Just tore down a mileage-unknown 12A that I’ve been sitting on for several years. Have a primo ‘84, inside and out, that needs an engine, so I’ve been hoping to rebuild this one.

At first cursory look, most components look to be in very good condition. The rear iron is shot and one rotor housing is missing a chunk of chrome surface. And that’s where my question lies. At the bottom of the attached picture you will see the extent of the chrome damage, a .004” deep, 2.5mm wide x 25mm long blemish along one edge of the housing. Thoughts on reusing this housing, assuming it has no other issues?

Thanks!

 

I had a GSL-SE rotor housing with a chunk like that, went something like 55k miles on it before I had to pull it apart for other reasons.

In 2023 that is as good as you will ever find, run it!

I'd take a fine round file and go around the whole rotor housing and bevel the chrome surface, just enough to break the sharp edge. This seems to help prevent flaking, keeps the side housings from fretting the chrome away. Clean the threads in the front end housing with a 10x1.0 thread chaser (not a tap) and torque the tension bolts to the low end of spec. I torque all of my engines to 23-25ft-lb.

If you still run the MOP, add 1oz/gallon premix to maximize life on these hard to find parts. If no MOP, premix 2oz/gallon.

 

that part ....

yes, run it and do your best to keep it happy for the rest of your time with it.

 

Thanks for the feedback, peejay. All good info and along the lines of what I was thinking, especially, needing to ease the rough edge of the gouge.

When disassembling, I was super happy that the rear housing was nearly perfect, then initially thought the same of the front, until I spotted the flaw. Still, overall, it does look better than any I’ve run across for sale, recently. Will reuse them.

Now, any ideas for sourcing good irons?

TY!

 

When you put it together, I would put the longer part of the 2 piece apex seal there, to keep the little piece from catching the chip.
that chip doesn't look like it is in the upper compression area of the rotor, so it will probably still make good compression.

 

+1, if its an 81-85 US engine, the easy way to do that is put the front rotor housing in the rear and vice versa

 

Irons/side housings is fairly easy, you can send them to Chip's in Warren to have them resurfaced and rehardened. The stock 12A in my '81 and the bridge port 13B in my '84 have Chip's-resurfaced units and I am pretty happy with them.

Note that this process is somewhat "traumatic" because of the heat and cleaning involved, all of the plugs and dowel pins have to be removed, and he taps the front's oil plug passages to take threaded plugs. It will not look stock again.
If you have a set of '82-85 side housings he also has to remove the press in water pipe for the heater/oil cooler hose(s) and these can be tricky to reinsert securely.
if you want to go this route and don't want to use what you already have, and don't mind a little drive, you can come down to my place and pick a set of my 12A collection for $free-fitty. I have more than I will ever use and they all need to be resurfaced.

 

As a matter of fact, I was looking at Chip’s site this evening because I am regularly in Warren and could just drop off my parts. Was thinking they were quite expensive when I’ve checked them out previously, but comparatively, they seem to be on par with others.

Thanks for the offer on parts. My worst surface of all four is the rear which has a step of about .003”. Front is near perfect and center is better than the rear, so I'd just resurface the ones that I have. Might be up for a drive if I ever get this thing up and running some year…

 

Sounds like a good plan, thanks!

 

Can you explain why swapping the housing positions helps? I thought about it a little, but haven’t figured it out and am too lazy at the moment to try harder, TBH. 😏

 

It doesn't unless you flip the apex seals around backwards. But given that the missing chunk is on the side that normally sees the long piece, it should not matter anyway

 

I don't like to speak negatively about anyone, but for me the jury is still out concerning Chips. I drove 8 hrs out to him the beginning of May to drop off a 12A and 2 spare housings for a complete rebuild. I explained at that time, that I wanted to install a flywheel off an 81 and also gave him an 81 front counterweight but did not bring the flywheel. (the engine was out of an 80) His shop looked impressive and he had several projects and parts in various states. I contacted him before coming but he neglected to tell me he required $2,800 up front, before starting, so I left my engine and PayPal'd the funds when I returned home. He told me, it would be 3 months.

In Sept, I inquired on progress and was told he had been away for 6 weeks on a family emergency. I brought up the 81 counterweight and flywheel again as a reminder and he seemed to not remember anything about it. He told me he needed the flywheel to be able to balance the engine. I also asked if he needed the front pulley and bolt too, since it was not with the engine when I dropped it off. I mailed that stuff off on Sept 20th and was told it would be another 2 weeks. So after another month, its been 5 1/2 months total and $2,800 dollars later and I'm still waiting.

I think I'll get it eventually and I'm not questioning his ability or work, but this not a good way to gain a customers confidence. Especially one that owns eight SA's (including my 1st one, bought new) and might bring more business in the future. My money spends just fine. I'd like to be treated like I have some value.

 

Well, that’s not a good story. Appreciate the heads-up. Good to know what I might be in for, if I were to go that route. Hope they get you sorted out, soon.

Another source I had looked at is Kyle Mohan Racing, in Cali, but I’d rather work with someone local.

 

Because of the nature of large scale work in a small business, he does things in batches. I used to work with a machine shop and some equipment takes so much time/money to set up, that we would batch things. We would only run the parts washer every two or three weeks, for example, because the parts washer had 250 gallons of cleaner solution that needed to be brought up to about 200F. This would be very expensive to be kept hot all the time, especially in the winter months, so blocks and heads and stuff would accumulate until we had enough to take up an entire day of cleaning. Which was my job.... kicking the door latch open and wading into lye steam with a pressure washer to rinse the parts off is a great way to get your blood flowing But a lot of processes are like that. You run things through in batches because the real time killer is the setup work, if you can do two or three or five of the same thing in a row, you can do more work overall. Maybe I was lucky and I dropped my stuff off right before he was ready to run a batch of side housings, they were done way before I expected them.

OTOH, having worked in a performance machine shop about the size of his operation, I was kinda expecting things to take about six months, not two weeks or so!