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Author Topic: '91 Capri XR-2 Resto-Mod  (Read 52849 times)

Aus Capri

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    • 1989 Capri Turbo
Re: '91 Capri XR-2 Resto-Mod
« Reply #60 on: March 07, 2021, 09:09:42 AM »

Any idea on how much you can get the double springs for? Or any cheap alternatives we could use? I remember reading something about volvo springs. Any idea how high the rpm can go on the stock springs? Sorry for all the questions.

 I bet your gonna need sunglass to look at those ports when there done 😎
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EShepherd

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    • 1991 Capri XR2, 1991 Capri XR2 Rusted out Shell
Re: '91 Capri XR-2 Resto-Mod
« Reply #61 on: March 07, 2021, 11:52:44 AM »

I'd expect in the $300-$600 range (USD) for a set of decent double valve springs for these. At least, new. I haven't looked around too hard yet, but I'm pretty sure that's around what I spent on the Miata I built several years ago now. I think with the factory valvetrain, a safe red-line is in the neighborhood of 7200 RPM's. At least, that's what Rocket says his chip can supply adequate fueling for. If you had a bigger pump and injectors, you'd probably be able to push it a little higher before you start running into valve float issues.

And thanks. I finished up the ends of the intake runners with the 400 grit rolls last night. It's definitely starting to look good in there. The only tricky thing is that my Dremel is too short to do the whole runner. I've gotta do the whole thing in stages. The ends of the intake ports, then through the bowls where the valves sit. Then the ends of the exhaust ports, and then through their bowls. It's annoying and tedious, but it's the only way I've got that'll work. I'm going to have to be extremely careful going in through the combustion chamber side, too. I REALLLLLLLY don't want to mess up any of the valve seats. I don't want to see the bill to get those re-cut. So, I'm sticking with the ends of the ports for now, and saving the difficult bit for last.

I ordered some wet/dry paper and some flap discs for the Dremel last night, to use on the combustion chambers. That's going to be fun. I think the paper goes up to 5000 grit, so those guys are going to be extra shiny. I've got my new bench grinder set up too, and it's beautiful. Tragically, I ordered the wrong brass wire wheel. I've got the correct one ordered, but it'll be a few days. I can't clean off the valves until that gets in. That'll be one of the last steps though. I've got to finish porting and polishing the ports, and I've got to polish the combustion chamber, before I can clean the valves and lap them in. This is a painfully slow process, but the results will (hopefully) be well worth the effort.
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EShepherd

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    • 1991 Capri XR2, 1991 Capri XR2 Rusted out Shell
Re: '91 Capri XR-2 Resto-Mod
« Reply #62 on: March 08, 2021, 09:35:11 AM »

Good morning everyone! I've got a status update for you guys this morning. So, as I stated previously, I've broken the head work up into 5 sections, due to the dimensions of the part and my tools. First, I started with the exits of the intake ports, then the same on the exhaust side. Then I'll go through the combustion chambers to get the intake bowls, then the exhaust bowls. Lastly, I'll do the combustion chambers themselves. After that will come lapping in the valves. Well, I finished with the easy parts last night. Both the intake and exhaust ports are done from the sides of the head, as far into the throats as my Dremel will reach. I'm now trying to mentally prepare myself for the struggle of working in the bowls, without touching the valve seats. It's not going to be fun, it never is. Hopefully, all goes well.

Picture time! First, lets take a look at the new tools that I got for this. Well, okay listen. I didn't buy the bench grinder just for this job. I've been meaning to put one on this workbench since I built it, (which was just in December. I made it for for my son, to give to him when he is older.) I just never got around to actually buying one. Well, it's here now, and it runs very smoothly. Unfortunately, I got the wrong brass wheel. The new one should be here sometime this week, hopefully. I don't need it until I'm ready to clean the valves. In fact, I think I could probably clean a ton of parts with it. Should be quite a time saver.




So next up are a couple of pictures of what I've been trying to explain. I've got to go through the valve opening on the deck of the head, with the Dremel, to smooth out the rough cast between the seat and the areas I've already done at the ends of the ports. I taped off the deck surface and have the head gasket secured with 4 head bolts, just in an attempt to keep the mating surface unmolested. I tried to do the same with the exhaust and intake manifold flanges, but I could not for the life of me get the painter's tape to stick.





Here's some shots of the ends of the intake ports, as they sit now. I used 80, 120, 240, 360, 480, and then 600 grit cartridge rolls to achieve this finish. I'm still hunting for some type of buffing wheel attachments for the Dremel to give them an even nicer finish. I'm perfectly content with how they look now, though. I could always go over it all with cotton bits and polishing compound. We'll see how I'm feeling once the rest of the work is done.





Lastly, here's the exhaust side before and after. I did the same thing here as I did on the other side. I put more effort into getting rid of the casting lines on this side, and on the whole did a little more shaping. I still want to work on knife-edging the dividers a bit more, but I'm pleased with my results here. These ports were in terrible shape when I started on them.



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Rocketman

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Re: '91 Capri XR-2 Resto-Mod
« Reply #63 on: March 09, 2021, 03:45:45 AM »

Looking real good. It has been a while since I've gone over a head to clean up the ports like that.

I would highly recommend looking into an flex extension for your dremel - I'm sure you've seen them. It drives a cable and gives you a little pencil tip that has much more reach into tight spaces.
Harbor Freight also sells a very inexpensive 3" bench grinder with that same attachment on it, I feel with a bit more oomph than the dremel, albeit at lower speeds. Use a coupon and you can get it super cheap. https://www.harborfreight.com/bench-grinder-with-flex-shaft-43533.html

If you're willing to shell out the dough, look into a Foredom unit, they have a foot pedal control and a 1/3hp motor that hangs over the bench, they are the choice tool for jewelry makers and I'm told expert port/polish guys use these as well.

The ports on these Mazda motors are really quite nice compared to many other manufacturers (of the same vintage), yes they're not perfect but they did a very reasonable job

All that said you're doing a brilliant job, it's refreshing to see someone taking the time to give one of these motors some love.
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


greywolf27030

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Re: '91 Capri XR-2 Resto-Mod
« Reply #64 on: March 09, 2021, 08:07:30 AM »

I did a set of single cam heads and they were absolutely terrible. Sharp angles everywhere plus the casting roughness. Your heads look nice now. That should be worth 10 to 15 HP.  Like it.
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Jack Byrd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #65 on: March 09, 2021, 08:17:15 AM »

Looking real good. It has been a while since I've gone over a head to clean up the ports like that.

I would highly recommend looking into an flex extension for your dremel - I'm sure you've seen them. It drives a cable and gives you a little pencil tip that has much more reach into tight spaces.
Harbor Freight also sells a very inexpensive 3" bench grinder with that same attachment on it, I feel with a bit more oomph than the dremel, albeit at lower speeds. Use a coupon and you can get it super cheap. https://www.harborfreight.com/bench-grinder-with-flex-shaft-43533.html

If you're willing to shell out the dough, look into a Foredom unit, they have a foot pedal control and a 1/3hp motor that hangs over the bench, they are the choice tool for jewelry makers and I'm told expert port/polish guys use these as well.

The ports on these Mazda motors are really quite nice compared to many other manufacturers (of the same vintage), yes they're not perfect but they did a very reasonable job

All that said you're doing a brilliant job, it's refreshing to see someone taking the time to give one of these motors some love.

Oh man, I'm kicking myself for not finding this a week ago when I ordered the bench grinder. I've seen similar setups used with a Dremel, but I didn't know about the whole setup with the pedal and everything. I'll be keeping an eye out for some kind of flex-shaft setup with that now.

Thanks for the compliments guys, it means a lot.
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EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #66 on: March 11, 2021, 09:25:43 AM »

Just a small update today. I took a break from the porting and polishing to try out my new bench grinder, now that I finally got the proper brass wire wheel for it. Behold, clean (enough to lap) valves:






Once that was done, I was out of things to procrastinate with. Time to suck it up and try to do the bowls. Fortunately, it seems to be working. I'm using both lower speeds and smaller sanding drums, but I'm not trying to shape anything. All I want to do is remove the rough texture and blend it in with the work I've already done on the lower ends of the ports. They aren't as reflective as the ends, but still better than how they were. I'd rather be extra careful in this area anyways, even if it means slightly less bling. I can't stress how much I don't want to have to get new valve seats put in. Anyways, check it out:







I'll probably need to order some cartridge rolls just to get in to the knife edge on the intake ports, but other than that I'm pretty happy with how these are turning out. I also need to find some finishing buffs that'll fit on the Dremel, or perhaps get some black emery and cotton roll bits. Something to try to take out the machine tracks. I've got a set of mini flap disks coming for the combustion chambers, and then I got a big stack of wet/dry sandpaper up to 5000 grit for finishing those off. The finished product is starting to show through, and I'm getting excited. Still a lot of work left, so I'll be getting back to it now. Cheers.
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greywolf27030

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Re: '91 Capri XR-2 Resto-Mod
« Reply #67 on: March 11, 2021, 10:36:33 AM »

Impressive work, that has to flow better.
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Jack Byrd

EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #68 on: March 11, 2021, 10:51:49 AM »

Impressive work, that has to flow better.

Thank you, I appreciate the compliment. I'd have to assume it flows better, too. I'm kind of kicking myself for not trying to get a before measurement on flow-rate. I don't remember how to do it, and I've never done it before, but I know one of my teachers at tech school had explained to us how to take apart a shop vac and use the parts to make a makeshift flow bench. You couldn't use it to get actual flow in cfm, but you could use it before and after to see the increase (or decrease) in the amount of air that it would flow in 'x' amount of time.

Does anyone know what I'm talking about, or how to make it? I've never personally seen anything to measure flow rate, but I'd love to. Even if I can just get a measurement of after on my head, I'm sure eventually I'd be able to measure someone else's factory head. I'd love to see how much, if any, improvement I've made here.

Then again, the car is going back together with all factory parts. I suppose I could put it on a dyno and compare those numbers to manufacturer spec. It won't be as easy to tell what's been changed from just the port flow changes, though. Lots of other factors come into play on a chassis dyno.
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Aus Capri

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Re: '91 Capri XR-2 Resto-Mod
« Reply #69 on: March 11, 2021, 09:54:58 PM »

That must be scary going in through the combustion chambers! Looks good though man, I would be interested to see the flow test results as well!
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EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #70 on: March 12, 2021, 11:51:36 AM »



Here's the progress so far. Sorry this is taking so long, but each bowl takes about an hour to do. I run through 6 different grits, and I'm trying to blend it into what I've already done. I also have to be extremely careful to not touch the seats the entire time. I'm part way through the fifth intake valve bowl so far, so I'm not even half way through this part yet. I still plan to go back and gasket match the other end, and do a bit more shaping. Then I've still got to do the combustion chambers, hit all the ports with a couple finishing buffs, then lap the valves in, then clean the whole head, then replace the valve stem seals, etc. etc. This is starting to seem like a long, endless journey. At least if you look at it from certain angles, you can kind of see the end result peaking through.

I'll finish it eventually, but it's going to be a while. Many, many hours. I have SO many spent sanding drums piled up now.
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greywolf27030

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Re: '91 Capri XR-2 Resto-Mod
« Reply #71 on: March 13, 2021, 08:01:28 AM »

I can empathize with you. I've done iron head V8's and expected that to take a while, but was surprised at how long it took to do these little things.
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Jack Byrd

EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #72 on: March 13, 2021, 09:04:04 AM »

I can empathize with you. I've done iron head V8's and expected that to take a while, but was surprised at how long it took to do these little things.

Right? I've done a couple small block Chevy head's, and I swear I spent less time on the pair of those then I have on this one head. Maybe it's the fact that everything is so much smaller, or that there's 16 valves here instead of 8 valves per head, or perhaps aluminum doesn't like to become smooth. I don't know what it is, but it's crazy. I'm sorely tempted to pull an all-nighter just to try and knock out the rest of the bowls.
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greywolf27030

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Re: '91 Capri XR-2 Resto-Mod
« Reply #73 on: March 14, 2021, 09:19:01 AM »

Don't know if I'd try that.....lol
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Jack Byrd

EShepherd

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Re: '91 Capri XR-2 Resto-Mod
« Reply #74 on: March 14, 2021, 09:51:12 AM »

I sort of did. I was up until 11pm last night, which is super late for me. I got 8 bowls done. The whole intake side is done, and I'm down to 4 left on the exhaust side. Home stretch! I feel like crap today now. :-X Worth it.
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