I am changing the spark plugs in my 1971 LT-1. The current plugs are AC Delco R45TS. Should I replace the plugs with the R45TS? Or, should I use a plug that would be better since they are not judged during events. I am not sure if the R45TS is the "correct" plug.
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Re: LT-1 Spark Plugs
Mark-----
Your owner's manual should show you the plug originally used and recommended for most driving conditions (and, also, it will possibly show optional plugs you can use for "special" driving conditions; these weren't originally used in the engine, though). My records show that the AC R43T was the plug originally used for 1971 LT-1. However, I would recommend the "TS" suffix plug (tapered seat, EXTENDED TIP) for most driving situations. The 45TS might be a little too hot, though. A R44TS might be the best choice. However, if it runs well with the R45TS, "don't try to fix something that ain't broken".In Appreciation of John Hinckley -
Re: LT-1 Spark Plugs
Joe, I think for everyday driving the R45TS would be a very good choice. However if he runs everywhere with the throttle bumping the fan shroud he probably should back up to the R44TS. I have found that the one to two heat range hotter plugs work better for normal driving in these older carsDick WhittingtonComment
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Re: LT-1 Spark Plugs
The car is a show car and sits in the garage most of the time. I drive it about 250 miles/year. I don't drive it hard since I have a 2003 ZO6 to get my thrills. I have had the LT-1 for three years and can't get above about 3500 rpm when it will start cutting out. The old plugs are pretty black but don't have too much build up on them. So is it best for the 44 or 45?Comment
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Re: LT-1 Spark Plugs
In your case I think that the R45TS would be your best choice. You hardly ever get the engine to full operating temperature.Dick WhittingtonComment
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Re: LT-1 Spark Plugs
sounds like you have a carb or ignition problem because R-45TS should work fine with out fouling unless you never run the car long enought to get it up to temp. and get the choke open. if that is the case i would go with a R-46TS if they are available and go for a leaner choke settingComment
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Re: LT-1 Spark Plugs
Mark,
I went through a similiar thing with my 70 LT-1. In my case I couldn't get it to go above 4500 RPM but it wasn't breaking up. I opened up the Holley and found the primary bowl to be virtually full of shellac from years of storage and non use. The car was starving for gas as the bowl size was significantly reduced. I cleaned the bowl and with Clem's guidance I rebuilt the carb. w/ a Holley kit from Summitt. Took the car to 6500 RPM during my PV and it now runs perfectly. If your car is breaking up it does sound like an ignition issue so you may have more problems than just the spark plugs.Comment
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Re: LT-1 Spark Plugs
At about 3500 its starts sputtering and cutting out, I may even hear some knocking. I decided to change the spark plugs because at idle it sounds like it has an after market cam. However, when I rev it up it just sounds like it is not firing on all cylinders. It is definatley getting worse over time. I may just have to get a tune up done on it.Comment
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Re: LT-1 Spark Plugs
"I may just have to get a tune up done on it."
It should sound like an aftermarket cam. That's the way they sound.
Do the tune-up and remember what Clem said about the carburetor. That may be causing your problem. 45's should run good in your car if everyting else is okay.Comment
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Re: LT-1 Spark Plugs
Mark..I've owned a 72 LT1 for over 25 years. The 45TS will work, 44's for the street are TOO cold. If it has points, put a HD set from Mallory or Accel in to help with the high revs, and the sputtering. BUT, LT1's were hard on plugs, even harder on points. They ran rich from the factory, try dropping the primary jets down to 69's and set the front float LOW, ( so it won't run out the sight hole at idle)and install the Holley "whistle" in the rimary side. This will stop it from loading up under hard braking.........Hope that helps.Comment
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