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PostPosted: 24 Jun 2011, 09:09 
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Not only do I always foolishly end up with orphan cars for which parts and even info are NLA, but I'm always modifying and trying to improve orphan engines that nobody modifies, let alone races. My modified orphan is an '87 Dodge Colt Vista (Mitsu Nimbus in Oz) with a rebuilt-by-me 2.0L SOHC non-turbo G63B.

Besides taking up less space in the motor-well than a 4-valve and/or turbo motor, my little 2-valve four should get decent torque in the lower rev-range I want to use, so I'm happy with a lower-tech engine than most of you would want. I'm trying to improve the cylinder-filling and residual-exhaust filling with a homemade 4-2-1 tube exhaust header. I've cleaned up the ports (the first thing an old 2-stroke racer does to any vehicle!), and got the cam reground with a hair more lift and duration. This rig came with two, count 'em, two catalytic converters; I got rid of the first, and am keeping the main cat for now, having checked that it's in good shape. Oh, the trouble-prone dual-EGR system is gone.

The factory computer-controlled Hitachi carb was unrebuildable, and I replaced it by adapting a Weber 32/36 DGV (Formula Ford carb) that's simpler and better. Since the simple computer was left with nothing to do, I tore it out one day, along with lots of associated wires and hoses, the happiest afternoon I've ever spent working on a car!! (computer, "Dave, what are you doing?"; me, "Don't worry, Hal."; computer, "Dave, will I dream?"; me, maniacally, "Dream? HAH HAH HAH HAH!!!!").

There's actually a question coming, but the guru that can answer it might want background. And others might enjoy reading about this goofy project.

The distributor in the carbureted version of this engine is a standard non-computerized unit with mechanical and vacuum advance. My vacuum advancer leaked, and is NLA. And I didn't want it anyway; with all the modifications I've made, the factory advance curves no longer are appropriate, and I'll have to come up with new optimal curves on my own. For a new vacuum advancer, I bought a Mr. Gasket adjustable advancer for a Chevy HEI dizzy. I knocked the stock advancer unit apart, saving the section that plugs into the dizzy. To that I brazed some plates to mount the Mr. Gasket advancer. The assembled combination looks like no dizzy you ever saw . . . the new advancer sticks out a mile, hilarious! But, installed in the sideways-mounted engine, the protruding advancer hangs vertically-down in an unused hole, out of the way, so it works out well.

Now I have to tune and time the critter. Stock timing specs for the original smogger engine are as follows:

Initial timing: 8 degrees BTDC at 700rpm

Mechanical advance: 0 degrees at 1200rpm
12 degrees at 2800rpm
max. 20 degrees at 6000rpm (!!)

Vacuum advance: max 28 degrees at 9 1/2" Hg
0 degrees at 2 1/2" Hg

(The original set-up used a ported-vacuum source for the vacuum advancer, which slightly helps ppm of unburned HC, and is undesirable in all other respects; I'll use manifold vacuum.)

And HERE is where I could use some educated input!! While I'll have to finalize my timing with road testing, I'd like to get closer to what the engine now needs than the above specs. l should say that I do not have access to a distributor machine that will check anything newer than a breaker-points dizzy, but I DO have a dial-back timing light, a vacuum guage, a tachometer, and a stopwatch. My notion is that the factory max. total advance at idle of 36 degrees (8 initial plus 28 vacuum) is going to be a few degrees high. I have fabricated an adjustable travel-limiter on that Mr. Gasket advancer to take care of that. And having thus dealt with the maximum vacuum advance, the adjustable preload spring will let me move the vacuum advance curve around with an allen wrench.

The mechanical/centrifugal advance is more trouble, and I think the factory spec is far from what I want, with the curve not coming all-in until 6000rpm. Usually modified engines have the mechanical advance all-in at somewhere around half of that. The 20 degree maximum might be pretty close, and can be moved one way or other with some effort. But what I need right now are some mech. advance SPRINGS, and you don't find an assortment of Mitsubishi (actually a Nippondenso dizzy) advance springs at your local auto parts store, speed shop, or even Mitsu dealer (Dodge dealers never heard of this car!). Like most mechanical dizzies, this one has one light and one heavy advance spring; since I want the curve to come in quicker, my first step is to find a second light spring to replace the heavy one.

Anybody still with me?? :) What I'd like from you is: 1) timing specs to shoot for based on your actual vast experience in tuning upgraded non-turbo G62B's :lol: ; 2) a factory timing curve for a higher-performance N.A. G63B than the Vista, preferably an Australia model without all the emissions stuff that comes on 'merkin cars; 3) any light springs you don't need that fit these Denso dizzies!! :D

Q: Did anybody (a group) ever race the non-turbo G63B's anywhere (Aussies could have done something this weird; haven't I seen a couple of them on this site?)? And if so, is there an experienced tuner/engine-man/guru who knows it all?

I thank you for your kind attention and patience!!

--Smitty


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PostPosted: 26 Jun 2011, 10:16 
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Joined: 23 May 2007, 21:21
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Awesome post.
My return isn't going to help you but have you thought about upgrading the engine? You sound like your clued up so you know that even after spending hours and hours and hours re-graphing/tuning the dizzy and sourcing some weights the gains will be minimal at best. If it has the 63b SOHC in it then you have quite a few choices engines, ALL of which will net you bigger gains in torque and power output.
I understand that sometimes you just wanna muck around with a car and the old "I wonder what will happend if you do this" and if thats your choice, have fun and goodluck.

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PostPosted: 26 Jun 2011, 16:50 
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Joined: 22 Nov 2007, 11:49
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The n.a. G63B is old and crude by the standards of anyone here, but it has some pluses for me. Understand that this is basically a station wagon. Pretty cool little station wagon, known to the few afficionados as "The Swiss army knife of automobiles," but still just a daily-driver. What that calls for is not an 8000rpm redline and second gear scratch, but good low-to-midrange torque and good fuel efficiency. By making the upgrades I did (4-2-1 exhaust header, de-smog, etc.) I hope to get good economy and sufficient power. I can't use surplus power in a daily driver anyway. Beyond that, it's a relatively simple (for nowdays!) engine that leaves a little room in the engine-well, especially since I cleared away most of the smog crap, for me to swing wrenches when need arises.

I don't really see what a turbo 4-valve supermotor would add. This isn't a toy, it's just a tool.

A year or so ago I was looking at a little 1977 Dodge (Mitsu) Colt coupe with the old 1.5L SOHC four. Now THAT would be a car to put your supermotor in, oh lordy!!!


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