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Old 02-27-2008, 09:39 PM   #1
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Default Build questions

I'm working on acquiring all the parts I'll need to get my forged build going in the right direction, but I need some help with suggestions as far as some parts go. Also, I'm not trying to build something insane here, just a strong bottom end for now.
Answers I have will be in red.

I have the ETD H-beam rods, what bearings should I get? Are OEM good enough? Forking out for OEM. Check.

I'm looking to get 9.0:1 forged pistons, what head gasket would be recommended? OEM again. Check.
Also, I'm keeping the stock bore, what kind of work should be done to prep the block since there will be no overbore?
And are there any pistons out there that reduce or have no piston slap?

Are there any other parts that should be upgraded as well (if the OEM parts are not good enough for a forged build), main caps, oil pump, etc.? Besides the main and head studs, already getting ARPs.

Last edited by RotorNutFD3S; 02-28-2008 at 12:22 AM.
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Old 02-27-2008, 10:43 PM   #2
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A decent set of rings.
Stock oil pump should be good if you're sticking with stock rev limiter.
I don't see any mention of the valvetrain or head, but a rebuild, unshrouding, and 3-angle job, plus maybe ceramic coating on the valve heads.
What about coating the pistons?

Exactly what are you planning to do with this motor?
I assume boost, but what turbo, how much boost, and what's the car gonna do?
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Old 02-27-2008, 10:57 PM   #3
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Ok I seriously doubt you can build a motor with forged pistons without boring it. The ONLY way your gonna get by with using the stock bore is if it's in perfect condition. That means no scratches, no out of roundness, no eggshaping, no ridge, etc. Still, you would have to lightly hone it out for the new rings to break in properly. Mind you the motor is still the stock bore.

Forged pistons have a higher rate of expansion than cast pistons. Putting forged pistons in a stock bore they will expand and bind, trashing your motor. You need to have a machinist who truly understands what he's doing bore the motor the correct bore to allow for the expansion of the forged pistons, based on what alloy they are. Different alloys have different rates of expansion. More silicon = less thermal expansion.

IMO you don't need any ceramic coating for a mild build. Save that money for head studs instead (ok, you said that already) or some porting. If your a DIY kind of guy, buy a book on modifying cylinder heads and read up. 100 bucks for a book and some bits could get you A LOT more HP. Run a Mazda head gasket, they are fine. Head studs will allow you to run more ft/lbs on the head safely and offer more resistance to a failing head gasket. Have the head decked if it's not flat of course.
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Old 02-27-2008, 11:00 PM   #4
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^samnavy - I'm not concerned with the head, valvetrain, etc. at the moment. The focus is only on the block.
For your answer, most forged pistons I've looked at come with rings as well, unless I'm mistaken. And why coat them?
And yes, staying with the stock redline.

The plan is to have a strong bottom end so I can cross the lines with the 2560R I have on there for now, and if I decide to move on to a larger turbo, I can go for it and the bottom end is already beefed up and can handle it. Like I said, no insane goals, just strong.

^patsmx5 - Thanks for the insight. The block would be going to a machinist anyway, just want to know what is correct procedure for having stock bore sized forged pistons. And it sounds like if I get a piston that has a higher silicone content, it will expand less which means little to no slap when cold. Correct? And the machinist would basically have to do a bore that would allow for the expansion, but not so much that it's an overbore. Right?
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Old 02-27-2008, 11:12 PM   #5
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Just put in the rods, some forgies, and bearings. You'll be good to go. I used ACL bearings because you can get them for cheap as **** on ebay. BUT you may have to pay for more machine work to use them, which will greatly offset any savings.

I say fork out for oem bearings because you can likely just drop them in, you will or your machinist will measure first of course.

My wisecos have 0.004" of cold clearance with confirmed 0% slap at cold start. My mains have 0.002", rods 0.0015", wrist pins I believe are 0.0015". Those are the main clearances of concern for you. I went bigger on my mains to the wide end of recommended clearance because I will be spinning my motor far beyond the stock redline.

EDIT: Also, the wiseco spec sheet states their pistons can be installed with as low as 0.0025" of p-w clearance for an NA installation. If you look at the shop manual this falls well below the max spec. They recommend 0.0035" for a general boosted app. I went with 0.004" because I plan on running high boost, and the coatings my pistons have will keep them cool under extreme loads as well. SOOOOOO, don't beleive all the forged piston crap you hear on the intarweb, either here or anywhere else. The amount of expansion between the 2 main Al alloys used in forged pistons accounts for about 0.0005" of difference in diameter. So its nearly insignificant..... You can always get a great price on wisecos at raceeng.com and they usually stock them.
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Old 02-27-2008, 11:19 PM   #6
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Sort of, it's hard to punch a block out .0018 to get the piston clearances to your spec. Much easier is to buy .010 over pistons and punch the block .014 per Neo's suggestion. (Neo that sure sounds loose to me, why .004? Planning on running 20PSI?) I'd bore it .010 myself. As for pistons with more silicone content, cast ones are good. Forged are stronger but don't have the silicone. It's a trade off. The clearances have to be just right for a forged motor. Too loose you get piston slap, which will score the walls and eventually lead to failure, too tight and thermal expansion causes them to bind, causing more friction and heat, and they seize up.
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Old 02-27-2008, 11:27 PM   #7
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You post speaks with inexperience.... Its just as easy to bore/hone out 0.0018" as it is 0.014. The silicon content in cast pistons obviosly makes them expand near 0, but what I was personally refering to was the difference in expansions btw the 2 main types of forged pistons.

Also, piston slap will have little effect on a cast iron block like we have. Aluminum is far softer. Worst case senario is that you have to buy new pistons in like 4 yrs and get your bores honed out 0.001". Then you'll be good for another 4 yrs. The simple matter is that piston slap usually only occurs for the first 30 seconds the car is turned on until they warm up and you drive off. There is no load during this period and I would hardly say it hurts them. You will only run into major longevity issues when you run like 0.006" of clearance or more on a drag motor.

I do plan on running over 20+psi on my motor. I have built it with 7.5-8:1 cr specifically to run as much boost as possible on pump gas. I can guarantee you that it is also making a good amount more power NA right now than a stock motor. Albiet, my cylinder head has a whole lot to do with that.

Ask splitime how his honda motor with vitara pistons is doing. I believe his slap all the time, even while driving and its been going strong for years now.
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Old 02-27-2008, 11:42 PM   #8
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Quote:
Originally Posted by neogenesis2004 View Post
You post speaks with inexperience.... Its just as easy to bore/hone out 0.0018" as it is 0.014. The silicon content in cast pistons obviosly makes them expand near 0, but what I was personally refering to was the difference in expansions btw the 2 main types of forged pistons.

Also, piston slap will have little effect on a cast iron block like we have. Aluminum is far softer. Worst case senario is that you have to buy new pistons in like 4 yrs and get your bores honed out 0.001". Then you'll be good for another 4 yrs. The simple matter is that piston slap usually only occurs for the first 30 seconds the car is turned on until they warm up and you drive off. There is no load during this period and I would hardly say it hurts them. You will only run into major longevity issues when you run like 0.006" of clearance or more on a drag motor.

I do plan on running over 20+psi on my motor. I have built it with 7.5-8:1 cr specifically to run as much boost as possible on pump gas. I can guarantee you that it is also making a good amount more power NA right now than a stock motor. Albiet, my cylinder head has a whole lot to do with that.

Ask splitime how his honda motor with vitara pistons is doing. I believe his slap all the time, even while driving and its been going strong for years now.
FWIW I have bored a block for forged pistons before, so not speaking out of my *** here. I bored it for .003 thousandths clearance, but this was a dodge 360 that was gonna be a nitrous motor, not a boosted motor. If there is any out of roundness, a ridge, etc, then trying to get it out with a single .0018 is tough. Wish such a light pass, it's possible for the cutter to skip, not cutting a perfect bore as there is more tension to making a light cut. It's much easier to do it .010 over.

IIRC, forged pistons are not as hard as cast pistons or Hypernumatic pistons. Agreed the bore is much harder obviously. Worst case scenario is he installs his pistons with insufficient clearances and they seize up under high load. If he ever overheated the motor or had a little detonation, the higher temps and tight clearances could cause a seize as well. I've seen this happen before. My advice is to have a reputable machinist build the motor with a knowledge of what you plan to do with it.

So you ever decide If my HG was sticking out into the cylinders the way I unshrouded my valves? I've seen motors with piston slap last a while too, but it's compeletly avoidable with a competent machinist.
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Old 02-27-2008, 11:46 PM   #9
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No, but I decided that you totally killed you quench.
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Old 02-27-2008, 11:50 PM   #10
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Quote:
Originally Posted by neogenesis2004 View Post
No, but I decided that you totally killed you quench.
Perhaps. I was detonation free with a 100 shot before the headwork, and had detonation afterward above a 75 shot. I assumed it was for lack of squish and leaner AFR's though, and sure enough with MS II I'm now running the 100 shot on the stock timing curve detonation free. Just as a test, I ran it with 87 octane and a bottle later still no detonation. Couldn't have hurt squish too bad, though it surely didn't help any. I'd rather have all the extra flow though.
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Old 02-28-2008, 12:54 PM   #11
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I've been doing more searching, and the 01+ block has the main bearing support plate which is a desireable feature it seems for heavy duty builds, but does it really make a huge difference, or would I be just as good off with a '94-'00 block?
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Old 02-28-2008, 01:12 PM   #12
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you'll be fine with the 94+ block
if you do not plan to over-bore, you should be fine with just honing, but again, a machinist will know best...
you seem set on the rest and i wouldnt change anything myself
i plan to build a block sometime soon so im trying to learn as much as i can from others posts
thanks to all contributing valuable info
Dan
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Old 02-28-2008, 01:37 PM   #13
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Quote:
Originally Posted by neogenesis2004 View Post

Ask splitime how his honda motor with vitara pistons is doing. I believe his slap all the time, even while driving and its been going strong for years now.
Heh, it's true. It sounds like my 1.6l is a diesel motor. 30k+ on it and no issues. Hell... i spiked to 27psi one night and all is good.

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Old 02-28-2008, 01:37 PM   #14
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Yea you'll be fine without the girdle support. Your already planing on using main bearing studs so the main bearings will be fine. The best way to reduce loads on the crank would be to buy lightweight pistons/rods and have them balanced. If you keep your RPMs below say 7-7.5K you'll be fine don't worry about it.
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Old 02-28-2008, 01:38 PM   #15
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Quote:
Originally Posted by patsmx5 View Post
...Putting forged pistons in a stock bore they will expand and bind, trashing your motor....
Nonsense - no different than sticking any size forged piston in the corresponding bore size. Think about it. If you have a XXmm bore then you spec an XXmm forged piston, it's all the same. Machinist should check the bores and if they're perfect you don't need an overbore.
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Old 02-28-2008, 01:47 PM   #16
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Quote:
Originally Posted by m2cupcar View Post
Nonsense - no different than sticking any size forged piston in the corresponding bore size. Think about it. If you have a XXmm bore then you spec an XXmm forged piston, it's all the same. Machinist should check the bores and if they're perfect you don't need an overbore.
Nonsense? I don't know what factory clearances are on the stock 1.8, but generally speaking forged pistons require more clearance because of higher thrermal expansion. If his stock clearance is .002 and it's perfect, and he drops in some forged pistons, they will seize. It's NOT all the same. If the bores were perfect he could have it honed and them put in pistons, not just drop them in. You guys go ahead and do whatever you want, I know how to bore a block.

EDIT: For example when I did the 360 block, the pistons were .040, so the block was bored 4.042 I think, then we honed it to get the last .001. Left a good crosshatching for the rings to break into and the motor has no piston slap and is still running.
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Old 02-28-2008, 02:28 PM   #17
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In researching forged pistons for my F stroker, both Wiseco and Venolia stated that I just need to spec a stock sized "non overbore" piston for my "mint" block. Nothing else is needed. I can only assume that the piston is designed to fit the stock bore.

I doubt his block is perfect, but if it is, I don't see the point in an overbore. I'd at least ask the manufacturer of the piston.
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Old 02-28-2008, 03:24 PM   #18
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Don't assume anything, find out what your clearances are and what they should be.
My Haynes Manual shows factory piston-to-bore clearance for 1.8L of:
standard: .0016 to .0020
service limit: .006
I would not trust these numbers 100 % since it's a Haynes manual. I'd make sure it's what the Mazda FSM shows.

Neo suggested using .0040 as that's what he is using for is forged pistons. That's fine. If I ever build a forged motor, I'll probably do the same.
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Old 02-28-2008, 04:02 PM   #19
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So it sounds that if the engine is in good shape, I can use a non-overbore piston. If there are some issues, overbore will be the next step.

Anyway, in looking at pistons, some companies list the overbore by +.010, +.020, etc. Now with the stock bore being 83mm (which is what I've read, please correct it if I'm wrong), what is an 83.5mm piston? Is that +.010, +.020?

Quote:
Originally Posted by patsmx5 View Post
Neo suggested using .0040 as that's what he is using for is forged pistons. That's fine. If I ever build a forged motor, I'll probably do the same.
Is that for a stock bore sized piston?
Don't the pistons come with a spec sheet telling you (or your machinist) how much they expand, and thus how much material to remove from the cyl. walls?
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Old 02-28-2008, 04:24 PM   #20
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Quote:
Originally Posted by RotorNutFD3S View Post
So it sounds that if the engine is in good shape, I can use a non-overbore piston. If there are some issues, overbore will be the next step.

Anyway, in looking at pistons, some companies list the overbore by +.010, +.020, etc. Now with the stock bore being 83mm (which is what I've read, please correct it if I'm wrong), what is an 83.5mm piston? Is that +.010, +.020?


Is that for a stock bore sized piston?
Don't the pistons come with a spec sheet telling you (or your machinist) how much they expand, and thus how much material to remove from the cyl. walls?
Ok, your not understanding everything. Buy some .010 or .020 over pistons and give it all to a good machinist and let him do his thing. Tell him you want .0035- .0040 piston-to-cylinder bore clearance. Why are you afraid to bore out the motor? It's extra displacement, which is HP. Not a lot, but hell if you can choose between 0,3, or 5 hp, which would you pick?
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