just recently worked with a friend on his scoobie block...and we used some sort of badass adjustable fixed width 3 stone hone...very nice piece...started out with 100 grit and with 180 grit and tranny fluid as lube and you can cut a thou off in a split second. Well not a split second but only a few minutes. We honed a block with only 15K on it w deck plate and the out of roundness was the biggest issue. [due to the deck plate of course] so we had to go out 2 sizes over "drop in" pistons.

IMO if you are "on the fence" stay with OE pistons or hone out for the "drop ins"

Tomas, I assume you have a good bore gauge? measuring .0005 aint easy...lol

edit: hone

http://www.enginehones.com/lisle15000.html

CP Pistons FTW? Lol...

Good to know @Tomas. Nice find.

Yeah, I am not worried about that 0.0005-0.001 clearance differences. I am sure a light honing alone would take care of that (plus the wear from the last 89k). Most of my piston ring gaps were within spec without filing. I think I only needed to file 2 of the top rings by .001 and 2 of the 2nd rings about .001.

The pistons slid down smooth and fit perfectly.

not to split hairs here but the ring gap is no indication of if the PWC is enough...its the piston to wall clearance :)

I am sure you'll be fine.

Lol. Fuck meassuring, This is a week end build. It's old pistons out, hone some, new pistons in see if the shit will run OK. I am not planning on wiggling a bore gauge in each cylinder to check clearance or out of roundness. I know myself. If I do that and I detect the slightest defect I'd stop everything to try to fix it and then I'd probably fuck it up. lol

I like theschrum's way.
Hone some, drop that shit in and go.

By the way. Out of roundness, or oval cylinder bores, is typical of boxer engines. Used to be a big thin on BMW bikes. The pistons lay on their sides on every start up and don't have the lubrication they need so shit gets all wobbly on those sngines. Straight cylinder blocks don't have that problem. At least not very often.

hahahahah

what you describe is EXACTLY what happened to us and why we went out 2 sizes over

still laughing...started out with Manley skirt coated "drop-ins" requiring .0005 over OE, and within and hour knew those were out after working on 2 cyls..lol went another size out and was close enough really...but by buddy is OCD for sure and wouldn't let it go...so we ended up at max over size which on a high boost race car would crack the top of the cylinder bore...lol

hes just DD the car so it would have been fine....I think he sold the block to a guy that was going to sleeve it and is going to get brand new case halves and really only hone them this time

damn what a story...story of fail hahaha

edit: oh and good to know about the roundness of the boxers...IIRC it was not really ovalized like you describe but all over the place...more likely caused by us using the torque plate and OEM not. no?

Yeah. That's another one. Fuck torque plates! lol

@Tomas, so have you made your mind up on what pistons you will be using.

I am wondering if i keep my stock pistons and only do rods, will it be ok for about 470-500whp?

Fuck dude. That's a hard question to answer.
I would say go forged if you want 500 hp. That's a lot.
And no. I haven't made up my mind. And probably won't for a while. I am as indecisive as a teenage girl about to loose her virginity.

Reason i said they high was just incase i ever did go that high...lol

yea but i was really going to do this like next month if i could just do rods and get away with it lol.

Wait wait so you won't be measuring ring end gap, or rod bearing clearance or anything? Just throwing shit in there and saying "eh, fuck it"? Jesus you've got balls the size of asteroids dude. Lol

lol

thanks for the new sig quote...lol

lol yes he does...hell if a rod or main is too tight that's the end of the motor in about .0001 seconds. at leas use some shitty plastiguage

have you priced a crank lately?

edit: IIRC dustin's OE sized rod bearings were .0022 too small for OE spec so he had them coated...if he didn't measure them he would have been lose but either side of good is no good.

That's right. I am gonna 1/2 way tighten the rods on the crank upside down and wiggle them. If it feels ok I'll leave it like that. And fuck plastigauge and ring end gap. If the piston slides in without having to pound it with a mallet its good to go. Lol.
But I'll do it in spite of my lil balls. Not because of them.

You sir, terrify me.

Rings butting up against each other is the prevailing thought as to why cyl 3 crapped out in my motor.

There were no signs of detonation there or in any other cyl.

I know there is time and money involved in pulling the engine and doing a proper build. I also know that tolerance precision and balancing effectiveness improve with each new generation of machine shop equipment.

I'm old school. I grew up in a family owned engine rebuilding plant and custom (racing applications) automotive machine shop and learned to operate every mill, boring bar, crank grinder and other piece of equipment before I even graduated from highschool.

Doing racing application work for speed shops and race car owners (sometimes to their specs) I learned just how much power can be gained and how much stronger an engine can be made by attention to detail and by true blueprinting techniques. I'm talking about machining those rods. I don't care how expensive. That means making sure that the distance between big eye and little eye are EXACT, rod to rod and that weight is too.

It means sometimes actually boring the block all the way into the water jackets and putting in sleeves so that you can make every damn hole exactly like the other one and each and every one square. It means boring with a torque plate. It means putting that finishing cross hatch micro finish on just right.

It means line boring the block. It means indexing the crank so that every damn journal is exactly the same number of degrees apart from the others and that every journal stroke is exactly the same.

It means setting piston to cylinder wall clearances all the same but on the "loose" side of the tolerance. Same with rod and main bearing journals. And, yes, we grind the crank with a dial indicator that reads in "tenths", down to .0001.

It means milling the deck of the block and the head with absolute attention to squareness and getting every combustion chamber cc as identical as possible.

It means three valve angle cylinder head work and getting valve spring pressures exactly the same with shims. This excludes any separate porting of heads or manifolds. We're talking basic blueprinting.

It means meticulous balancing of everything that moves.

It means a lot of tiny details.

My long ass post is to illustrate that (1) you can pick up huge amounts of "free" horsepower and a huge increase in safe rpm headroom by doing this, even with stock internals and (2) the life of the engine is greatly increased.

Now, you don't have to do all of this shit, and doing all of it is going to be big bucks. But if you want to make power safely, you ought to be doing at least some of the more basic things.

Just honing/deglazing the block and putting in new internals might get you by for a while, but you are still going to have an engine that for all practical purposes started out with sloppy factory tolerances and has a lot of wear and abuse on it.

This is not likely to work out very well on a high output forced induction engine being pushed to its limit with an aggressive tune.

Doing just the basic machine work without focusing on true blueprinting is still far superior to the suggested "shade tree mechanic" approach. Sorry for being so rough. At least consider pulling the engine and have someone or yourself go through it and do the basic machine work before putting it back to gether and in the car.

I know, I have a bias because I have access to all this shit, but damn it, don't skimp on an engine this fucking expensive.

..I guess I know what I'm looking at next with 117k on the clock..

What the hell just happened in here?

Lol.


Tappin

He can build an engine, but he still uses hypertech to tune......

back to topic......

well that's why you would need a BnB engine...to stay together with an HT tune...

lol

i keed...but the thread title is "drop in forged internals" not balanced and blueprinting 101.

we know its a cheap easy way to go and for most instances it would be just fine for a DD car...not a race car.

I agree....and if you make sure clearances are good on bearings, these aren't 50 year old iron v8's with ultra-loose tolerances from the factory that could gain tons of power from a good B&B........these motors are tight from factory, close tolerances with mostly precision machining. Cover our butts with good clearance on the rod bearings and make sure the bore is clean, with or without a new deglazing via ball hone, should be fine. And what, so you burn a quart of oil every 3k miles, no big deal. My s2k used to burn a quart in a day of autocrossing, and that was NORMAL! lol

Yes. Those are not inconsistent. If I actually thought I could make more reliable and usable power with a different tuning option with my mods on stock turbo and pump gas, and if I had the time and patience, I might look at something else. It meets my needs on a daily driver.

Agree on one thing: back to topic.

You guys might be surprised at how sloppy some of the tolerances are today (and yes on Mazdas) according to our shop foreman. Much better, but you'd be surprised what gets out past inspection. And put a lot of miles on it and it's not much better than one of those right off the assembly line V8's of the past.

I'm not advocating full blueprinting for this situation. I am a big advocate of basic machine work along with the internals upgrade.

BTW: Most machine shops today will not guarantee their machine work under these circumstances unless there is proof of (1) a new oil pump and pick up screen assembly if so equipped, (2) new timing chain and tensioner because of the likely wear on those components.

Patchwork solutions have a very high fail rate. When done to save $$$, it is understandable, but the fail rate is high.

The fail rate is also very high on old school v8 machinists that think they can build an mzr.

The bearing spec for rod bearing to crank clearance is .001-.002 that is pretty tight. That is only a .001 tolerance.

Lots if high hp guys running on stock block, and so far the main weakness is the rods. Replace those, pay attention to as much detail as possible, and viola, you have a solid motor.

Freekn tappin

Seeing as how I've done this nearly a dozen times now on cars ranging from ~400whp all the way to 800+, that the above statement is incorrect.

I appreciate your perspective and input but I made this thread out of personal experience, not just hearsay and guesswork.

Dammit I <3 you, can't wait to figure out what you guys are gonna do so you can rebuild mine.

Tight tolerances indeed.

Camshaft journals are 0.02
Valve tappets 0.01
Camshaft run out 0.03

I spent about 20 hours cleaning a used head I bought, porting the head, lapping the valve seats, and adjusting valve tappet clearance. If I would have measured every single item in the engine manual I could have spent another 40 hours. That's not an exaggeration. You have the above tolerances and then tappet bore ID, valve stem OD, cam lobe OD, etc etc.

It just comes to a point where you have to trust that some of the tolerances are OK from the factory.

On the pistons alone you have

piston OD 0.03
piston ring and piston rings groove ( that's 12 measurements right there plus piston ring gap another 12 = 24 measurements)
Piston pin and pin hole ID. 12 measurments.

That's 42 points of measurement on a single location (which you shouldn't. You should always measure on multiple locations)

I'll be damned if I am gonna fumble with each piston with a bore gauge in one hand and a micrometer screw on the other plus a feeler gauge in the crack of my ass to make sure everything is within spec. I am going to assume the new Gen 2 pistons I have are within spec from the factory.

This is what I will measure on a "drop in" rebuild.

*Cylinder block distortion
*Bore of the big ends of the connecting rods to OEM spec. If they come out OK, I am going to assume the OEM big end bearings are within spec and slap the two together on the crank. Wiggle the rods comparing that all 4 have about the same turning resistance and leave it like that. No plastigauge.
*Wrist pin OD and small end bore ID. Again making sure all 4 pistons with wrist pins with the small ends through them feel the same.
*Weight of con rods and piston assembly. If more than a few grams difference I will tighten the weight difference by grinding somewhere.

Things like bore ID, con rod length... meh.

The goal is total time from start to finish < 18 hours. So 1 week end.

Another reason I want to just change rods is less worrying about clearances. Only really need to worry about 8 points really, right?

^ If by that you mean check con rod big and small ends then yes. As mentioned earlier though there is of course more you can do. Probably going to be OK but once you take the head off it's possible something gets out of whack.
I think changing pistons at the same time and a light hone is a good idea. Whether OEM gen2 or aftermarket.

Well like I said i'm strongly thinking about just leaving the stockers in, so no need to hone...plus my block is in mint condition, great compression, 35k miles on it, no issues. I figure i'm really only shooting for a mild build, low 400's. Just want rods for piece of mind. The only thing I'm worried about is spinning a bearing. I don't really know what to look for or how to measure the journal bearing clearances.

Plastigauge.

Now, we know that genpu has stronger rods than genjuan, but are the pistons stronger as well? I'm thinking about dropping in some forged rods with OEM genpu pistons, will that work?

Is this what @@ wants to do as well?

I'm just suggesting that the block be bored for oversize pistons, that the crank be reground for fresh bearings, head and block decks checked for warp and that new chain and oil pump be used. These basics are the key, IMHO, to good success.
It is BECAUSE the tolerances are so tight that these things should be done. It does not take much wear to be completely out of spec and short life after a drop in rebuild.
Sorry if I offended. Just suggesting that a little basic machine work and checking a few specs could pay dividends.

Unless there was damage to the cylinder walls there's no way in fuck I'd ever comsider boring out the cylinder.

I always check the head and the deck for warping while the head is off as well.

IMO, if you don't want to go the route of forged pistons, get genpoo pistons and cryo them. That'll increase strength like 10-15%, and if you want, shot peen them too...that strengthens them.

Gen Pu pistons has a smiley face design meant to better fuel combustion. Iirc I read somewhere they also prevent hot spots in the chamber.

I don't know if in Romania the rods of the Gen2 are stronger than the Gen1 rods.
Most decidedly not in North America. They are both exactly the same.

The piston crowns are different between generations. That is all as far as internals. The Gen2s have smiley faces on them to improve flame propagation and avoid cylinder wall washing.

Are you sure the gen1 and gen2 rods are the same? The genpu rods are a bit heavier, differently shaped...

From Canada, with love, to Romania

http://www.mazdaspeedforums.org/foru...rences-110109/

A couple issues that put my engine out of spec when I had it machined... just a fyi.

- OEM sized bearings (mains/rods) were too small and out of spec from mazda. Had to get the oversized bearings and grind down the crank to spec.

- Car had 30,XXX miles on it, yet the cylinders where "ovaled" had to get it bored out with the oversized wiseco pistons instead of OEM size.