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Discussion Starter · #1 ·
Hello
I’m currently running a 85 Jetta 1.6 mechanical head NA in need of a rebuild soon. I recently found a supposedly rebuilt low mileage MK I Rabbit engine for sale. It appears to be a 12mm Head-bolt engine. 1.6D on crankcase and triple squared head bolts. I do notice a few differences in the 2 engines. The injection pump is different and the crank gear bolt size is different.(17mm vs19mm) What is difference in these 2 pumps. I also read the Rabbit has a different motor mount and you need to remove the timing belt to swap it out for the MK II Jetta mount . I also recently learned there is a small nose and big nose crankshaft (22mm vs 31mm) I assume the MkI has the smaller size. With a stock 1.6 NA engine is there any reliability issues with smaller nose crankshaft. I’m just trying to decide is the MKI engine worth buying or should I just rebuild my engine in the near future. Any info Appreciated.
Randy
 

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Grow a pair and do both. I have turbocharged the earlier variants of the 12 mm with great success. That smaller crank bolt is getting very hard to find now days. As I recall, a person could reuse the smaller crank bolts whereas the later 19 mm head bolts were supposed to be thrown away each time.

You probably will not feel a difference in the fuel pumps. Generally, newer pumps fed more advance in the timing.....that was esp. true with the 1986 oem fuel pumps which had the external fast-idle adjustment hardware and had the numbers XXX-XXX-081C on the pump body.

Who knows if the engine was rebuilt or not. My experience is that few people truly know how to successfully go through one of these from the crankshaft-out....and tend to lie and bullshiit about exactly WHAT they call a rebuild. some call emptying the ash tray a rebuild.

If the guy can tell you EXACTLY what he did to rebuild the engine with EXACTLY what brand of parts he installed WHERE....and not sound like Joe Biden while he tells the story....you have a 50-50 chance he is not lying.
 

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Discussion Starter · #3 ·
Grow a pair and do both. I have turbocharged the earlier variants of the 12 mm with great success. That smaller crank bolt is getting very hard to find now days. As I recall, a person could reuse the smaller crank bolts whereas the later 19 mm head bolts were supposed to be thrown away each time.

You probably will not feel a difference in the fuel pumps. Generally, newer pumps fed more advance in the timing.....that was esp. true with the 1986 oem fuel pumps which had the external fast-idle adjustment hardware and had the numbers XXX-XXX-081C on the pump body.

Who knows if the engine was rebuilt or not. My experience is that few people truly know how to successfully go through one of these from the crankshaft-out....and tend to lie and bullshiit about exactly WHAT they call a rebuild. some call emptying the ash tray a rebuild.

If the guy can tell you EXACTLY what he did to rebuild the engine with EXACTLY what brand of parts he installed WHERE....and not sound like Joe Biden while he tells the story....you have a 50-50 chance he is not lying.
Thanks for the info
Your thoughts on Rebuilt engines is right on point . Like you said the only sure way to know what is rebuilt is to do it yourself. So basically I could the swap that so called rebuilt engine with MKI Injection Pump and not really notice any significant difference from my 85 Mark II pump?
 

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Well, I am not going to say "exactly-that." Due to the fact that every one of these pumps runs a little different due to miles run and internal wear, etc.

But, for the most-ist part, the pumps ran pretty much the same until the 1986 models as described above. Sure, WAAAAY back in the beginning, there was what as referred to as the "Yellow-Dot" pump. This was on the early Rabbits and had internal differences which altered how it ran and how to set the static timing. But, I seriously doubt you have one of these in your possession.

Listen, anything you use for an engine absolutely HAS to get a new Continental or other quality (not ching-chong-chewwie) cam belt installed and then properly set the engine timing. You can NOT farrt around and take chances with some other bozo's work. End of story.

If you do not know how to perform this, leave your hands off the whole thing until you learn (from a Bentley manual) how to set this up. It is NOT brain surgery, but, these engines are extremely particular on timing due to this engine being a very SERIOUSLY interference engine.

I don't know why, but all of you guys overlook the topic of worn injectors. You think running one of these is all about the fuel pump. I mean, you are willing to work to get your lawn mower carb working sort-of-properly.......but, you give worn old-tired injectors (which were probably not set up right to begin with, when new) no thought.

These engines LIVE on their injectors and whether-or-not they properly atomize the fuel adequately or NOT. Injector nozzles really are well worn at 75,000 miles. Beyond THAT, they can fire early or dribble between shots (like the old guy down the block) or not even atomize their fuel worth a crap. Why oh why does the topic of proper-running injectors rarely come up?????? Everyone is always bittching about how their car smokes and such. But, injector function is a "black-art?"

If you are putting a MK. I engine into a Mk.II car, you need to spend time cleaning out the little engine block bolt holes on the back of the block where the MK. II motor mount (aluminum casting) bolts up. I made the mistake of NOT doing this once while swapping engines and all of a sudden I had partly-stripped threads. SO......take the time to CLEAN out and test those bolt holes PRIOR to the swap.....dig?
 

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Discussion Starter · #5 ·
Well, I am not going to say "exactly-that." Due to the fact that every one of these pumps runs a little different due to miles run and internal wear, etc.

But, for the most-ist part, the pumps ran pretty much the same until the 1986 models as described above. Sure, WAAAAY back in the beginning, there was what as referred to as the "Yellow-Dot" pump. This was on the early Rabbits and had internal differences which altered how it ran and how to set the static timing. But, I seriously doubt you have one of these in your possession.

Listen, anything you use for an engine absolutely HAS to get a new Continental or other quality (not ching-chong-chewwie) cam belt installed and then properly set the engine timing. You can NOT farrt around and take chances with some other bozo's work. End of story.

If you do not know how to perform this, leave your hands off the whole thing until you learn (from a Bentley manual) how to set this up. It is NOT brain surgery, but, these engines are extremely particular on timing due to this engine being a very SERIOUSLY interference engine.

I don't know why, but all of you guys overlook the topic of worn injectors. You think running one of these is all about the fuel pump. I mean, you are willing to work to get your lawn mower carb working sort-of-properly.......but, you give worn old-tired injectors (which were probably not set up right to begin with, when new) no thought.

These engines LIVE on their injectors and whether-or-not they properly atomize the fuel adequately or NOT. Injector nozzles really are well worn at 75,000 miles. Beyond THAT, they can fire early or dribble between shots (like the old guy down the block) or not even atomize their fuel worth a crap. Why oh why does the topic of proper-running injectors rarely come up?????? Everyone is always bittching about how their car smokes and such. But, injector function is a "black-art?"

If you are putting a MK. I engine into a Mk.II car, you need to spend time cleaning out the little engine block bolt holes on the back of the block where the MK. II motor mount (aluminum casting) bolts up. I made the mistake of NOT doing this once while swapping engines and all of a sudden I had partly-stripped threads. SO......take the time to CLEAN out and test those bolt holes PRIOR to the swap.....dig?
That’s very good advice on the injectors. Always know the condition of your injectors. Mercedessource.com has a good video on checking injectors with a pop tester and replacing the nozzles. You make one or buy one his for a around 175.00. You also can’t assume when you buy new or rebuilt injectors they working 100% to specs.
Randy
 

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yes, years ago, I purchased a ching-chong tester on ebay for about $79.00 at that time. The gauges are always a little "suspect." Occasionally, you need to renew the little o-rings on the central components as they wear.

You also MUST cover your body and EYES and NOT breathe the diesel fuel when it is pressure aerosol-ed (atomized). I cover my face with adequate eye protection and have several layers of material over my arms and upper body.

I begin by covering the injector with a empty anti-freeze container (gallon jug) and firing (priming and getting an accurate spray) the fuel into the anti-freeze container. After about 10 or so firings, then you can remove the jug and (keep yerr damned face away) pressurize the injector and see when it fires with the gauge.

You also need to bring the pressure up to the firing point and hold it there to see if injector body or nozzle weeps.

You do NOT need to obtain new hardened shims to set the pressure. You can use your existing hardened shim (against the spring in the injector body) and make and insert home-made shims out of feeler gauge stock the desired thickness to get the pressure you want.

If you need advice...contact me in private message. New injectors make a HUGE difference in how these run, start, and rock down the road. And, of course, the higher pressures do make more noise when they run as those internal components are SLAMMING back shut after firing.

If you want a quiet rig....go buy a gas car.

The home-made shim goes between the upper injector inside body.....and between the original hardened shim which ALWAYS HAS to go against the spring.

The rule of adjustment is: 0.002 inch equals 75 lbs of pressure (going either way (up or down)).

The hard part of this whole deal is getting the internal components sanded PERFECTLY flat. NO erosion on the intermediate disc can be left. I use a precision ground block to sand on and I, personally, take the sanding down to 3000 grit (yes, this takes a huge amount of time to accomplish). Why is everthing needing to be so perfect? Because steel-on-steel is your seal.

I always set n/a injectors to 2150 lbs. I run turbocharged injectors rather high at 2650 lbs. And, MY surfaces HAVE to be perfect to not leak at the injector seam. But, my engines benefit from really nicely atomized fuel (far less that a common-rail.....but, we ain't in common-rail land here).
 
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