5.3 spark plug and gap ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

C10CONFUSED82 · 09-10-2015, 09:43 PM

Can someone let me what spark plug to run on my 5.3? Also need the gap. Keep hearing platinum, iridium and some say TR55s. What do you all think?

**MikeB** · 09-10-2015, 10:13 PM

Precious metal electrodes like platinum and iridium keep the gap from widening and make the plug last longer. That's all they do.

Google the plug heat range and gap spec for your specific engine. More than likely the gap is .045".

indymachinist · 09-10-2015, 10:25 PM

TR55 is what I use in LS motors. I think the 55 means they are gapped .055 from the factory.

I never waste money on fancy platinum or iridium plugs for an LS motor.

softballnrd27 · 09-10-2015, 11:34 PM

Yes NGK TR55s here as well. Gap should be set but I would check it prior to installation.

C10CONFUSED82 · 09-13-2015, 12:33 PM

What is the GAP for TR55s? I would like to get a solid answer if I can. I keep on hearing different things. Like .060 or .040.

indymachinist · 09-14-2015, 01:05 PM

.055

**MikeB** · 09-15-2015, 09:32 AM

Hard to find anything but opinions on the web, but I was wrong guessing .045". Looks like it's either .050" or .055".

When GM introduced the HEI distributor in 1974, they recommended .060" for plug gap. That was changed the very next year to .045". I have heard two stories about why they did it. The first is plugs would tend to misfire and foul as the gaps widened with miles driven. The other is the in-cap coil would overheat and fail.

Neither of those is a problem on LS engines with external coils and precious metal spark plugs.

09-10-2015, 09:43 PM	#1
C10CONFUSED82 Registered User Join Date: Aug 2015 Location: Nashville, TN Posts: 49	5.3 spark plug and gap ? Can someone let me what spark plug to run on my 5.3? Also need the gap. Keep hearing platinum, iridium and some say TR55s. What do you all think?

09-10-2015, 10:13 PM	#2
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,599	Re: 5.3 spark plug and gap ? Precious metal electrodes like platinum and iridium keep the gap from widening and make the plug last longer. That's all they do. Google the plug heat range and gap spec for your specific engine. More than likely the gap is .045". __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

09-10-2015, 10:25 PM	#3
indymachinist Registered User Join Date: Jun 2015 Location: Indanapolis, IN Posts: 603	Re: 5.3 spark plug and gap ? TR55 is what I use in LS motors. I think the 55 means they are gapped .055 from the factory. I never waste money on fancy platinum or iridium plugs for an LS motor. __________________ -Curt My 1968 Chevy shortbed stepside build

09-10-2015, 11:34 PM	#4
softballnrd27 Always a work in progress Join Date: Jun 2007 Location: Harker Heights, TX Posts: 1,599	Re: 5.3 spark plug and gap ? Yes NGK TR55s here as well. Gap should be set but I would check it prior to installation. __________________ USMC Retired Never trust a man who can't laugh at his own fart! 2010 Silverado Crew Cab 73 SWB 5.3/4l80e Build Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=695168

09-13-2015, 12:33 PM	#5
C10CONFUSED82 Registered User Join Date: Aug 2015 Location: Nashville, TN Posts: 49	Re: 5.3 spark plug and gap ? What is the GAP for TR55s? I would like to get a solid answer if I can. I keep on hearing different things. Like .060 or .040.

09-14-2015, 01:05 PM	#6
indymachinist Registered User Join Date: Jun 2015 Location: Indanapolis, IN Posts: 603	Re: 5.3 spark plug and gap ? .055 __________________ -Curt My 1968 Chevy shortbed stepside build

09-15-2015, 09:32 AM	#7
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,599	Re: 5.3 spark plug and gap ? Hard to find anything but opinions on the web, but I was wrong guessing .045". Looks like it's either .050" or .055". When GM introduced the HEI distributor in 1974, they recommended .060" for plug gap. That was changed the very next year to .045". I have heard two stories about why they did it. The first is plugs would tend to misfire and foul as the gaps widened with miles driven. The other is the in-cap coil would overheat and fail. Neither of those is a problem on LS engines with external coils and precious metal spark plugs. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!



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