spark plug opinion
Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
spark plug opinion
These are from the right bank of cylinders, the plug on the right in the pic is the rear cylinder going to the front. The dark plug on the left of the pic is the front cylinder. I took these out of the engine after 2 miles of moderate performance. 327 350hp 1968
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Well, 2 miles isn't much. None the less.3 look great. One , well, you didn't really have to ask. Compression and leak down tests in your future.
older engine? Possibly bad valve stem seal? Rust in one bore? ???
older engine? Possibly bad valve stem seal? Rust in one bore? ???
Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
I was a little unclear,,,,, the plugs have a few thousand on them, it was just the last time I drove it, I drove it a few miles moderately hard and shut it down. They are ACDelco R43S. I replaced them with ACDelco R45.
Last edited by kodpkd; Oct 2, 2020 at 05:46 PM.
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
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Cruise-In VIII Veteran
Looking at the color of these plugs. If indeed you have a couple thousand on them, then WHY would you change heat range??? And why not just put them back in?
Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
Yes, I do have a lot of miles on the plugs. Doing research on plugs indicate that the R45 is the correct plug for this engine. Why not try to improve performance? I guess it is your suggestion that I use the R43. I'm going to check the compression and lash also.
Last edited by kodpkd; Oct 2, 2020 at 10:40 AM.
Racer
Joined: Jan 2008
Posts: 295
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From: Arvada Colorado
R43 is a little too cold a heat range for a street driven car.
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Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
I can check the resistance. Meter is set to 20k the reading is 9.42
The compression on #2 #4 #6 cylinder is 125
Also in checking things, I found the bolts that hold the exhaust manifolds on were not tight. I got 1/4 to 1/2 turn on most of them.
I did check the lash on #2 and #4, and set it while running to 1/2 full turn.
Last edited by kodpkd; Oct 2, 2020 at 06:04 PM.
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Why not an S plug with extended electrode ?
The resistance rule is 1k per foot of wire maximum.
Has the engine had anything done to it to lower compression, the number sounds low to me.
Did you do all 8 cylinders?
The resistance rule is 1k per foot of wire maximum.
Has the engine had anything done to it to lower compression, the number sounds low to me.
Did you do all 8 cylinders?
Thread Starter
Le Mans Master
Joined: Jun 2019
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From: Loveland
9200 ohms for longer wires, 5000 for shorter wires.
Last edited by kodpkd; Oct 3, 2020 at 12:47 PM.