Thread: Variations in 4BD1 motors

Originally Posted by Dougal

Maybe there are three piston types.

Here I have two. The aftermarket turbo pistons from my last 4BD1T rebuild, these are identical to the factory pistons and have the steel inserts (alfin?).
The other piston is completely aluminium, it was from a a 6BD1 rebuild kit.

These two pistons look quite different, but are exactly the same height from pin to crown. The ring lands are just cut higher on the turbo piston and one land is steel.

There are also taller pistons available. I know this because I accidentally ordered a set once. For what engine I'm not sure, but it was about 4mm taller than the correct set but the same 102mm bore, same gudgeon pin etc.

Well, it is amazing what google can find...

This document, says 6BD1 pistons are 6.3mm taller/longer than 4BD1 pistons!!!
http://www.cnparts.net/UploadFile//pistons.pdf


Also, 3 different length cylinder liners with 102mm bore. ISUZU

It would be great if someone could cross reference the ISUZU PN's???

EDIT

THIS site, lists 11 different ISUZU pistons with 102mm bores!
http://www.jccpiston.com/manufacturer/16757/16757.html
According to them...
4BC2 = 98.1 mm (the length that LMR posted)
4BD1T = 98 mm
and 6BD1T/4BD1 = 104.2 mm

I am slightly confused...

Could the shorter piston skirts in 4BD1T engines be to assist the oil spray???

Originally Posted by isuzurover

Well, it is amazing what google can find...

This document, says 6BD1 pistons are 6.3mm taller/longer than 4BD1 pistons!!!
http://www.cnparts.net/UploadFile//pistons.pdf

But the compression height of those pistons listed is the same ~59mm as both of the specimens I have here (4BD1T and 6BD1).

Originally Posted by isuzurover

Also, 3 different length cylinder liners with 102mm bore. ISUZU

4BD1T liners (same as 6BD1 liners) are 204mm OA.
None of those liners match.

Originally Posted by isuzurover

THIS site, lists 11 different ISUZU pistons with 102mm bores!
ISUZU PISTON manufacturer -- JIEH CHUENG INDUSTRIAL CO.,LTD. - Asia, China, Taiwan ISUZU PISTON manufacturer & supplier
According to them...
4BC2 = 98.1 mm (the length that LMR posted)
4BD1T = 98 mm
and 6BD1T/4BD1 = 104.2 mm

I am slightly confused...

Could the shorter piston skirts in 4BD1T engines be to assist the oil spray???

Yes, my 6BD1 piston has a longer skirt than the 4BD1T pistons.

Yet another:
http://www.spi-autoparts.com/Piston%...ue%20(SPI).xls

Dougal, could the pistons with a taller compression height have been from a DA640 - 102mm bore, but a few mm more compression height???

EDIT: http://www.partstw.com/Isuzu/isuzu_da640-4rings.htm

I think I may have the answers!!!

This site http://www.partstw.com/index_r.htm

says there are 5 different 4BD1(T) pistons!!!

The early 4BD1 Pistons (long skirt), which most/all LR 110s should have:


The late 4BD1 pistons - available in BOTH Alfin and non-alfin forms:


And the T pistons - available in SHORT AND LONG SKIRT - with different bowl geometries - which for some strange reason are very slightly different to the NA alfin pistons:



Note that there are also the (indirect) 4BD2T pistons:

Originally Posted by isuzurover

Yet another:
http://www.spi-autoparts.com/Piston%...ue%20(SPI).xls

Dougal, could the pistons with a taller compression height have been from a DA640 - 102mm bore, but a few mm more compression height???

EDIT: Isuzu DA640 4Rings

Dunno, the parts company had them listed as an alternative for early/late. But it would require either a different conrod or block to use them.
I just checked their website before and that option is gone, maybe they finally worked it out.

Definitely not a DA640 as the combustion bowl was the same rounded square that the 4BD1s use.

Those piston descriptions make sense.
Early 4BD1 pistons with the long skirt (same as the 6BD1 piston I have here).
Late 4BD1 pistons dimensionally identical to the 4BD1T, maybe half a point more compression with the 0.1mm taller height (someone else can do the maths).
4BD1T pistons always the same.
4BD2T pistons with no combustion bowl (indirect injection engine).

The 4BD1 pistons seem to have the option of alfin or normal style. Why? No idea.

Originally Posted by Dougal

4BD1T pistons always the same.

Sorry Dougal - I edited after you posted - there were 2 different T pistons apparently...

Originally Posted by isuzurover

Sorry Dougal - I edited after you posted - there were 2 different T pistons apparently...

So you did.
Longer skirt option.
My engine has the short skirts. Does that make it the hotter version?

Originally Posted by Dougal

So you did.
Longer skirt option.
My engine has the short skirts. Does that make it the hotter version?

Nah, just cheap