3.9L transplant comments

gbvona

gbvona

Member
I have recently declared victory for the 3.9 L transplant into my 1970 NADA 3500S. The procedure was necessary because when I received the car it had a '62 Oldsmobile engine. The Olds mill is lacking many of the mounting bosses for both engine mounts and accessories, and stability was dubious at best. The 3500 engine is simply unavailable in these environs, so I found a 1993 Range Rover 36D engine, absent intake bits.

After thorough cleaning and checking, the worn bits of the 3.9 were renewed (including bearings, rings, cam, lifters, rocker arm shaft) and put in place. (The new cam was a Crower ground for the performance Buick 215 @ 160 HP). The block is drilled for all of the 3500 mounting bosses (even for the NADA stuff--power steering and air) so very little improvisation was required. Some comments:

1. As many warned me (thanks again) this installation needs a 3500 timing cover, which I got from a dealer in England, used but in good shape. What is a little less obvious to the inexperienced (me) is that the rope front seal simply won't work without an oil thrower, which the 3.9L engine did not have. This required removing the cover and installing the lip-type seal (easy!). At the same time I installed a high-capacity oil pump kit. The original pump seemed inadequate, especially at low rpms (and despite a good crank and new bearings). No oil pressure problems now, although it drops some at idle. You also need to use the original Lucas distributor in order to retain the correct oil pump drive (or change over both the distributor and the pump driven gear).

2. I put the original Rover manifold back on, with a pair of HIF6 carbs that had come with the car. After some fiddling, works just fine (using BBV needles). Idles nicely at 650 rpm, mixture is good and has very nice power when you ask for it.

3. In order to accommodate the exhaust crossover pipe, I had to use the original oil pan, which has a lower capacity than what was on the 3.9L. I am a bit concerned about that, but so far so good.

4. The original flex plate for the torque converter fits just fine.

5. Although I had the radiator thoroughly cleaned, the engine runs a little warm. More than a few minutes at steady idle or continuous driving over 75 mph causes it to creep up towards the red, at least at current ambient temperatures (86 deg F). Are high-capacity radiators available?

Otherwise glad to be back on the road, and the car drives very nicely.

gbvona, in sunny Tennessee
 
Impressive work .
If you want to go down the electronic ignition route . I used a e-distributor out of a V8 Disco and swapped over the drive gear from my old P6b dizzy .
Starts first crank . No more battery fade, points and less regular tune ups.
Sunny Tennessee Eh .Bet you get a few puzzled looks in a P6.
Gerald
 
Hi Gbvona,

The engine will run hotter for the first few thousand miles, my 4.6 certainly did, and so does another local Rover with a new 4.6 litre engine. I expect it has to do with new rings and tighter clearances. After that, the coolant temperature will settle down.

Are you running the P6B rocker covers or did you fit the later design? The former will mean having drilled the 3.9 block to accept the 'T' piece for the engine breather filter, whilst the later covers have provision for breathers within.

I too run the P6B sump on the 4.6, and have had no cause for concern in over 126,000 Miles (203,000km), although in my case I do run an engine oil cooler.

Are you planning on replacing/modifying the original air canister, installing larger air filters and fitting new richer needles at around 2500 Miles?

Ron.
 
Thanks for your comments. I am running the rocker covers that came on the 36D engine. These required a little bit of creative crunching and welding to clear the HIF carbies. The original 3500 covers were long gone.

Tell me more about fitting richer needles at 2500 miles (BBV's are pretty rich)....

gbvona
 
gbvona wrote,...
Tell me more about fitting richer needles at 2500 miles (BBV's are pretty rich)....
Click to expand...

In the case of my Rover, for the first 2500 Miles, the engine was in a dull state of tune. Ignition timing was set to 3 degrees BTDC at 600rpm, needles were the orginal BBG (very similar to BBV) and the engine carried the orginal air canister and fiters. At 2500 Miles, the air canister and filters were replaced with ones that allowed substantially better breathing. At the same time, the timing was advanced to 12 degrees at 600 rpm and the needles were swapped for BBW items that are considerably richer than the BBG items. The needles were then polished and tested on a rolling road as in their original state, they were now too lean.

So, you will find that if you also replace the original air canister and filters with ones that allows better air flow, the needles will also need to be replaced so as to provide additional fuel. Now that may sound like a perfect way to increase fuel consumption, and on the face of it that does sound reasonable, but if your engine follows in the same footsteps as mine, then fuel consumption will actually decrease and performance will increase. Sounds like fantasy, but the proof of the pudding is in the eating, and I can be sure that if you go down a similar path, you won't be disappointed!

Ron.
 
Is very true Ron, additional performance does not necessarily mean additional consumption- only if you use the extra performance all the time.

There was an episode of top gear where they drove a Prius flat out around their track, followed by a BMW m3. The m3 achieved better consumption.
 
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