Spark Plug Heat Range

[jonszr1]

i on a whim am trying that e 3 spark plug . i have about 2k miles on them but seem to get about 1.5 mpg better milage on the freeway and dont have as many knock events .could be just that they are new plugs . i could be nuts but these things just might work. just thought id throw it out for ya

[Aurora40]

Originally Posted by XfireZ51

The NGKs I had were the TR5IX Iridiums.

The NGK Iridium plug listed for the '93-95 is the TR55IX. I wonder if the TR5IX is just some older identifier? I believe one range colder is the TR65IX, and two is the TR75IX.

This is a tapered seat plug, which is not correct for the early LT5. However, if it's already in there, I wonder if you'll need to use tapered plugs from now on?

[XfireZ51]

Pete,

I'm positive its a 41-630. But I will look again when I get home. One other
possibility is that if I do have heads with tapered seats, it would give more evidence that the motor had in fact been replaced as I was told. Supposedly, original motor had cam seize issue and GM replaced it with a new one. Sepaking with Ron Kreigh at BG, he said that the service engines were all 4 bolt, 93+ motors. Curiouser and curiouser.

[Aurora40]

Originally Posted by XfireZ51

Sepaking with Ron Kreigh at BG, he said that the service engines were all 4 bolt, 93+ motors. Curiouser and curiouser.

Wouldn't it depend on when it was done? If it seized in 1990, I doubt it would be a '93 engine.

[-=Jeff=-]

Originally Posted by Aurora40

Wouldn't it depend on when it was done? If it seized in 1990, I doubt it would be a '93 engine.

Agreed, but in Dominics case, being a 92, it is more possible that he might have a 93.. but then IF it was swapped for a 93, when they replaced the motors, was it Complete? meaning then his IH and plenum he took off would have been from a 93 then right?

[jonszr1]

Originally Posted by Aurora40

The NGK Iridium plug listed for the '93-95 is the TR55IX. I wonder if the TR5IX is just some older identifier? I believe one range colder is the TR65IX, and two is the TR75IX.

This is a tapered seat plug, which is not correct for the early LT5. However, if it's already in there, I wonder if you'll need to use tapered plugs from now on?

i cked with corey and he said you could go back and forth . i have used the ngk tapered in my car for over a year then when i tried the e 3 and found they were the old style with the metal gasket . and have had no ill effects at all . hope this helps

[Aurora40]

Originally Posted by -=Jeff=-

Agreed, but in Dominics case, being a 92, it is more possible that he might have a 93.. but then IF it was swapped for a 93, when they replaced the motors, was it Complete? meaning then his IH and plenum he took off would have been from a 93 then right?

Ah, I don't know why I thought he had a '90...

[-=Jeff=-]

Originally Posted by Aurora40

Ah, I don't know why I thought he had a '90...

No problem, but you know you made a valid point.. obviously anything for MY 93 to 95 had a MY93 motor anyway, the service assemblies were also MY93.. now did GM allocate x amount of motors for each MY as Service Assemblies? Then at what point would those have been used before going to the MY93 Service Assembly replacement?

Lastly, if I understand right, te Motor if replaced for warranty was a complete motor right? so if a 92 got a replacement 93 then it should have the IH and plenum for the 93 model right? would that then mean that the early cars were fitted with EGR if using a later motor?

I am curious more then anything one how that was all settled..

Dominic do you know what mileage your motor was swapped at?

[XfireZ51]

Guys,

A couple of clarifications. The car is a 92 #474. It was built in June of 92 so it was built in the last few days of that MY. The information I had received was that the motor had been replaced at 16K due to camshaft seizing. The owner (unknown) insisted and supposedly GM showed him a motor with a good dyno sheet. Wouldn't mind having that myself. I'll need to check out the heads and see what numbers are stamped on the back. According to Graham Behan, GM had decided to phase out the LT-5 during the 92 MY. Mercury Marine could build motors economically ONLY at a 1500units/annum pace. So they basically built all the motors that were going to be used for the next 3 MY in 1 year plus whatever would be needed as service engines. I have the same question as =Jeff= regarding the top end.
OTOH, IH were definitely 90-92 as was plenum. When I port matched the cylinder heads this past winter, the primaries were smaller than the secondaries. Secondaries were about 37mm. Primaries needed basically a crescent moon cut to match with 36mm IH.

As for the spark plugs, I pulled several and they were 41-602s. My mistake because I still had 41-630s in the cabinet. Those I had used with the 84. However, the ground strap still indicates that I could go with a colder plug and lean out WOT fuel.
Currently running .040" gap.

[flyin ryan]

Originally Posted by Aurora40

This is a tapered seat plug, which is not correct for the early LT5. However, if it's already in there, I wonder if you'll need to use tapered plugs from now on?

no you can go back to flat. that's what i would do. i've seen guys use taper plugs in flat seat heads & they crank it down to force a seal, next thing you know the top thread or two is squashed, go to take the plug out & grabs the thread, gall's, now you've got a problem . while i'm on it always use a bit of anti-seize on the threads but don't let it get on the ground strap, center electrode or any part of that area.