Calgary Jeep Association
4x4 Related Groups => Tech Talk => Topic started by: diamondjoe on November 12, 2007, 03:38:06 PM
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Hi All,
I'd like to pick your brains..
I have a 1990 YJ with the 4.2L I6. I'm looking into an igniiton upgrade, and I can't seem to find a definitive comparison of the TFI upgrade vs. an HEI upgrade. Can you offer any thoughts? tips? pointers?
I'm a fairly lazy dude, so I'd rather buy a full-kit than do some junkyard crawling. I can only find a TFI kit on buildyour4x4.com (http://store.buildyour4x4.com/product_info.php?cPath=57_122&products_id=403&osCsid=0893cddef2d65f64bb870cc9fd02588a); while there are several HEI kits available. For example (http://www.crtperformance.com/html/jeep_amc_hei_s.html).
I'm also considering combining this upgrade with a MotorCraft 2100 Carb replacement. From what I can find on the internet, I think this will match my budget to the best performance improvements.
I appreciate the feedback.
Thanks,
Joe
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How about this ,
Get yourself a distributor cap , spacer and rotor for a 1982 Ford F150 4.9l inline six , you will need the wires too. A stock coil or an Accel high output coil will work too.
What this does is spreads the contacts within the cap out to a wider circle , reducing the possibility of cross fire.
This is what I did on my 88 ( for a while ) before converting to an MPI high output power train.
I spent a weekend doing the following........
Removing all of the pulse air crap and associated BS , vacuum operated "engine management" controls , the microprocessor , the carter feedback carb , and so on. Most of the time was spent un-doing the wiring harness , removing the wires that were part of the feedback / pulse air operating circuits and be-bundling it all so that the untrained eye would assume it's stock , nice and tidy.
Some splicing ( soldering & heatshrink ! ) will be necessary , it's not easy . Plenty of thought and planning went into what wires were needed , what was not and how to arrive at a simplified engine harness cleanly and professionally , the goal being reliability. The Ignition module ( below the washer bottle on the left inner fender ) , can be wired directly to the distributor , I built a sub harness for this using waterproof deutsh connectors. that took care of the ignition system. The charging system can remain as it is , I just cleaned mine up and re-bundled it. The starting system needs little work , going from memory , I had to make a proper ground for the starter relay , clean up some additional wires , sort out some crappy wires for the backup lighting and there were a few splices needed to finish up.
The Vacuum circuits become far more simple , I retained the purge canister , AGR valve , the CTO , the TAC / VAC for cold / warm up , switched the vacuum source to the distributor to a "ported signal " from above the throttle plate .The stock / microprocessor controlled system uses manifold vacuum to control timing , combined with signals from several sensors , including an oil pressure switch ?? , an O2 sensor , a manifold heater , the pulse air solenoids etc. , etc , far to complex ! compared to later vehicles. Hey , thats how they did it in the 80's ! :roll: . Some knowledge of automotive tuning is needed to pull this off sensibly. The timing will have to be adjusted , using a timing light and a Vacuum guage ( old school style ) , 10 degree's of base timing is a good starting point. Use all new vacuum hose ! , you may have to buy a couple of tee's . I went with an Accel coil ( I still have it & for sale ) , Oh , I should mention , the starter relay limits voltage to the coil by way of internal connections and some resistor wire in the circuits , it gets a full 12 volts while cranking and 6 volts when running , this is how these Jeeps are wired from the factory , take that into consideration when re-configuring the wiring.
I used a reman CJ carb (1981) , no stepper motor on that one and connected the electric choke .
Before this my Jeep would stall , was hard to start , would stumble and hesitate , the detonation was out of contol , fifth gear was useless and the engine would barely rev beyond 3000 :cry: . After , it would idle cleanly , start easily , had more power and would rev higher . 8)
I have not used the Motorcraft 2100 carb but hear is far better than any of the Carter carbs AMC / Jeep used.
The HEI conversion is also said to be a vast improvement too.
Some additional reading
How 80's stuff works .....
http://home.sprynet.com/~dale02/list.htm
A simple bypass ......
http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/
What ever way you choose to go , think it through , be methodical in how it's done and good luck.
Ultimately , all of these old Jeeps are better off with a proper conversion to MPI , it's the best way to prevent stalling on steep or off camber terrain.
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I got a new rebuilt motorcraft 2100 if your interested
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I did the junk yard crawl the other day and stripped a 90 blazer with 4.3ltr TBI.
-Computer, complete harness, dist and TBI and all sensors for $70.00.
All I need now is the carb to TBI adapter plate (will build) and a 14 - 17 psi fuel pump. This will be married on to my 90 YJ with 4.2l.
"can't wait as fuel injection for under 300 dollars"
Anyone got a 14-17psi fuel pump for sale?
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gearhead Thanks for the details! From what you've described, I think that might be just a bit beyond my current skills. I know it's definitely beyond my shade-tree garage. Especially as winter rears it's head. Going to such an extreme might be reserved for some time in the U-Wrench; or at least after I move to a place with a garage.
The MPI is definitely out of my price range; no matter how I try to justify it. I'm thinking carb/ignition upgrades to provide the most "bang for the buck". While I'm in there, I plan on doing the Nutter Bypass (http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/) which you linked me to.
That how stuff works link (http://home.sprynet.com/~dale02/list.htm) is awesome
caltrex How much do you want for the MC2100?
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someone bought it last night
cheers
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someone bought it last night
Just my luck.
Oh well, they seem to come up regularly on eBay.