Probably the easiest way to tell the two apart is to look at the way that the injectors are attached to the head. The 4BD1 injectors are held in with two bolts that pass through a bracket at the top of the injector whereas the injectors on a 4BD2 screw in. Also, the block has an identifier cast into the side below the turbo just above the the oil pan. However, this id could be misleading as the engines can be converted back and forth, using the same block but by switching the heads and pistons.

 

If the head is off it's even easier. 4BD1T have deep combustion bowls in the pistons, 4BD2T's don't.

 

Thanks for the responses. The head that is off is on the 1994 that I assume is the 4BD2T anyhow and is stamped as such on the valve cover. I will check the recommendations above tomorrow, maybe somebody switched the valve cover.

I guess anything is possible, but with 86k on the odometer it seems the engine would still be good and not need a swap, but then again, the transmission is bad... Any other help is welcomed!

 

The only way to tell from the outside (easily) is the injectors and the way they are attached to the head as Dougel said.

 

1t

2t

The noise baffle valve cover thingy is missing in the second picture FYI. But just take note of the injector lines style and bolts. Also fuel filter location. Usually 1t's fuel filters are in the front of the engine. 2t's are in the rear, near the throttle cable.

:beer:

 

Hey guys, I don't post often, longtime lurker, new to Isuzu's...

"Stumped on 1989 NPR How to tell difference between 4BD1T and 4BD2T?"

On my 4BD2TC I just got has 1" tall ID characters embossed on the block, just ahead of
the starter:

Mine shows "4BD2"

Forgive me if I don't understand the question but emphasis seemed to be on the cylinder
head identification, which of course is available as well...

George

 

Hey guys, I don't post often, longtime lurker, new to Isuzu's...

"Stumped on 1989 NPR How to tell difference between 4BD1T and 4BD2T?"

On my 4BD2TC I just got has 1" tall ID characters embossed on the block, just ahead of
the starter:
View attachment 18046

Mine shows "4BD2"

Forgive me if I don't understand the question but emphasis seemed to be on the cylinder
head identification, which of course is available as well...

George

Hello George,
asta (Andy) in post #2, did mention that, but added the cautionary note, that someone could have built up a 4BD1T (or converted a 4BD2T to 4BD1T) using the parts including engine block from a 4BD2T, and parts including head, injectors and pistons from a 4BD1T.

Although not common it has been known to have been done with 4BD2T's that have had problems with cracked heads, and you were probably not aware of that.

 

I wasn't John and thank you very much! I will research it, I know the temps are better
for more boost with DI, my 4BT was like that. Plus, that is another thing I will look for
is cracks. I might consider "swapping over" once I find some more info in the forum...

George

 

So Ive been looking at my two engines... The running one, I assume has had a cab change now. Everything points to 4BD2T. The block, the injectors, the engine cover, and it does in fact have a intercooler. Whats interesting, is my other truck, that has a builder motor I assumed was a 4BD2T and its a frankenstein. 4BD2T block, and what looks to be alot newer 4BD1T top end. The head is stamped 4BD1, and has the two bolts for each injector. Interesting....Anybody looking for parts or anything? I assume this isnt the right place to sell the parts, so I will post another listing.

Thanks for all your help!

 

Your "Frankenstein" engine may be the better one, assuming they also installed the 4BD1 pistons, the ones with a recess in the top.

 

Scratch that, I do not believe I have the capability to post for sale stuff yet!

 

Can you tell if these are 4BD1 Pistons from this photo?

 

View attachment 18110

Can you tell if these are 4BD1 Pistons from this photo?

Yes and they are.

 

As Dougal said.

Direct injection diesel engines like the 4BD1, have the combustion chamber in the crown of the piston - as per the photo.

Indirect injection diesel engines like the 4BD2, have flat top pistons, possibly with shallow valve relief pockets only, and a pre-combustion chamber in the cylinder head.

Edit: the fuel injector sprays into the combustion of both types. The injector nozzle for direct injection has multiple nozzle holes angled to cover as broad a distribution as practical, in the case of a 4BD1 into each of the 4 corners of the combustion chamber. The injector for indirect injection is usually a pintle type with the single nozzle on the axis of the injector.

Edit 2: Small direct injection engines, unlike large diesels used in locomotives and ships, need substantial swirl from the intake ports to mix the air with the fuel in the combustion chamber. An indirect injection engine doesn't require swirl as the violent turbulence through the small opening to/from the pre-combustion chamber ensures good mixing of air and fuel.

 

Thanks!