Thread: Variations in 4BD1 motors

Originally Posted by Bush65

Well! All I can say is I'm flabbergasted - that Land Rover determined/justified different pistons and heads for the 4BD1 and more so that they changed the piston again for the few 4BD1-T that they would have anticipated.

You made a point that both had square combustion bowls. Do you mean both turbo and non-turbo Land Rover pistons, or both Land Rover and Isuzu.

It's not surprising that Isuzu's have the square-ish combustion bowl, as AFAIK this shape bowl was an Isuzu development.

I must say I am quite surprised too. Any more info LMR?

I think it is possibly more likely that Land Rover used a stationary-spec engine rather than the NPR-spec...???

Dave_S on here is the only person I know who has ever needed to rebuild a LR 4BD1... Will have to ask him...

Originally Posted by Bush65

Well! All I can say is I'm flabbergasted - that Land Rover determined/justified different pistons and heads for the 4BD1 and more so that they changed the piston again for the few 4BD1-T that they would have anticipated.

You made a point that both had square combustion bowls. Do you mean both turbo and non-turbo Land Rover pistons, or both Land Rover and Isuzu.

It's not surprising that Isuzu's have the square-ish combustion bowl, as AFAIK this shape bowl was an Isuzu development.

ALL pistons are square bowl, turbo, non turbo, Isuzu and LR.

I dont think it would be LR's decision on the final outcome of the engine specs. As I said, the original Isuzu spec is truck and due to the rev range and general usage, this isnt really suited to 4WD on road use. The same basic piston designs wouldnt really need to be changed, but due to a more free and higher revving need for 4WD, a shorter and lighter piston and a revised injector and pump arrangement would be the most viable option.

Originally Posted by LOVEMYRANGIE

What you have is a NPR/NPS truck spec piston and is not suitable for LR use.

I'm afraid not.
You see my 4BD1T engine is from a wrecked japanese truck (Yes the NPR), it has pistons different to the one I mentioned above.
The original landrover Isuzus do appear externally to be be industrial spec engines, but this in no way means they were a special design for landrover.

Can you please let us know the source of your information, because it disagrees on some scale with all that is already known.

Ok well it appears that I have opened a can of worms with reference to the diferences in the motors. But irregardless of what has been said those who have truck motors in their rig need not worry about performance or longevity. This is the second truck motor that I have had in mine. The first one I bought second hand with 200k on it and it lasted another 500k without any problems and performed extremely well even with an aftermarket turbo assembly. It eventually got low in compression but after these K's I think it is acceptable. The new motor is the later type and performs well so I cant think why it wouldnt last as long if not longer than the original as I am pretty fastidious about servicing etc. I change oil/filters every 5K. Thanks for all your input, and happy motoring.

Originally Posted by isuzurover

I must say I am quite surprised too. Any more info LMR?

I think it is possibly more likely that Land Rover used a stationary-spec engine rather than the NPR-spec...???

Dave_S on here is the only person I know who has ever needed to rebuild a LR 4BD1... Will have to ask him...

I'm afraid I can't help. That was at least 5 years ago and I just ordered a complete rebuild kit from Kyatts. I should have taken a lot more interest but that was before you could easily access all this info and people weren't swapping notes like today.

Originally Posted by Dave_S

I'm afraid I can't help. That was at least 5 years ago and I just ordered a complete rebuild kit from Kyatts. I should have taken a lot more interest but that was before you could easily access all this info and people weren't swapping notes like today.

Well that alone helps Dave. Kyatts (Brisbane) only stock TRUCK parts. No LR parts, No stationary engine parts.
Don Kyatt Spare Parts (Qld) Pty Ltd: citysearch

So you would have bought a full rebuild kit for an NPR truck from Kyatts (which I assume included pistons?), and it was fitted to a LR 4BD1 with no problems.

Originally Posted by isuzurover

Well that alone helps Dave. Kyatts (Brisbane) only stock TRUCK parts. No LR parts, No stationary engine parts.
Don Kyatt Spare Parts (Qld) Pty Ltd: citysearch

So you would have bought a full rebuild kit for an NPR truck from Kyatts (which I assume included pistons?), and it was fitted to a LR 4BD1 with no problems.

I wouldn't say no problems. The guys who built the engine were pretty incompetent and the head gasket blew within 30,000 kms. It never seemed to have enough power either. The timing wasn't set up properly so that had a lot to do with it. So I'd say the parts were fine, but the dipsticks who put them together weren't

If the pistons were a different hieght, does this mean the compression ratio was different?