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I started posting in this thread but i may have more going on than a hot plug or lean mix so im starting this thread so as not to thread jack
Recent build 455 w an RV cam maybe 300 miles on it. ran 210° around town and if i got on the highway it headed up to 225° and probably would keep going but i got off the highway.
thought it might be lean so i pulled the plugs my plugs AC r43s were white.
i put in a 70 MJ instead of a 69 my plugs were white
I put in a 74 MJ instead of the 70 my plugs were white
car did run cooler w 74 MJ 200° around town but 220 ish on the highway (5 miles)
The rad is a 3 core from my SBO in good shape, factory shroud and clutch fan all worked fine on SBO.
Carb is a rebuilt Qjet w 50 rods and 74 mainjet, secondary rods are CH w a K or L hangar essentially 72 455 toro jetting except 74 MJ instead of 69.
fuel is 92 or 93 octane premium no abnormal engine noises and pulls hard w no hesitation when stomping on it from a stop or at speed.
question what to make of the plugs ? pics show 1 or 2 plugs in different lighting but i pulled 1, 3 ,2 and 4 and all looked the same.
I think you have three problems. Engine temp, the plug may be to hot still and there seems to be maybe a lean condition. Fix the engine temp first. Then try a cooler plug.
How long did it run after the jet change but before you did a plug reading?
same plugs and i drove about 40 mins and about ~25 miles, 10 miles in town, 7 miles hiway at 70+ mph, and 8 miles 2ndary hiway 50+mph in that order....w several full throttle pulls
Originally Posted by distributorguy
The lean condition is likely causing the high engine temp. Fix mixture first.
OK but i already jumped from a 69 main jet (stock 455 jet) to a 74 w no apparent change thats why im posting not sure where to go from here i thought the intial jetting would be close ?
I did spray around the carb and intake manifold looking for a Vacuum leak and found no apparent change in idle
same plugs and i drove about 40 mins and about ~25 miles, 10 miles in town, 7 miles hiway at 70+ mph, and 8 miles 2ndary hiway 50+mph in that order....w several full throttle pulls
You need to keep it at a steady throttle for as long as possible, then shut it off while at speed. Then check the plug color.
i admit i did not understand how to read the plugs when i made the first post, i was looking at the insulator.
now im using these images for reference.
based on that im thinking the jetting is to rich now plug reading was taken after steady cruise at part throttle.
temp runs close to thermostat temp ~195ish until i get on the hiway (3k+ rpms)then it will get to 215-220 but cool down to 195ish at 55mph and below speeds. radiator is a 3 core that cooled my 350 fine but i think doesnt have the capacity to cool the 455 at hiway speeds. car definetly runs cooler at 75° ambient temps VS 90° temps. so at this point i dont think my jetting is affecting engine temps.
i welcome any comments on my plugs for jetting or heat range or cooling
Last edited by RetroRanger; September 8th, 2016 at 01:54 PM.
I'd look at ignition first. Retarded timing creates a LOT of heat. Depending on cam timing, your distributor position may b e much farther advanced than you would suspect. Start with 5-7 degrees further advance (higher number BTDC) and see what that does to temps versus pinging. I'm also not sure why everyone thinks 4 jet sizes is a huge change. Its just not.
A richer fuel mixture makes for cooler engine temps,leaner just the opposite. It's very hard to get a reading from plugs because of no lead. A R43 is a cooler plug than what came in most Olds engines. A vacuum leak will cause a leaner condition and higher temps. It would be very hard to blame high engine temps solely on fuel mixture unless it's so far out of range.
A 17:1 fuel mixture only takes a tiny mis-adjustment or tiny vacuum leak and that WILL cause a higher than stat temp. This can be from idle adjustment or float adjustment, not necessarily anything big. 5 degrees of retarded timing will do the same thing, at about the same level. Combine the two and you have a really big problem.
If your block and/or heads are shaved and the intake is not machined to match those angles, or of they are not machined at the right angles, its very possible for a vacuum leak to be inside the engine, and not in a place you can discover by spraying ether, carb cleaner, or other combustibles outside the engine.
Thought i would post these pics of my plugs. I just had them out to see how they looked
all 8 plugs look about the same these are 2 different plugs one plug pic was taken 2x in slightly different lighting
i understand reading plugs can be difficult w todays fuels. Despite that i think the heat range is fine based on the ground strap showing a change ~halfway down on both plugs. Jetting appears ok for conditions judging on the base ring.
if nothing else i think the plugs say all cylinders are running similar, and no gross deficiencies are present in the mixture
Thanks for re-posting, Eric. I missed where RetroRanger posted that pic toward the beginning of the thread from five years ago. That's where the View first unread link got me!
So youre saying a colder plug would be a better choice? Im willing to try that but these are ac delcos r43s, im not sure if thay make a colder plug at least from delco.
i thinki read something about the r43 VS the r43s ill do a little research on that and post back (in another 5 yrs lol)
backinthegame re 2strokes FTW
the engine is a 1970 455 w E heads.
Last edited by RetroRanger; August 2nd, 2021 at 06:25 AM.
found this link on reading sparkplugs. It goes more indepth than the previously posted pictures. Im still digesting the info, but thought i would post the link as it appears useful. I also some much of this exact text on a chevy site so dont be fooled by the honda in the URL
Any changes to the carb or cooling system? A CH secondary rod is pretty lean for a 455. Nearly all the later carbs even come with the CV secondary rods. I did get a stock 307 to ping with those secondary rods.
I dont have my notes in front of me but yes i do recall some carb changes, the intial post was 5 years ago. Im pretty sure the secondary rods are AUs now.i might have changed the MJ too ill have to find my notes
Retro,
Might be a little off topic, but consider use of a wideband Oxygen sensor in the exhaust for tuning. I use Innova DLG1, (Innovative?) but this is a vibrant market with a bunch of good solutions.
A wideband 02 sensor will allow you to really dial in your carb settings with its feedback. With the real time feedback, not only will you see the mixture at idle, but cruise and WOT too.
Once you know you’ve got the air/fuel ratio right at all RPM’s, you can move on to other challenges. My engines have never run better.
I use an HEI distributor in my big blocks, with an oddball Buick fixed vacuum canister (to avoid ping) and NGK plugs gapped at .045. Theoretically HEI’s can run bigger gaps, but I’m running street motors on big cars so I’d rather they be smooth than requiring tip top electrical signals for that last few HP.
One thing that made a big difference to my big block idle/cruise/WOT temps were a good fan shroud in back of the radiator and good rubber curtains in front.
agreed the WB would help a lot, its on the list just hasnt made it to the top of the list yet.
I have an HEI too w a mechaniical stop on the vac advance. My plugs are about .040
CFair what NGKs are you running ? next time you have one out can you post a pic on this thread (if anyone else that wants to post a plug pic that would great as well)
That link is pretty interesting as it talks about timing indicators on the plugs besides just mixture and heat range, next chance i get ill pull the plugs again and get some better pics, like inside the insulator.
August 8th, 2016, 05:21 PM
i thought the intial jetting would be close ?
