So based on that your way on the safe side. Some of those drag engines run tight rings.
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So how did you determine what your ring gap should be? Did you use a formula
This is from the Isuzu 4bg1t manual:
Piston Ring and Piston Ring Groove Clearance mm (in)
1st Compression 0.35–0.50 (0.014–0.020)
2nd Compression 0.60–0.75 (0.0236–0.0295)
3rd Compression 0.60–0.75 (0.0236–0.0295)
Oil Ring 0.30–0.50 (0.014–0.020)
I put them in and went "yep, they're on the loose side". The 4BD1T manual says 10-18 thou for the top ring and 8-16 thou for the lower two.
I've got the same figures here. Plus a "limit" figure of 1.5mm (huge). I've heard rules of thumb of 3 thou per inch of bore plus 3 thou. But I prefer to trust Isuzu figures over rules of thumb. Great to have the Mahle reference too.
Interesting that they are so large. I would be really interested to compare 4BG1T pistons to 4BE1 pistons (same 105mm bore). There were truck applications of the 4BG1T and 6BG1T and also marine applications. I don't know if automotive pistons are different to marine and industrial (excavator) but it would be interesting to find out.
Did you get a look at your bores yet? If it is ring-end-cap then it should be obvious by the damage and scuffing. But even with broken rings on one cylinder I'm not getting oil soaked glow-plugs. So I'm wondering about holed pistons!
Here's the chassis number for a 1989 Isuzu NPR with the 4BG1 engine (non turbo): NPR61P-7102045 I found one for sale and ran the plate.
4BE1 Alfin piston: Best Portable Marine Generator for sales
Would have to check the little end pin to crown height (compression height). It may be much taller for the 4BG1. 56.4mm for that 4BE1.
Compression height 55.2 for this 4BG1 piston: [Hot Item] Isuzu 4bg1 Piston 105mm OEM 1-12111-3660 for Hitachi Excavcator Ex100-5
I believe the 4BE1, 4BG1 etc all use the same head.
A very hot fire could have weakened the pistons. But it would have weakened them all.
Regarding the marine engines, I think you're seeing them phased out of the US market due to environmental regs. They certainly still make them. I know a guy who bought a new Hitachi excavator last year with the 6BG1T in it. His last one of the same model had the 4H in it.
Isuzu marine link is broken (doesn't appear intentional), but industrial is still showing them.
ISUZU INDUSTRIAL DIESEL ENGINE
it seems to me that the 4bg1t piston recess is more ideal because it is round, I would think having a square recess would be less ideal, thoughts?
I'm going to stick with the 4bg1t pistons regardless, but I find the topic interesting.
I believe you are correct for the US and canada market and marine engines, they are a tier 2 motor as far as emissions go, and new standard is tier 3. The marine dealers in the US and Canada cannot sell the 4bg1t, but the industrial dealers will still sell brand new long blocks, if only they sold the short blocks too...
My motor has a long and terrible history with air-cleaners that leak dust, valve guides that got loose and fed debris into the oil pump and even using the wrong rings which chewed out a set of liners in 27,000km.
Currently has about 10 years and a bit over 50,000km on a set of cheap ungraded chrome liners on aftermarket pistons with genuine rings. The rings are broken on at least one cylinder from oil ingestion from a terrible oil/air seperator which sucked about 15 litres of oil out of the sump and fed it into my intake. That episode resulted in a head-gasket blown on all cylinders. I put a new headgasket in and will deal with the liners and pistons when I have more time.
Still driving great with good power/torque and excellent fuel economy. But it burns a bit of oil.
couldn't find your clay doll?
its amazing how much things can be in bad shape, and still keep going!!
Good to find the problem is not catastrophic, but still bad.
If you need a good injector shop, let me know. I have been using an old guy in Santa Ana, CA who does a great job on pumps and injectors. He is very reasonable and fast. I have referred several people to him, and all seem happy with his work.
Let me know.
Here's the chassis number for a 1989 Isuzu NPR with the 4BG1 engine (non turbo): NPR61P-7102045 I found one for sale and ran the plate.
4BE1 Alfin piston: Best Portable Marine Generator for sales
Would have to check the little end pin to crown height (compression height). It may be much taller for the 4BG1. 56.4mm for that 4BE1.
Compression height 55.2 for this 4BG1 piston: [Hot Item] Isuzu 4bg1 Piston 105mm OEM 1-12111-3660 for Hitachi Excavcator Ex100-5
I believe the 4BE1, 4BG1 etc all use the same head.
A very hot fire could have weakened the pistons. But it would have weakened them all.
Regarding the marine engines, I think you're seeing them phased out of the US market due to environmental regs. They certainly still make them. I know a guy who bought a new Hitachi excavator last year with the 6BG1T in it. His last one of the same model had the 4H in it.
Isuzu marine link is broken (doesn't appear intentional), but industrial is still showing them.
ISUZU INDUSTRIAL DIESEL ENGINE