Need Help Building a 350-400hp engine!!!! Bearing clearances and ring gap - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-20-2013, 08:58 PM   #21
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Originally Posted by ctdrftna View Post
I have built some honda, i have used honda factory specs, but i may run the rods and mains a tad looser for race motor. If your using aftermarket rings/pistons, they will tell you gap specs. And you can use the old saying .001 per inch of journal diameter for clearance
That is pretty much what I have come up with. I will use the ring gap wesico recommends and the bearing gap will be within manufacturer specs just on the loose side of it. I will be using OEM bearings and hastings rings and I have pretty much found stock or a tiny bit looser than stock is good for about every street car under 500hp.
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Old 01-20-2013, 09:42 PM   #22
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you shouldnt have any problems with that, people will tell you what they think the clearances will be, and they will tell you what it should be down to .0001" . Most people dont have the measuring equipment to do this, nor the climate controlled enviroment required to measure this precise. The setting fixtures that engine builders use to set dial bore gauges have a accuracy tolerance, as well as human error, and the dial bore itself has a accuracy tolerance. The things stack up to a larger error. So the best advice i give you is measure the best that you can, and use some common sense and feel. Every thing should spin free, only drag from the assembly lube and rings. and slightly less drag at tdc and bdc. Dont ***** foot it on break in, put in not detergent oil and run the car at 2000 rpm for 10-20 min, get it up to temp and check for leaks and no over heating, then go find a nice big hill and put good load on the motor and make runs up the hill. Bog the motor down in a high gear and let it pull up to about 4000-4500. Do this a good many times then start increasing rpm a little by little
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Old 01-20-2013, 09:47 PM   #23
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Yea the I have access to all the tools I need within a tolerance of .0001 and I have a nice climate controlled inviroment but there is still human error to come into play and if I can hold a tolerance of .0005 then I will be happy with that as for break in I will take your advice and being I moved to the mountains about 8 months ago I dont have much choice. I did something to this with my last motor and it seemed to work well now I just have a bigger hill I can use.
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Old 01-21-2013, 03:42 PM   #24
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So this is what I came up with


So after lots and lots and lots and lots of searching and reading. Plus some calls to the local honda machine shops this is what I have come up with. These are the specs recommended to me by some very reputable machine shops for my build and from the manufacturer.

piston to wall - Piston manufacturer specs if you are really gonna push the motor add .0005"

Ring gap - Piston manufacturer specs and if you are really gonna push it (like high compression with boost in my case) add 0.001-0.002"

Bearing clearances - using honda OEM bearings set clearance to stock but on the loose side of stock. This is also for an engine that will never see more than 8000 rpm

I though this information would be helpful to anyone looking to build a 400hp honda engine. I would highly suggest contacting your local honda engine builder and some of the bigger ones like inline 4 to see what they have to say if you do not feel comfortable with factory specs or if you are using another type of bearing.
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