G'day All,
Recently built a mild motor on an 02 TJ block to fit into my '99 and couldn't find a lot of information about what was different between them. Thought I would post this here in case someone else decides to do this. This should be applicable to any 01-06 block into a '99 - I'm not certain about 00 and 98 blocks so cannot vouch. I only found one online video that touched on this scenario and the guys who did the conversion were a bit clunky in how they did it by welding up a bubba bracket.
. The approach I outline below is fairly simple to do, took me about 4-5 hours but that included a bit of stuffing around.
I wanted to convert the 02 block so that it effectively left my '99 with a full 99 motor and accessories setup. I reused the A/C, distributor, power steering and water pump etc so anyone working on the Jeep in the future doesn't need to know what parts to order, just stick to 99. This approach also completely leaves the 02 block still usable as an 02 and all accessories for the 02 will still work on it.
Here is the short list of what you need to do:
1. Drill and tap an additional hole into the water pump jacket to allow a 99 style water pump to be used.
2. Remove the cam position sensor and replace it with a distributor
3. Drill and tap one of the coil mounting bosses
4. Grind away some of the back of the block where the timing cover bolts into and drill through holes for the A/C bracket and alternator bracket
5. Drill and Tap a couple of additional bosses
6. Grind the A/C bracket to suit (see below)
Tools Needed
3/8 x 16 UNC tap (intermediate tap is all you really need but a bottoming tap too would be good)
5/16 x 18 UNC tap
Drill and decent set of drill bits
Grinder with a cut off disc and a grinding disc or a carbide burr on a die grinder tool or similar
Something to clean up - cast iron makes a hell of a mess when you cut it!
STEP1 - Water Pump Housing
(No photo - sorry forgot) - you need to drill and tap a 5/16 hole at the "3 o'clock" position on the block. This is the only hole that moved between the 99 block and later block and the casting impression of that hole is still visible so its obvious where to drill it but just put your water pump on there to double check. Its an external hole so don't drill too deep or you will pop out the side - not a problem but best to avoid. This allows you to mount a standard 99 water pump that has the power steering bracket holes in the right spot and ensures the original 99 hose to the radiator doesn't foul.
STEP2 - Cam and distributor
Remove the cam position sensor that sits where the distributor normally goes and swap in your 99 distributor.
STEP3 - Coil mounting bosses
The 99 coil bolts to a pair of bosses just in front of the engine mount. On 99's these are both tapped for a smaller bolt, 1/4 UNC I *think* but on 01-06 only one of these is tapped and that's for a 3/8 UNC. I mounted the coil using one 3/8 bolt, centre punched and drilled/tapped the other boss to 3/8 also for consistency. You will need to clearance the holes on the coil to accept a 3/8 bolt. No, I don't know why the existing hole is off-center on the block, they are all like that so just measure to fit!
STEP4 - Clearance the back of the timing cover
OK pucker up time! On the 99 block the factory used a fly cutter to remove about 3mm of material to the right side of that blue line in the photo below. With a 1mm cutoff disc (no freedom units here, sorry guys) its pretty simple to replicate that cut by coming in from the side. If you cut too deep you can always pack it with a washer so the depth isnt super critical. Once you have removed that material drill through the 3 spots shown - use the bolt holes on the front of the timing cover as guides. I would suggest making these a bit larger than the bolt diameter to give you some wiggle room. The top hole supports the AC bracket, the bottom 2 holes support the alternator bracket.
Getting the orientation of these bolts right is a bit tricky - the AC bracket mounts in 4 places and it will take some trial and error to get each surface to the right depth. Make small cuts, test fit, adjust, rinse and repeat. Don't rush this part as having the brackets line up on all 4 mounts ensures that the belt will be aligned.
STEP 6 - Grind the bracket
So what we need to do now is to make clearance for the back (inside) of the AC bracket to clear the large tapped boss that you can see in the above photo (this boss is not used for a 99). There are two ways to do this: you can remove that boss with a grinder or you can remove part of the webbing of the bracket. I wound up doing a bit of both which turned out to be unnecessary. I thought the boss was still catching on the back of the bracket but it turned out to be something else. As before, just go slowly and test fit - you wont compromise the strength of the AC bracket doing this - that sucker is massively over engineered.
STEP7 - Grind, Drill & Tap Boss
Next step is to grind down the lower boss as shown in the photo below and drill & tap that to 3/8UNC. Yes, my grinding was pretty ugly but I did subsequently clean and paint the area - suggest you use a die grinder on this for a neater result. You need to remove a fair bit of material from that boss to allow the bracket to fit - comparing that boss on a 99 and 02 block shows about a 1/3 inch difference in height.
To be clear - the boss with the tap in it in the photo below is for the lower mounting point of the AC bracket. The ground down boss in the middle of the photo is unused in the 99 and if you grind the back of the bracket properly you dont need to butcher it like I have done!
STEP8 - Alternator Bracket
The alternator bracket mounts to the pair of untapped bosses that are shown in the above photo just to the left of the tap. These can be tapped to 3/8 but be cautious of depth here. The top boss in particular looks really quite deep but the camshaft sits just behind that boss so I would suggest drilling not more than a half-inch into that boss and if necessary shortening the bolt. I measured off my old 99 block and still stuffed this up so just err on the side of caution here.
You may need to tweak the thickness of the mounting points for the alternator bracket - easy enough to shave a bit of each one to get the bracket to properly align. The bolts through from the front of the timing cover that go into this bracket were a bit off-kilter on my engine so I had to trim and tweak a bit.
And that's it! Everything else is now a 1:1 fit and unless you really know what you are looking for its not obvious that this was anything but a 99 block. Hopefully this helps someone else out down the track...
Recently built a mild motor on an 02 TJ block to fit into my '99 and couldn't find a lot of information about what was different between them. Thought I would post this here in case someone else decides to do this. This should be applicable to any 01-06 block into a '99 - I'm not certain about 00 and 98 blocks so cannot vouch. I only found one online video that touched on this scenario and the guys who did the conversion were a bit clunky in how they did it by welding up a bubba bracket.
I wanted to convert the 02 block so that it effectively left my '99 with a full 99 motor and accessories setup. I reused the A/C, distributor, power steering and water pump etc so anyone working on the Jeep in the future doesn't need to know what parts to order, just stick to 99. This approach also completely leaves the 02 block still usable as an 02 and all accessories for the 02 will still work on it.
Here is the short list of what you need to do:
1. Drill and tap an additional hole into the water pump jacket to allow a 99 style water pump to be used.
2. Remove the cam position sensor and replace it with a distributor
3. Drill and tap one of the coil mounting bosses
4. Grind away some of the back of the block where the timing cover bolts into and drill through holes for the A/C bracket and alternator bracket
5. Drill and Tap a couple of additional bosses
6. Grind the A/C bracket to suit (see below)
Tools Needed
3/8 x 16 UNC tap (intermediate tap is all you really need but a bottoming tap too would be good)
5/16 x 18 UNC tap
Drill and decent set of drill bits
Grinder with a cut off disc and a grinding disc or a carbide burr on a die grinder tool or similar
Something to clean up - cast iron makes a hell of a mess when you cut it!
STEP1 - Water Pump Housing
(No photo - sorry forgot) - you need to drill and tap a 5/16 hole at the "3 o'clock" position on the block. This is the only hole that moved between the 99 block and later block and the casting impression of that hole is still visible so its obvious where to drill it but just put your water pump on there to double check. Its an external hole so don't drill too deep or you will pop out the side - not a problem but best to avoid. This allows you to mount a standard 99 water pump that has the power steering bracket holes in the right spot and ensures the original 99 hose to the radiator doesn't foul.
STEP2 - Cam and distributor
Remove the cam position sensor that sits where the distributor normally goes and swap in your 99 distributor.
STEP3 - Coil mounting bosses
The 99 coil bolts to a pair of bosses just in front of the engine mount. On 99's these are both tapped for a smaller bolt, 1/4 UNC I *think* but on 01-06 only one of these is tapped and that's for a 3/8 UNC. I mounted the coil using one 3/8 bolt, centre punched and drilled/tapped the other boss to 3/8 also for consistency. You will need to clearance the holes on the coil to accept a 3/8 bolt. No, I don't know why the existing hole is off-center on the block, they are all like that so just measure to fit!
STEP4 - Clearance the back of the timing cover
OK pucker up time! On the 99 block the factory used a fly cutter to remove about 3mm of material to the right side of that blue line in the photo below. With a 1mm cutoff disc (no freedom units here, sorry guys) its pretty simple to replicate that cut by coming in from the side. If you cut too deep you can always pack it with a washer so the depth isnt super critical. Once you have removed that material drill through the 3 spots shown - use the bolt holes on the front of the timing cover as guides. I would suggest making these a bit larger than the bolt diameter to give you some wiggle room. The top hole supports the AC bracket, the bottom 2 holes support the alternator bracket.
Getting the orientation of these bolts right is a bit tricky - the AC bracket mounts in 4 places and it will take some trial and error to get each surface to the right depth. Make small cuts, test fit, adjust, rinse and repeat. Don't rush this part as having the brackets line up on all 4 mounts ensures that the belt will be aligned.
STEP 6 - Grind the bracket
So what we need to do now is to make clearance for the back (inside) of the AC bracket to clear the large tapped boss that you can see in the above photo (this boss is not used for a 99). There are two ways to do this: you can remove that boss with a grinder or you can remove part of the webbing of the bracket. I wound up doing a bit of both which turned out to be unnecessary. I thought the boss was still catching on the back of the bracket but it turned out to be something else. As before, just go slowly and test fit - you wont compromise the strength of the AC bracket doing this - that sucker is massively over engineered.
STEP7 - Grind, Drill & Tap Boss
Next step is to grind down the lower boss as shown in the photo below and drill & tap that to 3/8UNC. Yes, my grinding was pretty ugly but I did subsequently clean and paint the area - suggest you use a die grinder on this for a neater result. You need to remove a fair bit of material from that boss to allow the bracket to fit - comparing that boss on a 99 and 02 block shows about a 1/3 inch difference in height.
To be clear - the boss with the tap in it in the photo below is for the lower mounting point of the AC bracket. The ground down boss in the middle of the photo is unused in the 99 and if you grind the back of the bracket properly you dont need to butcher it like I have done!
STEP8 - Alternator Bracket
The alternator bracket mounts to the pair of untapped bosses that are shown in the above photo just to the left of the tap. These can be tapped to 3/8 but be cautious of depth here. The top boss in particular looks really quite deep but the camshaft sits just behind that boss so I would suggest drilling not more than a half-inch into that boss and if necessary shortening the bolt. I measured off my old 99 block and still stuffed this up so just err on the side of caution here.
You may need to tweak the thickness of the mounting points for the alternator bracket - easy enough to shave a bit of each one to get the bracket to properly align. The bolts through from the front of the timing cover that go into this bracket were a bit off-kilter on my engine so I had to trim and tweak a bit.
And that's it! Everything else is now a 1:1 fit and unless you really know what you are looking for its not obvious that this was anything but a 99 block. Hopefully this helps someone else out down the track...
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