Brake distribution block - getting piston out ???

[DAVEN1256]

I am rebuilding my brake distribution block. I got out the brass fitting and the spring out from the one end but am not sure how to get the piston out now. Tapping the block on a hard surface didn't budge it. I put a paper clip in the opposite end and pushed and that didn't budge it either. I know it's not's possible but looking at the end of the piston in the bore, it looks larger than the bore size.

Any advice on this. I don't want to mess something up trying to get it out.

Thanks.....Dave

[TRLAND]

Muscle Car Research has a lot of technical articles on these brake valves.  Try this one. I think it addresses your issue:  https://www.musclecarresearch.com/1972-gm-pd-valve-autopsy

Post your results.  I need to do mine soon.

[69Z28-RS]

I am rebuilding my brake distribution block. I got out the brass fitting and the spring out from the one end but am not sure how to get the piston out now. Tapping the block on a hard surface didn't budge it. I put a paper clip in the opposite end and pushed and that didn't budge it either. I know it's not's possible but looking at the end of the piston in the bore, it looks larger than the bore size.

Any advice on this. I don't want to mess something up trying to get it out.

Thanks.....Dave

You may be able to get the piston moving by adding lubrication, and air pressure..  but be careful with the air pressure and make sure that you leave the spring/restraint in place when you apply it to make certain taht the piston just *moves* but doesn't become a projectile... (depending on the amount of air pressure required)..

[DAVEN1256]

I looked the MCR "autopsy" on these blocks. He says to use a dental pick to get the spring and piston out. That makes sense to me about the spring but not sure how I would hook the piston with a dental pick.

I tried air pressure by itself but that didn't move the piston. It's probably rusted in there. I have some PB Blaster here that can I put in there but I don't know if that, or other rust breakers,  might damage the brass seats.

Out of curiosity, are all the brass seats (cones) just press fit in or is there some kind of seal on them that chemicals could damage.

Thanks.......Dave

[Mike S]

Hi Dave,

  If I remember right some of the seats were machined, or at least they didn't have a brass look to them so I left them alone.
If you can get a small brad nail or 'finishing' nail and file the pointed end flat, that may fit into the other ends plug hole and you can gently tap it out that way.
It is amazing how much crud develops inside that body even though the outside may look good.

Mike

[sah62]

I am rebuilding my brake distribution block. I got out the brass fitting and the spring out from the one end but am not sure how to get the piston out now. Tapping the block on a hard surface didn't budge it. I put a paper clip in the opposite end and pushed and that didn't budge it either. I know it's not's possible but looking at the end of the piston in the bore, it looks larger than the bore size.

Any advice on this. I don't want to mess something up trying to get it out.

Push with something sturdier than a paper clip, like a drill bit or finishing nail. You may need to tap on the bit or nail with a hammer.

[TRLAND]

Scott, I hope you don't mind me referencing your technical article above.  Is that the right one for rebuilding the distribution block discussed here?

[DAVEN1256]

Ok, I'll try something a little beefier than a paper clip.

And by the way, Scott, I ordered your rebuild kit a couple of days ago. I am trying to get a head start before it gets here,

Dave

[DAVEN1256]

Yep, that's all it took. Tapping on a small finishing nail with a hammer. I started with the finishing nail that I ground the point flat on. It got the piston moving but it was too short to push it all the way through. I finished the job with a longer piece of a wire hanger.

Now, how to clean it up inside?....... Rust and crud in all the threaded ports and the main bore. I don't want to damage the brass seats.

Dave

[Mike S]

 I sprayed carb cleaner inside to clean it initially and then 1000 grit wet/dry paper wrapped around a pencil using a twirling motion to clean/hone the bore. If there is rust you can try soaking in Evaporust for an hour. That shouldn't damage the seats. If you clean the paint off then Evaporust will restore the natural gray color.

Mike

[sah62]

Scott, I hope you don't mind me referencing your technical article above.  Is that the right one for rebuilding the distribution block discussed here?

Not at all! Yes, that's the disassembly article. The rebuild is described here: https://www.musclecarresearch.com/gm-pd-valve-rebuild

[KurtS]

Scott,
I was looking the other day and if you search by https://www.musclecarresearch.com/parts/Chevrolet/Camaro/1969, it doesn't show the distribution block.
Thanks!!

[janobyte]

Just did mine around 2 weeks ago, downloaded the "autopsy" and re-build procedure off his site. I ordered a couple more brass seats from him(that was me on the phone with you that weekend Scott)thus replacing both of them. Easy enough to pull them, then simply pushed the piston out from the opposite side with a slightly smaller diameter flat brass punch. Didn't want to risk any possible damage to the piston.

Great resto tip Mike, came out looking like new, if I have some time, will post pics this weekend. Thank you Scott for this in-expensive service you provide!

[sah62]

Scott,
I was looking the other day and if you search by https://www.musclecarresearch.com/parts/Chevrolet/Camaro/1969, it doesn't show the distribution block.
Thanks!!

Yes, I know. I haven't consistently added applications to that part of the catalog because I don't always know for sure exactly which valves (and associated rebuild kits) are appropriate for specific cars. Rather than guessing, and potentially selling someone the wrong item, I leave it off.

[KurtS]

Well, that one is correct for 69, so adding it would be a good thing.