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Old 09-15-2010, 03:26 PM
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spark plug heat range

When I put my 350 together 2 yrs ago, I used AC R44TS plugs. While chasing a miss last yr I replaced them with AC R45T's and although the engine ran ok, I felt the engine liked the R44TS's better. A week ago I decided to go back to the R44's and mistakenly bought T's instead of TS's.
I understand that the heat range of plugs is determined by the length of the insulator and electrode length beyond the shell of the plug body but here's the deal. The R44T's and the R45T"S are identical in looks whereas the R44TS's extend quit a bit beyond the plug shell. What gives?
Both the 45T's and the 44TS's looked good on removal but the R44T's are being a little *****y on cold starts.
Anyone think I should go back to the R44TS's?

Engine is basically stock with holley, high rise performer, headers, Factory HD cam, and 8:5:1 comp ratio. Thanks!

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Old 09-15-2010, 05:47 PM
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Quote:
Originally Posted by sqzbox
When I put my 350 together 2 yrs ago, I used AC R44TS plugs. While chasing a miss last yr I replaced them with AC R45T's and although the engine ran ok, I felt the engine liked the R44TS's better. A week ago I decided to go back to the R44's and mistakenly bought T's instead of TS's.
I understand that the heat range of plugs is determined by the length of the insulator and electrode length beyond the shell of the plug body but here's the deal. The R44T's and the R45T"S are identical in looks whereas the R44TS's extend quit a bit beyond the plug shell. What gives?
Both the 45T's and the 44TS's looked good on removal but the R44T's are being a little *****y on cold starts.
Anyone think I should go back to the R44TS's?

Engine is basically stock with holley, high rise performer, headers, Factory HD cam, and 8:5:1 comp ratio. Thanks!
It gets confusing, there is space for some trading. The R45 is a hotter plug than R44 which is hotter than R43. While it's thought that insulator length is the control of heat range, that can also be controlled with doping materials in the porcelain.

The 44TS' put the tip a bit further in the chamber which is something I like as it puts the ignition point closer to the center of the cylinder, but here you need to be sure it doesn't interfere with either valves or piston movement, which apparently in your case does not. The longer tip also tends to stay cleaner.

Your compression ratio is pretty mild with a warmed up cam and a hot rod intake with headers, this leads to fairly mild combustion chamber conditions when you're not running wide open, so a hotter range plug will tend to keep itself cleaner and, therefore, will deliver reliable sparks more often. Given winter's comin' on and getting the engine hot enough to keep deposits off things will be more difficult for it, a warmer plug than a 44T will be just fine. so I think either the 45T or the 44TS will make good choices when it's cold outside.

Bogie
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Old 09-15-2010, 07:24 PM
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Hi I was just wondering what thermostat temp do you run in the winter in Indy/
Thankd?
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Old 09-16-2010, 03:15 AM
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Oldbogie, thanks. I'll check on some R45TS's and see if the electrode is farther out of the shell. 6 out of 8 R45T's were real clean but two were a little dark after a year of WOT, groceries, and off road driving. (cyl 8 and 5)

Randolphi, I run a 180 in summer and 195 in winter. Dec. jan. and feb. has 30* day's and temps down as low as single digit's at night. Even with the 195* thermostat in winter it does good to get to 185*. My temp gauge is spot on checked with my lazer temp gun at the therm. housing and the crossover where my sending unit is mounted.
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