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rebeldryver
Master Fabricator
Joined: 28 Jun 2007
Posts: 3026
Location: Los Angeles, at least today.
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 Posted: Sat Nov 07, 2009 12:15 am Post subject: |
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| 1fast72nova wrote: | cool.
from here they don't look too big.
You could make a small investment right now, a 6 sq/in piece of plexi glass
and a trip to the local drug store to get a 6occ syringe from the drug store (ask for a large saline syringe) and a feeler gauge. Oh, and make sure it's a good syringe that has it marked down to the CC.. some will say this isn't accurate enough but compared to guessing it's exponentially better.
Ok, start off by bring a piston to TDC, laying the plexiglass (or straight edge if you have one) across the deck and use the feeler gauge to check how far in the hole the piston is.
write that number down. You can check a few if you like to make sure everything is somewhat square.
now determine the thickness of gasket to bring your quench to .040-.050" (feeler gauge + available gaskets)
Now move the piston down the bore, put the plexi glass over the bore and move the piston back up until it just touches the glass. now use a pair of calipers to measure how far in the bore it is. replace the glass and add rubbing alcohol until you fill the bore to the glass, measuring the CC's it takes.
calculate the volume in CC's and subtract the CC's it took to fill it up. this will tell you the dome of the piston. in CC's
volume=pi × r^2 × h
but there are calculators you can use too
now check your heads CC
now that you have the CC of the piston and CC of the head + know the feller gauge you need use a calculator to determine your compression ratio.. |
I don't think the cc of the piston in the bore will work because the domes most likely are higher than the deck.
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gamble71
Master Fabricator
Joined: 30 Jun 2007
Posts: 4521
Location: Clarksville, Tn
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| Posted: Sat Nov 07, 2009 12:28 am Post subject: |
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that would be correct. I was trying to think of a way to make it work, but thinking it's a physical impossibility  
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DieselGeek "wow, that made so much sense. I'm amazed at your awesome-ness" |
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1fast72nova
Rat Rod
Joined: 21 May 2007
Posts: 871
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| Posted: Sat Nov 07, 2009 12:50 am Post subject: |
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put the plate on the deck, rotate the crank until the piston just touches the plate, fill with alcohol from the syringe. Count the CC's
now calculate the total volume of the cylinder at the pistons present depth (excluding the dome).
for example:
piston is 1/2" down the bore, a 4.250 bore = 116.2 CCs
subtract the number of CC's it took from the syringe to fill = the domes CC
make sense?
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gamble71
Master Fabricator
Joined: 30 Jun 2007
Posts: 4521
Location: Clarksville, Tn
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| Posted: Sat Nov 07, 2009 1:22 am Post subject: |
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kinda.... I'd have to do it, and post the #s to see if I did it right. Kid's sick, no don't think I'll be in the garage much this weekend 
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