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Old 04-22-2011, 11:04 AM   #1
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So, as a few of you may know, my engine got bored with a measly 15psi and 7500 rpm limit, and decided to make a new crankcase ventilation system. Time to rebuild. (I cant load pics just yet because I am working carnage will follow as I disassemble and heal)









I have belfab rods already, I am picking up a engine for 150. Obviously, the engine build will include fresh seals, w/p, and timing belt. I will probably do a reroute as well. I have a semi-worked 95 head on it now (mildly P&P and eibach springs), I am not sure if it got damaged in my engine death, If it didn't, that will be re-used. Sorry, a 99 head isn't in the cards as of now.

My goals are mid 300's (325-375 to the wheels is that to me and I would probably be happier on the lower end) I have a blox honda intake manifold, and spare miata IM as well. I have 1000's for when I go E85 and more power. My primary goal is to get a decent bottom end to handle my power and durability goals and have the car back on the road in the next 1-2 months. I would like it to be able to handle the occasional track day, but autocross mainly, and still be a good street car.

Choices/Questions.

2 engine choices for 150.

1- 97 Kia engine, known good condition. I understand these have the MBSP, Is that much better? Do I need an oil pan off an 01-05 to make this work? That would be $75 off planet miata.

2- Miata engine that is said to have blown HG. I can also trade in unused and un needed miata parts on it. I dont know if I will need a head or not. Potentially less than 150 dollars.

Oil Pump

Boundary engineering either way, but I am on a budget. Is it really worth it to get the entire assembly, or would just the gear suffice for my needs? I am in a tough spot on this one. I don't want any explosions of gears at 7500-8000 rpm's. I know the extra oil flow down low is nice to have, but is it neccessary for my goals and useage.

Pistons

1. Supertechs. 2mm over bore, 9.x:1, I would probably order them from emilio.

2 Stock pistons, potentially treated. I will be running ethanol. From what I understand, it would be hard to make your car detonate on this stuff. Do people usually change pistons for safety margin on gas, or because something else actually fails on them at the power levels I want.

I am basically at the point to where I could afford to do either nice pistons, or the nicer oil pump, instead of just the gear.

To Machine shop or not.

Should I have the machine shop build the entire short block, or just machine the block, and I do assembly? I can and have put together engines, none of them have blown up. However, I would like to place liability on someone else if it scres up. Problem is, around here, I don't know of good machine shops. I could use local reccomendations. I also know that machine shops try to always place the blame on you, and don't like to pay for mistakes they make. Promise you one thing, do another, and over all rank very very poorly in customer service. Basically, it is like paying your buddy good money to do something, and if he messes up you are just out if he is the type that doesn't care if he sees you again.

That about covers my Short block options, which is what is pressing right now. Ideas and opinions welcome. Pics laters.
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Old 04-22-2011, 11:49 AM   #2
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I don't know why you would drop compression if you're going to run E85, but I'm no expert either.
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Old 04-22-2011, 12:12 PM   #3
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I thought my car had a 9.0:1 compression.
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Old 04-22-2011, 12:31 PM   #4
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For pistons, I think for the power level you are shooting for I would pony up for forged pistons. I have cracked a few stock pistons. Stock pistons are pretty hard, but are brittle.

MBSPs supposedly helps eliminate crank flex, which robs some horsepower. Miata cranks are pretty good, and you are not likely to tear a crankshaft away from the block unless you are going mega rpm. Don't go through the trouble seeking one for your build.

As far as the assembly, have you done it before? (Edit: I see that you have) If you have, I would say absolutely go for assembling it yourself. It will save a lot of money. If you haven't, at least try to get a helper that has done it before. There is a lot of peril involved when assembling everything.

Same goes for the oil pump. If you are willing to go through the steps to check all of the clearences and make any adjustments, then why not. However, If you are going to go with a lot of camshaft, and plan to spin the motor hard, then I would be more inclined to let the experts set the pump up for you.

Think about the abilities that you are confident in, how much you have to spend, and how much time you are willing to spend doing the work yourself. Even though it is expensive, spreading the work load among a team of experts will ensure that you get a more reliable end result.
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Old 04-29-2011, 09:12 PM   #5
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Craig and I talked about things, and I am going with coated stock pistons, and we will see how it goes, I think it will be fine, especially on ethanol, detonation should not be in the cards with the 2871 I am planning's upper limit on 1000's. I am between swaintech and performance coatings, and leaning toward swain tech.

I am ordering a boundary oil pump assembly, what PSI should I get, I was thinking stock, or just 1 shim.

Also, I expect rods tomorrow, along with an oil pan with no holes. Pics will follow.
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Old 04-29-2011, 11:55 PM   #6
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I would go with supertechs, it's pretty cheap insurance over brand new OEMS that are treated with anything. I would consider bumping the compression if you're going to be running corn to something around 10:1-10:5.

EDIT: Just saw that you are deciding to run OEMs that are coated, wouldn't that be more expensive then Supertechs?
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Old 04-30-2011, 12:09 AM   #7
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At the power level you're shooting for I'd definately run the MBSP. I'd also (and most will disagree) run ARP main studs. I've personally seen a Miata engine in that HP range that broke two main caps and a stock main cap bolt. The ARP studs are way cheaper than a new block, caps, crank, and machine work to fix it later.

I'm also inclined to disagree with the assertion that Miata cranks aren't too bad on flex. I'd make the case that the main cap/bolt breakage (uncommon) and oil pump gear breakage (not uncommon) are caused BY crank flex.

I wouldn't go with 2mm oversize pistons. On the 85.5mm bored block that I personally sonic checked (a 2001 block), there were spots in the bores as thin as .049"... wayyyy too thin for the cylinder pressures a 300+whp engine will make. The thin spots were also right at the top of the bore just under the deck, the worst possible place for it to be thin. A half mm less (~.020) isn't going to add enough wall thickness that I'd consider it safe at that power level. I'd personally not go larger than 84.5mm at most and would likely use 84mm.

Last thing, if you have the proper tools (a rod bolt stretch gauge, micrometers, etc) put it together yourself, NO ONE will give a **** about how it's put together more than you will, and you will take time to make things just right that a shop simply can't economically. If you don't have the right tools, find a shop that does (particularly the rod bolt stretch gauge... torquing them doesn't cut it on highly stressed engines), and let them do it.
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Old 05-02-2011, 12:29 AM   #8
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Quote:
Originally Posted by Rennkafer View Post
At the power level you're shooting for I'd definately run the MBSP. I'd also (and most will disagree) run ARP main studs. I've personally seen a Miata engine in that HP range that broke two main caps and a stock main cap bolt. The ARP studs are way cheaper than a new block, caps, crank, and machine work to fix it later.

I'm also inclined to disagree with the assertion that Miata cranks aren't too bad on flex. I'd make the case that the main cap/bolt breakage (uncommon) and oil pump gear breakage (not uncommon) are caused BY crank flex.

I wouldn't go with 2mm oversize pistons. On the 85.5mm bored block that I personally sonic checked (a 2001 block), there were spots in the bores as thin as .049"... wayyyy too thin for the cylinder pressures a 300+whp engine will make. The thin spots were also right at the top of the bore just under the deck, the worst possible place for it to be thin. A half mm less (~.020) isn't going to add enough wall thickness that I'd consider it safe at that power level. I'd personally not go larger than 84.5mm at most and would likely use 84mm.

Last thing, if you have the proper tools (a rod bolt stretch gauge, micrometers, etc) put it together yourself, NO ONE will give a **** about how it's put together more than you will, and you will take time to make things just right that a shop simply can't economically. If you don't have the right tools, find a shop that does (particularly the rod bolt stretch gauge... torquing them doesn't cut it on highly stressed engines), and let them do it.
I am going with coated stock pistons, So no extreme bore.. In my original post, I meant .010-.020. so 84-84.5mm, but that is out the window. I am concerned about my micrometer, and that it is shitty cause it came from harbor freight.
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Old 05-06-2011, 02:30 AM   #9
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****.... I pulled apart my new engine that had a blown hg and it looked like water had been sitting in the freaking cylinders for a month. To disassemble, I had to remove the crank, and hammer the **** out of the bottoms of the pistons after it was soaked in MMO for about 4 hours. There is definate rust in the cylinder walls, since the piston rings were rusted to them, there is even a couple of uphevals of rust sticking off the cylinders. GD it. Looks like I am buying supertechs.
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Old 05-06-2011, 05:45 AM   #10
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It's called a ball hone, rust never hurt anything.
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Old 05-06-2011, 06:13 AM   #11
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If you were doing supertechs youd go up a size and youd just bore, and then hone that rust off. Surely your not saying theres rust on the pistons. Impossible?

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Old 05-14-2011, 10:55 PM   #12
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No, the rings were rusted to the block. Anyways, I am still on the fence about the pistons. I am also going to need a rebuild kit. I was thinking about acl race bearings. (Are these required?)I currently have the belfab rods, arp main studs, nice stock pistons, and the boundary engineering oil pump assembly. I am going to take the block and crank to the shop to get them checked at some point. So any good ideas on a rebuild/engine gasket kit, I would be happy.
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Old 05-15-2011, 03:14 PM   #13
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Finally got pics of the cyl walls after I honed it. I was skeered to take off too much material.









It feels smooth, I have to find my caliper to see where I am at.

Edit: would this be good for mic'ing the crank?

http://cgi.ebay.com/1-2-MITUTOYO-DIG...item1c1baf41eb

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Old 05-15-2011, 04:16 PM   #14
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Quote:
Originally Posted by chicksdigmiatas View Post
(picture of ugly cylinder bores)
Well, I guess the rings will seat quickly. And often.

Did you hone the bores because you're now considering not using oversized forged pistons? Or was that just for fun?
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Old 05-15-2011, 04:42 PM   #15
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Quote:
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Well, I guess the rings will seat quickly. And often.

Did you hone the bores because you're now considering not using oversized forged pistons? Or was that just for fun?
A little of both. I am not swinging for the fences, I wanted to see if the stock size would be acceptable. I was going to use coated stockers. I will slide piston down there and check with a feeler gauge as well. What does the rings will seat quickly and often mean?
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Old 05-15-2011, 04:45 PM   #16
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are those stains or impressions on the cylinder walls?
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Old 05-15-2011, 04:54 PM   #17
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are those stains or impressions on the cylinder walls?
Where the rust was? Umm looks like stains meow. They "feel" smooth. Except one, it still catches a little on the nail.
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Old 05-15-2011, 04:59 PM   #18
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hopefully just a little more honing is needed to fix that, or you may need to bore

ninja edit: or sleeve it.
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Old 05-15-2011, 05:27 PM   #19
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hopefully just a little more honing is needed to fix that, or you may need to bore

ninja edit: or sleeve it.
Might just toss in 84mm's and call it a day if the honing doesnt work.
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Old 05-15-2011, 05:29 PM   #20
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sounds like a plan.
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