Thicker Head gasket/Push rod length

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Thicker Head gasket/Push rod length

Post  Tore on February 1st 2012, 9:29 am

I had to lower the compression on an engine I have and bought some .080 Cometic Gaskets. I am feeling I might have to get longer pushrods becuase this can throw the geometry off I have heard. ANy idea what increasing the thickness .040 will require?
I am going to try to get the heads bolted on Sunday.


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Re: Thicker Head gasket/Push rod length

Post  dfree383 on February 1st 2012, 9:59 am

Fit up and look at what you got, it may be acceptable as is.
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Re: Thicker Head gasket/Push rod length

Post  quick 52 on February 2nd 2012, 11:02 am

dfree383 wrote:Fit up and look at what you got, it may be acceptable as is.
x2 .040 isnt much

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Re: Thicker Head gasket/Push rod length

Post  Tore on February 2nd 2012, 1:04 pm

I kind of wondered if I would be lucky and they would work. Just wanted a couple opinions.


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Re: Thicker Head gasket/Push rod length

Post  jrocco on February 3rd 2012, 11:28 am

Tore wrote:I had to lower the compression on an engine I have and bought some .080 Cometic Gaskets. I am feeling I might have to get longer pushrods becuase this can throw the geometry off I have heard. ANy idea what increasing the thickness .040 will require? I am going to try to get the heads bolted on Sunday. Thanks Tore

I just did a check on the engine I am building and changing the push rod length .050" moved the pattern on the valve tip from slightly off center on the intake side to slightly off center on the exhaust side. I do not know how this would equate to increasing the gasket thickness, but when changing the push rod the result is magnified by the rocker ratio. So I would not think you would get that much of a change with the gasket thickness.
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Re: Thicker Head gasket/Push rod length

Post  bbf-falcon on February 5th 2012, 7:45 am

Will be interesting to find the answer,because you are raising the head up .040 extra . Gonna kill the quench,but it's mainly a street engine so can't be too bad.

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Re: Thicker Head gasket/Push rod length

Post  LivermoreDave on February 5th 2012, 9:14 am

dfree383 wrote:Fit up and look at what you got, it may be acceptable as is.

As Dave has replied, do your homework! Pushrod length usually is offered in .050" increments. You just never know unless you check. The rocker tip/valve tip relation could be a bit off, changing the effective height of the cylinder head in relation to the block could make it better or worse. With light valve springs, component wear may not be accelerated as with stiffer springs. Although we always seek perfection, in the area we discuss, one may get by with a bit less perfection!

Dave.

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Re: Thicker Head gasket/Push rod length

Post  Larry Williams on February 5th 2012, 10:07 am

shaft rockers takes the worry out of being close
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Re: Thicker Head gasket/Push rod length

Post  Lem Evans on February 5th 2012, 12:11 pm

Larry Williams wrote:shaft rockers takes the worry out of being close

As the head gasket gets thicker it will require running the adjuster out of the rockerarm more...at some point it'll make the rockerarm more prone to breakage. There is no free lunch with either style rockerarm.

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