Hello, everyone. New member here. I'm not familiar with older trucks and was hoping for some advice from the enthusiasts.

My Grandad handed down his 1985 D100 to me with 60,000 miles that has been sitting up for a while now. Runs smooth and shifts beautifully. Has the 225 Slant and 727 TorqueFlite transmission. I'm doing some maintenance to bring it back up to par like changing plugs which are original (No, I am not joking), wires, distributor cap and rotor, trans fluid, antifreeze flush, etc. My Grandad used to run Castrol 20W50 oil and I changed it with Rotella T 10W30. Seemed a bit heavy of a weight to me.

So my question is: What brand plugs are you guys running in your Slant 6's and which have worked the best for you, which brands to stay away from, etc?

My second question is: What trans fluid is recommended for the Torqueflite? And is there a filter in the trans that needs to be replaced as well? Any help is appreciated. Thanks!

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2007 F-150 5.4L

1985 D100 225 Slant 6

Welcome!
I'll leave it to the experts on what is best for your truck.. They can help you determine what is best for your application.

CJ

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Part of Tyrde-Browne Racing

Welcome! It sounds like your truck is in great shape.
I use NGK spark plugs, part number 6630.
Yes, there is a trans filter.
For the trans fluid, Dexron III is what I have in my '78. I'm pretty sure an '85 will use the same stuff. Others will reply and confirm this, or not.
Again, welcome!

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318

Thanks for the replies! I will be looking into the NGK plugs. Does anyone know where they should be gapped? Or are they already pre-gapped to the proper spec? Thanks, again!

By the way: Here is a picture of the truck.

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2007 F-150 5.4L

1985 D100 225 Slant 6

Never trust a pre-gapped plug..........

Stock is .035

I prefer .045

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I agree with Ed.

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"Ja, Ich fahre ein altes auto."
'78 Volare 225
'67 Charger 318

Sounds good. Thanks, everyone!

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2007 F-150 5.4L

1985 D100 225 Slant 6

If you go with the HEI conversion you should run a bigger gap. I've run 0.45 in mine for the past several years after the HEI swap. Like mentioned above, NGK is the way to go. I also run Rotella oil because it has the zinc levels that were in motor oils when these beasts were new. Never run a Fram filter. After 32 years I still have 50 pounds of oil pressure so I am sure the Rotella hasn't hurt it. My trans is a manual so can't help you there.

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If it was easy, everybody would be doing it.

Thanks for the reply! Yes, I have heard about Fram being trash and I won't even run one on my riding mower. I went with Wix on the Slant 6. I'm not sure of the quality on those, but have heard people having good luck with them.

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2007 F-150 5.4L

1985 D100 225 Slant 6