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The Wife and the Car
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Discussion Starter #1
My engine has done 1.3 Lakh kilometers.
Initally I thought my compresion was off.
But after geting a friend to help me they all checked out at 180 PSI.

I am thinking of freshening up the engine.
And dont know if I should get 75mm pistons or 75mm pistons.

When you guys open old engines.
Do you normally find that its the liner that has worn or is it the rings and pistons.

What is the exact size from the factory. Between makes i.e.
on a Bike a Wiseco piston would come as 74.925 as they recommend .075mm clearance. If you buy an art piston it will be 74.970 because they want you to run 0.030 clearance. You get what I mean.

So are there companies out there that make pistons in sizes larger than what the stock honda pistons.

Does any company do a 75.25mm piston.
 

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Little bit confused by your post. They do make 75.5 and 76mm pistons that just take a bore and hone for these blocks. These cylinders do have a tendancy to turn egg-shaped with high mileage so you will want to have your bores checked for all that before starting a project like this. Hope that answers some of your questions

-Luke
 

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The easiest way to do it is to buy bigger pistons and take them to the shop that is going to machine your block. You won't have to worry about anything. If you don't have the block at least honed to straiten the cylinders then it won't be long until you are burning oil, or pressurizing the crank case.
 

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I went with 75.5mm on my pistons when I was doing my rebuild on a z6
usally when you buy a set of pistons you'll get the info on what size & information to know & tell the machine shop what size you want it honed at.
but giving them the pistons is also a good idea, usally its cheap I think I paid 28$ for it to be honed & cleaned, they offered me to bring it back & balance the engine for 56$
its actually fun buying/building the engine just a decently long process. goodluck
 

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Buy 75.5mm pistons (.020 over). Take your Pistons to the machine shop and tell them what piston to wall clearence you want, have your block bored and honed so you start with fresh cylinders. Always use new piston rings and if you assemble it right it should run like a top! Take your time assembling it and ALWAYS MEASURE TWICE AND ASSEMBLE ONCE.
 

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The Wife and the Car
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Discussion Starter #6
Thanks guys I build Bike engines for a living.
Let me try and re-word my question.

1. When you buy a 75mm piston new. Do all 75mm new pistons come at the same size or are some larger or smaller than the honda unit.

2. When you open a high miles engine. Do you find that the liner has worn more or the piston. Or both.

Ive been told to avoid boring out the blocks to 75.5 because the Honda Liners are not as thick as the Suzuki ones. Where we can got even +4mm on the pistons in some engines.

My engine is not burning oil And has good compression. (I made a mistake while measuring it the first time). Now Im getting 180 PSI on all cylinders.
 

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95 CX Hatch
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I think the confusion is trying to translate what you have learned on bikes, over to the d-series 4cyl. These engines are much tougher, or in your bike building you weren't pushing them to the limits to find what you can and can't do with a stock block. We have quite a few members here with many years building these little engines and have yet to truly find their limits.

On a bone stock engine I have found mainly out of round wear and bearings. Not so much rings as the bearings tend to fail far sooner than blow-by. Any good engine builder would naturally re-ring and hone while doing bearings. 75.5mm is no problem at all on these blocks and have seen many cars in the 400+ whp range. A stock bore is ideal just for the extra wall thickness, but I don't think boring effects the strength of the sleeves much if at all. It mainly lies in the setup and tune in the car on how its reliability will be.
 

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All Hondas if tore down with about 100,000 miles on them need to be honed. Even if they are not smoking or having blow by problems. The cylinders become egg shaped, oval, or how ever you want to say not a perfect circle. When you buy pistons you are buying the size that the cylinder is honed to. I mean if you buy a 75mm piston it means that if you bore the cylinder to 75mm that piston will fit into it. I want to say that the piston is 74.94mm or something close to that. I am going to buy a digital caliper tomorrow and measure my SRP's. I'll let you know for sure. Remember that these specs are for a stock engine. If you are adding a power adder those specs will change. Same thing goes with ring gap. Being that engine parts are machined a lot better than they were 10 years ago, and that engine oil is far more advanced than what it used to be, you can build the engine a lot tighter too.

Don't worry about boring the engine out to 75.5mm. Some D series engines came that way stock.
 

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The Wife and the Car
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Discussion Starter #9
its a rather simple question and Im supervised there is no table or sheet out there listing piston sizes. Im 100% sure that each piston maker will have their own number based on metallurgy.


What most piston makers do is. they will adjust their final size to match their metallurgy.
When you say 75mm it refers to the liner hole size. Pistons will come in different sizes.
No two guys will use them same size.
If you know how to exploit this little trick you can get to keep the same size and just need new pistons and a hone.

I guess I should just lift the heads and measure up.
But its a pain. Cant even get original head gaskets here.

Could I have some idea as to numbers when you say Egg Shape.
i.e. On a RXG Motor you will typically see an oval-ity off 50-80 Microns on an engine that has run a lot of miles.
The piston will normally wear more typical values are in the range off 80-100 Microns.
So you can normally just get away with a hone and fresh pistons. All depends on how worn the engine is. On a RXG Id put that cross over point at 20,000 ks, on a RD at 30,000 Kms. Befond which you will need to go over size and need to counter bore and then hone.

(Thats the kind of Info I was looking for on the Honda Engine).
 

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I doubt you will find that information because it is of no use.

In your post you even say why it is of no use. Piston manufacturers do in fact finish their pistons to different sizes due to metallurgy. They do this to obtain the correct piston to wall for that particular piston at the nominal bore size. While changing piston brands changes the piston to bore clearance, it does not change the required bore size.

For any particular manner of use, the required piston to bore changes for a specific piston.

If a bore is worn it will be out of shape as it never wears evenly. It always wears more on the thrust side of the piston and mostly about 1/3 down the bore so you get both oval shape and barrel shape.

New rings help a bit for a while, but they can't work all that well without a straight round bore.

If the bore can be honed straight with suitable piston to bore for your intended use with your pistons and the rings groves are within tolerance, use your old pistons.

If not, decide if new pistons for a std bore will bring you within tolerance.

If new pistons won't stay within spec after you straighten the bore, buy next oversize piston and bore the block.

You obviously need the new piston size for your pistons and the required piston to bore for your pistons. That data should be supplied by the piston manufacturer.
 

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its a rather simple question and Im supervised there is no table or sheet out there listing piston sizes. Im 100% sure that each piston maker will have their own number based on metallurgy.


What most piston makers do is. they will adjust their final size to match their metallurgy.
When you say 75mm it refers to the liner hole size. Pistons will come in different sizes.
No two guys will use them same size.
If you know how to exploit this little trick you can get to keep the same size and just need new pistons and a hone.

I guess I should just lift the heads and measure up.
But its a pain. Cant even get original head gaskets here.

Could I have some idea as to numbers when you say Egg Shape.
i.e. On a RXG Motor you will typically see an oval-ity off 50-80 Microns on an engine that has run a lot of miles.
The piston will normally wear more typical values are in the range off 80-100 Microns.
So you can normally just get away with a hone and fresh pistons. All depends on how worn the engine is. On a RXG Id put that cross over point at 20,000 ks, on a RD at 30,000 Kms. Befond which you will need to go over size and need to counter bore and then hone.

(Thats the kind of Info I was looking for on the Honda Engine).
Your best bet is to just call the piston manufacturers to find out their particular specs if youre trying to get the biggest "75mm" pistons out there, although I doubt there will be much variance.

Ive built a handful of motors for myself and have never overbored, just a quick hone job w/3 stone hone and tossed in new std bore pistons. The bore would have to be pretty trashed for it to not work, I've taken out big scratches/damage from broken ringlands and it still came out fine. Will it always work? Probably not, but I've had good luck doing it.

-Jay
 

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The Wife and the Car
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Discussion Starter #12
Thanks Jay Ill be e-mailing you shortly with my shopping list.
None of the other shops like FJ / Heel Toe etc have been able to help me.
Hope you can.
Ill PM you a copy of my e-mail.
Sitting half way across the globe to really need to make sure I get the right stuff.
Im pretty sure I can get away with a light hone because there is no way a motor can pull like this one and hold such high comp. If the bore was oval this is my gut feeling.
 

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Discussion Starter #13
As to why the info may be useless.
i.e. For a 75mm Bore Wiseco will say make a 74.920 piston and tell you to keep 80 micron clearance. So you will sink a 75mm hole.
But as an Engine Builder I do not blindly follow what the piston guy says.
the number the piston guy is giving you is a play safe number. Allowing for mistakes and different and unknown power output level.
So I don't go on the basis of what the guy who makes the pistons says but rather on exp. and the predicted BMEP of the engine. So custom clearance numbers are not totally useless.
A lot like your boosted guys running a lot of ring end gap.
 

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High performance pistons generally get a range of clearances recommended and you use the one they recomend for your application.

Stock pistons have a recommendation that applies to normal use and you need to correct for that, BUT all are made for a nominal bore for normal use and you increase the bore for the higher power output.

Some pistons are made from alloys that expand more than others and therefore are made smaller so the still fit the same bore so that at maximum load in a std engine they all end up with the same clearance.

For extra clearance for higher power output you increase the bore size.

The difference in the increase for different pistons is very small.

Forged pistons tend to use higher expansion stronger alloys and are therefore made smaller. They are also made for high power outputs so are made smaller still. Bottom line, either way you end up needing the same bore size for the same power level.
 

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Alright I mic'd the pistons. The SRP Piston is 74.97mm and the bore in my block is 75.16mm. Now granted that is a stock bore with a lot of miles on it, and those are brand new pistons. The pistons also have to tuff coat on them. I am sending the block to Inline Pro to get Darton sleeves installed, so the bore is going to be different. I'll let you know in a month what they matched.
 

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The Wife and the Car
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Discussion Starter #16
SO Id say your bore has worn .16mm Which is quite a bit.
If you where to put on a hone in there. At the very least your going to get another 5-10 microns cut.

And the guy who made your pistons Expects you to run 30 Micron Clearance.
I dont like liner jobs. Lets just say haven't meet anybody who can match the factory work and metal here.

Im still trying to find somebody who can sell me pistons for my B15c2,
 
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