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Inspired by Robert’s Chevy/GM inline 6-292 conversion thread, I recently took on and just completed an engine conversion in my 1992 RHD Exmod Defender 90. All I can say is that the conversion is AWESOME! My 90 is now enjoyable to drive, can pull into traffic without fear of getting rear ended and doesn’t have the smell and knock of a diesel, which for me, was wicked desirable (I know diehards like the diesels). It is actually quite fast now and pulls great in all gears (hills I use to have to drop down to 2/3 gear are nothing in 4th). I still have some local reliability runs to make before I take any long trips, but I’m feeling optimistic.

I replaced my pitiful 12J (2.5NA) with a Chevy inline 6 (250/4.1L) from a 1968 Chevy Camaro. Although there are cheaper options, I chose to rebuild the engine locally, which did cost a bit more than some online options, but I wanted that local connection and ability to talk to the rebuilder face to face. This option did take a long time and did screw up my summer deadline, but it eventually came together and I’m hoping to enjoy at least 2 months of New England weather before putting her away for the winter.

Some details...

-I ended up getting a Scotty’s Adapter from Robert because his bell housing adapters weren’t ready yet and I was trying to get it on the road before summer, however I do plan to swap it out once his become available because I like his design better. They are the same depth, so it is an easy swap. Engine and transmission fit bell housing adapter with ease.

-I ended up having the motor mounts fabricated locally by a local hot rod shop, as I again was hoping to get it in the road for the summer and Robert’s RHD 250 mounts weren’t ready yet. Because of this I paid much more than I suspect his will cost, but it was the decision I made to try to get on the road faster. The mounts use the original chassis mount locations and original rubber pucks, so no changes needed and they just bolt in. The engine aligns with the mounts like it was meant to be there.

-My stock bonnet clears the top engine bits no problem.

-My engine had a 1 barrel Rochester Monojet carburetor, so I just rebuilt that and plan to use that for now. I would like to get the Holly Sniper EFI eventually, but need to figure out a new intake manifold too, so I’m going to wait. The 1brrl Monojet seems to work fine so far.

-Although I didn’t have to, I ended up switching my LT77 with a R380 stumpy from Ashcroft, but I still have the 1.4 LT230 and it seems fine even though it isn’t the 1.22.

-I decided to buy a new fuel tank and run a new fuel line rather than cleaning out and reusing the 27 year old tank. It was cheap enough, so I figured it was a good choice.

-I decided to buy and use the Revotec V8 electric fan kit and install it on my 2.5NA radiator, which was only a year old. The electric fans work great and eliminate the manual fan, which was around 3.5” away from radiator (with a 2” extension). The fans keep the engine running at 180 degrees no problem. the top radiator hose is from a BMW 318i. The fans weren’t designed for this radiator, but fit great and use the stock mounting pins and lower brackets.

- I have no crowding in any areas the engine at all, so the alternator and starter both have plenty of room. I currently have manual steering, which I don’t mind at all, so I don’t have a need for a power steering pump bracket. That said I will likely get a bracket from Robert in case I ever add it back (had PAS on it originally, but it never worked, so got a manual box to simplify).

-I purchased an inexpensive starter and alternator from DB Electrical for under $120 for both.

-I added an Electrical VDO oil pressure gauge and sender along with an Electrical VDO water temp gauge with sender. Both seem to work great...runs at or below 180. I did have to get a small 1/8” npt extension (1.5” from Lowe’s) to extend the oil pressure sender due to the thickness of the side covers and the block shape.

-I purchased nice cast valve and side covers from 12Bolt.com. These are thick, but very nice. The fins on the side cover had to be dremeled a bit for the distributor cap to fit.

-I am currently using my original exhaust with a hodgepodge downpipe, but plan to either get a new downpipe made this week or an entirely new exhaust at a local muffler shop. Current exhaust is fine if I get a new downpipe, but I would like to add a little rumble to it.

-The install can definitely be done in a weekend with a kit. Mine took longer since I pieced it together myself, but the install and removal is easy and with a kit would take out the guess work. I didn’t have any experience taking an engine out before this year and now I can remove and replace it within 1 day no problem.

-I used a throttle cable from a LHD 300tdi, which is pretty cheap and made my own bracket that mounts off the exhaust manifold.

Here are some pics...









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I took it out again today for a couple of additional reliability runs aground town and it went well. Pulls nicely and has plenty of power...very enjoyable.

I have not had a chance to get above 50 mph yet due to only being on windy backroads and I’m trying to take it easy for the 1st week or so, but I’m sure it will cruise fine at 65-75mph all day long if I wanted to. I don’t have a RPM gauge, so I won’t be able to report back with an actual RPM at highway speeds, but I’ll likely give the highway a try this week and still see how it goes.

Here are a few more pics of my 250 conversion from today...






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Quick update on my 250 conversion...I’ve put around 180km on my 92’ 90 over the past week since putting the engine in and it continues to impress me. Smooth, strong, and no smell.

I had a chance to jump on the highway between exits and it got up to 70 mph very fast. I was able to pull away from the guy behind me on the on-ramp and keep up with traffic with no problem...could have cruised at 70 mph comfortably, although I do have the 1.4 in the LT230, so I’m assuming it would have likely cruised a bit better at those speeds If I had the 1.22. My driving is mostly local and frankly I don’t feel safe over 70mph in the 90, so I’m fine with the 1.4 in my LT230.

I was also able to conquer a long, fairly steep hill today in 4th that would have normally required me to drop down to 2nd gear with my old 12j, so that was great.

I replaced the temporary exhaust (it was my original 2.5na exhaust with a hodgepodge downpipe) with a new stainless exhaust (manifold all the way back) from a local shop today and now it has a nice throaty sound.

I do seem to have a slight oil leak despite a rebuilt Chevy engine, which I think is just the valve cover gasket leaking. I retightened it, but didn’t seem to cure it, so perhaps a new gasket will do the trick ($10 gasket available locally, which is nice). Guess I’ll never get rid of all the leaks...




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Here is a video I had my son take of my 90 with the 250/4.1L inline 6 conversion (R380 stumpy and 1.4 transfer case)...from 0-100 Km/h. I couldn’t keep accelerating in the video since I was in town, but it cruises nice in 5th and will still pull nicely even if your speed dips. As noted in prior posts, I can now accelerate quickly onto the highway and into intersections as well as keep up with normal traffic.

As you can see, I’m not getting on it too hard at all in this video and it gets up and goes nicely...capable of much more for sure.

As you can hear...my transfer case does have a whine, which is quite loud at higher speeds. It is definitely coming from my LT230 transfer case and I believe this is the input gear bearing, so I’ll be sorting that out this winter. I think I’m actually going to get a rebuilt Ashcroft 1.2 LT230 to replace it since it has the 1.4 and has a few leaks (I want to improve drivability and reliability so that next summer is headache free as much as possible).

https://youtu.be/pGufq_vk_8g

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Here are some photos of Robert’s bellhousing adapter installed in my Chevy 250 conversion if anyone is interested. I did the conversion last year and love it, but was using an old Scotty’s bellhousing Adapter without a proper dust shield and wanted to switch it with Robert’s version that has holes to mount a proper dust shield. Everything fit perfectly and I really like the ability to bolt on the dust shield, however I did have some interference with the flanged head of the smaller starter bolt hitting on the head of the top dust shield bolt, which preventing it from tightening down...no big deal though, grinding the flange head of the bolt and/or picking a different style bolt easily solves the problem...I actually just left the top dust shield bolt out for now, as it still has 6 others and isn’t going anywhere.
 

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I took my 90 out for a quick blast around the neighborhood yesterday for the 1st time this year and it was as good as I remembered from last fall. The 250 started right up and ran perfectly...sounds awesome. Eager to get out there more, but I am going to take it easy for a few more test runs to make sure everything is good to go since I rebuilt both axles (upgraded rear to discs) and swapped out the transfer case over the winter. I’m psyched to get a chance to see the difference the new transfer case makes (1.4 to a 1.2) and how it handles after installing front and rear anti-sway bars.

Now if I just had somewhere to go...
 

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Thanks for the info. Mine is RHD as well so I've been scratching my head on the extra length needed and routing. RN has a LHD D1 200tdi cable in the clearance section for cheap that I've been considering, just not sure if it's long enough.
RN sells the 300tdi cable I used for $25.

 

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Robert’s conversion is great and truly made my Defender enjoyable.

My 2 cents on the transfer case ratio...I ended up swapping my 1.4 TC for a 1.2 TC after about 500 miles after the conversion last fall due to a super loud TC whine and a frustrating TC leak, but both ratios performed very well with the 250 in my 90. The 1.2 seems to be the better choice, but I personally didn’t have any issues at all with the gearing and wouldn’t discourage anyone who wants to do the conversion and doesn’t want to replace their existing 1.4 TC. I would not have replaced mine if it didn’t have the whine and endless leaks...that said, replacing it was a win win with the exception of my wallet (1.2 ratio, no whine, no leaks, larger sump, sleeved casing, heavy duty cross pin).
 

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I know of a running Chevy 250 in southern NH (Londonderry, NH) if anyone is looking for one in the area. It is from a 1970 C10 panel truck and is believed to have around 80k miles on it, but true mileage is unknown. Seller is putting in a Vortec, so he no longer needs it. It isn’t pretty, but runs. He is looking for $300 (edited as I was mistaken at $400). Message me if interested.
 
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