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4jg1t "franken-engine"

Share and discuss mod ideas here that make your Isuzu safer, faster, more homely, more user friendly or just crazier! The best from here will be made into a full DIY write up for the FAQ and DIY mod section.

Re: 4jg1t "franken-engine"

Postby paulthepilot5 » Tue Jul 28, 2020 8:13 pm

handymanny01 wrote:cheers paul, good to know!,, i just got cheapish ali-express nozzles, for the purpose of testing,, will see if my fuel tech can make them work or not.... my current and bigger problem is keeping the head on it! lol another blown head gasket! curses! (even with ARP studs) im actually thinking of making a solid copper one, and fitting steel o rings into the head... then sealing all coolant and oil passages with viton o rings.. begining to wonder if the 2.8 head gasket with its smaller bores is less prone to failure? im pressing on with this 3.1 direct injection engine none the less! my other thought is maybe the toyota cam plate in my injection pump is too aggressive ,, i (MAY) also be running too much advance... which is prob adding to my excessive cylinder pressures..

Are you using genuine MLS type head gaskets? If not you will probably have failures. Could also got to the higher grade arp studs as well (ARP 2000) about 20% more clamp pressure. I would say it is most likely injection advance causing the issue though. I am just running stock pump timing, but also have reduced compression so peak cylinder pressure would be significantly less, water methanol is also pretty hard on head gaskets, as it will cause advance too. I was also thinking copper gasket is eventually the way to go for high boost build. If you o-ring the head make sure it is inline with the liner protrusion so it seals on that. If I build another engine I’m going to modify the top flange of the liners to taper more of a point and run a little more liner protrusion, this would provide a similar crush effect to seal the gasket and not have an o-ring wire
Isuzu Junior
Posts: 87
Joined: Thu Apr 05, 2018 8:56 pm
Age: 34
Country: Australia
City: Brisbane
Vehicle: 1995 Isuzu Rodeo 2.8d
Compound twin Turbo
12mm fuel Pump
+50 injectors
Water/meth injection
14s 1/4 Mile

Re: 4jg1t "franken-engine"

Postby handymanny01 » Sat Aug 01, 2020 1:13 pm

Hey Paul, yes was a quality steel shim gasket, permaseal brand , looked very well made,, But I guess the peak cylinder pressure I seem to be generating was just too much for it,, So going to make up a copper gasket, and yes, will have a careful look at the best place to position the steel oring relative to the cylinder liner protrusion, as well as backing off the advance, we might need to put the pump back on the test bench, and check how the advance is actually coming in,,, maybe there is too much down low, and not enough up top, Fingers crossed the head stays on this time! Lol
Isuzu Baby
Posts: 47
Joined: Tue Jul 12, 2016 9:39 pm
Age: 43
Country: NZ
City: Wellington
Vehicle: Isuzu MU 3.1 Direct injection 4JG1 conversion, Vf10 hybrid, ported wastegate, mild port head, custom 12mm pump, 3"dump and system, 3" inlet / pod filter, EGR delete, 2" body lift, 2" (ish) suspension lift, 33" on 15" steelies , recaro seats, nardi wheel,,, rear LSD , front "lokka"


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