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post #1 of 5 (permalink) Old Mar 5th, 10, 12:05 PM Thread Starter
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Question for engine builder

If you take .030 or so off a stock 64cc iron head, how many cc's will it be reduced? How many thousandths of an inch can you take off a stock head, before you have intake alignment issues? TIA
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post #2 of 5 (permalink) Old Mar 5th, 10, 12:28 PM
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Re: question for engine builder

A .030" cut will reduce your chamber by @4.5~5cc
A general rule would be @1cc for each .006" of cut - slightly more for an 'angle-mill'.

But, .030 is quite a cut for a stock head.
You will have intake fitment problems at that amount and will have to shim the dist.
You can usually only cut @.010~.015 with out any major stock gasket issues.
With use of some aftermarket gaskets and silicone on the manifold ends you can get away with a .020" cut most of the time.

Keeping valve to piston clearance also becomes an issue and may require the valve slots be deepened on cuts over @.020"
Normal quench spec.s of .040~.045" are also hard to maintain by standard gasket selections when using excessive cuts.

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post #3 of 5 (permalink) Old Mar 5th, 10, 01:39 PM Thread Starter
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Re: Question for engine builder

That is good information. I guess if you go beyond .020, you can always increase the head gasket thickness to make up for it. I guess there is not too much to gain compression wise from surfacing the head....... Trying to figure out how to get the most compression out of this 327 with 4 valve relief flattops .040 over, with 64cc heads.........

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post #4 of 5 (permalink) Old Mar 5th, 10, 03:28 PM
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Re: Question for engine builder

Without changing heads or pistons, the easiest way to increase the compression (or more truely, 'Cylinder Pressure' ) would be by carefull selection of a cam that acts to enhance the DCR rather than reduce it - as many of the present cam designs do to allow use of lower octane values with higher compression ratios.
Selecting a cam with a moderate overlap, quicker intake valve closing and a decent LSA should help the engine 'think' it has a higher compression ratio than it really does.

You should get all your engine spec.s then call some of the cam suppliers and talk about your needs/wants to increase your DCR and see what they would recommend.
The choice of a good cam could very well give you most the results you want without any mechanical changes.
Discuss the use of different rocker ratios with them also, may be some small gains to be had there with certain cam choices.

Choice of Head Gasket may also show a slight increase in static compression that may help.

Be sure to evaluate your intake and exhaust systems in this also, they an make significant gains/losses to you DCR.

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post #5 of 5 (permalink) Old Mar 5th, 10, 05:53 PM Thread Starter
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Re: Question for engine builder

If the LSA is smaller like 108 vs 112 let's say, doesn't that give the effect of having a higher DCR?
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