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98TM heads on a '93 Ranger 4.0L

Discussion in 'Modified 1991-1994 Explorers' started by Carguy3J, October 22, 2013.

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  1. Carguy3J

    Carguy3J Well-Known Member

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    OK, so I have a '93 Ranger, 4.0L-OHV. I have a serious exhaust leak on the drivers side, at the manifold. The problem is, attempting to remove the manifold, to replace the gasket, could very well lead to needing new heads (or at least the left one, I guess- but it would really bother me to do only one side).
    Here's why: When I replaced a cracked manifold a few years ago, the top bolt of the middle cylinder snapped. In the process of trying to remove it, that corner of the head, containing the hole for that bolt, cracked and broke off!
    I have "rigged" it for the last few years, with JB weld, muffler cement etc, with varying success and durability. Now, the gasket has burnt out at the first cylinder. I started to try to change it a while back, but as soon as I tried to remove one of the other bolts, it didn't "feel" right, and I stopped. I am pretty certain that any attempt to remove the bolts/manifold will result in more snapped off bolts, and possibly more damage to the head.

    I REALLY can't afford to buy new heads, not even just one for the left side. However, I have a pair of 98TM heads I removed from a motor I junked. The "post-mortem" showed a a blown head gasket, on the right rear cylinder, with "intrusion" only on the BLOCK side of the gasket. The motor showed signs of being run with poor lubrication, including scored cylinders and wiped bearings, but the heads "look" good.

    I know that the 98tm heads are higher compression and have smaller exhaust PORTS. What I need to know is, are they otherwise identical to the 93tm? By that I mean:
    1.) In regards to the combustion chamber, are the valves in the same relative location within the chamber, and in relation to all holes/ports,etc...? Are the valves the same size? In other words, could I just "port" the 98tm smaller chamber to larger, to reduce the compression increase, and unshroud the valves, to come close to being indentical to the 93tm chamber shape/size?

    2.) I know the exhaust PORT is smaller (98tm), but is the bolt pattern the same? Is the port "centerline" still the same as the older heads (93tm)? What about the runners inside the head, leading up to the port? Are they also smaller, or the same size as the 93tm, and just choked down at the port? Couldn't I just use a 93tm gasket as a template to port match the 98tm head exhaust port to the same size dimensions as the 93tm? Actually, I would do it slightly different, leaving a higher floor vs the 93tm, and concentrate on the roof and long-side side wall.

    3.) Is there anything else about the 98tm head that is NOT just plug and play with my '93 4.0l/Ranger? Are the later heads less prone to cracking, such that I can maybe save the time/expense of a pressure test?
     
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  3. jd4242

    jd4242 Explorer Addict

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    Your have to run 90+ gas also but to answer your questions
    1-they are the same and you could port the CC but it would be tons of work and you would have no clue how much or where to port.
    2-pattern is the same and yes you could use the ""round/larger"" 90-97tm gasket and match it.
    3-and yes the later models are stronger.
     
  4. Carguy3J

    Carguy3J Well-Known Member

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    Well, that's what I was trying to avoid, by re-designing the chamber, to not only improve flow, but also to increase the size, and get compression back down a bit. I drive this thing too much to use/pay for more then regular 87

    Well, I would have an old 93tm head side-by-side, and a head gasket, as a guide. I wouldn't necessarily be looking to create an exact duplicate. I would just use 93tm as a guide as to how far I could go in certain areas. My purpose would be to unshroud the valves, eliminate sharp edges (hot spots)- which would also reduce detonation and increase tolerance for low octane fuel, and to enlarge the chamber volume- to reduce CR.
    I would need to just sort-of "wing it" on the first chamber, and then do my best to get the others the same. I would also need to cc the finished chambers, to determine the largest one, and then take a little more out of the rest to match.
    Does anyone know the actual, stock combustion chamber volumes, for 93tm and 98tm heads?

    My hope is that the port work in the chamber, as well as the exhaust work, would bring the compression back down enough not to need premium gas. I am also considering the "exhaust mod which shall not be named", which would also reduce back pressure, increase scavenging, lower residual combustion chamber temps, and hopefully reduce detonation. I may also consider doing the cam upgrade at that time, which would also reduce dynamic compression, and lower detonation tendencies.

    Does anyone know if there are various thicknesses of head gaskets available? I know there is a wide range of options, for, say the small block chevy, from .015 steel shim to .060 thick gaskets. This might be another way to "give back" some of the unwanted CR increase; assuming they are available.

    Now, another "big" question..... Would I be able to get away with not having any tune (stock ecm):

    1.) with just the modified 98tm heads

    2.) heads AND 410 or 422 comp cam

    3.) heads, cam, "evil" exhaust mod
     
  5. snoranger

    snoranger Well-Known Member

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    I have a pair of heads off a '91 4.0l. I was going to throw them in the scrap metal dumpster. (I'm done playing with these 4.0s.) If you want them, they're yours... just come pick them up from my shop in Perth Amboy. I'll have to dig them out of my garage and check the condition of them, but it was a good running truck I stripped for the manual trans.
     
  6. Carguy3J

    Carguy3J Well-Known Member

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    Oh wow. Thanks. That would be awesome. Just curious though, aren't those early heads still part of the "ticking time bomb just waiting to crack" club? I guess, if it came off a known good running engine, then I guess it would at least buy me some time......PM sent.

    To everyone else, please continue the discussion. This proposed project is still something I'm interested in later, when finances allow.
     
  7. Anime

    Anime EF YEAH!! Elite Explorer

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    The 90TM heads from the 91-92 are slightly weaker than the 93TM heads of the 93-94 vehicles, but it's not much of a difference, any of them will crack if the motor overheats just because of the design and lack of material.

    Aftermarket heads are better long-term, especially for something as expensive to repair (in terms of the hassle of removal and expense of gaskets, head bolts, and other parts) as heads.

    The thing about the 98TM heads is they were an even more extreme "quick burn" design than the 95TM heads, and with the smaller exhaust ports (for higher exhaust velocity and higher temps to get the converter to operating temp quicker to meet emissions standards) they may not be the best thing to use with an older motor.

    If you're going to use a 410 or 422 cam, you're probably going to need to spend $$$ on pushrods, double valve springs, and head work to make all that work.

    I'd say you'd be better off putting the $$$ towards two brand new aftermarket heads and replacing the worn out rocker arms. Being cheap on the heads themselves then putting money into performance stuff to stick on them is a recipe for disappointment and disaster.

    Better to invest in the core stuff for now, then add the performance stuff later. Try to do it backwards and you'll just be doing all the work over again to put on new heads.

    Also, don't do any "evil" exhaust mods if you drive the vehicle on the road.
     
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  8. Carguy3J

    Carguy3J Well-Known Member

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    Yeah, but I thought the early ones cracked if you looked at them the wrong way on a Tuesday?

    Yes, but they wouldn't be that anymore, if I did all the porting I intend. Both the combustion chamber and the exhaust port would be opened up, negating much of the "negative" you pointed out above. Maybe, when I was done, I would be at 9.5:1, instead of the 10:1 that just bolting them on would do?

    Yes, which is why I was hoping to save money on the heads themselves, by staring with the 98tm heads I already own.

    I thought that the 98tm heads were "stronger" anyway. How much are already ported/polished NEW aftermarket heads? If I were going to this level of effort, I would want the heads ported and polished,, and I would be reluctant to take a grinding stone to a brand new un-ported head VS a used 98tm head I already have for nothing.

    Yes, I understand how that works, but it doesn't automatically mean you have to start with all brand new stuff. If re-using/modifying free or low cost stuff is possible, then doing so can save money for use on the stuff that does HAVE to be new.

    C'mon, I was nice enough not to "name" it. Don't bust my chops or lecture me. I will decide what is best for MY vehicle and MY wallet (mpg increase). It can be "undone" once every 2 years, for certain purposes.
     
  9. snoranger

    snoranger Well-Known Member

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    If it were me... I'd take the free heads and get my truck fixed. Then find another engine to build.
     
  10. Carguy3J

    Carguy3J Well-Known Member

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    Yes, that is the immediate plan. Thanks again for the offer.

    I'm just hashing what ifs here. I think its still interesting to discuss the how's and why's, for future plans.
    With the weather starting to turn cold, I just want to get it running reliably for the winter, but that doesn't mean I've stopped "dreaming".

    I guess maybe "building" a second engine would be easier, in terms of having something to throw in and go, but it then requires the expense, and the "unknown" of a whole 'nother motor. Bottom-end,etc... wise, I have no issues.

    Of course, I just junked a 4.0L (the source of the 98tm heads), but as I said the cylinders were scored, I think one piston was cracked, the cam was worn (bearing journals and lobes), the crank had wear on the journals and would have needed grinding, and the later block/crank would have complicated things a bit (flywheel bolt pattern, timing gear,pan rails, etc...)

    So anyway, back to the "what-if", do you guy think I could get away with no tuning, with the previously discussed mods? I know, its not ideal, but would it be "mild" enough to work? Thoughts?
     
  11. snoranger

    snoranger Well-Known Member

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    Here's a what-if for you:

    What if I happened to have a 96 4.0L w/ just over 80k miles on it. Best running 4.0 I've ever owned. 410 cam, new timing set (chain, gears, and tensioner), delta rockers (old ones, when they built quality stuff), smith bro pushrods... All with 0 miles on them. Maybe a set of Borla stainless steel headers, a BBK throttle body, and some other stuff that could all use a new home. ;)
     
  12. Carguy3J

    Carguy3J Well-Known Member

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    I'm drooling all over my keyboard:D......... I doubt I can afford it though:(

    I guess PM me a price, just for the heck of it.

    I would need a new flywheel too, right? Bolt pattern on a 96 crank is different?
     
  13. snoranger

    snoranger Well-Known Member

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    No, '96 still had the 6 bolt.
     
  14. Anime

    Anime EF YEAH!! Elite Explorer

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    The 90TM heads aren't excessively fragile, they just weren't as good as they should have been. There are plenty of 4.0L's with stock 90TM heads that have no cracks or issues. It's also very possible for the heads to have cracks between the cylinders but show no issues.

    If you have the machining skills and equipment to modify a 98TM head backwards to 90/93TM specs, go for it.

    It's certainly possible to modify them, at least by porting, but without some real engineering knowledge, it'd be just a guess and trial-end-error as to what effect the porting has with respect to the compression and how well it works with an older OBD I control module.

    98TM heads are an "improvement" on the 90/93/95TM design, at least in terms of durability, but even aftermarket 98TM heads are likely an improvement over any of the stock head designs, just by virtue of having more material.

    Porting and polishing is usually something that has to be done at a machine shop, and some head suppliers that also do performance work will port/polish the base heads then assemble them for you. You could call Clearwater Cylinder Heads in Florida to get an idea of what new 90/93TM heads would cost, both bare and assembled, and what they'd charge for porting and polishing them.

    Sometimes modifying stuff to try to make it work is a bad idea and winds up costing more in the long run when you wind up with ruined parts. Generally, the way to make 98TM heads get lower compression is to use the dished/domed pistons for the newer 4.0L, rather than the flat ones from the 91-94's. Obviously it's a lot more work to take apart the bottom end and swap pistons, but that's the general way of doing it.

    I'm not saying modded 98TM heads won't work, I'm certain they could be made to work, and you could modify lots of other stuff to make it a hybrid of newer and older 4.0L parts. Whether it will run smooth and be reliable with the stock ECU is hard to say, that depends how well the work is done, but if you do everything towards that end, it's possible. Whether it will be cheaper than just throwing on aftermarket 90/93TM heads is something you'd have to analyze before deciding which way to go.

    As for the exhaust, it's best for your vehicle and your wallet to obey the law. It's also best for your health and the health of those who will be around your vehicle and behind it. The fines for "evil" exhaust mods are pretty hefty. Better to spend a few bucks to keep it legal and safe and do it right than take a chance and throw thousands out the window for nothing.
     
  15. snoranger

    snoranger Well-Known Member

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    Last time I was in a car with someone who got that ticket for the "unnamed exhaust mod" it was 1996 and he got a fine of "up to $5000 per missing cat". He wound up paying $8000 (4 cats x $2000 fine for each... 91 mustang) and having to put cats on. They would consider it 2 missing on your truck. It could be a higher fine by now. Can you afford it?
     
  16. Carguy3J

    Carguy3J Well-Known Member

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    and 1996 was probably the last time anybody got such a ticket.......

    Actually, I'm not even sure you can get a ticket for it. The Clean Air Act is a federal law, administered by the EPA. It has nothing to do with police issuing "tickets". Sure, I guess if it also caused your exhaust to be too loud, there are tickets for that.
    The EPA is interested in "big fish", such as importers bringing in "grey market" parts and cars, as well as SHOPS that do unapproved mods on a commercial level. Unless you have personally pissed off someone very high up, they don't give a crap about going after individuals. It is not an efficient use of their resources. In any case, do you really think a cop is going to climb under my truck on the side of the road to look? I highly doubt it, as that would put them in an uncomfortable situation, from a safety stand-point, and is most likely against regulations.

    In any case, I'm smarter then you guys seem to give me credit for. IF I were to do this, I wouldn't be dumb enough to just put in a straight pipe. If anyone looked, they would see two not-so-shiny aftermarket cats, poorly re-welded, and muffler cemented,where the pipe had been "cut for access during repairs". Without unbolting it and looking inside, no one would see the aftermarket shells are simply wrapped around the outside of a pipe running through them.

    But no, of course I couldn't afford that kind of fine. Even if I could, I would never pay it. That's ridiculous. However, the chance of ever being caught, or being "hit" with those fines is slim to virtually none.

    In any case, that's not what this thread is about, and I don't want anyone getting their "panties in a bunch" and ruining the rest of the fun. So, forget I mentioned that part of it, I guess.
     
  17. snoranger

    snoranger Well-Known Member

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    IIRC, as he was walking up to the car, he dropped his doughnut, it hit his foot, and rolled under the car. When he went searching for it, he found that there were no cats, and wrote a summons.

    It was a long time ago... I may not recall all the details exactly as the occurred. :D
     
  18. mr cribb

    mr cribb US Army Retired Elite Explorer

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    Well I had the 90tm heads, I went 225,5xx k miles on them before they had a come apart.

    I looked at mine the wrong way all the time :D.
     
  19. snoranger

    snoranger Well-Known Member

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    My '90 4.0L made it to 210k. It got the oil changed every 10K miles, leaked a little antifreeze (ran hot every couple of months, then I filled it up.), saw the speed and rev limiter everyday, blew 3 transmissions, and still had original head gaskets!
     
  20. jd4242

    jd4242 Explorer Addict

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    Without a way to measure the cc of each cylinder or the flow of each port you can hurt the performance VERY easily. Its not a ""wing it"" type of deal trust me, I have spent THOUSANDS of dollars of the ohv doing research and finding what makes power and doesn't.current motor has close to 20k into it.......the early heads 90-93tm have 60cc and 95-98tm have 48cc..all head gaskets are the same design, there is a slight differences in thickness from different companies but not enough to bring you down a point.

    If it was me I would just clean them up and not remove much of anything. Then hone the cylinder walls and replace the pistons.pistons are cheap and sure better than spending DAYSSSSSS porting a head and ending up just hurting the motor.

    410-422 do not require a tune but always helps.422 requires dual springs and seat work.both require longer pushrods.both could benefit from premium gas also..

    Also unless you have A LOT of work done to the motor "test pipes"" will hurt the performance of the motor, better to run high flow cats..

    Just a fyi going to 10:1 and running 90+ gas makes the motor MUCH more efficient and increases power and mpg.in my case it was worth the added cost of gas to get better mpg, ended up using less gas than the cost of 90+......10:1&422 cam goes very nice together also
     
  21. jd4242

    jd4242 Explorer Addict

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    Pic of the two cc
    [​IMG]
     
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