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Old 07-08-2015, 01:15 PM
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4.0 pistons

Does anybody know if the stock pistons in a 4.0 are cast or forged? I'm assuming they are cast. I'm never had one apart and was curious if you could use forged pistons without rebalancing.

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Old 07-08-2015, 05:16 PM
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Re: 4.0 pistons

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Originally Posted by frenchdragon View Post
Does anybody know if the stock pistons in a 4.0 are cast or forged? I'm assuming they are cast. I'm never had one apart and was curious if you could use forged pistons without rebalancing.
If you are rebuilding a 4.0, be very careful. Factory engines would come with mismatched piston sizes, indicated by stamps on the engine.

Mike every cylinder before you order any replacements.
Dimly recall the factory ones are cast, where you can get forged ones from a pretty good number of aftermarket suppliers.
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Old 07-09-2015, 06:02 AM
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Re: 4.0 pistons

I only asked the question because some kid I barely know asked me if I though he could put nitrous on a 4.0 and I told him I wouldn't use cast pistons with nitrous. Why is it everybody wants to squeeze more horses out of this poor tired engine? I can see massaging a 5.2 or 5.9, but please, leave the old 6 along!
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Old 07-09-2015, 03:54 PM
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Re: 4.0 pistons

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Originally Posted by frenchdragon View Post
I only asked the question because some kid I barely know asked me if I though he could put nitrous on a 4.0 and I told him I wouldn't use cast pistons with nitrous. Why is it everybody wants to squeeze more horses out of this poor tired engine? I can see massaging a 5.2 or 5.9, but please, leave the old 6 along!
If that tired old 6 has a Clifford kit in it, or even a Monster Forged 5.0 6, yes, leaving it alone if you only have a V8 is a good idea. Hesco blowers also are best left alone.

That tired old 6 banger is the bastard stepchild of the old racing Hudson 6's....
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Old 07-09-2015, 07:10 PM
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Re: 4.0 pistons

Okay, Maybe my years are showing, but adding intense mods to a stock 4.0 is dangerous to it's health. I realize straight 6's have been around for eternity and are strong, I remember watching Chevy 6's running against Ford flatheads and winning, but most of those engines were rebuilt for the purpose, not taken off the street.

What I DO know is superchargers and nitrous tend to melt cast pistons and other nasty stuff, so precautions should be taken. I laud anyone who wants to hot-rod a 4.0, but they take responsibility for major problems.

JMHO, however. Trying to get more horsepower out of your engine is bred into the American spirit and will never end. When I was young, I did all that stuff, drag racing, road racing, boat racing, motorcycles, you name it. I'd be willing to help anyone who wants to build a hot engine, but personally, I'm looking for reliable transportation in my later years. Off-roading sets totally different parameters on an engine.
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