2.8 head on a 3.1 motor?

[varnz10]

Hey has anyone done this before? I havew a couple of good heads off a 4jb1t engine and i think that my 4jg2 has a cracked head... sooo.. I know it would fit, with larger valves would it work? I think the main issue would be injectors...

[geeves]

Big issue is they have a very different piston design. I have heard rumours of a version of the 4jb1 with indirect injection which is the opposite of what your trying but it was a lot more than just a head swap

[slightlydodgy]

Takes me back to playing with ford crossflows, minis and ford and holden straight sixes. No help to you though just cruising down memory lane

[varnz10]

Ok so what does the piston design have to do with the head? is it the valve clearances? I thought that so long as you have the correct head gasket, there should be enough clearance..... I have been more concerned about weither the injectors would supply enough fuel.

[geeves]

the 4jb1 is direct injection and most of the combustion chamber is in the piston top. It also has a swirl design which makes them very efficiant. The 4jg2 is indiect injection and has a injector chamber in the head and a much flatter piston.
It has come up before that the bolt pattern or the heads is the same which is a suprise but if so then it makes me wonder about the possibility of swirl style pistons and direct injection head on a 4jg2 which would result in the engine that should of been built

[MattMu]

As Geeves said...by putting the 2.8 head on the 3.1 you eliminate the combustion chamber totally and it will not run at all. You may even strike the injector with the piston!!

Cannot be done without swapping the pistons but if the bore is larger then the pistons wont fit.. cant be bothered checking the bore size but bet its smaller for the 2.8.

Matt.

[geeves]

3.1 95.4 x 107
2.8 93 x 102
bore and stroke
Custom pistons anyone??

[varnz10]

bugger!!! thanks for your help..... But makes me wonder what idiot at Isuzu didnt think about making the 3.1 they should have?

[MattMu]

The two engines are like comparing an old 253 to an old 308 v8. 253 is quicker revving crisp but not alot of torque while the 308 is slower revving in comparison but oodles more torque.

Same with the 2.8 and 3.1 (ive owned both in the same vehicle) the 2.8 was zippier to drive but put it under load and it struggled in comparison to the 3.1...it oozes torque and would walk up hills like they werent there, but was thirstier due to the loss off thermal efficiency by having the combustion chamber in the head. These are also alot quieter than the 2.8....direct injection always has more engine knock.

So I guess they have their place, quiet and torquey and they and do it well, witht he trade off being higher fuel consumption.

Matt.

So

[geeves]

You have to remember that just about every other 4wd diesel of this vintage was indirect injection. Isuzu probably had to make a quiet engine to sell. The trade off though is blown heads down the track

[shinz]

From what I have ever read, the indirect 3.1 was simply an attempt at a bit more refinement, the 2.8 was one of the first small direct injected diesels in series production & while a bit rattly was wonderfully frugal. I have often thought about rebuilding a 3.1 with a 4JG1 head & pistons. AFAIK, the blocks etc are identical, the bore & stroke certainly are & I suspect the crank is too. One day I intend to raid an Isuzu parts book & find out. In marine applications http://www.isuzumarine.co.jp/english/product/image.html#UM4JG1TCX they are rated at about 125Hp for medium duty which is at about 3200 rpm for up to four hours or 135 Hp for light duty which is for a lesser time, I think about 2 hours. An automotive engine generally does less high speed or continuous running so it may well be possible to equal these sorts of figures. I know that industrial/plant versions of the 4JG1 have inline pumps, but it shouldn't be too hard to set up a recalibrated version of the 2.8 pump for this. Vauxhalls Fronteras with the 2.8 in the UK had the larger VICC turbo from the 3.1, bigger injectors & an uprated pump & were good for 113 Hp. They also had a front mounted IC.
Steve

[geeves]

bore and stroke are different as above. The basic blocks apear to be the same with just the machineings differen for the larger bits. They are still 2 out of the 5 best ever small diesels excluding new common rails. Has anyone ever thought about building a common rail for these engines

[walruz]

OK trippin' down memory lane, had 253 with twin balanced pipes. Nice throaty burble unfortunately mostly all show, not alot of go

[geeves]

it was faster than the diesels of the day (just) (only diesels in those days were in trucks buses and trains)

[mulover]

With all the mods i've done to my 2.8, not including intercooler and at 16psi boost, according to a G-tec meter I'm getting about 110 - 115 hp, I'm guessing that would be at the wheels though. With the boost set at 11 i only got about 100 hp.

[Drift]

Ive just done a fuel test, UK gallons.

63 Litres gave 398 miles = 28.72 miles per gallon = 10.16 Kilometres per Litre.

http://www.geocities.com/mpgcalc/

This aint bad for 1995 2.8tdi (Frontera) with suspension mods.

The particulate filter and cold start flap has been removed from the exhaust and the EGR valves have been removed along with most of the pipe work also the pipe from turbo to EGR valves.
Ive also removed the cold start flap on the air inlet between the intercooler and inlet manifold.

This has noticeably increased the lower rev range and it pulls a lot better down there.

Im not sure which made the most difference as they where all done over a day, but it has transformed the drive.

113bhp stock.

It made that much of a difference I was considering upping the fuelling but Im happy as it is and I will not be fettling with the fuel pump no, thus saves a few miles in fuel lol.

[geeves]

thats about what we are seeing on 2.8 bigfhorns and mus esspecialy when you consider your 70mph speed limit against our 60mph

[moseswal2]

Hi

We should be able to do this and I'm determined to find a way.Could some one please please post some pictures of a 3.1 head mainly detailed picture of the combustion chamber.The 3rd pic I found on the net but I cant see anything.

The other picture is from a 2.5 which is the same as a 2.8 exept for the shape of the hole shape in the piston and stroke.In the 2.5/2.8 head the glow plugs and injectors are longer and more centered.

So I was thinking that if you put the 3.1 glow plugs and injectors in a 2.5/2.8 head but they are short and will not stick out the head.So why not machine a cylinder type hole in the head as per my drawing.

any thoughts guys.