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hardflex's Avatar
 
Join Date: Sep 2002
Location: dfw tx
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MPS diaphrams and aftermarket heads

I have some MPS's which leak, and now that I'm completing this car I need a good one. Does anyone have experience with the newly available diaphrams pieces to fix it? I hope they're still available. I think Bowlsby made some up. Any experienced people out there?

Also, 2.0 liter heads some time ago were getting scarce. Are aftermarket heads the way to go now if you need them, or are factory heads still the best option.
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72 914 2056: 74 9146 2.2: 76 914 2.0
Old 12-01-2014, 06:23 AM
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Racer Chris from Tangerine Racing sells the diaphragms. I haven't used the repair kit, but I'd have no hesitation in using anything that he builds and sells.

The aftermarket heads are not 2.0 914 heads. The spark plug is in the 1.7/1.8 location, they have three intake studs, and so on. Len at HAM uses the AMC castings, moves the spark plugs, changes the intake stud pattern, re-shapes the ports, and up-sizes the valves to the 914 2.0 stuff. Those are about as close as you'll find to new heads nowadays. Oh--and Len is another person whose stuff I haven't yet used, but would not hesitate to if I needed it.

--DD
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Old 12-01-2014, 06:58 AM
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I found the kits and I'll plan on it.

So it sounds like factory heads are still the best option. Just curious, is that also true for type 1 engines?
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Old 12-01-2014, 09:28 AM
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One advantage of the AMC heads is that they have not been heat-cycled a zillion times, nor overheated on a semi-regular basis. You can't be sure of that with used heads.

Oh, and the AMC hardware (valves, springs, keepers, etc.; not sure about seats or guides) should never be used. It is of low quality, and if you get an AMC head with their hardware on it, break it down and throw all of that stuff away.

No idea on the Type I stuff. I do know the market for that is a couple of orders of magnitude greater than for Type IV stuff, so there has been a lot more incentive to develop aftermarket parts. Some of them are supposedly better than the stock parts for one reason or another. But again, I really don't know any details.

--DD
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Old 12-01-2014, 01:36 PM
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I just installed the MPS repair kit from Chris at Tangerine last week. The instructions provided are very good overall. If you have questions on this process, let me know. I did take a bunch of pictures as I did the repair.

One question: are you sure your MPS is leaking (have you tested it with a vacuum tester)? I've seen different references like "it should hold a 15 psi vacuum for 5 minutes." Mine definitely did not. It leaked down to roughly 5 psi within one 1 minute, but according to Anders' MPS documentation that's probably ok (any more than that is not good). Bottom line: my MPS PROBABLY wasn't unserviceable, but I repaired it anyway. I also now have the ability to tune it.
Old 12-01-2014, 03:27 PM
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I didn't put it to the vacuum gauge test, just sucked on the hose and when it didn't build vacuum I pulled it apart to find the cracked diaphram. I think I have a couple like that, maybe more.
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Old 12-01-2014, 06:39 PM
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If you've pulled it apart already and found a cracked diaphragm I'd say that's a pretty good indication! You can buy the Tangerine kit with only the diaphragm replacement or with the tuning kit as well. Good luck.
Old 12-02-2014, 01:42 AM
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tuning the MPS is a royal pain, so be prepaired for that. I made a long extension cable and long hose so that the MPS could be in the cockpit for adjustments while driving. Of course you need a helper to make adjustments on the fly as you drive (or Visa Versa,) and a an exhaust O2 monitor. take lots of runs on a course and note the O2 reading and adjust as needed.

Also note that even a bone stock factory NOS mps will likely need adjustment as the factory adjustment was based on real gasoline form the 1970's. the government mandated crap that is forced on use is full of oxygenates (thanks corn farmer lobby and bribed politicians) not only does this new gas cost more, deliver fewer miles per gallon, and has caused a spike in food prices, it also makes the mixture burn lean, so a stock MPS needs to be adjusted to take into account todays crap fuels. this was in part brought on by the big lie of global warming, and reducing carbon foot prints. then they later figure that using corn for fuel actually releases more carbon than using petroleum fuel. stupid isn't it???? more waste fraud and abuse by elected leaders. Oh and don't forget the MTBE that used to be added as an oxygenate, so toxic it had to be banned!
Old 12-04-2014, 10:35 AM
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