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| Tweet Topic Started: Aug 21 2014, 12:25 PM (13,315 Views) | |
| freegeo | Sep 12 2014, 01:01 AM Post #46 |
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I have read about using clay and cc the heads before but have never done it. Where would I buy the clay at. Is it just a modeling clay? Does the gasket side of the head need to be covered with a plexiglass piece to do cc of the head. Plug installed and use like a syringe to fill it up to full. That gives you the cc, right. Been a while since I've read about it. Are you talking about the math to do the compression ratio? There wasn't much taken off the head. Maybe .005" or .006". |
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| econoboxer | Sep 12 2014, 08:09 AM Post #47 |
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I am the one on the left.
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Modelling clay- I used crayola- make a little ball (cherry size)and place gently om the piston on the side where the valve comes down. Use your already compressed old head gasket. Place head on and use. Your old bolts torque down. Rotate the crank several times and take apart. Examine clay- cut a cross section at the thinnest part- use feeler gauges to determine thickness of the thinnest part of the cross section. There was a reason you didn't throw away those old things;) To cc your head- you can do a few inexpensive ways. The cheapest- go to pharmacy and ask for child oral medicine syringe- they are free- and pretty accurate. I used a 50 mL volumetric flask that I had laying around. Prep your head ad you stated- plug in, valves closed. Measure how many cc's it takes to fill the dome remember that there is a meniscus to liquid and you just want it full flat- a piece of plexiglass- or regular glass will suffice. I used combustible liquid because I was able to pour pretty fast, and keep accurate measurements- I wasn't worried about minute evaporation. Once done you can let evap- or use to clean parts- it isn't that much I would expect anywhere from 26 cc- 30 cc Not required for general calc to measure all combustion chambers, as 1 should be representative of all- and you aren't building a race motor. Remember mL=cc Edited by econoboxer, Sep 12 2014, 10:51 AM.
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| freegeo | Sep 12 2014, 10:49 AM Post #48 |
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I still have my old gasket but it is not in the best of shape. That thing was stuck pretty good. I think I still have my head bolts. I bought new ones with the allen head. They are re-useable. |
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| econoboxer | Sep 12 2014, 10:53 AM Post #49 |
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I am the one on the left.
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Doesnt have to be ingood shape- you are using it as a template spacer for hand revolutions- You could Use your new headbolts- its up to you- I know semantically they are re-useable- but he otherones are toast anyways- no harm done |
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| freegeo | Sep 12 2014, 11:42 AM Post #50 |
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I'll have to get the other 2 pistons in so I can try and do the claying. I looked at my old head gasket and the metal rings around the cylinders are what will press against the block and head while doing the claying. So 1 mL = 1 cc? If that is so it will make it very easy to figure it out. Thanks for the help. This is all needed to figure compression ratio? |
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| econoboxer | Sep 12 2014, 12:09 PM Post #51 |
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I am the one on the left.
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I already know your bore/ and stroke- only missing key is head volume(cc) Determine the swept volume -- volume displaced by the moving piston -- of one cylinder in centimeters. Formula: bore x bore x stroke x .0031416 = single cylinder swept volume. Next: Calculate the clearance volume, which is the distance from the top of the piston to the engine block deck surface. Formula: bore x bore x deck height x 0.1996 = clearance volume in cubic centimeters. Deck height is the distance from the piston top to the deck in centimeters. A piston that's completely even with the block will have a deck volume of zero. Note that pop-up pistons -- where the piston pops up over the block deck surface -- has a "negative volume." Next is where you take the compressed thickness of headgasket(from manufacturer) and cc the head- sincw you are no longer stock ![]() Obtain the manufacturer's specs regarding your cylinder head's combustion chamber volume, the head gasket's compressed volume and the displacement of the piston's dish-valve reliefs or dome, all in cubic centimeters. For this explanation, you'll consider a dish or valve relief as a regular "positive" cc . Nearly there:) Add your derived figures up to get cylinder volume with the piston at TDC. Formula: combustion chamber volume + gasket compressed volume + clearance volume minus clearance volume for pop-up pistons + dish-valve relief volume minus volume for a domed piston = chamber volume at top dead center. Add CV-TDC to your swept volume to derive cylinder . Last step: Divide CV-BDC by CV-TDC to arrive at your final compression ratio. or- cheat. ![]() https://www.rbracing-rsr.com/compstaticcalc.html bore:2.93 (you have overbored from stock 2.91 to 2.93) stroke:3.03 head gasket thickness: look for your specs on the one you bought. piston top volume- about 1 cc combuston chamber: you are about to go out there and measure it. ![]() now you know. Edited by econoboxer, Sep 12 2014, 03:03 PM.
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| freegeo | Sep 14 2014, 10:02 PM Post #52 |
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When claying the engine the cam, lifters, timing belt all have to be installed correct? |
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| econoboxer | Sep 14 2014, 10:50 PM Post #53 |
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I am the one on the left.
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Yes- that is right You are checking piston to valve clearance, and piston to head clearance- so you can measure what you cant see. Edited by econoboxer, Sep 14 2014, 10:54 PM.
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| freegeo | Sep 14 2014, 11:10 PM Post #54 |
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Well i either didn't do it right or I see why this is a non interference engine. I started with 2 marble sized pcs of clay over each relieve in the piston above the valves. Put my old head gasket back on and torqued the head down. Turned the crank over a few times and took the head back off. No marks were visible in the clay. ![]() Made a larger size ball of clay and put it in the center of the piston. Put the head gasket back on along with the head and torqued it back down. Turned the crank a few times and then took the head back off. this time there is marks left in the ball from both valves. ![]() Don't need a feeler gauge for this. Used my calipers and it is .473" Does this sound right? Edit - I have to do it again I didn't have the cam, lifters and timing belt on. I just rotated it with the head on and turned the crank. Edited by freegeo, Sep 14 2014, 11:13 PM.
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| freegeo | Sep 15 2014, 12:59 AM Post #55 |
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Did it again but didn't change the results any. I did cylinder # 1 and 2 this time. Still get the results of a range of .470" to .490". That explains why it is a non interference engine.![]() ![]() I did check the stroke on a couple of the cylinders and you were right on the money at 3.02" econoboxer. I still want to cc the head just to see what it is. Have to get me a syringe yet though. |
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| econoboxer | Sep 15 2014, 11:09 AM Post #56 |
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I am the one on the left.
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not quite the right placement- but you are still closer enough to not worry about it. ![]() ![]() as you can see, my tolerances are way tighter than yours. here is a cross section measured to determine squish. ![]() ya know- I never posted the clayed motor photo's before- some tricks you want to keep to yourself, you know- otherwise everyone knows how to do voodoo magic Edited by econoboxer, Sep 16 2014, 06:26 AM.
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| freegeo | Sep 15 2014, 11:42 AM Post #57 |
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Yes I didn't want to get the clay pressed over the piston into the cylinder or rings. You must have a lot taken off your head and block to get that type of squish. Now to figure out the head cc. got find me a piece of plexiglass. Is that the engine you put in your vert, and does it have almost 12-1 compression? |
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| econoboxer | Sep 15 2014, 11:47 AM Post #58 |
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I am the one on the left.
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Well- we took alot of the block- 3-tech took alot off the head since we got the performance cam and head package from him. this pic was taken a looong time ago... when the head was off briefly. This is the motor that is now in the convertible- yes. 11.89:1 compression. Edited by econoboxer, Sep 15 2014, 11:55 AM.
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| freegeo | Sep 15 2014, 12:30 PM Post #59 |
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No wonder you don't care to drive a normal geo engine. That thing has to have some get up and go. You are lucky to have a spouse that likes the same thing as you do and wants to help. That makes things much easier. |
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| nwgeo | Sep 15 2014, 12:37 PM Post #60 |
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Holy toledo. 11.89:1 compression. Can you say premium gas with added octane? |
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