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Discussion Starter · #1 ·
I replaced the plugs in my car today,it had R43`s in it and i replaced them with R44ts.
The car fired right up but ran rough. When I pulled two of the new plugs the tips of them had been slammed shut. The guy i bought the car from said it had a 355,I`m not sure of the year of the block,stroke,or cam specs.
How do i fined out what lenght of plug to run?
 

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They discontinued the old style R43 and substituted I think R43T or R43S but if you have R43TS I think those might be tapered seat? Anyway, the domes will hit the electrode on many engines from this era with extended tip plugs. I suggest you go for NGK's or some other brand that has less reach. I wish I could remeber more stuff as I remember a similar thread about the discontinuation of the AC plugs spec'd for many of our engines.

-Mark.
 

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Discussion Starter · #6 ·
Here is what i have found out so far,My car had R43T plugs.When i did the tune-up i installed R44TS plugs(DON`T ASK WHY!!!)
I went to Autozone and the guy told me to go back with a R44T. He said the 43`s are too cool and will create alot of carbon build up.
I installed the R44T`s and everything is back to normal. I think?
Example- R43T,Are short.
R43TS,Are longer.
Thanks for the help!!!!1
 

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Hmmm. I have a high compression 355 and run the R45S. The R43S was a bit too cold for street driving. The S is an extended tip, the T is a tapered seat . If you have a GM small block, it will not use the tapered seat. You can tell by looking at the spark plug hole base. I would think the tapered seat might let the plug settle deeper but I'm not sure. BTW - I have domed pistons , too, with no clearance problems.

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Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).
 

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posted 06-28-2002 04:57 AM

We've done some testing at my shop and here is what we found to be the best IMHO.
Spark plugs are graded like eggs. The OEM manufacturers get grade "A". A set of AC spark plugs you buy in a parts store will not last as long as the ones that came new in the engine from the factory.
The best spark plug we have found is Autolite standard (non platinum). A USED Autolite plug produced better spark in a spark plug testing machine than any other new plug we tested.


Here is the AC cross reference.
If you want to try the Autolites
R45T converts to part # 26
R44T is a # 25
R43T is a # 24

Good Luck

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Drew

69' X-11 350, Turbo 350, Factory Air, PS, PB, 12 Bolt (410 gear) & NOT AN SS

[This message has been edited by drew69 (edited 07-18-2002).]
 

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Has anyone tried the AC RapidFire #4 in their BB.

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1967 Camaro SS/RS 396-375
 

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just a question... what is the difference between automotive plugs and "small engine" plugs?

I am curious because I had used two or three Champion CJ8Y (or something like that) small engine plugs to get some extra header clearance. Seemed to run fine.

I now have a new motor (hopefully going to fire it tonight) and am curious if these would have any negative effects?
 

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Drew69, what is the cross reference for the 43S, 45S?

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Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).
 

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I find my self refering to this page a lot www.ngksparkplugs.com/techinfo/spark_plugs/ it's full of some of the best info I've found about plugs...

If you reference factort specs from 60's vintage Chevy mills, you will find the higher HP engines use a colder plug than the lower HP engines do. The rule of thumb is 1 step colder per 75-100 hp. I like the NGK's but AC Delcos' and others I'm sure are fine. the key is the right design or style for your heads. My World SPII's use tapered threads but stock Chevy heads don't. Read through the 3 sections (or links) on the NGK site it will answer most questions.

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...Dennis
"The '69, the '96 & the club"
 
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