4JG2 Bent Pushrod / Head Gasket Rebuild Advice

[Mudbomber]

Hello folks So I bought my first Isuzu a few days ago althought I'm usually a VW guy. It was a rebuild project for my wife and is a 96 wizard with a 4JG2 that is in really good shape except it apparently had a blown head gasket and cracked rad. So I've embarked on stripping it down and found that there are some more dubious problems at play here.

Here's the good: Cam belt and water pump done 30K ago. 4 new tires, body is in excellent shape, no rust, interior is tidy, ran rough but ran when I bought it, wife loves it.

Here's the bad: Rad is cracked but I got a second hand one today and apparently the head gasket is gone, little bubbles in the old rad. Last person maintained it well except put water in the cooling system so I need to flush all the brown rust and crap out.

Here's what I did and discovered. Degreased and cleaned the whole engine bay. Took off the head and the block and pistons look really good. The head looks decent too except for some small cracks between the valves but I've seen this before on VW diesels and it was no biggie. It has 4 bent push rods, seriously bent.

Here's what I wanted to know:
1- Bent pushrods mean the valves have hit the pistons, the pistons and valves look mint and when I filled the chambers up with water none leaked through so valves are likely good. I'm going to take off the cam belt cover and check the timing, it must be out right? I mean there is no other way the valves could have hit the pistons to bend the rods?
2- How do I check the lifters? Does it have them? Should I pull the cam out and inspect it to see if it's damaged? I doubt pushrods push straight on the cam. What is the chance that they are damaged?
3- I read you can't skim these heads, I know there are 3 different thickness head gaskets. I want to do it right and so would like to skim and pressure test the head. Should I? If I do should I use a thicker head gasket?
4- Here are my prices, head gasket 80$, head set 80$, shave 50$, pressure test 40$, push rods 50$ head bolts 50$. All up $400. Would It be cheaper to try and find a used 4JG2 long block? This engine has 230,000 km on it and only really had an exhaust leak at the header, turbo is nice and tight.

See pics, what do you guys reckon!?

[stardog]

I think I would be looking for a new head if it was me those cracks arnt looking good especially the 1 on the pre combustion chamber and the other 3 on the head as well.
The timing belt has slipped to do that damage to the push rods and the head.

[Mudbomber]

Hmm, yeah I agree I wasn't happy about the cracks. I'll re-align the timing belt, I guess it wasn't setup properly when it was last done 30K ago. Is it a matter of changing the rods or is my cam and lifters probably toast too? Strange I always have those cracks on my VW diesels too. They are not idea but I'm running 20psi on my 95 1.9l and have turned the pump right up and there are no worries. Hmm. Well one thing at a time I suppose. What do you reckon about the pushrods/lifters/cam? No rods and I'm away? Maybe I should just look for a new engine?

[geeves]

head replace. Thats where these go and it is a known problem. Push rods replace. Rockers and cam inspect but chances are they are ok Pistons inspect the tops for damage. They are robust
Chances are the cam belt broke and when it was replaced the tappets adjusted to allow for the bent rods. Rockers will break before the cam is damaged

[Mudbomber]

I see darn I'll get new rods from ebay as they're 50$ then. I'll pull the cam and lifters tonight and inspect then both, then reinstall if ok and set the timing correctly. I couldn't find a "how to" post to setting the timing belt on this site though. I reckon the rad burst, it overheated and as it got tight the belt skipped a few teeth maybe? As the rockers were way way way out of adjustment, like 10+mm. New heads seem to be worth the same as whole engines... Might have to sit on it then and wait and see what comes up at pick-a-parts. I may gamble the 110$ to shave the head and get it pressure tested. If it's a known problem maybe I'm throwing my money down the toilet though I'll take the cam out and lifters and post some more pics up tonight Thanks Geeves

[geeves]

head machinist wont touch that head. Chinese heads are about 1600 and as good as original. Reconditioner in Wellington says they are better. I used one on my wizard and it was fine but the radiator ended up with steel shavings in it. Im guessing they arnt as fussy cleaning after milling

[Mudbomber]

Ouch! Like ouch for the shavings and ouch for the $1600! My machinist said he'd shaved and pressure test it at my risk, IE it's a gamble. At the moment someone on trademe said $1250 for a whole 4GJ2. I know where there is a longblock for the next gen with the cam on the head, it's a DOHC. No injectors or diesel pump but I can get that whole engine for $200. Won't work with what I've got though. Hmm. I think I'll pull the cam and lifters tonight and gamble on the mill and pressure test

[geeves]

You take your chances on the internals of any second hand engine. You might get lucky but you might get through the warrentee period and no more. The basics of your engine look pretty good although I would check the piston hight on all cylinders just to confirm no bent crank.
I went through the same exercise with my Wizard. It went in for a leaking exhaust manifold and turbo whine on shut down. Engine was running fine apart from this. Even the turbo was serviceable but how long for and it had to come off for the manifold repair. 1100 for a turbo bought and paid for then told head has to come off to repair broken stud. I suggested it was a good idea to crack test while it is off. $160 for the pleasure of being told its not cracked yet but there are marks around the valves where they start to crack. He did say its not cracked yet and may last years. I thought if it had been left alone that might be true but now the stresses have changed I would be wasting money on a head gasket if I put the old head on. Total bill 4500 I did consider pushing it across the road from the garage to the local picapart but fixed it and ran it another 2 years before selling

[Mudbomber]

True man. I suppose with a second hand engine it's a gamble. My internals do look good. How do you suggest I check the piston height? Just turning it over and checking with a level or is there a tool? I think the valves hit the pistons and bent the rods when it got hot it got tight and the cam skipped a few teeth. Only 4 pushrods are bent so that's good. They are hollow and designed to be the weak link, at least in chevy 350's where I used to tinker. Man I miss Canada some times, 350's for a couple of hundred bucks. Someone quoted me $1500 for an engine, lol, not the whole truck lols. What do you reckon about second hand pushrods? They do have a bend tolerance that can be checked. Man I feel like I'm going through the same thing as you I dropped the head off at the engineers place this evening so I'll get my answer tomorrow. He'll let me know how much he shaves, then I'll check which gasket I have and get one that is thicker by how much he shaves. If yours lasted 2 years that is sweet man! Pulling the head to do a broken stud seems a bit crazy to me? I have one broken on this head, right at the front, and I'm going to drill and put an easy out in it. All the other studs came out with a pair or vice grips. $1100 for a turbo too ouch man! I remember living down in Wellywood and there wasn't many wreckers around I think. I moved up here to Aucks and I've got 2 zebra's and 3 pick a parts to visit but they rarely have diesel engines. There is a 2000 wizard with a 3.0l that was rolled and the engine is mostly complete except injectors and diesel pump. Maybe I should go pick it up for someone who needs it, longblock is only $200.

[Mudbomber]

Just did a trawl of the site with no luck, how do I figure out which thickness of headgasket I have? Is it the holes punched in it like on VW's or should I bust the micrometer out. I can't see any part numbers on it :S

[geeves]

there are notches in one side of it.
You can get the complete manual here
http://www.mediafire.com/?i36dwl1pkhb4g

[Mudbomber]

Greeves you're a legend. I'll gonna upload pics all as I go when I get my head back You reckon I should EGR delete while I'm at it? I know it'll take the EGTs up a pinch but I'm not gonna increase boost or fueling. It's for my wife but I though I'm there and it's easy and apparently they run just a little bit better

[Mudbomber]

Sad news, my head is gone... It pressure tested bad and is cracked. I'm on the hunt now. I know where there is a 4JX1 longblock that is mint, do you reckon I should pick it up for the $200 and see if someone wants to swap me for a 4JG2 head?

[geeves]

4jx1 is an engine no one likes. Its not a good canditate for a swap. Wreckers sell garunteed 4jx1s for 5k+ so not sure how mint the $200 one is
picapart often has bighorns that should yeld a good head or 4x4isuzu.com for a garunteed one

[Mudbomber]

Ah true man. It is in a wizard that has rolled and so the body it totally wrecked. The engine is probably mint. Recon I should get it? Cool man I'll peruse the pick a parts. Nah I don't want a 4JX1, I just thought maybe it would be something good to get and maybe chuck up on trademe to make some cash for my 4GJ2

[Dinger95]

I always wondered if the 4jx1 head would fit on the 4JG2 block ...

[geeves]

I think the 4jh1 does but not the 4jx1. Has lots of extra fuel and oil holes

[Mudbomber]

Hey would a 4JB1 work on a 4JG2? Following from the post above. Like with all my injectors and stuff? Still hunting for a head or whole engine

[geeves]

Yes but far from that easy. Have a search for posts from superturbocompound. Hes done some incredible things with isuzu 4j engines.
Apparently there is such a thing as a 4jg1 engine which would of been the true successor to the 4jb1. Essentially the 4jg1 was a 3.1 direct injection engine so its head would of been identical to the 4jb1. Its pistons were the same design as the 4jb1 but because of the different bore size you cant use the smaller piston. Trying to get 4jg1 pistons comes up blank but the 4jj1 has the same bore. Unfortunately the piston sits 1mm too high so you need to machine the top. I dont know the result
Superturbo compund was into drag racing isuzu 4j series engines. I think he managed 18 seconds for a quarter with a 4jb1 but dont know what vehicle it was in. He was running 25psi boost. Then he started playing with 4jj1s and magic results.

[Mudbomber]

Wow 25lbs boost! I just want a good ride for my wife as she's losing her company car when on maternity leave I'll have a trawl of the forums. Just thinking the head pic below looks pretty similar... Bit if the block needs machining I'll just wait for the proper head or a whole 4JG2
http://www.trademe.co.nz/Browse/Listing.aspx?id=1156345298