What You Need To Know About Spark Plugs For Your Foxbody Mustang or other 5.0 Ford. 

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There is a lot of tech content on here if you look through the back catalog on my channel. Thanks for watching!

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It can make a genuine difference.

It’s an old but effective technique.

If it is NA I would use NGK FR5

I thought I had answered this question somewhere here already, but it doesn't look like it. I would use NGK TR5 or TR55 with an 0.045" gap in that application.

@@tecmotiondyno thank you

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I know you are running meth, but if it was me I would go one colder for that combination. Autolite 3923 or NGK BKR6EY. It’s not that it won’t run, but one step colder would be a touch safer with no downside. I’d run the colder plug at .030” too, assuming you have a strong ignition which seems like a safe assumption.

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I would have gone one colder, like the 3923 or BKR6EY in the NGK lineup, especially if you don’t have an intercooler. The 3924’s will run fine, but my choice would have been one step colder for your combination.

@@tecmotiondyno thank you for the quick reply !

NA I would gap them .045”.

I’d gap them .045”. If it will take 32* total timing on 87 octane without pinging, go ahead. In most cases you will need 91 octane to run optimal timing. As a rule of thumb you want to run the most volatile fuel you can with optimal timing and without pinging.

@@tecmotiondyno thank you could you also help me with a question I have an lx vert and it’s mint but when I drive it has Creeks and rattles from underneath going over small cracks in the rd. that I can’t figure out any advice greatly appreciated

You might have some suspension problems like worn or tired bushings, ball joints, or tie rod ends. You could also just have an old car with some creaks and rattles. I’d start with an inspection underneath and a close look at the suspension and chassis.

I know guys do this to try to unshroud the spark kernel and it is supposed to help. I have never tried it myself but I have tested indexing in back to backs on the dyno and it DOES work on these pushrod motors.

I normally recommend .045” if the car is NA and .030” if the car is supercharged or turbo as a starting point. Those gaps are good unless the car is well outside the norm in terms of the parts and power.

By the way, there is a video coming out tomorrow at noon Mountain Time on five things that are usually wrong with these cars, and I talk about one that I did recently which had the wrong plugs and a prior dyno, and when I fixed the plug problem and retuned it, I picked up 20 RWHP, so they can make a real difference at the top end too. Take a look at that video tomorrow ...

@@tecmotiondyno Awesome and thank you so much for taking the time to reply!

I like the MSD wires but they have gotten VERY pricey in recent times. The 9mm Ford Racing wires are a great choice and more reasonably priced these days. I just used a set of the Ford wires on a car to replace a damaged set of MSD wires a week ago actually.

@tecmotiondyno Funny you mentioned this. I just purchased this 88 LX coupe and the previous owner had a shop install brand new MSD wires but the boots are straight instead of angled and burned on the header causing several to arc. I figured I'd just replace them with the Ford Racing wires just like you suggested. Thanks for the help! Much appreciated sir!

@@royenri01 the MSD wires can be bent but if you bend them too extremely you will have problems. I worked on one just yesterday with an MSD set where I had to straighten the #1 wire to put it back on, and in the case of #1, there was really no reason for someone to have bent it.

I'm no encyclopedia of Autolite numbers, especially for stock heads. In the NGK lineup I would think about UR6 for this application, which is 1 heat range colder than stock. Lots of guys get away with stock or UR5 plugs with that combination too.

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