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Does anyone have access to a full set of 4jh1 timing gears including the twin scissors gear, and the injection pump timing gear pully that bolts to the corosponding gear?
Like the ones pictured here

I am thinking of making this setup work on my 4jg1t setup. So I will need anything that will be related to bolting the gears to the case or block...spacers, bolts, all of it.

No replies Rapidrabbit! Are the 4jg2 gears not suited to the new engine combo?

Roderunner wrote:No replies Rapidrabbit! Are the 4jg2 gears not suited to the new engine combo?
I'm actually running a combination gear combo. 4ja1t cam gear, 4ja1t crank gear, 4ja1t idler gear A, 4jg1t gear B, 4ja1t pump gear. And they all mesh perfectly and the engine runs great. I am looking to use a quieter running set of gears. The 4jb1t gears that I originally ran were extremely loud. I have a 4ja1t gear B scissor gear but the aluminum spacer plug that goes behind the gear is too tall and machining it is not an option since returning to a standard gear would be out after machining. I am unable to source the correct aluminum plug since it is an out of USA part only. Any suggestions?

Have you thought about getting a new aluminium spacer machined up by a local machine shop?....
I haven't actually got any experience with the gear drive, but would assume that each engine would get a "matched set" of gears from the factory as there would probably be minor variations in the various gears dimensions/keyway locations after casting and machining. The belt drive is one option, and is fairly quiet and usually reliable if the belt/idler bearings are changed within the specified service interval, but if you have your heart set on the gear drive then maybe you could source the insulated cover that comes standard on the Aus spec. 4jb1T engine if yours doesn't actually have one fitted.

Roderunner wrote: The belt drive is one option, and is fairly quiet and usually reliable if the belt/idler bearings are changed within the specified service interval.
I converted over from belt drive and am not impressed with belt components. The gear drives seem to be the most reliable with the longest service intervals. The term (bullet proof) has been used in reference to the gear drive and direct injection of the 4jb1t motors and that is what I'm really trying to achieve in this setup.

Would 4JX1 timing gears work, there is a UK guy on ebay with them http://stores.ebay.com/Internetscrapyard

pretty sure 4jx1 runs double cam shafts 4jg1 and 4jg2 run single cam shaft.
Could be a problem if im right I am not a fan of 4jx1 engines but they do make good target practice for a 458 win mag or a 460 weatherby mag is even better.

I just remembered something that might be relevant to your noisy gear drive.....the distance between the centres of the crankshaft/camshaft/injection pump tunnels vary a small amount from engine to engine, I think that using gears off a different motor might result in incorrect mesh when they are mixed together, much like a diff crown and pinion that doesn't have the correct heel and toe- they howl a bit. I wonder if a diff centre specialist could use engineering blue to verify correct meshing?
Another possible cause of valvetrain noise could be caused by unusual engine harmonics which can be transferred from the crank to the valvetrain / drive. This sounds unlikely, but I wonder if the swap to pistons that don't weigh the same as the originals might have upset the engines balance enough to get a vibration going. I don't suppose you weighed the new pistons before they went in?

4jg1t and 4jg2t from what I can tell have the same crankshaft and rods.

rabidrabbit001 wrote:4jg1t and 4jg2t from what I can tell have the same crankshaft and rods.
I don't know how Isuzu balanced these engines in their manufacturing plant, maybe they weigh the pistons to get matched sets, or maybe they just drill some holes into the flywheel. That's what we're up against when modifying unusual brands/models. If this were a small block Chev or ford engine there would be 10 guys who could pass on this type of information, not to mention at least 10 books on how to hotrod them too.
BUT, where is the fun in doing what 500,000 other guys have already done! Unfortunately (or fortunately depending on how you look at it) fooling around with the isuzu diesel engine is fraught with apparently unsolvable problems which really try out ones mechanical aptitude (and attitude), I usually get beaten by the tough technical questions, not finding out the answers until the particular engine/vehicle is passed on to the next owner when I upgrade to something more powerful and reliable. (That's why I purchased the Isuzu)
I only offer the harmonics theory as a possible contributor to the valve gear noise, probably because I destroyed 3 sets of conrod bearings in my last diesel performance build because no-one (including myself) had a clue as to what was happening in the engine via crankshaft harmonics. While I'm ranting (I've been drinking lots of bourbon today), did you peeps know that a 4 cylinder inline engine has a bad vibration band at 3000 and 6000 revs...which is concentrated onto the no.3 bearing, well, now you do, so if you can avoid it don't run your hopped up engine at 3000 revs for an extended period of time (like at cruise speed), also don't shave the flywheel for the same reason- vibration is satan's spanner!
Maybe the gearnoise that you can hear is at the normal sound level, and the change from belt drive to gear drive has made the gear whine more noticable. I can't hear the gear drive noise when I listen to my 4jg2 at idle or at any revs for that matter, but my hearing is a bit dull these days, all I hear is some mild combustion knock at idle, and the fan when it is engaged. I did a short video of my engine running, and posted it on you tube so that you can compare it with yours, Maybe the insulated cover over the geardrive muffles the noise a bit ( that's what it is there for so I think that's a reasonable assumption). This video makes the engine sound louder than what it is when the hood is closed, at 100 km/h I can't hear the engine at all over the tyres and wind noise. The buffeting noise in the vid is the fan engaged, and it dis-engages toward the end of the vid. https://youtu.be/6Xg1pLmCDSY