs were used in delivery trucks, taxicabs, and other inner city vehicles that did a lot of short trips, cold starts, and other uses that would foul the plugs. 43 or 44 plugs were "colder" and worked better on vehicles that got warmed up once and driven for longer distances. The extended tip plugs work better because the ceramic insulator sticks down into the flame front in the combustion chamber and is less prone to carbon fouling.
Jerry

R44 is discontinued, however NOS can be found online

R45 can be ordered, AutoZone will order if they don't have in stock.


The recomendation is city driving to the local coffee shop use the 45 heat range, if working the truck hard use the 43 range.
I've attached a photo from the 58 factory manual......