The Stovebolt Site Forums The Parking Lot Big Bolts 366 VS 454

My 1977 C65 dump truck has the 366 in it. I have read where people are happier with the 427 (both being tall decks if my memory serves me well). With that said, I have a 1982 motor-home with a 454 and low miles (45k). The motor-home has sat for a decade. It's pretty ugly, and doesn't offer much other than the Onan 6500 generator, fridge, and some other interior parts I can sell. I thought about demolishing it after pulling some of the parts and using that 454 in my dump truck. Would that be pointless? My 366 'diesels' after running for awhile when I shut it off which makes me think valves and carbon build up. I have to put it in gear for it to quit or pull the choke. Timing is dead on. Meanwhile, the 454 shuts off right away.

Thoughts?

Steam clean the valves...put your thumb over the top of a water bottle and drizzle the water into the carburetor with the engine running at about 1800 rpm (fast idle). You don't want to stall the engine, but making it cough and sputter is a good thing, just take it slow and give it the full 20 ounces and see if that helps.

Mike B

It depends on several things, how many miles on the 366, how you want to use the truck if you swap motors, are either of the engines burning oil/smoking? The dieseling can be addressed and probably has nothing to do with the valve train. The 366 is a true truck engine, low RPM torque and heavy duty castings, the 454 is a good motor but not the same animal. The 366 probably has a Holley carb on it with an anti-diesel solenoid and a governor, I can't say if the 454 has a governor but probably a Q-jet carb, both carbs can be rebuilt if they have not been tuned with a hammer. Just a gut feeling here-I would keep the 366 in it.

Dieseling is caused by too-high idle speed on shutdown, not timing or carbon buildup. A water dribble occasionally won't hurt anything, but I doubt that it will solve the problem. A motorhome 454 won't have the heavy duty parts in it that the tall deck engines have.
Jerry

The truck has always done this 'dieseling' thing since I bought. Initially it had a Holly carb on it, and I bought a newer Holly after purchasing it years ago. While it ran better at that time, it still did the dieseling thing. The truck has sat for years until I brought it out of the yard late last year. On top of the dieseling, it would backfire out of the exhaust and ran like crap. I noticed a leak from the Holly on the intake manifold, so I replaced it with an Edlebrock as internet searches led me to that being a preferred carb. I also replaced the cap, rotor, wires, plugs, and set timing. After this point, I had taken the C65 to a truck shop where they changed out the older split rims with R22.5 wheels and tires. I asked them to look into the 'dieseling' and the shop owner came back with the possibility of valves and carbon build up as he couldn't get it to stop either. He said my timing was perfect. Idle speed is very low. I wish I could attach a video for you to hear it run. Supposedly the mileage is roughly 40k on a newer crate motor, but I can't verify that. It doesn't smoke or seem to burn oil. It's not running rich or lean, seems about right, in fact, with this Edelbrock carb, it runs better than I can member, I just have to pull the choke to stop it after I turn the key off or put it in gear.

I never heard of the 'Steam clean the valves' as Mike B suggested. I could get my wife to help me try that.

Thanks for the information regarding the 366 vs the 454. I'll keep the 366 in there for now. Ultimately I wouldn't mind putting a Duramax or a Cummins in it some day, but I need to get the truck back on the road. I have some jobs lined up and am gonna need her.

I did the water dribble today, and it seemed perhaps a little smoother, but after I had changed everything mentioned above, it has been running really well aside from the dieseling. I played around with the idle on the truck per Hotrod's suggestion. If I turn it way down to where it will barely run, then in may cough once or twice, or not at all. I decided to slowly increase the idle until I found a spot I could tolerate and left it there for now. The idle is lower now than when I began, but it still dieseles albeit not as bad anymore. Prior to doing anything, it wouldn't shut off on its own. I had to pull the choke or put it in gear to stop it. Keep in mind this is only after the truck has warmed up. When the truck is cold or hasn't been running for very long, it never would do it.

Attached is a video of my progress today. In the beginning of the video, the idle is as low as it will go without starting to die. At about 34 seconds, I shut it off and it gives a little cough. At 46 seconds I shut it off again and nothing. I start to gradually increase the idle after each shutdown from there. I left the idle where it is at the end of this video for now. At least it will shut off. My only concern about turning it back down to where it was at the beginning of the video is that it is very low and won't stay running until it warms up.

Big Blue Dieseling

Here's another suggestion- - - -install an "idle stop solenoid" It's a device that is used to set the curb idle speed, connected to the ignition switch. When the ignition is turned off, the magnetism goes away and lets the throttle plates fall fully closed. No airflow- - - -no dieseling. Here's one of several dozen examples that are on Ebay today.

https://www.ebay.com/itm/403516468951?

Search "idle stop solenoid".
Jerry

You're awesome, Jerry! Thank you so much for the suggestion. Perfect solution to my my problem.

Cheers!

Yeah, you did mention the anti-diesel solenoid and governor for the holly carb, I missed that, however, it was absent from the truck when I bought it and no wires or anything to suggested it was ever there. I took the carb off and went to Auto Zone and they sold me another Holly carb similar to the one that was on it at the time with no mention of a anti-diesel solenoid. I guess the Holly that was on the truck when I bought it was not the original, and when I took it in for a replacement, they gave me something similar. In their defense, they can't even look up my truck in their system as it doesn't exist. Too old I guess. It would seem you nailed it on the solenoid too.

But now I have an Edlebrock AVS2, so I'll start purchasing idle stop solenoids from Amazon until I find one that works. As you also suggested, I'll keep the 366 in it. She runs good.

Thanks for taking your time to help me out.

Find one with a bracket that looks close to what you need, and make your own mounting. I'd use one of the carb mounting studs and some steel flat stock bent to fit. The solenoid won't care what it's on, as long as you can make it contact the throttle linkage somewhere.
Jerry

I waited for someone to bring up the solenoid.

That truck never had one or, at least I never saw one any of my 70's big GM 366 or 427 trucks.

But I think getting one will help.

Look for 70's GM cars and light trucks with AC.
They were used as a fast idle solenoid while the compressor was engaged.

What you can do is back the idle screw out so the butterfly completely closes.
Then drive the truck, Remembering you have no idle, so you will have to give it a little to keep it running at a stop.
The goal here is to completely warm the engine.
When back home, try to idle the truck as close as you can with your foot.
Then turn off the Ign. while lifting your foot at the same time.

If it dies correctly proceed hunting a solenoid and it's bracket, If not I guess we need to
Keep looking for the cause.

I agree with the other post's about 99% of the time run on is caused by fast idle, Vacuum leak, or rich condition.

Yes carbon and timing can contribute but only in a small percent.

My 74 C65 with 427 never runs on, or the 64C80 with 409 either.

I wish I could give you a direct cause for your problem.

Good Luck

Tom

Yeah, Jerry. I was looking at a Edlebrock solenoid kit for a whopping $200. Forget that, I can fabricate a bracket myself.

Thanks for the heads up.

"Kits" are for people who are too timid to try to fabricate something for themselves. It doesn't sound like you fit into that category! Good luck!
Jerry

Bowtie Junkie Seriously don't let your wife near that truck engine,it can hurt any of you bad during that valve cleaning !! It is possible that your timing mark is not in the right place. I think they once had a solenoid incorporated to let the throttle plates close completely on shut down,like you do with your choke now. Except each shutdown didn't soak it with gasoline.

It would be greatly appreciated if you would take the time to read the entire thread before responding. I don't mean disrespect, however, the process was already done, and I wasn't about to have my wife stand over the truck and dribble water in it. Also noted by my previous posts that the timing is dead on and verified.

Thanks for trying to help.

Thanks for the input, Tom. As you can see in the video I posted, the truck will barely 'run on' with that low idle -and sometimes it won't as indicated in the first 45 seconds of it. I believe that Jerry's solution is the way to go for my situation.

I really do appreciate everyone's advice and willingness to help.