Click on image for the lowdown. 
====
| | | Forums66 Topics128,042 Posts1,055,516 Members48,424 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Jan 2022 Posts: 114 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 114 | What is the difference between a R43 and R43S spark plug? A/C Delco. | | | | | Joined: Jan 2022 Posts: 2,439 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 2,439 | The S plugs have an extended tip, May help prevent fouling. May also hit the piston. Use the proper plug for your truck.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
| | | | | Joined: Feb 2004 Posts: 29,755 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,755 | Like the slogan Sun used to put on all their equipment- - - -"We Test Not Guess". Measure the distance from the gasket to the plug tip and the distance from the gasket surface of the head to the piston top. If there's no interference, run them. The heat range is the same.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Aug 2017 Posts: 660 'Bolter | | 'Bolter Joined: Aug 2017 Posts: 660 | I think the R43S is for V8 GM vehicles. (283 & 350)
Maybe someone can confirm.
What engine are you working on? 235?
1950 Chevy 3100
| | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | The S type plugs work on o-head valve engines without interference. Should not be used on flat heads. They are much superior to the older type plugs.
George
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Jan 2022 Posts: 114 'Bolter | | 'Bolter Joined: Jan 2022 Posts: 114 | Sorry about that there Bolters but it is a 235 6 cyl.. chevrolet. Now what is the best way to check T.D.C. with out removing the head? I have seen those tools that you thread in the head to duplicate a spark plug? | | | | | Joined: Sep 2009 Posts: 5,778 Gearhead, Stovebolt Tech and Parts Tracker, Mod for Swap Meet and GTT | | Gearhead, Stovebolt Tech and Parts Tracker, Mod for Swap Meet and GTT Joined: Sep 2009 Posts: 5,778 | Ol'55
That question actually is better asked in "The Engine Shop" forum please. A whole different animal not related to "The Electrical Bay".
~ Dan 1951 Chevy 3 window 3100Follow this story in the DITY Gallery"My Grandpa Carl's Truck and How it Became Mine"1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
| | | | | Joined: Oct 2021 Posts: 6,720 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,720 | Take out the plugs and turn the engine over by hand with your thumb over the spark plug hole. You'll feel the compression as the piston comes to the top of the cylinder.
You can also put a straw in the hole while you turn over the engine by hand. The piston will push it up. When it reaches its highest point, the piston is at TDC.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: Feb 2004 Posts: 29,755 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,755 | The plugs in a 235 are at such an angle that a regular "positive stop" tool will not touch the piston. When the "UC" mark on a 235 flywheel aligns with the pointer in the window above the starter both #1 and #6 pistons will be at TDC. The ignition timing BB will be close enough to top center to check for spark plug interference.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Dec 2018 Posts: 2,450 'Bolter | | 'Bolter Joined: Dec 2018 Posts: 2,450 | OL 55 If you hunt for top dead center disconnect your battery,that tool will kill your piston in an instant if you engage the starter. | | |
|
|
