98 4.0 ohv

Denisefwd93 · Jun 21, 2018

I'm finally reaching the point where we are going to prep the (ohv) 4.0 from the 98 to go into my 94 and replace the 4. 0 ohv that is in there.

I think we established that the lower intake is the same and only the upper plenum intake has to be changed ?

Exhaust manifolds, are they the same or should I plan on having them changed over when they do the engine?

(Yes, much as I want to do this engine swap with my old friend Hank; I'll probably have it done, we really struggled with the transmission swap physically. )

I'm planning a new flywheel and clutch assembly. Are there flywheel shimming adustments for takeout bearing to clutch fingers?

RonD · Jun 21, 2018

The 1998-2000 4.0l heads had narrower exhaust ports so I would use the 1998 exhaust manifolds.

Yes, lower intake is the same but fuel system in 1998 was Returnless with 60psi pressure, 1997 and earlier used Return system with Fuel pressure regulator and 30psi pressure, 1994 computer will want the Return system, also 1994 fuel lines will hook up

And 1997 and up crankshaft uses 8 bolt flywheel or flexplate, 1996 and earlier used 6 bolt

Denisefwd93 · Jun 21, 2018

Thanks Ron, I know this is getting redundant because I've been at this for going on 4 years,. I understand everything you're saying but are the exhaust manifolds physically different, meaning will my existing y-pipe fit the newer exhaust manifolds?

The older fuel rail should go on to the newer lower intake?
Do not use CPS crankshaft position sensor, does it get removed? I have yet to really look at this stuff.

The plan is to use the older harness and as much as necessary from the older engine put onto the newer engine which I believe is what most shops and garages do, (we did it with Jasper long block into my Pontiac Fiero many many years ago, it went very well, )

the transmission in my truck now, is the transmission that was mated to this engine, and yes I'm aware of the number flywheel bolt holes.

Denisefwd93 · Jun 21, 2018

I think I may have discovered a problem, the older y-pipe may not fit the newer manifolds? 98 I believe is a year they put the catalytic converters on the y-pipe, on the 94 they were farther downstream

RonD · Jun 21, 2018

You can use the 1994 exhaust manifolds with the 1998 heads, they will fit/bolt on

The 1994 ports will be larger, so not as smooth a transition with the smaller ports, and I think you may lose a bit of scavenged power but can't say for sure
The narrower ports in 1998 were to increase the velocity of the exhaust to heat up the Cats faster for lower emissions on cold start.
Velocity is how scavenged power works, and exhaust manifolds(headers) are designed based on velocity of exhaust at a given RPM, ALL Rangers came with Mid-RPM band "headers".
If you can make the 1998 manifolds work I would use them, but won't hurt anything to use the 1994's
I would think the 1994 "Y" pipe would bolt to the 1998 manifolds but never looked at both, side by side, to see if they are longer or shorter

The 1994 computer is programed to expect 30psi fuel pressure at the injectors, so it "knows" how much gasoline will flow out of an injector if it opens it for 100millisecond, for example, if fuel pressure is 15psi then less fuel flows out and you would get a Lean Code because computers calculations were off, Lean code is not ALWAYS a vacuum leak, lol
If fuel pressure was 60psi then too much fuel flows out so computer would set a Rich code, for the same reason, its calculations were off

Crank sensor will be the same type of sensor, Variable Reluctance, although not sure about connector on 1994 harness fitting 1998 sensor, but you get that anytime you use different years

Cranks nose(where pulley goes) was changed in 1995 and again in 1997, so you will have to use 1998 crank pulley, not sure 1994 pulleys will line up if you are using the old accessories, I would think they would but........

Denisefwd93 · Jun 22, 2018

I found a discussion on another forum and the guy used a 99 4. 0 OHV, he did not have to change the exhaust manifolds which was good to know.

And the number of people just advised him to use the older wiring harness and not use the cam sensor which I already know.

No one's mentioned anything about any differences on air conditioning, alternator, water pump, power steering mounting so assuming they're going to be okay.

Denisefwd93 · Jun 26, 2018

I guess I'll take this engine down to basically a long block with exhaust manifolds they'll do all the rest at the shop my friend Hank and I will probably install the rear seal, flywheel, clutch, and valve cover gaskets that don't leak? ( is there such a thing?)

RonD · Jun 26, 2018

Use Cork valve cover gaskets
And straighten the valve covers, the gasket areas get deformed from over tightening.
Use sealant on both sides of gasket on the lower edges, especially around the lower back corners, that's where the most oil sits

Make sure PCV system is in good working order, it creates a slight negative pressure in the valve cover areas, so prevents oil leaks from starting.
Blow-by pressure causes oil leaks to start if PCV system isn't working as it should, because system is sealed for PCV to work

Denisefwd93 · Jun 26, 2018

Will do !'Well the reason I'm so keen on this engine and I personally saw the odometer on the donor truck with 62, 000 on it. This is really my last chance to have a dependable vehicle that I can drive and go places with.

RonD said:
Use Cork valve cover gaskets
And straighten the valve covers, the gasket areas get deformed from over tightening.
Use sealant on both sides of gasket on the lower edges, especially around the lower back corners, that's where the most oil sits

Make sure PCV system is in good working order, it creates a slight negative pressure in the valve cover areas, so prevents oil leaks from starting.
Blow-by pressure causes oil leaks to start if PCV system isn't working as it should, because system is sealed for PCV to work

Denisefwd93 · Jun 27, 2018

Got a call from my state revenue office that my seniors real estate rebate is going to be in the mail probably in about a week so this engine swap is looking like it's really going to happen!!

Vincenthdfan · Jul 18, 2018

Im going to be watching this swap.

I found a local guy with a 4.0 out of a 99 with 60,000 miles on it.

Seems an ideal candidate to swap into my 93 Ranger as well, since I intend to keep this little rig for a long time.

Denisefwd93 · Jul 18, 2018

I can't seem to get much input about a 98 going into my 94,

I guess it's a non issue!

RonD · Jul 18, 2018

Different crank, 1994 was 6 bolt, '98 is 8 bolt so need flywheel or flexplate for 8 bolt

98 4.0 ohv

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