72 3.0 CS 2240344 Restoration

rsporsche said:
Scott, I presume that you have already revised the intake to comply with the porting Don would have done on the head of your new m90. the beauty of 3d printing is the ability to 'tune' the trumpet to match the head to avoid turbulence / eddies in the air flow. the more precise of a match the better the flow.
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Yeah, I did the original design to the B30 head, so I’ll need to modify it for the M90’s wider and flatter shape. Was waiting until I got the engine, so I can measure it carefully. And yes, being able to iterate quickly and cheaply is wonderful. Unfortunately the intake area is pretty constrained, so not too many options on trumpet length when using an air filter. After some research I settled on a simple bell mouth design. Apparently other tapered trumpets don’t work well because they do too good of a job matching the acoustic impedance, so you lose the reflected wave. So you want a low turbulence inlet but not a smooth or exponential taper to the trumpet
 
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Flywheel Question:

The M90 engine I just got has no flywheel. Can I use any M30 flywheel (like the one on my 3.0 engine, or do I need something different?

I looked at lightweight flywheels, but while these do allow faster spin up, they also apparently negatively affect drivability and shifting.
 
OK, so here are some pics of the rear passenger side rocker with all of the really bad stuff removed. Obviously needs more cleanup, but all of this is solid. I think I'll try my borescope to see what lies forward of the B-pillar. Might be better to just clean and treat is as opposed to cutting into what appears to be good metal...
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I am a fan of using chemicals to etch and clean the metal and then convert the rust in areas where you have good structural integrity. There might be areas here that I would consider hitting with a small spot sandblaster to get into the seams where possible and then find a way to keep the etch product in contact and flowing in and around those overlapping metal joints.

I have used KBS Rust blast in the past, but will admit that I do as much prep on the metal as I can, then use it liberally.
 
boonies said:
I am a fan of using chemicals to etch and clean the metal and then convert the rust in areas where you have good structural integrity. There might be areas here that I would consider hitting with a small spot sandblaster to get into the seams where possible and then find a way to keep the etch product in contact and flowing in and around those overlapping metal joints.

I have used KBS Rust blast in the past, but will admit that I do as much prep on the metal as I can, then use it liberally.
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Yeah, that's my plan. Not super sure about blasting, but I may go there. definitely treating and then painting it. The surface rust basically goes only about as high as the main horizontal cut.
 
I do see spots where the rust has started to eat into the steel, and created these shallow pits. Especially noticeable on the lower B-pillar reinforcement.
I'd have it sandblasted, as it'll be difficult to get the rust out of it with steel wire brushes alone.

Íf you don't go the mechanical route (sandblasting), then do opt for the chemical route: etching Epoxies convert the rust into FEO4, turns a darker shade. When the rust is really bad, I sometimes grind out the dark spots where the etch finds rust, and reapply until the etch doesn't turn dark anymore - a sign the rust is gone. Everything that remains that isn't visible with he naked eye is hopefully covered by the chemicals. then paint it over.

While you're in there - I'd route the rubber tube out into the wheel well. Just drill a hole, find a rubber donut grommet, and push it through.
 
eriknetherlands said:
I do see spots where the rust has started to eat into the steel, and created these shallow pits. Especially noticeable on the lower B-pillar reinforcement.
I'd have it sandblasted, as it'll be difficult to get the rust out of it with steel wire brushes alone.

Íf you don't go the mechanical route (sandblasting), then do opt for the chemical route: etching Epoxies convert the rust into FEO4, turns a darker shade. When the rust is really bad, I sometimes grind out the dark spots where the etch finds rust, and reapply until the etch doesn't turn dark anymore - a sign the rust is gone. Everything that remains that isn't visible with he naked eye is hopefully covered by the chemicals. then paint it over.

While you're in there - I'd route the rubber tube out into the wheel well. Just drill a hole, find a rubber donut grommet, and push it through.
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Yes, exactly what I was planning to do.. I am also going to open up the rocker covering forward step by step until I either run out of rust, or run out of rocker cover. At a minimum, that will allow me to treat any minor rust I can't get to, and paint the entire inside of the rocker assembly.

One question that has been bothering me. To paint the inside, I will then have painted surfaces that I need to weld, and removing the paint there and welding will then expose those areas to rusting again. How did you deal with that issue? For the spot welds I was going to drill holes in the outer pieces and then mark the locations of the holes and remove paint at those spots, but for the seam welds that isn't really possible. Souldl I leave some openings where I can wand paint the inside and then somehow plug those holes? Wondering if maybe I should leave a hole in the inside of the rocker cover, under the rear side windows, and another under the door sill trim. Then I can access those areas in the future for cavity waxing, an plug them with rubber plugs... thoughts on that?

One other question about the rear wheel arch area. In the pic below, at the lowest end of the arch, there seems to be a ragged bit of metal. It seems like the arch ends prior to that, but then there is a small tag of thin metal at the very end. It seems like that is part of the arch, but then the place where the heavier metal of the arch actually ends is very strong and the edge is abrupt. So I am wondering if that is a remnant of the rocker cover, or a rusted bit of wheel arch, or something else...

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Looking at Walloth photos, it looks like there is a small tab on the bottom of the arch. This extra tab I appears to be visible in the pics above (green lines - dashed line is the fold), attached to the intermediate rocker beam and the C pillar.. So, any idea what this little tag belongs to?

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To answer your questions: indeed welding after painting will burn of the paint and leave a bare open spot, with flaky remnents of charred paint. Weldspots are even the first rusting point, as heated metal (when it turns blue on solidification) is a steel type that rusts faster vs the virgin steel around it. So yes, a valid question.

I opted, and bought, a spotwelder exactly for that reason. spotwelds can be made through weldprimer and the weldprimer seals the weld as a small circle around it, having a high zinc conctent. Some spotweld primers even carry bitumen (EuroPAX - I love that stuff.) that doesn't burn off.

You'll be happy to learn that you can reach the entire sill from the inside passenger compartment. Look at the inner sill, and you'll find a 5 or 6 (i think) 20 mm round openings that will allow you to inject the sills with your favorite paint or wax after you weld everything up.
One route would be to paint everything that you intend to sandwich. Then clean comfortably around weld locations to have clean, fresh steel. Then weld away. Next tape up the drain holes of the sill. Pour in 3 gallons of paint, let it sit for 10 minutes, possibly holding something that vibrates to it to shake the bubbles out (belt sander?). Then remove the tape and catch 2,5 of the 3 gallons that you poured into the sills.

Mind you, the sills have a funny construction with the middle sill not reaching down into the bottom: the leading bottom edge is just the inner and outer sill. The intermediate sill is (originally) spotwelded to the outer sill ; but that seam is about an inch higher up vs the leading bottom edge. It's a rust strap as water from the rear glass will follow the inside of the outerskin, and firstly encouter that seam. That is why i choose to pour in a lot of paint, to also rise above, and fully flood (capilliary) that seam. Let me dig up some pics. Also @nosmonkey has some pics up in his resto thread, though Ahmet (like me) also replaced full sill panels.

second question about the flange hghlighted in red. I'll have to look at my pics. I was quite anal to get those details right, an in my car not a lot was recognisable.
 
I keep these NOS panel pics as reference, i pull them of adds.
Here you can just make out the tab (bottom right, pointing almost horizontal to the left) that you have encircled in red :
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Though I honestly think i left that bit out, to create a nicer (my opinion :-) ) water drain: here are the parts in place prior to welding:
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some pics that maybe of assistance to make sense of the brown lump you might be looking at. Your approach will be different as i took my car apart to almost every loose panel. but the pics show the approach of welding clean steel, and then painting after all welding is done.

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Here's also a suggestion to reinforce the jack pick up point:
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In this pic you can see that i partially painted the inner sill piece, keeping the area clean for (spot) welding.

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with EuroPax weldprimer:

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also on the sill side:

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structural glue to the inner sill to outersill connection (to avoid the welding and associated burning of paint)
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and spotwelded in place:
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USed materials:
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eriknetherlands said:
some pics that maybe of assistance to make sense of the brown lump you might be looking at. Your approach will be different as i took my car apart to almost every loose panel. but the pics show the approach of welding clean steel, and then painting after all welding is done.

View attachment 213778
Here's also a suggestion to reinforce the jack pick up point: View attachment 213777View attachment 213779

In this pic you can see that i partially painted the inner sill piece, keeping the area clean for (spot) welding.

View attachment 213780
with EuroPax weldprimer:

View attachment 213781


also on the sill side:

View attachment 213782

structural glue to the inner sill to outersill connection (to avoid the welding and associated burning of paint)
View attachment 213783

and spotwelded in place:
View attachment 213785

USed materials:
View attachment 213784
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WOW!! Thanks for the super detailed reply!! I'll study this closely.

So the structural adhesive you used was to replace those spot welds between the center beam and the rocker cover, right? I recall there being about 5-6 of them located where the rocker cover contacts the risked portion of the central rocker beam (the "zig zag beam" as I call it) Interesting approach..

I had thought about filling and then draining the entire rocker.. good idea...

I see what you were talking about leaving off that little tab. Seems to serve no purpose other than trapping water so it can rust. :cool:
 
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e9Leveque said:
You going to weld in some more jack points while you’re already there?
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Yeah, I think I will I was rather surprised to find that the rear jack point was not attached to the inner structure. It basically is welded to the bottom of the quarter panel, and gets welded through some holes to the rocker cover, but there is no structure above it to spread the jacking load to the center rocker beam, which is the strongest of the set.

I was convinced I would have to grind the whole thing off, but then it just fell out once I detached the spot welds..
 
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OK, so I spent several hours removing the entire outer rocker cover on the passenger side. I ended up doing this after probing up there with my borescope. It was a mess. Lots of surface rust and crud. I figured it was better to just replace it than leave a bunch of rust residue in there. All that will do is trap water (even if it is painted) and start the rust process over again. This way I can clean everything, paint everything and then prep it all for welding, and then paint it again using @eriknetherlands fill-and-drain approach.

What I found was that the lower edge of the rocker cover, and the lower edge of the intermediate rocker were rusty enough to have shed a bunch of crud into the crevice where they come together. The A-pillar is cleaner than the B- Pillar, but the lower section if that is also fairly rusty, but solid. Tomorrow I'll slice off the lower few inches of the front side covering to expose the front of the A-pillar, so I can clean everything. I'll probably set up a blaster and sand blast what I can just to be sure I have all of the rust out. That should go pretty quickly and not be too messy.

I already have the right side outer rocker, and the right and left rear quarter patch panels. So today I ordered the left side outer rocker, the two front patch panels and the front jacking cups.

I like Erik's jack point reinforcement, so I'll probably work out how to fab that and install it before putting the outer rocker back on.

I have taken my time on this, since I was sort of exploring as I went. I plan to also do the other side, even though there is less rust. Might as well get rid of all of it!! I'm sure that will go much faster now that I better understand how it goes together, and where the various welds are.

Looks like Eastwood has an interesting jig that allows you to create resistance style spot welds using a MIG welder, so I may try that. If I don't like it, I'll just buy an electric spot welder. Those seem pretty inexpensive these days!

Pics tomorrow..
 
bluecoupe30! said:
Well along the slippery slope, but I applaud your reasoned approach to correct amelioration of existing rot. Always more than we want to see, but you have been getting great advice and I am sure you can bring these corroded areas back to spec. ;)
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Yeah. I considered that slipperiness today as I decided to slip.. So far (other than at the back, which was a $hitshow) the rust has been localized to about 1/3 of the way up the inside of the outer rocker, and primarily heavy surface rust.. so not structural, and probably could be left alone...for a while anyway.... The reasons for opening it up is really to assure that I get the existing rust out, and/or treated. I would hate to paint over crumbly rust chards, as that is just re-inviting the tin worm back into the buffet.

I am pretty confident that I can address all of this with cuts below the rocker trim-line, so while it seems moderately extreme, it is easily repaired without bodywork heroics..
 
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