'91 #473 Plugs - ZR-1 Net Registry Forums

jss06c6 · 03-12-2017

After reading Roadster's write up on pulling and replacing plugs, I thought it would be good to do the same to #473.. Just turned 40K miles and have done a lot of tuning, but never put in a fresh set of plugs. I've ordered the NGK's, which should be here tomorrow or Tuesday. Pulled the old ones out to look at them. Not too bad, but interesting that #5 & #6 area a bit brown on the insulator, while the others are pretty clean, especially 1,2,3,4...

Having trouble again posting pictures.. I'll try as independent post..

Not too much trouble pulling #7 & #8, just used two universals and a 5/8" plug socket.. Mine all had never seize on them, so not hard to remove. Torque value was not consistent on all 8 however.. I'll correct that with the new plugs when they arrive.

jss06c6 · 03-12-2017

no luck posting pictures. 800x600 jpg.. should not be an issue. I encounter this frequently on this forum.. not always, but more often than not..

Will try later..

jss06c6 · 03-12-2017

Go figure. 5th time worked..

jss06c6 · 03-12-2017

Gents,

I note that the AC-Delco's I took out have a compression gasket rather than a taper.. The NGK's have a taper seat.. Is there another Iridium with a compression gasket??

Steve

Roadster · 03-12-2017

Quote:

Originally Posted by jss06c6

Gents,

I note that the AC-Delco's I took out have a compression gasket rather than a taper.. The NGK's have a taper seat.. Is there another Iridium with a compression gasket??

Steve

Steve, here is a link to the showing a plug with the washer. Don't know what heat range it is, but it is listed for the 91 ZR-1. They also show the tapered seat plugs for the 91.
http://www.autopartswarehouse.com/sk...-1/NG5464.html
I think either style plug will work in any year LT5 head, IIRC what I have read..

My plugs look similar to ours, but you got more mileage out of yours....lol

jss06c6 · 03-12-2017

Thanks! Looking at the plug seat in the head, it appears to be cut for compression gasket.. the ones you sent in the link look like the ones I removed. Hmmm.. don't want to install the wrong profile..

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Roadster · 03-12-2017

Quote:

Originally Posted by jss06c6

Thanks! Looking at the plug seat in the head, it appears to be cut for compression gasket.. the ones you sent in the link look like the ones I removed. Hmmm.. don't want to install the wrong profile..

Sent from my XT1585 using ZR-1 Net Registry mobile app

Here is a post from efnfast from 2 years ago with an email from
Marc Haibeck on this very issue....

"This was an e-mail from Marc H."

"For high load operation I recommend a spark plug that is one AC heat range cooler than the OE plug. The best spark plug is the NGK TR7IX. Part number 3690.

It has a tapered seat. All LT5's are machined for both tapered and flat seat plugs. Carefully open the gap to .050"

Best of luck.

Marc"

These are the plugs I am using in the 94, after today's ride, I am very satisfied with them. Although it is mentioned above, Hib also suggested this "colder" plug in recent posts. I took his suggestion, then found the above post at a later time. Glad I went with this plug....

jss06c6 · 03-12-2017

Golden!

Thanks!!

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Roadster · 03-13-2017

Quote:

Originally Posted by jss06c6

Golden!

Thanks!!

Sent from my XT1585 using ZR-1 Net Registry mobile app

You are welcome sir!!!

jss06c6 · 03-16-2017

Gents,

Completed the job with no issues. I used a 7" piece of vacuum hose to thread the new plugs into the heads. Then slipped a 5/8" plug socket (with the rubber retainer removed) into each plug seat to tighten to around 15 lbft. Only one you need to be careful with is good old #8. I held the plug socket against he valve cover and popped on the 3/8" drive universal joint (actually used two but really only needed one) then eased the socket down onto the plug. Worked like a charm. When recovering the socket, just reversed the process and held the socket against the valve cover, removed the universal and recovered the socket.

Fired up the engine. All good. Will take it out for a WOT pull when the weather clears here in Houston..

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03-12-2017	#2
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: '91 #473 Plugs no luck posting pictures. 800x600 jpg.. should not be an issue. I encounter this frequently on this forum.. not always, but more often than not.. Will try later..

03-12-2017	#3
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: '91 #473 Plugs Go figure. 5th time worked..

03-16-2017	#10
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: '91 #473 Plugs Gents, Completed the job with no issues. I used a 7" piece of vacuum hose to thread the new plugs into the heads. Then slipped a 5/8" plug socket (with the rubber retainer removed) into each plug seat to tighten to around 15 lbft. Only one you need to be careful with is good old #8. I held the plug socket against he valve cover and popped on the 3/8" drive universal joint (actually used two but really only needed one) then eased the socket down onto the plug. Worked like a charm. When recovering the socket, just reversed the process and held the socket against the valve cover, removed the universal and recovered the socket. Fired up the engine. All good. Will take it out for a WOT pull when the weather clears here in Houston.. Sent from my XT1585 using ZR-1 Net Registry mobile app

03-12-2017	#4
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: '91 #473 Plugs Gents, I note that the AC-Delco's I took out have a compression gasket rather than a taper.. The NGK's have a taper seat.. Is there another Iridium with a compression gasket?? Steve

03-12-2017	#6
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: '91 #473 Plugs Thanks! Looking at the plug seat in the head, it appears to be cut for compression gasket.. the ones you sent in the link look like the ones I removed. Hmmm.. don't want to install the wrong profile.. Sent from my XT1585 using ZR-1 Net Registry mobile app

03-12-2017	#8
jss06c6 Join Date: Aug 2015 Location: Magnolia, Texas Posts: 884	Re: '91 #473 Plugs Golden! Thanks!! Sent from my XT1585 using ZR-1 Net Registry mobile app