I am starting to plan for the actual assembly of the engine I am rebuilding. Thanks to everyone who has helped me with my questions up to this point. So here is my next question.



What is the common thinking on using some sort of a sealant on the rotor housing mating surfaces as the stacking takes place?



I have read where one rebuilder uses and endorses the use of black RTV. I think I saw where another uses Permatex 300. In one of the videos I watched they just spread a little extra hylomar on the surface as they were applying it in the o ring groove. But they didn't cover the entire surface.



My housings are used, probably have some surface imperfections and I think they would benefit from the use of something. Since this is my first rebuild I want to take the stacking slow, and not be "pushed" by the time it takes for certain sealants to set up. I plan on using hylomar in the o ring groove on the cast iron housings. In case I have a problem I don't want my coolant rings swelled by vasoline.



So you any of you have some recommendations? If I use something besides hylomar on the mating surfaces outside of the o ring do I need to keep it off the o ring?



Thanks for any advice you can give me,



Jeff

No, Hylomar or silicone on the "O" rings is of no concern.



I glue in the rings with a very tiny bead of silicone in the bottom of the groove. And from the ring groove down each leg of the rotor housings right to the pan gasket serface. You must use a sealant here or the engine will leak oil.



I use GE 100% silicone tub and tile caulk. Hylomar works fine but is hard to find and very expensive. Mazda uses some kind of grey stuff probably silicone based.



Very little is needed. But it is needed everywhere.



After a day of rest, turn the engine over backwards a few times, and remove any excess sealant through the exhaust ports.



Another 80 degree day in Zephyrhills....



Lynn E. Hanover

i use a very thin beed of hylomar in the water ring grooves and oil o ring grooves around the dowel pins and the oil filter pedistal. then use mazda grey sylicone on the bottom of the irons from the oil pan mating surface up about 2 inches to keep the oil from seaping out. no need for any type of sealent on the iron faces or housing faces ever.



randy

i do what lynn says... if the engine comes apart again, the inner water seals really look nice, almost reusable



not into hylomar at all, remember it was developed for engines that are notorious for leaking oil!

i have built 40 motors now all have used hylomar in the water jacket gooves and none have had any oil leaks or water leaks. another thing interesting mazda now offers three bond in a calk gun size tube. it has a mazda part number. i did use the mopar black sylicon one time in place of the grey mazda stuff on an engine on the bottom 2 inches of the irons to prevent oil seapage and that one did leak after a short period of time. i have since stocked up on the grey stuff and only use it. i have used the mazda grey stuff from the engine ( even used it inplace of the frount cover gasket and oil pan gasket ) to sealing the trans to the diff. i do know the permitex version of hylomar does not work very well. stick with the real hylomar. hylomar is not that hard to find, just need to go to a real engine shop or a real race suply shop. autozones napa and places like that will not have it.

i hear you but ive used wheel bearing grease and not had a problem either https://www.nopistons.com/forums/pub...#>/biggrin.gif





could you get the part number of the mazda silicon in the caulking gun? ive been using the mazda grey stuff in the tube forever.



also as an aside, you might wanna look up all of mazda's silicon part numbers, a few years ago they screwed up and you could buy the millienia trans pan sealant for like $0.30 a tube...

the dealer i work for only stocks 2 types of sealent. the vw white crap that smells like a very very strong douch and the mazda grey stuff. ill get the part numbers on monday for the three bond and the grey stuff

Thank you everyone for all of the replies. I had been wondering whether to go with Permatex 300 or the silicone/Hylomar route. It looks like silicone or hylomar is mostly what everyone here is using.



My guess is it is probably as important to prep the surfaces properly than whether you choose hylomar or silicone. I have wire brushed everything real well, cleaned the grooves with a small scraper, taken it all to a car wash (I ended up as wet as the parts), and will clean everything with acetone before I put it together.



Again, the only reason I might choose hylomar over the silicone is the increased time I will have to put everything together. Since this is my first engine I would be foolish to think everything will go together quickly with no delays (why do I have this extra dowel o-ring?)



Thanks again,



Jeff

i like to do things in a sequence. and since its your first one, you might wanna even do a proper mock up.



but anyways, i clean everything. build the rotors. lay out all the gaskets and seals, make sure you have the right ones etc.



then you stack it.

The mock up is a good idea. I am a little unclear on a couple of things right now. Maybe I should just start a new thread but I'll list them here for now.



How important is the placement of the rotors in the housings? I see generally how the first one is supposed to go but my guide says it just needs to be close. Is that true?



I have replaced timing belts and put camshafts in other vehicles and you have to be exact with timing marks, etc.! Doesn't seem like the emphasis on exactness is the same here.



And how critical is the placement of the second rotor relative to the first?



Jeff

ok let us clarify , you need 2 types of sealent. one is hylomar wich is for the waterjacket seals and oil o-rings. the other is sylicon sealent for the bottome edges of the motor to keep oil from seaping. there is no need for sealent on the entire housing face. the water jaket rings seal plenty good.





anyways j9 you asked for the part numbers for the sealent i get from mazda. the grey stuff wich i use everywhere is 8527-77-739 that is the mazda silicone sealent SH780M and the one in the calk gun tube is zjy1-10-431 and that is threebond 1217G. and i get my hylomar from Pegusis racing in newberlin wisconsin. and any real engine shop will have the real hylomar. the permitex crap does not work very well.

yeah clean everything up, and just put the big parts together without seals and gaskets.



since the rotors are geared, the placement of the first rotor automatically times the second. in other words you cant get it wrong unless you have a really big hammer!



it IS easier to set the front rotor at a tdc or bdc so you know where to put the rear one.

Once you do it a few dozen times it won't matter where you place the first rotor as long as the second rotor is in opposition. Side to side works fine also. First rotor at TDC fireing, and second rotor at TDC overlap.



No worries, if you are off a tooth the rotor will not sit inside the housing. I just sit the first (front) rotor on with an apex seal groove pointing straight up. The actual orientation is helpfull when installing the center iron. If alone you must lift the crank nearly out of the front rotor bearing to get enough room to work the center hole aroung the crank center. The TDC method makes this a bit easier. Here are two things that can help.



Slip the dowels out of the front housing to gain some more room. Lower the center iron onto the crank with the top of the iron 90 degrees to the right or left. Easy to hold onto. Goes over the crank easy. Then rotate 90 into the correct position, and install the dowels again.



Make a bracket to support the crank nose that clamps onto the engine stand. Just slide the bracket up until the crank is nearly out of the front bearing and tighten the clamp.



If you have help, install the crank into the center iron first, and lower the assembly onto the engine.

Piece of cake.



If alone, tip the engine to nearly horizontal. Put the crank through the center iron and hold the assembly against your hip. Ease the assembly into place. Turn the engine nose down to complete assembly.



Lynn E. Hanover

i have an engine stand, but its got a really big base, so getting the engine OFF the stand is hard.



i used a milk crate. this particular one only has 3 sides. so iron goes on top, and when you need to put the center iron, i use the jack from the car to raise the e shaft. nobody's lifting anything, so i can do it myself, and take as long as i want.



http://www.youtube.com/watch?v=1AxHx3x9HV0



its easier to spin the center hosing on like that if the rotor is in a certain position...



oh also when you're doing this all the bearing/sliding surfaces should have a little oil/assembly lube or something on em

Thank you all for the replies and information. I think I understand now, it looks like the rotor "timing" is built into the eccentric shaft.



The video was good. Sure makes it look easy.



Jeff