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Author Topic: '91 Capri XR-2 Resto-Mod  (Read 10150 times)

EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #30 on: February 28, 2021, 09:44:46 AM »

Thanks for the info on the crank issue Rocket. After reading up on that, running back and forth and looking at my crank, then reading up on the loctite fix.....well I've had a stressful morning hahaha. I'm pretty sure I've got the short nose crank here, but I need to go out to the garage and get my calipers before I'm positive. I found a detailed guide on the loctite fix that the article you linked mentioned, and it doesn't really seem all that bad. It's just a bit scary that Mazda let such a bad design flaw get through R&D like this. I don't think my keyway looks worn out at all, but until I measure it I don't know for sure how bad this situation may really be.

I'll be editing this post later with some pictures and more information. Thanks for making me aware of this problem. I'd be incredibly upset if I didn't find out about this until it was all back together.

And GreyWolf, thanks man. I figured with the service manual, anyone should be able to follow instructions and take apart/put together their engine. I'm trying to show the things they don't mention in there, that'll give you a better chance of success.

Also, does anyone know if I should pack the oil pump with vaseline, or use assembly lube on the gear set? I've done the vaseline trick with a couple older small block Chevy's, and I like the peace of mind it gives. Would the same principles apply to priming the oiling system on these cars? Or is it better to just disable fuel and spark, and spin these engines over with the starter in order to build oil pressure before first start up?

EDIT:
-------

Well, damnit. I had a feeling, and this confirms it. I have the problem child. So it looks like I need to track down a new woodruff key, crank pulley, crank bolt, and some loctite 660. Lovely. That loctite 660 is extremely expensive, too. Looks like tiny 5oz tubes are going on Amazon for about $30. Is this something that absolutely needs to be addressed? Or is it something where if I'm extremely careful torquing the crank pulley bolt down, it may never be a problem? Damn it..... I guess either way I'll probably end up doing the fix. For anyone who finds this in the future, here is the guide I found:
https://www.miata.net/garage/hsue/Loctite%20Crank%20Fix%20-%20Part%201.htm

So I put the nose of the crank back together, not torqued or anything, just kind of placed the parts where they should go. I don't see any wear or signs of slop on anything. Do I necessarily HAVE to replace these parts? For example, do I NEED the OEM Mazda crank bolt (Part# 630-11-406C)? Is it the larger one, and does it require the higher torque setting? Or can I just clean up these parts I already have, and simply apply the Loctite 660 to the woodruff key and the gear? That bolt alone is $30 too, so I'll be spending probably $200ish to fix this correctly if I follow that guide I linked (Depending on price of harmonic balancer and gear).


ANOTHER EDIT:
------------------
Alright, I've done some more reading. Looks like my tentative plan is to replace that crank bolt and woodruff key with new OEM parts, then use the Loctite 660 stuff on it when I reassemble. Should only cost me around $60 or so, and it seems like the best way to go about fixing the issue for my goals with this car. Just a bit annoyed that now the crankshaft bolt is going to have to be a maintenance item. If this engine ever comes apart again for more serious modifications, I'll be going into that project knowing I need to replace the crankshaft, front covers, and oil pump.

I know the Loctite 660 is supposed to be used on the keyway and the back of the gear. I'd imagine that stuff is crazy strong, and NOT what I'm supposed to use on the threads in the nose of the crank that the pulley bolt goes into, correct? What should I use there? Red? Blue?
« Last Edit: February 28, 2021, 01:54:34 PM by EShepherd »
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Rocketman

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Re: '91 Capri XR-2 Resto-Mod
« Reply #31 on: February 28, 2021, 06:47:40 PM »

The Loctite fix is ONLY for a worn out keyway. Instead of welding new metal in & re-machining the keyway to fit the "fix" was to fill in the gouged out area with loctite. Hence the expensive specialty loctite. I don't recall seeing a worn out keyway on your crankshaft.
You can re-use the stock bolt & key if they are in good shape, just be sure to torque it properly when you re-install it. For extra security you could use the removable loctite on the crank bolt threads, don't use the permanent stuff.

There was an issue with crankshaft snouts shearing off clean. Time has tended to weed out the problem crankshafts, if yours has survived it's probably fine for another 30 years.

Regarding the oil pump priming: Maybe throw a little engine oil in the pump when you assemble it, but you will be fine to disable fuel/spark and crank to build pressure. The stock oil gauges suck, don't go by it.
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #32 on: February 28, 2021, 07:50:53 PM »

I read about the Vaseline trick after I had it all together but not started yet, it had me worried but I cranked it with no fuel/spark and i could see the oil pressure rise quite quickly while cranking it over. I broke the lower timing pully getting it off so needed replacing and a bloke on the ford laser forum advised me to put a new key and bolt too, they don't cost much and are easy to get, I think the crank bolt is a torque to yeal strech bolt
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #33 on: February 28, 2021, 07:54:21 PM »

Also check your timing mark on the v pully, if the key way is at 12 o clock the mark should be around ten past 12, mine had spun and was 180 deg off, I replaced it with a good one but I wish I had found it before it all went back together
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EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #34 on: February 28, 2021, 08:43:29 PM »

Thanks for the advice, both of you guys. I really appreciate it. I think I'll go ahead and replace the bolt and keyway, then just be careful with the torque. Maybe some blue Locktite on the crank pulley bolt. I'll be sure to look at that v-belt gear next time I'm out in the garage and make sure I don't run into that same issue. Seriously, thanks a ton. That eases a lot of the anxiety I was feeling.

Anyways, I got a bit more work done today. Started off by finishing off most of the cleaning on the parts I need ready to reassemble the bottom end. The oil pan bolts had a bunch of old RTV stuck in the threads, so that had to go. The engine was disgusting when I pulled it out, and a leaky oil pan is just sloppy workmanship. I still need to figure out how to clean all the silly crevices in the oil pan, then get that masked off and painted. I took the piston and spring out of the oil pump, cleaned out the bore and parts with brake clean, hit it with compressed air, coated it in assembly lube, and put it back together with a new cotter pin. Just like the service manual says. Finally, a use for the box of cotter pins I bought at Harbor Freight months ago.  ::)





« Last Edit: March 01, 2021, 10:39:25 AM by EShepherd »
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #35 on: February 28, 2021, 09:09:29 PM »

Are they new gears for the oil pump? I didn't touch mine just cleaned it and put it back on, I'm a bit worried about it as most of the  high horsepower miata builds I've watched, they upgrade the oil pump for a boundary pump with billet gears. I heard the stock pumps gears let go under high power. Any one know anything about the pumps and what kind of power they are good till?
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EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #36 on: February 28, 2021, 09:21:48 PM »

I just reused my old gears, after cleaning and oiling them. You can absolutely find pictures and stories of higher power Miata engines shattering those oil pump gears. If you read through Rocket's posts on the second or third page of this thread, he talks about it and provides a link. You can find billet gears, and you'll apparently want to upgrade the crank pulley as well. At my power goals, I shouldn't run into problems. With the power you are making, that's definitely something you should look into. It's not going to be cheap, though. Flyin' Miata has the damper and billet gears, each for around $600. Maybe there are better deals on your side of the planet.

I've got a few extra pictures. I'm FINALLY about to start putting stuff together, instead of taking it apart. I opened the first new parts for this thing today. My next steps are going to be rebuilding the oil pump with new gaskets and seal, and then installing the rear main seal. Once this is done, it's just a matter of cleaning the crank and the block (or having them cleaned for me). It's great to finally be on assembly.

Looks like new intake and exhaust manifold gaskets, oil pan and valve cover gaskets, and the new head gasket.


The rear main, a bunch of oil seals, all the paper gaskets, some valve stem seals, and more oil seals and misc. stuff. Almost none of it is labeled, so this will be fun to figure out.


And here is how I left my workbench waiting for me. So, so excited to start putting it all back together finally.
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #37 on: February 28, 2021, 09:41:04 PM »

I don't think the flyin miat damper is for the short nose crank, I could be mistaken though. I'll look back over your thread I'm interested about the oil pump
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #38 on: March 01, 2021, 12:08:59 AM »

Found it, cheers for pointing me to that I must have skimmed over that bit when I read your build.  I'm gonna need to get one, I wanna hit at least 402hp 3 times factory power. And I've sunk heaps of cash into it already I will be shattered if the gears shatter! There's no way I can afford to build it again any time soon.
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EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #39 on: March 01, 2021, 10:37:57 AM »

Yeah, the oil pump and harmonic balancer are definitely something you should look into upgrading, then. I know on Flyin' Miata, their stage 2 (god I hate than nomenclature) oil pump will fit on the short nose cranks, so if you also have that issue that should work for you. I don't know if their upgraded crank pulley will fit, though. The pulleys on the two cranks look different, I'm not sure if they are the same sizes or not. You might have some decent luck finding those parts used, if you look hard enough. If you don't mind shipping from the State's, I know a guy who runs a business selling used Miata parts. I'll get his information if that's something you'd be interested in.

Of course, those oil pump gears aren't super complicated, either. If you know anyone who works in a shop with a CNC machine, all you'd have to do is buy a lump of some nice billet steel, and bring them that and the gears you already have. Shouldn't be too hard to get them made, and I'd bet its far cheaper than buying that $600 oil pump.
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greywolf27030

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Re: '91 Capri XR-2 Resto-Mod
« Reply #40 on: March 01, 2021, 12:03:08 PM »

The Flyin Miata gears are thicker and require milling the pump body. They supply the body for the long nose crank, but you have to provide yours for the short nose to me milled out.
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Jack Byrd

EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #41 on: March 01, 2021, 08:42:32 PM »

Ah, I wasn't aware that there was a depth difference between the pumps. That'll be good to know in the future if I end up going that way with the engine some day,

Good news. I just spoke with the gentleman who runs the machine shop that Rocket recommended to me. His pricing is absolutely fair. I'm going to call him back tomorrow to confirm and set everything up, but I should be getting my machine work done this weekend. I'm planning on having the block cleaned and ball honed, and the crank polished. I may end up getting the block decked as well, and if he thinks I need it (and I can talk my wife into the extra bill lol) I'll get the mains line honed/align bored too. My hope is to drive up there either this coming Friday or Saturday, drop the parts off with him, then hang out at a hotel in the area until Sunday. If all it needs is cleaned/honed/polished, that should absolutely be doable. Then all I'll need to do is paint the block, and put the whole bottom end back together,

In other good news, I ordered a few more things for the build today, which should be showing up over the next several days, I've got a nice Mobile1 oil filter coming, some blue Loctite, spray on gasket-tack (LOVE this stuff), gray RTV, and a couple cans of engine paint. I went with VHT, a light gray/aluminum color. Hopefully it'll give me a nice, clean, almost factory look. I plan on doing the engine bay itself in satin black, and the car is going to be a metallic gunmetal color. That's the plan as of right now, at least.

Today, all I really accomplished was cleaning the oil pan. I didn't have much time to work. I've still got to mask off the pan so that it is ready for paint, and I've still got to put my oil pump together. Other than that, I've just gotta clean and wrap the crank so that it's ready for it's trip to Pennsylvania, and give the block the same treatment. Really, not too much left before we start seeing some real progress here. Once the bottom end is all together, that's when the real fun will start. I have big plans for that cylinder head...  ;D


Quick question for you guys. I've actually never taken an engine to a machine shop to get properly cleaned before. Should I pull out the freeze plugs before I bring it to him? If so, are replacement ones a universal deal, or will I need to find freeze plugs specific to this engine? That is, assuming I can't reuse the ones in there currently. I've never had to remove or install them before.
« Last Edit: March 01, 2021, 08:44:37 PM by EShepherd »
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Rocketman

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Re: '91 Capri XR-2 Resto-Mod
« Reply #42 on: March 01, 2021, 08:58:14 PM »

AFAIK freeze plugs are standard sizes, I think you'll need to get a measurement on them to order new ones. Call the guy and ask him if it's necessary to remove them, you shouldn't have to.

They will be destroyed during the removal process. You puncture them to get a grip on them to pull it out.
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #43 on: March 02, 2021, 01:01:32 AM »

The plugs are only a buck or 2 each I'd do them, it's a pain in the ass trying to do them in the car if thay leak after, I'll have a look when I get home for you I think they are 25mm and 35mm, the new ones on my motor are stamped ill check the size for u
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greywolf27030

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Re: '91 Capri XR-2 Resto-Mod
« Reply #44 on: March 02, 2021, 08:20:18 AM »

I'll have to disagree with Rocketman on freeze plugs. They are cheap and it is much easier to get your block really clean with them removed. Your machinist should be able to replace them for you because it does have to be done correctly to prevent future leaks.
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Jack Byrd
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