Engine build questions
 

I bought a block that has supertech rods and pistons, bearings, billet oil pump gears. The cylinder bores need to be rehoned so I wanted to ask the peoples of miataturbo.net's advice. I have a 3071 and would like to max out the turbo. I also have a WI kit to be installed. My car is a genuine DD but I can't live without moar boost so I'd like to do whatever I have to on the engine while it's apart to make it reliable and solid. I actually have the block and the head in my garage so this build -will- happen. Not trying to waste anyone's time here.

Here's my ponderances:

I saw the billet steel main caps set on FM - Flyin' Miata : Engine/Drivetrain : Internals : Billet steel main cap set and was wondering if they are necessary if I'm touching 400whp.

I already have an ACT extreme HD with an organic disc (and about 20K miles) which is rated for 300lbs. I was thinking about upgrading to the 6 puck sprung plate which can hold 400lbs. FM says that the organic disc can hold more but I'm wondering if anyone's running over 300lbs on that disc. I'm concerned that the stop and go DC area traffic will make me hate life with a sprung 6 puck.

The pistons in the block are the 8.6:1 pistons. Would it be a bad idea to source a nonstock head gasket to raise the compression ratio? Everyone seems to thumbsup the stock gasket.

For the block, other than the bore, I was going to have it decked and tanked, and the crank balanced. What other machine shop work would be beneficial?

I have a FM polished head w/ upgraded valves but no upgraded springs. I understand best power is around 7500 RPM but I'd like to be able to hit 8500 RPM just for psychological/acoustic awesomeness and to lengthen each gear out. I can't really tell the difference between the supertech and FM springs. Any recommendations?

You can get used to the 6-puck. For a pure street car, I might go with FM's stage 2, though. You'd better not need billet mains, since I have the exact same motor (Supertechs, Belfabs, and OPGs) and I am aiming to track it at 375whp+. Stock HG is fine, it's a 4-layer metal gasket rated for 500 or 600tq, so don't touch it. If you're going to have the crank out, you might consider having it bullnosed or knife-edged, though, while they balance it.

I have 8.6:1 pistons in my car with a .86AR compressor housing and not complaints.



mineral water!

What's the point of having billet steel main caps? Are the stock ones made out of crackers?

Billet main caps are a useless upgrade. Anyone that brings up crankflex can kiss my the intestines deep inside my asshole. If you have an issue with crankflex that other aluminum blocked 4cyl motors aren't even having then think about getting your rotating assembly balanced (which you should do anyway).

ARP cap studs?

Argh knife edging is expensive. F that S.

Any opinions/experiences with the valvetrain? What springs should I buy?

Also relatively useless IMHO. Its rod bolts and head studs that need to be strongest.

Knife-edging is also something I wouldnt recommend. The crank needs the mass for longevity sake. One thing some builders do is polish the counterweights before getting the rotating assembly balanced to help reduce windage. That is something you can do yourself as long as you are very careful around the journals.

Just go with the supertech valvetrain, you can't go wrong with it. I'f you plan to rev that high though you WILL need to get the oil pump gears in order to be at all reliable.

Yuppers I have the oil pump gears woo hoo.

I've read snippets about shim under bucket and solid lifters etc etc.. do I need to worry about that crap? I'm going to have the shop assemble it. Should I ask them to do any other stuff?

You are getting into an very expensive game of if I do this why not just buy that.

Exactly. I am starting to get into the same situation.

Whenever you start talking about spinning 1k+ over stock redline add at least 1.5-2K to your budget. And thats being realistic.

Truthfully, I love the sound of a high reving motor as much OR MORE than you. But the miata already suffers from tq drop because its pretty anemic, so spinning it higher without supporting mods is pointless. To do this correctly you are talking: oil pump gears, shim under bucket lifters, custom cams, valve springs/retainers, some head work. That's at a minimum. Already you are talking: 200+, 300+, 700+, 300+, and 400+ if you don't have the ability knowledge to do it yourself. That's already 1900+ in parts and porting. That doesn't involve any associated labor.

If you think building the bottom end is expensive you have no idea how much it costs to build a head....

I paid $700 for supertech pistons and CAT rods, then $1300 in machine work/bearings/whatevers and i promise that I'm having as much fun as the people with $10k motors. You can either spend $700 on a real p&p or turn the boost up 2psi. Pick your poison.

I am crying right now :*(

I already have the gears and headwork. How much gain would there be seen from "to do it right" vs halfassing it? I don't know if I'd want to spend the extra thousand.

The other day I heard a Ferrari F430 scraping redline and though it sounds gay to say, I want my car to sound like that.

I know what you mean. I want my dick to grow another 3" and that's more likely to happen than your miata sounding like a $300k v8 Italian chariot.

:bowrofl:


If i were to build a motor which i might end up doing soon i would do it once, do it right.. I would ask myself does my motor need to spin an extra 1k? honestly i would say no; thats what the next gear is for.

I cant put it anymore eloquently then hustler just did. You car will never sound like a Ferrari.

$500 for 8lbs of material removal. People routinely pay near that for the same amount of mass removed from the flywheel.

True, but you'll see more difference from the flywheel since the mass removed is much further out. Knifedging looks pretty and does have some benefit IF you plan to tear the engine down every X number of hours like we do with race engines, but it's unnecessary and a PITA for a street driven car.

Neo, I'm curious about something here. You said you don't think steel main caps/Arp main studs are needed... but you think the oil pump gears ARE needed. Are the stock gears not coming apart from being banged around when the crank starts flexing? (This is what I've heard... no direct test knowledge). If that's the case wouldn't it be prudent to use studs/better main caps?

The stock gears are sintered metal and will....unsinter at higher than stock rpms and also at high tq levels. With an all iron block and a balanced rotating assembly there is 0 that billet main caps are going to do extra for you. They will cost you a ton, but that's about it. Sure a 4cyl is naturally unbalanced, but crankflex is imo not a failure point for the stock oil pump.

Honda B series motors have all aluminum blocks with cast iron main caps, and very similarly design oil pumps. They have no issues with oil pump gears shattering for the most part and they have weaker blocks than ours. The main difference is that their oil pump gears are not sintered.