View original topic: the joys of discovery
Bambus Tue Jun 26, 2007 8:52 pm

the more you probe, the more you find.

so several of you have been helping out w/ my '85's resurrection from neglect (a wee bit mine, but mostly PO). Billion thanks for ea and every bit o feedback. Those that schooled me on fuel pressure regulators deserve especial thanks and mass quantities of whatever you like, to be put on my tab for later payback.

Well. In tracking down oddly lowered compression values since the last comp test i did previously (2005 some time, less than 10,000 miles ago), i went today to adjust the lifters to see if i have any mushies. While i'm turning the engine over manually, eyeballing the pulley looking for the OT mark, my eye strays over to the engine number stamp. I wipe away the grime (from a previously leaky breather tower gasket) and behold ye: an MV case code. On an early '85.

Not *entirely* surprising, since the PO told me he'd had the orig motor replaced (thrown rod, he said) at a GA dealer w/ a low-miles engine they happened to have on hand. All FI and management electrics (and intake parts) are orig 85 Digijet, from square airbox to AFM to idle stablizer to Hall control unit-- there's no MV sandwich oil cooler either. I've looked and looked for the MV's second/rear oil pressure switch, and i see zip. Aside from the MV engine # there's NO visual evidence that this is not a stock DH powerplant. So i'm guessing the dealer in question put in the MV motor and bolted the PO's Digijet FI syst right on. How that mating worked out of the box is a mystery to me. 2.1 motor being managed by a Digijet system?!

After this MV transplant the PO went on to do a top-end rebuild (leaking heads, he said) a few years later with new AMC heads (which i can physically see) and new pistons & cyls (purportedly). What i'm wondering is if he (PO) slapped on 1.9 heads and cyls on top of a stock 2.1 bottom end (incl rods). This does'nt sound like a horrible combo, but i'm wondering how these combinations might be playing together w/ Digijet management???

Another clue is that the exhaust parts (front and rear cross-pipes to elbow, and then back to the cat) are 2.1 parts-- clearly different from 1.9 (i double-dog checked it on the ETK too). All this stuff *works* (relatively speaking), but i'm still puzzled over how this conglomeration worked together when the dealer did the original swap of 2.1 block with 1.9 intake and FI syst.

More pressing is what the hell timing data i should be using-- my MV case has the MV pulley, with the timing notch some degrees before TDC. The 1.9 (according to Herr Bentley) has a timing pt of 5deg *after* TDC. I have no clue what dist this motor has-- it has a vac unit on it so it looks to be 1.9 liter spec!

THAT'S entertainment!

I've recovered all my old emails w/ the seller that have some details, and am trying to track him down all these years later, but his contact info seems to have blown away like instant grits in the wind...

Any ideas? With a 2.1 case and bottom end i'm tempted to think that if i should ever want to replace heads/pistons/cyls i should try and score a Digifant FI system and all related parts and do the re-upgrade to 2.1 specs.

It's a whack-attack

wbx Tue Jun 26, 2007 11:14 pm

You are over thinking it. The digijet system is more versatile and adaptable than you are giving it credit for. You are only talking about .2L difference in displacement. If it makes you feel any better, i'm using a digijet system on a franken-engine with a displacement of 2275, and it seems to be holding up fine (although there was some tweaking of the AFM necessary).

Anyway, point being, a 1.9 FI and cooling system on a 2.1 block has been done many times, and is not something to worry over. In my very meager opinion, it is the best of both worlds - simplicity of the earlier system with the power of the later system. The only thing i like better about the digifant system is the heated O2 sensor, but that is easily enough retro-fittable.

Regarding timing, start with the 5* ATDC like digijet wants, and you can experiment with going as advanced as 5* BTDC for a little extra kick. There can be emissions disadvantages to that, though, if you are concerned about such a thing.

Good luck, and enjoy your franken-engine.


Bambus Tue Jun 26, 2007 11:42 pm

good stuff. I've been accused of 'overthinking' before, as well as under-thinking (see: list of ex's)

timing question remains-- i'll confirm tmw what dist i have, but i know damn-straight i have the 2.1 pulley with its TDC and time marks on it. The degree difference is'nt earth shattering, but it's an appreciable spread too. Do i defer to whatever dist is in there, or stick to the pulley marks? W/o intel this seems rather arbitrary ("hey, split the difference, dumbass!!)


wbx Wed Jun 27, 2007 12:44 am

I'd bet dollars to doughnuts that you have the digijet dizzy in there, but it wouldn't hurt to verify. I don't think there are too many distributors out there with both vacuum advance and retard...

Also, i'd defer to the distributor.


Bambus Thu Jun 28, 2007 8:52 pm

so the crickets chirping in this thread (aside from wbx's kind comments) prodded me on to doing my homework on the Franken-boxer. I ascertained via the manual and common sense that the installed dist type trumps whatever else one is seeing wrt timing marks. I indeed have the 1.9's vac dist on this 2.1 case/bottom end, so i followed Bentley's instructs for making my own timing mark on the pulley (i have the stock 2.1 pulley on a 1.9 spec motor, if you have'nt read the above)

Bentley sez make a mark 7.5mm left (*after* TDC/OT) of the rounded OT notch, so this i did with a sharp chisel, and put a drop of white paint on the new notch. Will warm up and time to 1.9 specs tomorrow. I suspect there'll be a difference in tune-- the paint spot that had been used was def the 2.1 BTDC setting (right of the OT notch)

This mssg brought to you by Overthinkers Anonymous. ('overthinking' gets the job done too, it just results in overly wordy posts...) (typing out loud? lonely? sun-baked? combo of all)

PS: will post some air conditioning stuff for sale in the Samba classifieds in next day or so. I'm pulling the entire AC syst from this '85, and will list compressor, bracket, and interior A/C vents, switches etc. AC was operable, but prolly leaked down as i never use it. It did blow cooler than ambient temp the last time i switched it on. Prices will be dirt cheap, i just want the stuff off and out of the van. It'd be easier to take this stuff to the scrap yard, but i'll list the parts anyway for cheap in case someone out there is just dying for them. Not trying to make a buck-- keep an eye out on the classfieds or PM me.

thanks gang



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