4.0L OHV head compatability?

[Duber15]

I'm looking to pick up a set of heads to replace the ones on my 94 4.0.

My question is what head cast numbers would fit and run good?

Which head could possibly bump compression up a little?

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[PlumCrazy]

Any 4.0 OHV heads will bolt up to your 94, but anything newer than 95 will bump up your compression. 95TM heads will give you the higher comp and keep the larger exhaust ports, 98TM will give you the higher comp ratio, but you will have the necked down exhaust ports. If you are looking aftermarket you will only find 98TM and 90TM. The 98TM aftermarket have thicker castings than OEM so they can be ported and polished.

So 90-94 heads are what you need unless you plan to tune it accordingly. (90TM)

 

[Duber15]

Knew that any ohv head would bolt up, was just curious of which would be the best upgrade over the 94 heads.

Who makes good new casted heads? I've located several sets locally but just the thought of the high miles and possibility of getting a bad set makes me hesitant.

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[RonD]

95TM-AD or 97TM will increase compression, slightly
'90-'94 pistons had a shallow depression for use with larger head chamber.
'95 and up have deeper piston depression to keep the 9.0:1 ratio when head chambers were made smaller.
So combining the two increases compression, but..........if you don't have an EGR system you may get some pinging under load, so are forced to run 89 or higher octane.

The '98+ heads, 98TM-AD, have narrower exhaust ports for higher velocity to heat up the Cats faster, it is not recommended to use these on '97 and older exhaust systems

All this is in this article: http://www.therangerstation.com/tech_library/40rebuild.shtml

 

[Duber15]

Any idea of what the compression increase would be with the smaller dish pistons and the smaller 95tm cc heads?

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[RonD]

Probably 9.2:1

 

[PlumCrazy]

10:1. It bumps a full point.

 

[PlumCrazy]

Knew that any ohv head would bolt up, was just curious of which would be the best upgrade over the 94 heads.

Who makes good new casted heads? I've located several sets locally but just the thought of the high miles and possibility of getting a bad set makes me hesitant.

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Alabama Cylinder Head makes nice HD heads for these motors.

 

[Duber15]

Alabama Cylinder Head makes nice HD heads for these motors.

Do you happen to know which casting style they're using?

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[Duber15]

Just looked them up and they have since closed up shop.

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[PlumCrazy]

Just looked them up and they have since closed up shop.

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All you will find aftermarket will be 98TM and 90TM

 

[Duber15]

I've found some off a 96 explorer 15 minutes away still on vehicle, just a hard bottom end knock, claims it's never overheated but does have 300 on vehicle.

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[Duber15]

I may be able to pick them up on a trade but just concerned that I may find a crack after I close the deal and pull them.

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[Duber15]

What are some tell tale signs I should look for if I go for them?

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[PlumCrazy]

Chances are...they are cracked if they are used. Not necessarily problematic, but chances are they have small cracks regardless.