Plugs for Crappy Gas

I have an 89 PCM 351 with a Holley 4160 carb. It has started sputtering/backfiring under load so I am going give it a bit of a tune up.

The PCM recommended plug is an autolite 24. Currently, the boat has AC Delco R43TS plugs installed. They were installed last spring by the local boat mechanics (who are very well respected) before I knew anything about the boat.

These plugs are one step hotter then the recommended Autolites. I have some vague recollection that the hotter plugs were used to help compensate for all the crap (i.e., ethanol) that is in gas these days. Does that make any sense? Anybody believe this?

Alternatively, could the hotter plugs be better for a well worn engine (750 hours) that may have low compression on one side?

I already have some autolite 24s I bought at wally world last year. Should I install them, or stay with the hotter plug?

I also have a set of PCM plug wires and a new condensor courtesy of SkiDim. I am hoping this is going to solve my sputter problem.

Thanks

Jared

And I am sorry if the "which plugs" question is asked all the time. I searched for ethanol and didn't find anything related to plugs, so I don't think anyone has asked this particular question before.

Thanks Boat Dr.

I certainly agree that going with what PCM recommended is a good idea. That is why I bought the autolite 24s in the first place (when I realized the boat mechanics had installed the non-standard plugs)

But I am still curious about the "hotter-plug-for-ethanol" theory. I doubt that PCM had ethanol in mind when they designed the engine.

If a person wanted hotter plugs and wanted to stay with autolite (which also seems like a good idea) couldn't they go with the autolite 25s?

But now that I write this, I think it is probably a bad idea. Better to start with what PCM recommended. Maybe the hotter plugs are part of my sputter/backfire issue.

So I will take your advice and go with the autolite 24s

Thanks again

Jared

I run the CR43TS, I like them a lot andd they are not hotter than the autolite 24's, they are a direct match.


Change plugs if you want, but look elsewhere for your root problem.

GottaSki,you seem to have a lot of knowledge about this engine thing, and I tip my hat to you on a lot I have learned from you, thanx.
But, the CR43TS,those fit a lot of the M/Cruiser - GM engines,I try to run only the MR's they have a S/S barrel, and seem to not gall as bad as the CR's.....JMHO...boat dr   

GottaSki wrote: Dr, thanks, for the kind words Ah Yes, my next batch will also be ss, either Autolite or AC; I see the std Autolite 24's are not ss either. AR24's would be the SS autolite number, their site indicates. and my humbling err, apparently there is a heat range difference just as he indicated.

Just to clarify-- the stainless Autolite 24's are numbered AR24? They are otherwise the same as the recommended "normal" 24s?

I thought 24s were 24s, and everything else was different.

Are stainless AR24s worth the difference? Even if you end up replacing them every year or two?

Jared

yes,
yes,
I think so, and the price difference is minimal.
Yes, 2-3 seasons are typical. Plugs only go bad early when something else is amiss.

One can Compare the autolite models here:

http://www.autolitesparkplugs.com/search_char.asp?threadSize=14mm&hexSize=5%2F8%22+%2816mm%29&gap=&seatType=tapered&terminalType=&heatRange=4&reach=11.6mm+%28.460%22%29&resistor=yes&action.x=58&action.y=13

crap, doesn't work

IM having the same issue. intermittant hesitation and backfire.

Just want to add that you should be careful with getting hotter plugs, easier way to get detonation.

oh yeah, once it gets going a little faster, ie cruise speed ect. it runs great and has lots of power.