I picked up some NGK Laser Iridium Spark Plug IFR5N10

I know they come pre gaped but what is the actual gap suppose to be?

I've seen anywhere from .033" to .040" or up to 1.02 mm

Anyone know?

 

1 mm.

 

So we have a 1.0 mm which is 0.0393"

Thanks!

 

Yes, 1.00mm or if you were running on LPG could be down to 0.80mm.

 

Unfortunately the LPG kits / conversions available there, are not available here. It would be nice to try. Share your thoughts on it though, probably not many folks here have heard of it. Perhaps start a thread on it..

 

The economy of LPG is all down to the price differential between it and the price of gas. Here in the uk LPG is anything from about 65p ($1.02)/L and 76p ($1.20)/L and gas is around £1.129 ($1.78)/L and £1.209 ($1.90)/L. Based on the price alone this means you'll get almost the equivalent of 20mpg cost wise.

In practice LPG is about 10% less efficient than gas, so if you were getting 13mpg on gas you'll get 10% less on LPG.

One of the drawbacks of LPG is that over time VSR (Valve Seat Recession) occurs and (as I'm having to deal with right now) you need to do a head job including fitting hardened valve seats. Having said that my Disco is 10yrs old and has had LPG all that time and done 110,000 miles. Despite this drawback LPG is popular in Europe and makes the gas engine more affordable to run.

 

I would be curious about part numbers of the head job stuff, valve seats, etc. etc. feel free to PM me so we don't derail the thread here.

 

Just happened on my old post and seeing no one really answered it. I got the answer from NGK while inquiring about fake vs real NGK Laser Iridium plugs on the market.
This is for a USA LR3 V8 4.4 motors 2005-2009

The gap should bewithin .004" +/-. The LR3 gap specification is .039", the allowance is .035" ~ .043". We prefer them to be on the smaller spectrum since the gap will grow larger as the plug wears.

If you are going to err maybe on the side of narrower like 0.38" in anticipation of the gap getting larger with time. (they don't by much even at 100k miles) The wider gap limit is imposed by the actual coils, the wider the gap the more work for the coil more heat and possibly early ignition issues.

Not sure how wide is too wide for a LR3 coil. As long as the coils have not failed they should work fine with new plugs, they either work or they don't.