How to messure cylinder head CCs

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How to messure cylinder head CCs

Post by 39coupe on Wed Jul 22, 2009 10:32 pm

This is the first time I'm building an engine from scratch. I have the lower end put together and putting the jugs and pistons on now but I have a question. I've measured my deck height and it is at .124". I'm now trying to measure the CCs so I can check my compression ratio. But I'm not sure what level I fill to to measure. If I measure just to the top of the center most indentation I've got 50cc, if I fill the whole thing it takes 110cc. Which is correct?

Oh and here is just some test fitting of the tins.



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Re: How to messure cylinder head CCs

Post by rpm750 on Wed Jul 22, 2009 10:47 pm

I've seen post with 50 in them so I'd say 50. Also an old HP book I had for Chevy engines showed most of the old double hump heads were like 67cc from the factory.

I'd say the 50cc is correct.

Edit........ just remembered Jason's post... Notice his combustion chamber size.

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Re: How to messure cylinder head CCs

Post by 39coupe on Wed Jul 22, 2009 11:01 pm

OK found it. Mine measures 50CCs - so here are my measurements from aircooled.net

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Re: How to messure cylinder head CCs

Post by Clyde on Fri Jul 24, 2009 2:55 pm

You should have a plastic disc that fits snugly into the bore of the head. Put a little white grease on the outer edge, so it seals well against the head, and fill it up. Stock DP heads are around 58 cc's form the factory, + or - 2 cc's.

.124 deck is pretty deep. You might want to get some spacers under your cylinders. Is there a specific compression ratio you're shooting for, to make the most of a cam?
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Re: How to messure cylinder head CCs

Post by EngineerTEN on Mon Jul 27, 2009 9:34 pm

I got the 50cc measurement for the heads from Steve at Pro-flow Performance for the heads Emil is purchasing from him. I did the same for my engine when I purchased my heads from CB Performance, I asked them what the combustion chamber measurement is.
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Re: How to messure cylinder head CCs

Post by 39coupe on Mon Jul 27, 2009 10:16 pm

Clyde wrote:You should have a plastic disc that fits snugly into the bore of the head. Put a little white grease on the outer edge, so it seals well against the head, and fill it up. Stock DP heads are around 58 cc's form the factory, + or - 2 cc's.

.124 deck is pretty deep. You might want to get some spacers under your cylinders. Is there a specific compression ratio you're shooting for, to make the most of a cam?

Measured the CCs and it came to 50CCs. Also double checked my deck height and you are correct I was not at TDC. I rechecked before putting my heads on and I was actually at 3/32 not 1/8. So deck hight is .09375 putting my compression at 6.5. I've heard that 7.0 is too high and will require higher octane fuel so I'm good with the 6.5
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Re: How to messure cylinder head CCs

Post by Clyde on Mon Jul 27, 2009 10:39 pm

I've heard that 7.0 is too high and will require higher octane fuel

It depends on who you talk with.
Bergs are all about low compression.
Raby's all about raising compression, depending on the cam.

It all depends on your goals...
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Re: How to messure cylinder head CCs

Post by 39coupe on Tue Jul 28, 2009 7:27 am

Well, I'm looking to get a little more pep out of a 1200 without going radical.

I'm running 83mm big bore pistons and jugs, 1300DP heads, engle 100 cam, clearanced cam followers, and dual 34 webers. With the original 64mm crank that was polished (didn't need turning). Don't have rockers yet. Still saving for those, don't want radical on that either, this is my daily driver.
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Re: How to messure cylinder head CCs

Post by Clyde on Tue Jul 28, 2009 8:23 am

".124 deck is pretty deep. You might want to get some spacers under your cylinders." Sorry, I said that backwards. You'd need to spot face the case to lower your deck height. Or face your cylinders down.


Try it in the car, and if it has poor throttle response, you can always flycut the heads a little to raise it up.

For a rocker upgrade, just use stock 1300-1600 rockers. They're 1.1:1 giving you 10% more lift than the 40 horse ones.
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Re: How to messure cylinder head CCs

Post by 59suicide on Tue Jul 28, 2009 8:51 am

I run 7.8:1 with 89 or 87 depending on how much I wanted to spend on gas that day with no problems. The lower compression is a good idea because the % of ethenol in the gosoline is slowly climbing.
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