Newbie '73T 2.4 MFI Engine Rebuild

[Inkblot]

Figured I'd pull the fuel tank and check it out- wouldn't want a bunch of rusty crud messing with my eventually rebuilt motor. Glad I did!

I thought it'd be a simple job, but the weather stripping-like sealant foam between the trunk and the tank was super nasty to deal with. It had me double- and triple-checking that I had removed all of the hold down clips/bolts, because it really held the tank down! I put a floor jack under the tank to try to break the adhesive grip, and nearly got both front wheels off the ground before seeing any play. Eventually a sacrificial box-cutter blade into the sticky and tar-like adhesive broke it free.

Here's the tank, removed. You can see remaining strips of the adhesive foam. There's no record in the car's history of any work that would require tank removal, so I guess that's the original stuff; it's a goopy mess that won't be fun to clean up.







I spent an hour or so rinsing and flushing w Simple Green. Lots of rusty material came out, so it'll need some work. My plan is to have the tank professionally flushed and coated, assuming no major flaws are revealed.

Here's the fuel outlet "filter". Hard to imagine this working properly- it looks like it must have been restricting the flow in a bad way. I guess that's why Porsche went to the swirl-pot design shortly after this gen...





Glad to check this off the list!

Jake

[Rodney Nelson]

Great thread! Best of luck with your rebuild and note taken on what you show your daughter!

[MAH77]

Jake, any update on where you stand?

[Inkblot]

Thanks for asking- and good timing!

My project has been on hold, as my personal life got a bit messy there for a while. Divorce sucks, in case anyone had any doubts...

Good news is that I moved my project into a new, well-kitted workspace, and I'm just getting set up to dig back in to my rebuild.

Actually, I should say the good news is that I still have a project


Here's a preview:







More to come, soon.

Jake

[Inkblot]

Ok everyone, I'm finally getting back into my rebuild. As I previously mentioned, I'm in a fantastic new shared shop space, with access to some great new tools (blast cabinet, parts washer, big lift, etc.). Better yet, the other folks here are all car-nuts (though not necessarily P-car), which helps keep things fun and motivating.

First step was to unpack everything, and to try to remember where I left off. I still have some parts out for service, as I haven't been lighting a fire to get them done... fortunately, I have this thread to look back on- really helps jog the memory!

So, after getting re-acquainted with my inventory of stuff, and minimally organized, it was time to start prepping my crankcase for assembly- aka clean clean clean.

From earlier in the thread, I'm reminded of how much time I spent trying to clean up the outside surfaces of the mag case. I'm here to say: wasn't worth it at all! My case sat in a garage, in plastic (though not air-tight) for a just over a year, and all that shine is gone. That's magnesium for ya. Take a look below- the left shows before I started polishing (back in Oct 2017), and the right after polishing.




I thought it was looking pretty good, at the time. I gave it a good spay with Gibbs, but it wasn't gonna last...

Here it is from a few days ago:



...definitely still better than where I started, but clearly the time I put into getting it all silvery and shiny was not exactly well spent. I can't say I wasn't warned


Next up: Soda Blasting!


Jake

[Inkblot]

After re-inspecting the case halves, I still wasn't happy with the remaining amount of gasket residue, and little pockets of gunk (inside and out). My new shop space has a big-ass air compressor, so I figure it was a great opportunity to try my hand at soda blasting.

For the uninitiated, soda blasting is like sand blasting, except you use baking soda. The idea is that it's a little less abrasive, less toxic, and most importantly for this application- it dissolves in water. The fear with traditional sand/media blasting is that little bits of the media could get stuck in some of the small oil passageways inside the crankcase, which could lead to big big problems down the road. With soda, the thought is that a good wash after application would remove/dissolve any leftover media.

My original plan was to just farm out the work. But, turns out it's really hard to find a place with a dedicated soda blasting setup. After calling around to some local shops, I learned that there are some clear reasons for this. Soda is a one-time use media, which means you can't recover/recycle it within a traditional blast cabinet as you would with sand/glass, etc. This makes it a lot more expensive; you have to use new media for each job. And, soda is a lot smaller than traditional media, so you have to use a smaller nozzle on your blaster, and probably a different type of adjustable flow-valve. Also, the soda is supposed to "pulverize" when it hits your parts, which makes it really dusty. This can really clog up the filter in a traditional cabinet, which of course can be cleaned, but creates a big PITA for the user.

So, though I have access to a big media blaster, the process of converting it over for soda use (and for only one job, at that), seemed daunting.

I read about a few places that would do the work, but they weren't local, so I figured for the same amount of time, $ and effort I could give it a shot and maybe learn something. So, off to Hazard Fraught I went!






Given that it's "non-toxic" and dissolvable, I figured I could give it a go outside, and cleanup wouldn't be too bad. There are warnings about how soda can discolor plant leaves and grass, so you do have to be a little careful about where you do it.

True to form, my HF blaster was DOA- the media flow-valve was busted:



But, my expectations were low, so another trip back wasn't too much of a bummer. I just made sure to open up the replacement there in the store to check it all out, now that I knew what to look for.


Ok, here's my setup:





Filling up the pot is an annoyingly slow process. You definitely need a funnel, but the pot's opening only allows a funnel with a relatively small neck. It was a lot of fill the funnel, wait for it to drain, fill, wait, repeat...

Once I got it filled and ready to go, I first tried blasting a test part- some random oily thing I had laying around. It worked great! removed all of the oily gunk with no issues.
Now on to the first case half:




I can tell I'm doing *something*, but the progress is not exactly mind-blowing.




Here you can see the completed half (left), next to the remaining one. Again, you can see that a difference was made, but it's a bit underwhelming.




The process itself was really messy. The soda gets on and into everything! I was wearing decent protective gear and coveralls, and I swear I had it in my socks and between my toes by the end of the day. Everything in the side yard where I did the work had a layer of white powder on it.
The HF blaster itself held up pretty well. Again, expectations were low- so I wasn't really disappointed that the filling procedure was a pain, and that the unit would clog and frequently require a good shake to get going again.
I think most surprising to me, being completely inexperienced here, was how much soda I went through. I think this means that I wasn't using the soda efficiently- that my ratio of airflow to media flow wasn't optimal. That said, I had the tank pressure all the way up (and a little past) the recommended max of 90psi, and the big shop compressor has no problems keeping up the CFM. I was also really surprised at how much media was left on the ground and everywhere- so much for the idea of "pulverizing" the soda! There were Medellin-caliber amounts of it left for me to sweep up:




Still, I'm glad I did it. Though the aesthetic results weren't what I had hoped for, I can see that it clearly removed any remaining oily residue, and it leaves a more uniform surface texture on the magnesium. Would I do it again? I dunno... it was messy. Without the fun part of learning something for the first time, I'd have to have a really compelling reason to do it again.


Next up: more case prep.


Jake

[Quinlan]

You’ll want to really rinse off your side yard if there is any vegetation there that you care about. The baking soda is a base which will burn everything if left untouched. Ask me how I know…

[Inkblot]

Yep. I got lucky with the timing, and we had some nice rain to help rinse everything down


Sent from my iPhone using Tapatalk

[Inkblot]

Back in action... was off on a tangent, trying to organize and tailor my shop space more to my needs. Ended up building a welding table, which will also double as a workbench.



It turned out pretty good; you can see my build thread here:

https://forums.pelicanparts.com/porsche-911-technical-forum/1029323-building-welding-table.html

Ok, now back to the motor.

After soda blasting everything and a quick cleanup, I ran the case halves back through the parts washer.




All of the gasket residue was now gone, and the mating surfaces had a uniform look:




... but I decided that the machined, mating surfaces should be as clean as possible before they eventually get sealed up, so I hit them with Scotchbrite pads on the die grinder. I used the green 2" Roloc-style discs, which worked great. For some of the tight areas right around the bases of the studs I used a non-abrasive polishing disc on the Dremel.



One half done; lookin' pretty good!






Polishing the surfaces really helped reveal some of the imperfections, like the pitting here on cyl 1. This was the worst one, but it still looks like there's plenty of contiguous machined surface to get a good seal once the gaskets are in place (...so says I!).




Before and after:



Both sides cleaned up well.




Once I was happy with that, I gave everything another liberal coat of Gibbs, hoping to slow the inevitable oxidation of the magnesium.




Next, checking the oil squirters.


- Jake

[Inkblot]

With the major case cleaning done, I wanted to make sure my oil squirters still looked ok. Part of my reasoning for doing the whole soda-blasting thing was all of the concerns I had read about getting the squirters clogged with blast media, so I wanted to be extra careful.

Some of the squirters have a passageway which feeds them directly from inside the case; these ones are easy, as you can just blast some brake cleaner from the inside and see the spray come out of the squirter. Wayne's book says you should see a nice spray here, not just some bubbling out.

The other squirters share an oil passageway, which makes it kinda tricky to just do the blast test, as you have to somehow block off the shared part of the passage. I couldn't find any rubber tubing (what Wayne's book recommends) that was the perfect size, so I fashioned something quick and dirty to do the trick:




I could orient the split in the tubing away from the squirter feed hole, and jam my makeshift tool in there to block the passageway. I'd then get some compressed air going, which would be blocked my my tool and forced out the squirter. Worked well!




At this point I was using compressed air, instead of an aerosol cleaner, so I couldn't really see any spray misting out of the squirter. But, I could feel a nice strong blast of air, so I figured that was good enough.




I did have a couple of squirters which just didn't feel as clear as the others, so I went back around with some small Mig welding wire, which fit right into them.






All squirters looking good!


Next up, cleaning the crank and rods, and checking tolerances.


- Jake

[Inkblot]

Wayne's book says you can stand the crank up on the flywheel, but that fitting the rods would be easier with a horizontal stand- so I threw one together out of some scrap.

I found that a 2.25" hole saw makes an ideal diameter to match the main bearing journals. I drilled the hole first, then carefully cut through the center to make two uprights.




I was careful to make sure that the 2 uprights were equal height and symmetrical. I sanded everything smooth, especially the inner surfaces of the holes. Seems to fit pretty well:




Added some supports, and there you have it.






- Jake

[Inkblot]

Next step is to inspect and clean everything.








Looking good. Everything was already checked before leaving the machine shop, but still good to verify.

Following the book, I wiped the new rod bearings clean with rubbing alcohol, and pressed them into place.




Here's my first attempt at using the Plastigage, which should show whether the rod-bearing-crank interfaces are within tolerance. I've never used it before, but the concept is simple enough- just squish it into place and see how wide it becomes. Here it is, in place, in its pre-squished state:




It's kinda tricky to get the rod into place, and the rod cap torqued down while keeping the Plastigage in place, aligned and not smeared around. I think this would be much harder without a horizontal crank stand. First one worked good:




Here I'm using the included gauge to check the spec. It's right about .051mm, nicely fitting between the spec'd .03 to .08.




Next I'm checking the gaps between the rods and the crank. After looking up the spec, it wasn't obvious to me if it referred to each side's clearance, or the total gap (the sum of the 2 smaller side gaps). After measuring all of the gaps, it became clear that the spec refers to the total gap, i.e., the sum of each side (with the rod torqued down).

Here's a view with the rod bolts loosened a bit, which allows the rod to shift off center so that I can get a feeler gauge in there to measure the total clearance:




After torquing it down, here you can see the that the side gaps add up nicely to the previous total:






All 6 checked out, so now on to final assembly of the rods.



- Jake

[David Borden]

Really enjoying this thread! Those Rolocs will remove material, hopefully that didn't happen on the sealing surfaces. Maybe some experts will chime in.

[Inkblot]

Really enjoying this thread! Those Rolocs will remove material, hopefully that didn't happen on the sealing surfaces. Maybe some experts will chime in.

@David- Thanks for the feedback! You've got me thinking about the Roloc discs... my understanding was that they really shouldn't be removing any of the base magnesium. Of course, they are removing something- hopefully just the outer layer of oxidation! I can say that I was very careful to use them as evenly and lightly as possible. I can see no visual evidence, like gouging or uneven surface levels, to indicate that there's an issue... but then, maybe I wouldn't be able to?

Any other opinions out there?



- Jake

[ed mayo]

Are you replacing the rod bolts?

[Inkblot]

@Ed Yeah definitely replacing the rod bolts. I used the old ones just to do the Plastigage tests; Wayne's book says that you're really only supposed to torque down the rod bolts once, as they're designed to stretch just the perfect amount. When I'm ready for the final assembly (probably some time next week) I'll use the new hardware.

- Jake

[jim49ers]

my 2.4 is almost done

[Inkblot]

@jim Lookin' good! Your fan looks very clean- what did you do to finish it? Paint or powder? Any "gotchas" you experienced along the rebuild you'd care to share?

Thanks-

Jake

[Neil Harvey]

Originally Posted by Inkblot

@Ed Yeah definitely replacing the rod bolts. I used the old ones just to do the Plastigage tests; Wayne's book says that you're really only supposed to torque down the rod bolts once, as they're designed to stretch just the perfect amount. When I'm ready for the final assembly (probably some time next week) I'll use the new hardware.

- Jake

There are many ways to do something, but I would like to suggest you re think your method here.

When rods are rebuilt/"resized" the fasteners the engine is going to run with have to be used in the resizing operation. The free length should be recorded, then stretched. To be sure you have not gone past their yield length, they can be loosened and remeasured. As long as they go back to their original free length you are Ok. Factory spec's will not over stretch them.

They (BE) should be measured then (after honing when cold), disassembled and cleaned. The same stretch should be done when using your method of checking the bearing ID size. Changing fasteners more often than not, changes the bore size.

Not sure why its said you can stretch these bolts only once? Too much fear is placed into the minds of many about rod bolts.

[Trackrash]

Neil. Good advice. I think the "gotchya" here is the fact that you will need to know the length when the bolts are new and unused. So old bolts coming out of a motor are an unknown. But when using new bolts it doesn't make sense to only allow one torquing as you mention.

Also good advice on using new bolts to measure the big ends. I had, on my recent build, one BE that measured at the limit of spec. I put in new bolts and it measured perfect.