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98tm heads on first gens


Makahveli

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I was just wondering due to the size of smaller exhaust ports on 98tms head if put on a first gen with or without headers would that mean back pressure increase for those those of us worried about losing bottom end torque with specific engine modifications.
 


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goliath

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Makahveli said:
I was just wondering due to the size of smaller exhaust ports on 98tms head if put on a first gen with or without headers would that mean back pressure increase for those those of us worried about losing bottom end torque with specific engine modifications.
i was under the impression that the later heads are "fast burn" combustion chambers and will roast your motor withing a few thousand miles if used on a 91-94 that came with the "slow burn" style heads. this is what i was told when i rebuilt the top end of mine.

-joshua
 




Makahveli

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i hear you but, i understand that the two engines aren't too far apart
 




Makahveli

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just that now i have borla headers to aid the flow and with aiming towards a 422 cam the fast burning it does should help a little better in trying to pass emissions. well atleast thats whats floating around in my head
 




goliath

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Makahveli said:
just that now i have borla headers to aid the flow and with aiming towards a 422 cam the fast burning it does should help a little better in trying to pass emissions. well atleast thats whats floating around in my head
i would talk to a engine rebuilder or an expert on the 4.0s before making assumptions about putting different style heads on your computer controlled engine. new engines are awfully expensive, and if the computer, compression, and heat capabilities of the combustion chamber dont match, at best it may ping, at worst... well you know $$kaching$$

-joshua
 




Makahveli

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goliath said:
i would talk to a engine rebuilder or an expert on the 4.0s before making assumptions about putting different style heads on your computer controlled engine. new engines are awfully expensive, and if the computer, compression, and heat capabilities of the combustion chamber dont match, at best it may ping, at worst... well you know $$kaching$$

-joshua
Well I can use that as an excuse to put in a 5.0
 




Makahveli

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but do you all understand my theory?
 




Rhett

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I have (at home) a big detailed writeup on the head castings, and if I remember correctly, you would want to use the computer from the donor truck that had the 98TM heads in it.

I wouldn't try using my existing computer with 98TM heads. You could have running issues. You might as well start from a known starting point if you're trying to tune the truck properly with headers and so forth. I believe the 98TM heads give slightly higher compression, if I remember the writeup. It's been a long time since I read it.
 




Creager

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It would work technically.. the problem is compression

They all have different size 'dishes' on the piston heads and what not. If you put a newer style head on its going to change compression, and you would have to retard the timing to fix it and it would end up being less power, more fuel consumption, and a lesser life span.

If you want to go with 98 style heads, just get a whole 98 OHV motor and convert everything to OBD-II. That way you get 160 horses. AND you can mod the SHIT out of it with OBD-II
 




Makahveli

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Wow, thats alot more than I want to do. Why not just get a SOHC while I'm at it. I wouldn't be able to use the same headers with the 98tm's huh? If it comes to the point that I much convert all of those things over then I'd rather not do this and its starting to not sound daily driver at all anymore
 




Creager

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Makahveli said:
Wow, thats alot more than I want to do. Why not just get a SOHC while I'm at it. I wouldn't be able to use the same headers with the 98tm's huh? If it comes to the point that I much convert all of those things over then I'd rather not do this and its starting to not sound daily driver at all anymore
SOHC swap would be bascially the same as a 5.0 swap

no really converting it all over to OBD-II isnt as difficult as it sounds. You can use the same tranny and what not. You just have to use the OBD-II computer and stuff. in the long run its much better.

ill find you the thread that disscuessed EVERYTHING you need to know about upgrading from a OBD-1 4.0 to an OBD-II 4.0 in a first gen
 




Creager

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Doug904(AKA 4.0-GOD) said:
Originally Posted by Doug904
Well, being that it is a OHV to OHV swap it's pretty straight foward like before mentioned but there are a few differences that can confuse a simple guy.

1) The intake studs in the fuel rail are longer because the plastic intake is thicker the the aluminum one, this really doesn't matter except for the front stud, you have to put the nut on the stud before you put the throttle cable bracket back on.

2) The CMP drive and/or sensor. All 95-00 will have this and use it,the 91-94 4.0's either won't have it OR you will have a different style. If you older truck doesn't have it then I wouldn't even take it off the block, it doesnt hurt anything sitting there.

3) All of the sensors, and don't forget the crank sensor in all of this. The temp sensors in the front of the intake must be swapped as well and finally all of the wiring harness from the vehicle it is going in must be used. Like before mentioned their won't be a low oil level sensor on a 98 and newer 4.0 so you'll either have to swap pans or not worry about it and let the wire hang, or tie it up out of the way. I think I would know before the oil level got low enough to trip this light anyway so I wouldn't worry with it.

4) The Exhaust manifolds must be used from the older Explorer but there too they bolt right up. On a 98 and newer there will be exhaust studs that must be removed from the heads, they won't work in the early model exhaust manifolds.

5) Upper intake and possibly fuel rail if your using a 98up returnless system. You can use the new injectors, don't remove them but the rail itself must be changed. Also the 96-up OHV's have a plastic spacer plate below the fuel rail and you must reuse this plate between the lower intake and fuel rail or the injectors will bind up and you'll get an vacuum leak because of the difference in height.

6) Finally the flywheel on a 98up are 8 bolts, you can use the new style flywheel on the old style transmissions no matter whether it's an auto or manual. Now if you have a C4 behind it that's a whole different ball game but I doubt anyone else has ran into this problem, if you do I have a special made flywheel lying around .

That's all I can think of right off hand but it's a very straight foward swap. It's the same basic long block just the heads are different. The exhaust ports on the 98up's will be smaller then your old ones but dont worry with that on a stock setup.

One important thing to remember is you can go late model to early model but you can't go early model to late. The reason being is the number of engine mount bolts on the side of the blocks. They used new castings for new bolt locations every couple of years and it's very specific on that. The way this goes is pretty much...

91-94 used one bolt setup
95-97 another
98-00 the final

You can use the 98-00 on any year model but the 95-97 can only go back, not foward.

Thanks, Doug904
Good luck man. I think i might go this route insted of rebuilding a 92 4.0. you know for the extra 5 hp hah
 




Makahveli

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wow, thanx! good info
 




Rhett

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Your A4LD transmission is not computer controlled. Keep that in mind if you are planning on switching the rest of the drivetrain to OBD-II. I'd ask the trans guys here about that issue. I don't know what running problems (maybe none?) it would cause having an OBD-II PCM with a vacuum A4LD. But I would ask if it were me.
 




Makahveli

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It should be easier since I have a 5 speed, y not try it some body pieces from a '98 are on my sport anywayz
 




Josh

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I put a 2000 OHV in my 91 10,000 miles ago. I just moved everything over like doug said. I also talked to him about using the newer heads on the older motor, and I think he said it would bring the compression up 1 point, 10:1 I think. He said you would have to run 93 all the time as well. I can't remember our talk about the fast burn chambers though. I would think if you went with a colder plug, that might help, but donno?? I was looking for more torque.
 




Kirby N.

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I have a 1998-2000 short block I want to put in my 91 ranger. Any more details from you Josh on what you did would be helpful. I need to get some heads and pushrods- then did you swap everything else over? Did OBD1 handle it ok?
 




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