I've got an '85 D100, S6w/4 speed, all original, body good. Will remain my daily driver. Would like a few more horses without having to change any of the stock drivetrain. Any suggestions?
omegashire

Open-up the exhaust system and recurve the distributor. (you need to review the ignition advance system, the later systems had painfully slow and limited timing advance)
After the steps above, checking and adjusting the Air / Fuel mixture can unleash more power.
DD

Define "without having to change any of the stock drivetrain." Do you mean not changing anything on the engine at all or just not putting in a whole new engine?

If you don't want to make any major changes, check to make sure your leanburn unit is working correctly. If not, consider swapping out to stock electronic ignition or doing the HEI mod.

If you're willing to consider getting a little more radical, a cam swap and a supersix would have you in business. I'm not sure if it's true on your '85, but my '82 had a fairly large (about 2-1/4") pipe coming off the manifold when I got it. If that's the case for you as well, I don't know that I'd worry about making that upgrade one of my top priorities. (Doc, if I'm wrong on that being large enough, please correct me.)

If you really want to get ambitious, pull the head off for some porting and oversized valves. Mill it down so you get compression in the mid-9:1 ballpark. Add a two barrel with your preference of carbs. I love mine, and don't think I'd do much different at all if I had to build it all over again.

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Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion

Would this be a hydraulic lifter engine? And if so, can you mill the head without problems?

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Excuse me, does this smell like chloroform to you?

Ah, good point... Stock, yes they are hydraulic lifter engines. I forgot to say that when doing the cam swap, I would put a solid lifter cam in. All you should need is a new set of rocker arms, which aren't that hard to find. Other than that, it should be a direct replacement.

_________________
Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

My other passion