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emoore924 · Joined: 13 Apr 2004 Posts: 2815

Not sure I have the right termonology, but here's what I'm wondering...

If you have a bad fuel distributor but it has a good control piston (that thing you don't want to drop that goes in the hole in the middle of the dizzy...), can you swap the good piston from the bad dizzy to a good dizzy that has a bad piston?

Just hoping to make one good fuel dizzy from the parts of bad ones...

Has anyone successfully swapped pistons or is it like the cam bearing caps on the head -- does the piston go with the dizzy it was made for and that's it or can you change them around?

Anyone with rebuilding experience know?

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

I thought the cone shaped piston was matched to the distributor...
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1987 951 - M193 Version for Japan

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

If it has a good piston, you can simply rebuild the dizzy. all it really requires is replacing the o-rings. the whole unit is actually really simple. The problem that I've read that alot of people have when doing this is getting the two halves to seal once put back together. I solved this problem by applying a very thin layer of JB weld between the halves. Another common problem when rebuilding them is that the torque screws with shear off. I had this happen to me on like 3 of them when i rebuilt mine. I would recommend buy all new ones. All in all the rebuild shouldn't cost more than $10-$15.

Pretty sure there is a write-up with pics in the how-to section. Hope that helps.
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1980 924 NA
1982 931

emoore924 · Joined: 13 Apr 2004 Posts: 2815

Yeah, I checked out the other threads but none of them commented on switching pistons. I'm not worried about the rebuild part, I've got that. I'm more worried about whether the pistons are swappable...

Anyone else agree or disagree with Chrenan?

I'm inclined to make the swap and see what happens..., not that I have much of a choice.

RC · Joined: 25 Mar 2007 Posts: 2636 Location: Australia

Thats the advice from Bosch, Haynes, and many CIS pros. Sure Porsche say the unit is not rebuildable and expect you to buy another for 2K.

Can`t recall the figure offhand but Bosch data specs an extremely fine tolerance and piston to bore clearance. They are (were) matched as a set.

Any S/H ones these days are likely well out of tolerance anyway. Would cause a slightly richer mix I should imagine, but not necessarily a linear progression. Should be doable unless there is decreased clearance and friction. Certainly worth a try or 2 IMHO, before trying Special T.

Definitely would not recommend anything like JB weld, not even fuel resistant. Have successfully used a Loctite sealant, cant recall grade. Good results also from making up 2 thin paper gaskets each side of diaphragm. Use hi tensile cap screws, (hex socket head) and allen key for more and equally applied diagonal torque.

Min · Posted: Fri Jun 19, 2009 2:03 am Post subject:

they are probably a lapped fit to each other, which as rc mentioned, means they are a matched set.

Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

El Chato · Joined: 22 Aug 2006 Posts: 205 Location: El Paso, TX

dont wanna still the threat only that i had the same thing with three i have I think they all look different pistons, but my doubt was i saw two of them had like ajusters or some like that screws next to each injector lines, does this make a difference when swapping distributors?
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1979 924 N/A, Snail Shell
1980 924 N/A
1976 924 N/A

It may be that your whole purpose in life is simply to serve as a warning to others.

Today's weirdness is tomorrow's reason why.

emoore924 · Joined: 13 Apr 2004 Posts: 2815

Some of the fuel dizzys have small adjusting screws on each of the individual lines -- I've seen this on all the 924 turbos I've seen -- but I think the adjustment is more for *balancing* between the 4 lines than it is to set up overall flow.

That being said, if it is a 924 dizzy (just check the part # on the bosch tag), it should work for a 924, adjustors or not. If it is from a turbo (shiny silver, not black) IDK if it would work. Same comment if it came from a golf or a jetta or whatever...

If the pistons are in any way different between the dizzy with adjustors and the dizzy without, I would think swapping pistons between adjustor and non-adjustor dizzys would NOT work. But no telling for sure until you give it a shot I would think....