miatamania

iTrader: (9)

Thanks guys, I may have to call them when I understand exactly what to ask.

As far as not needing forged because its all about detonation...but I'd like to have a bit of safety.

iWeasel410

Don't forget to consider piston side loads...Side loading won't kill a piston as fast as detonation, but it can definitely cause some damage. Boosted engines build fairly high cylinder pressure (dependent on many factors) during firing which will push the thrust side of the piston into the cylinder, generally creating compressive stresses in the struts and tensile stresses in the crown. Now couple that with thermal loading (expansion and stress), and you'll see another reason why forged pistons are a much better choice than cast.

flier129

iTrader: (7)

i love threads like this dont have to ask a thing and learn a lot.

its nice to know that a BP's stock pistons will do 250+whp, 275+whp with head work yeah?

patsmx5

iTrader: (16)

They will probably do 400 fine. But if you have knock you will break them quick. Tuning is key. That's not just a sentence. It's the truth.

miatamania

iTrader: (9)

However, I am right in understanding that if tuned safely, the forged parts are more resistant to blowing the **** up that stock parts?

patsmx5

iTrader: (16)

Yeah, forged is more resistant, so to speak. If you have a little knock, the forged pistons will hold up to it better than a stock piston. But any knock is bad and will quickly break everything. I personally just run a stock head gasket with stock bolts and let that be the fuse. If i get severe detonation, I hope that the fuse (head gasket) blows before it breaks a ring landing or bends a rod, etc.

miatamania

iTrader: (9)

makes sense...the stiffer it is, the more likely something major will break. So overall would you recommend pistons? I know some people like to just toss in stock pistons...but I just want to try to have a decent motor that I know can make power when I want it to.

jc_rotor

The most important thing is that it is tuned correctly. It doesnt matter what parts you have in there if the tuning is bad. I have said this before and will continue to. TUNING!!!!!!!!! Most important thing you can do when modifying your car and best place to spend the money. If youre going to spend money, buy a stand alone ECU and have it tuned. Will make the most of all your mods.

patsmx5

iTrader: (16)

It's really hard to say, and it would all depend on circumstances. My car runs fine right now. It has good compression, good leak down numbers, and it's burns < 8 oz of oil after 5K miles. So I have no intentions of pulling my motor apart before boosting it since it's fine. Plus I don't think forged pistons are needed anyways for the power I'm looking for. Add to that, I have a good 81K mile spare engine sitting on a engine stand that's ready to go if I ever do blow an engine. If my motor took a **** tomorrow, I'd swap motors and buy another spare to keep.

Personally, I'll probably never build a motor because it's easier and cheaper to keep a spare and IMO, it's better. You could build a nice motor, have detonation, and break it. Then you'll be out a lot of money and down time while you build another. That's expensive and inconvenient. In my case, I bought a good used motor for 88 bucks, and if my stocker dies I'll swap them out and get another 88 dollar motor to keep as a backup. Personally, I feel better beating on it knowing I have a spare if it breaks. Some would feel better beating on their car knowing it's got 3K dollars worth of forged internals.

I wouldn't because I know anything can happen and it could be lost. You could loose a radiator hose or water pump, etc, overheat it, and blow a head gasket or lock it up. The oil bypass valve in the oil pump could stick and you could loose oil pressure. An injector could stick and you could hydro lock the engine. A foreign object could get into the engine (such as a broken spark plug tip) and destroy a cylinder in the engine. It could get low on oil and spin a bearing. Ship happens.

We all do our best to protect our engines. Some build 2K dollar engines. They buy expensive (though now more affordable) oil pump gears to protect their investment. The do it because it's taking out another weak link, killing off one more point of failure. They buy them because they don't wanna have to do this again. Nothing wrong with do it once, do it right, but it's expensive. The more they spend, the stronger and more reliable the engine becomes. However, it's not immune to failure. Just less likely to succumb to it.

In my case, I'd rather buy 4 engines instead of a set of pistons, or 4 engines instead of a set of rods, or another engine instead of a set of bearings, or another engine instead of a paying a machine shop to polish my crank, or two more engines instead of paying to have my pistons coated, or two more engines instead of buying oil pump gears, or another engine instead of ARP studs. BP's have been around for a long time, and here they can be found in good shape for cheap. Given my circumstances and preferences, it makes sense to use a stock motor and keep a spare.

jc_rotor

Pat, dont mean to say youre wrong or anything, but most of the cost of a built motor is the initial investment of the rods and pistons, and whatever machine work you have done.

Example: I spent 500 on pistons, 700 on rods, 300 on main and head studs and 500 on machine work. thats 2000 and then the gaskets and bearings. It netted me +40 whp over stock, naturally aspirated. Ive now rebuilt my motor once at the cost of a head gasket, $100, rings $79, and rod bearings $45. But I do all the work myself so that may be an issue to others. I re-ringed the motor after 3 years just out of precaution for the upcoming turbo build. Im running 11:1 compression and will be turbocharged very soon.

patsmx5

iTrader: (16)

Yeah, I agree 100%. I think I just wrote a short book saying that...


Yeah, a good machinist's labor isn't cheap. Here it's 600 for a 4 cylinder for standard labor. If the block requires sleeving, or a crack has to be repaired, that's extra.
Go start a thread on compression ratios and boost. I want to discuss that.

oilstain

Link to plethora of pinatas Motors for $88 a piece? I mean, hey I live in a small apartment with my wife, but for $88, ****, I need a new coffee table!

patsmx5

iTrader: (16)

http://www.barrysupullit.net/products.php
Hence the name, you have to pull the motor. For some this is not an option. It's not a problem for me as I prefer to pick and choose my own engine, and pulling one take about 4 hours from walking in there to driving off in my truck.

They sell "engines" for 163.99, but that's with all accessories, brackets, flywheel, etc. The engine and all its peripherals as if you cut the motor mounts and slide the transmission off. The "motor" I speak of is their price for a long block. Everything from the valve cover to the oil pan. No manifolds, brackets, or flywheel.

oilstain

In MD, the pick n pulls haven't seen a miata in a year.

...another reason to leave MD.

miatamania

iTrader: (9)

I never see any in NC either...

patsmx5

iTrader: (16)

I haven't seen a miata in over a year at the local yards. I have seen Ford Protege's out the *** though, and 95-97 Kia Sephias, and 323's, and Escorts. They all have 1.8 BPs. My motor I have on the engine stand cam from an automatic Kia Sephia. It's a mazda BP 1.8L and has the MBSP stock. Granted it doesn't have the 99' head. I'll swap mine if I ever use it, though I wouldn't have to. But seeing how it cam from a low mileage, clean clean car that was totaled in an accident, and through tedious inspection, I feel confident I have a good motor that has never seen a hard life. I doubt it's every turned 7K in it's life. Being an auto I think it has lower compression than my 99, but I need to verify that. Still, for 88 bucks after tax with the motor set in my truck, it's not a bad price to pay for a ready to go motor that I feel is as close to new as one could expect for its age.

hustler

iTrader: (6)

I'm in this crew.

that's primarily a machining issue according to my machinist. However, I still went with a somewhat loose bore because I see so much track time.

miatamania

iTrader: (9)

^What pistons did you end up with Hustler?

patsmx5

iTrader: (16)

Hustler had low comp Supertech's, but he sold them and bought Wiseco's I think.

hustler

iTrader: (6)

i sold them an bought another set...lol. I have supertech's, but never ran the motor yet. It should start on 10/27 if my MS settings are right for the IAC. I plan on bringing it back to Houston with me (and parking it in the secure parking lot at work, so don't think you're going to steal my wheels and ****).

I bought the supertech's because I wanted the lower expansion rate at the cost of strength within reason. Its going to be a 220-250whp car, so I don't need the strongest thing out there, but not a bad idea considering my car sees roughly 30-hours of track time per year. If I could do it all over again, I'd just coat new stock pistons. Actually, if I could do it all over again, I'd keep the 1.6. Maybe that will change when the 1.9l 99 motor fires over.