What is the 340 gasket bore in inches?

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dibbons

dibbons

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Using some on line programs to figure static and dynamic compression ratios. One parameter I don't have is the gasket bore size in the aftermarket head gaskets. Anyone have a head gasket laying around they could measure for me please? So far, I am just guessing at 4.125". Thank you.
 
Just measured Fel-Pro 1008 gasket: 4.160 inches, this is a crushed, used gasket.
 
Results:

BScreen shot 2017-01-30 at 11.22.49 AM.png


AScreen shot 2017-01-30 at 11.23.26 AM.png
 
I don't know why they make the bores so freaking big. For a 360 they only need to be 4.090 max and a 340 should be no bigger than 4.125.


Any bigger than that is just stupid and a waste.
 
yellow rose said:
I don't know why they make the bores so freaking big. For a 360 they only need to be 4.090 max and a 340 should be no bigger than 4.125.


Any bigger than that is just stupid and a waste.
Click to expand...
and even worse when you have to use that size on a 318 ! unless you go MLS.
 
Watch out!
Check out the method of determining the ICA; they use the 050 number plus 15*. That is not right. Or at least not right for a flat tappet hydraulic.

Here is a comparison. I have a 276/286/110 cam in at 106.
The 050 numbers are 230/237/110

This cam has an ICA of 64* using the advertised.
It has an ICA of 41* using the 050 numbers.
Adding 15* to 41* equals 56*.
This is 8 degrees short, and this will throw your Dcr waaaaaay off, right into soggy bottom end territory, if you are not careful.

Also, be very careful to enter your piston pop-up or dish correctly, as a plus or a minus.
 
Last edited:
AJ/FormS said:
Watch out!
Check out the method of determining the ICA; they use the 050 number plus 15*. That is not right. Or at least not right for a flat tappet hydraulic.
Click to expand...
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Thanks for the reminder. I actually did not use that method, I used the actual intake valve closing at ABDC per the camshaft grinder.
 
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