Project 924 S engine replacement

[HondaDustR]

Thanks for the heads up. I was well aware of that. The block, crank girdle, and balance shaft housings are all machined together and are to live and die together! I've heard the balance shafts are also balanced to each particular motor, but that could be wrong.

[HondaDustR]

Now the pistons get a little R&R...













I used the Dremel for the tops, but the sides I scrubbed with a no scratch scotch brite and some purple power.


Lots of ziploc bags are just as essential to an engine rebuild as anything else!







Cut out this section if you ever have the clutch bellhousing off. It will allow you to adjust the speed/reference sensor gap with the bellhousing removed, and you'll be able to do the clutch without having to remove and re-gap the sensors.

[HondaDustR]

Got new mains in today! ...and some head bolt washers, 'cause I decided it was worth $20 to avoid having to deal with failure if the old ones spin on torquing.




SWEET!

[HondaDustR]

Ok, what is probably the most significant part of this whole project is finally coming together! Re-lapping the cylinders to seat the new rings with Sunnen AN-30 silicon compound.

Here's the materials I've gathered for the project: cylinder hone, craft felt, duct tape, Sunnen AN-30 silicon compound, SAE 20 non-detergent mineral oil, heavy duty magic erasers for cleaning cylinders afterwards.




First, I prepared the hone by covering any of the metal parts that could possibly contact the cylinder or deck surface. I also covered the honing stones with 3 even layers of duct tape to prevent the stones from ever contacting the cylinder.




Then I cut 3 sets of 2 ~3x4" squares of felt to wrap around each stone. I'll find some safety pins or something similar to secure them tomorrow morning.





The process I have in mind basically follows the factory manuals description of final lapping of the cylinders as closely as I can with what I have. Soak the felt in honing oil, put a thin coat of AN-30 on the cylinder and some on the felt pads, insert hone with light pressure and hone at ~230 rpms and ~80 strokes per min. with as close to a 2mm protrusion at each end of the cylinder as I can manage, and perform the honing for 80 seconds. Then wash with purple power using magic eraser to ensure all AN-30 is removed from cylinder surface.

Actual trials on my old block will commence tomorrow!

[cvriv.charles]

HDR,... you have a compressor? If so stop using a dremel and get a Clarke Siphon Blaster. Soda blast your parts. It works soooo great. No joke. It will blast away all that crap so quick. Soda dilute in water so just spray parts off with water and dry. So awesome.

[HondaDustR]

I would, but that would invovlve spending at least another $200 for a compressor and I'm getting really tired of spending money. I even saw a cheap way to make a soda blaster. It would have been a heck of a lot easier. For now it's the hard way, but I'm pretty much done with the cleaning parts of the project, anyway.

[Slam]

Fantastic! I'm really looking forward to seeing the honing.

[HondaDustR]

OK, honing was pretty interesting. Mostly R&D today. The paste straight out of the can is pretty thinck and needs some oil to dilute it down a little. I found the best way is to liberally smear oil on the cylinder and then smearing some AN-30 paste on top of that before it has too much of a chance to run down the cylinders. Work it into the oil on the cylinders and it thins nicely. Use enough so you get an even brown coating that almost hides the cylinder surface. Also, the new felt needs to be oil soaked first, then some paste worked into the felt.

The cylinders were initially prepped with a scotchbrite and purple power scrubbing straight up and down with very light pressure to avoid scratching the surface, rinsed and dried. The first run, in cyl 4, the paste was a little too thick and I ran the lightest stone pressure I could for 80 sec. It seemed to clean the walls pretty good, but not much else. The second run, in cyl 3, I ran less paste with a little more oil and max stone pressure for 90 sec. Seemed to dull the finish somewhat, and felt slightly rougher than the untouched cylinders, but still on the ineffective side. I ran the 3rd run in cyl 2 with more paste, but thinned like I had it in the second run, max pressure, and 160 seconds. Not much different that the second run.

lightly scrubbed, not honed. Notice how shiny it is on the bottom section below the rings. The upper part of the cylinder is also pretty reflective, but not quite as bright silver colored. There is no wear ridge I can feel, but it might measure out on a micrometer. It doesn't really feel any soother or rougher than the rest of the cylinder.



3rd run. There is a more even and dull grey finish. It feels slightly rougher than the unhoned cylinder, but is still pretty smooth.



I wasn't too impressed with the results. They looked certainly better than nothing, but I was hoping for more. I decided to go at it with the scotchbrite on the last cylinder. I scrubbed nice and hard for about 2 minutes total, putting a fine crosshatch pattern in the cylinder. It was making grey soap suds, so it was definitely taking something off. Here's the cylinder after scotchbrite.



Then honing. I prepped the cyl for honing as for run 3. I also realized I needed to have the hone running faster, ~230 rpms and ~80 strokes per minute, rather than 80 rpms and 230 strokes per minute... (c'mon!). I honed for ~90 seconds. The cylinder looked much more like what I was after! The scotchbrite crosshatch marks were nearly gone but still noticable on close inspection, the cylinder was a dull grey that was finally not reflecting things clearly, and definitely felt somewhat rougher.

Now we're getting somewhere!


Compare to run 3.



Another view. The 4th run pic is slightly out of focus on the cylinder area, but it still doesn't exaggerate the difference by much.






The plan now is to develop a 2 stage honing process, first with scotchbrite pads and purple power, and then with the AN-30 and felt as done on the 4th run. I'm just going to start back at cyl 4, and just have to figure out about how long is good to run the scotchbrite pads. The cylinders on the new block should break in the new rings pretty well now.

[cvriv.charles]

Your awesome.

[very~worn~944]

Beautiful work! Let me know how the two stage process works out! Are you running the scotchbrite pads with any sort of power like a drill or are you hand scuffing? Also what are you using to lubricate the pads?
Did you have a lip at the top of the cylinders where the rings stop? If so, did you take any measures to remove it, and did your pistons get hung up on it? Thanks man!

[HondaDustR]

There was a very small lip at the top of the compression ring stroke on the old block, although the rings didn't have any problems getting over it. I can't remember what the good block had. It's been in a plastic bag for a week. I had to scrub the top edge fairly hard with the scotchbrite to remove the deposits.

The scotchbrite job I did on the cylinder above was just a quickie by hand in a spiral up and down motion to replicate a crosshatch pattern. I just wanted to see if it changed the game at all and it definitely did. I will be developing a method of scouring with the hone so it is done as evenly as possible to prep for the AN-30 honing. I used purple power degreaser as a "lubricant" (basicly rebranded super clean). The hone is a standard 3 arm de-glazing hone I got at Sears for $25 that chucks into any 3/8" drill.

I might have time before work tomorrow for some more R&D with the scotchbrite pads and the hone.

[JivenJim]

Go to hardware store and get the biggest rotory Wire brush (Silver not Gold) you can find. Mount on Drill and Viola. You can buff out your rusty and diry spots on the engine. Saves countless hours of cleaning and makes its look better than new. Then some Cleaning agent like Purple Power. Nice..

Oil relief info: 924S




Cranks can be ground down to 1 size over up to 2 or three times. Just by the oversized Rod Bearings. Make sure you get the right size or you will be be in for a Long re-ordeal...

I was told by Porsche guys, Blue color on Crank is from coating from Porsche and Not from over heating.

[HondaDustR]

Originally Posted by JivenJim

Go to hardware store and get the biggest rotory Wire brush (Silver not Gold) you can find. Mount on Drill and Viola. You can buff out your rusty and diry spots on the engine. Saves countless hours of cleaning and makes its look better than new. Then some Cleaning agent like Purple Power. Nice..

Cranks can be ground down to 1 size over up to 2 or three times. Just by the oversized Rod Bearings. Make sure you get the right size or you will be be in for a Long re-ordeal...

I was told by Porsche guys, Blue color on Crank is from coating from Porsche and Not from over heating.

Interesting. The only problem with a big wire brush is it won't get into all the little corners. Soda blasting works really well, but I don't have a compressor. As far as I know, there is only one oversize available for the 944 (0.5mm), and they are twice as expensive, plus the extra machine work for the crank, so I just hunted down a good used motor. I'm holding on to the old crank in case it's not too bad.

[JivenJim]

I've had cranks ground down for about 200$ Why you are there you can knife edge and cross drill and lighten a bit for about 400 more. good stuff for race engines.

I always liked fixing my problems rather than buying someone eles unknown problems and abuse. I tear down every bolt on my rebuilds. That way you know where things are. That is if you have the down time... and or it's the spare engine. Hope things go better for you this round.

[very~worn~944]

I was under the impression that there was only one oversize bearing available as well. Sounds like you are doing the exact research I needed literally a week before I attempt the same. Your write-up is saving me countless hours of testing and doubting my own ideas.
I was thinking about putting some SOFT scotchbrite pads under the arms of the hone and lubricating them generously with honing oil. I don't know about using a degreaser as lubrication for the scuffing process. I could be wrong but I think a fluid with more "slip" and less "bite" might make a smoother cut in the cylinderwall...On the otherhand using the degreaser with the pads might help break-up the old ring material better.
Good luck with the research! Your info is priceless!

[HondaDustR]

Originally Posted by very~worn~944

I was under the impression that there was only one oversize bearing available as well. Sounds like you are doing the exact research I needed literally a week before I attempt the same. Your write-up is saving me countless hours of testing and doubting my own ideas.
I was thinking about putting some SOFT scotchbrite pads under the arms of the hone and lubricating them generously with honing oil. I don't know about using a degreaser as lubrication for the scuffing process. I could be wrong but I think a fluid with more "slip" and less "bite" might make a smoother cut in the cylinderwall...On the otherhand using the degreaser with the pads might help break-up the old ring material better.
Good luck with the research! Your info is priceless!

I have 3 more cylinders that haven't been scotchbrited, so I may try both with degreaser and oil. Soft scotchbrite pads probably won't work. I have a couple of the no scratch blue pads I've been using for parts cleaning and they really don't scratch the aluminum parts much at all, so probably would not accomplish the material removal I need.

Originally Posted by JivenJim

I've had cranks ground down for about 200$ Why you are there you can knife edge and cross drill and lighten a bit for about 400 more. good stuff for race engines.

I always liked fixing my problems rather than buying someone eles unknown problems and abuse. I tear down every bolt on my rebuilds. That way you know where things are. That is if you have the down time... and or it's the spare engine. Hope things go better for you this round.

I considered sending the crank to Lindsey Racing for their balancing and medium lightenning package, but decided I must save spending that kind of money for another day. I'm going to have the crank out of the "new" engine checked and polished at the machine shop down the road before I use it.

[fast924S]

I built my motor, did about everything you can do without droping serious money, Only things I left out was crank work and serious head work, I bumped CR from 9.5 to 10.2, Race valve job, Port matched everything,. Plus some extras. I love the way the motor runs, I didnt hone the cyl, I was told do this only if you have large scratches in the cyl wall, On these engines its ok not to see cross hatch marks, just a dull gray. You dont need to go to crazy on Performance stuff, The gain is very minimal unless you go crazy. Safe the extra cash and do suspension mods... Trust me

[Rasta Monsta]

Originally Posted by fast924s

safe the extra cash and do suspension mods... Trust me

+10!

[HondaDustR]

Originally Posted by fast924S

I built my motor, did about everything you can do without droping serious money, Only things I left out was crank work and serious head work, I bumped CR from 9.5 to 10.2, Race valve job, Port matched everything,. Plus some extras. I love the way the motor runs, I didnt hone the cyl, I was told do this only if you have large scratches in the cyl wall, On these engines its ok not to see cross hatch marks, just a dull gray. You dont need to go to crazy on Performance stuff, The gain is very minimal unless you go crazy. Safe the extra cash and do suspension mods... Trust me

Did you put new piston rings in the old cylinders?

I did work on the scotchbrite honing today. Overall, I'm happy with the results. I did have a couple scratches in the cylinders deep enough to catch a fingernail. The scotchbrite hone obviously did not remove them, but they no longer catch a fingernail, so...

I also determined it worked best when lubed with mineral oil instead of degreaser. I couldn't tell much of a difference, but the oil honed one looked a little cleaner and more consistent. It also worked best at minimum pressure set on the hone and run at ~120 rpms 80 strokes/min for about 45 seconds. It's also crucial not to extend out of the cylinder too far or the extra pressure of the stones concentrated at the edge will take more off than the middle. It definitely leaves a fine crosshatch surface. One guy on the 911 rebuild forum said he honed his cylinders for new rings with only the scotchbrite pads attatched to a glaze hone and his rings broke in just fine. I found the surface comes out a bit better when honed with the felt and the AN-30 after the scotchbrite. I also found that doing the AN-30 honing as described above twice seemed to smooth out the scotchbrite crosshatch marks a little better than just once. With all that in mind, I did manage to successfully hone all 4 of the cylinders on my good block with my developed method. The surface is a nice smooth matte finish that has kind of a micro-rough fell to it. There are still faint crosshatch marks, but that probably can't hurt and might help.

The scotchbrite hone. I used 2 sewing pins for each one to hold the pads on, same as with the felt.


Here's after 45 sec of honing. There's a little aluminum material in the oil but not much.


Here's the scotchbrite finish. It's very fine and it made kind of a grey rough finish. It would probably work fine, but of course I've got to be all high tech about it.


AN-30 paste and oil ready for felt honing.


Here's what I get after one AN-30 honing run. The crosshatch marks are still detectable, but not as "sharp" looking.


Ok, enough screwing around! Let's get to the point. Here's the cylinders on the good block. they are actually in much better condition than my old one. Fewer scratches and virtually no wear ridge at the top. The old block had a very small one.


I found out that cutting off the leading corner of the felt helps it not to fold under the pads while honing. Be sure the pads are pinned up very tightly around the stones. They will want to spin around the stones and will get all bunched up, or even put the pins onto the cylinder wall if they are not tight. There my be a better way to attach them, but this is what I had for now.


The last cleaning before assembly. It is crucial to clean ALL the AN-30 out of every nook and cranny. There was a bunch that ran down all over the crankcase area. I pretty much did a full cleaning/flushing the oil galleries again just to be sure.


All done and ready for pistons, crank, final assembly, etc. These were all done with 1 45 sec. scotchbrite run and 2 80 sec. AN-30 runs. I just have to set ring gaps and get the crank ready. Hopefully this will break in the rings, actually have 100% compression, and will last a long time again!

[John_AZ]

HondaDustR this is a terrific writeup on honing the cylinders. Your research and explanation is very detailed and complete.

Great work.

John_AZ