I don't know how thick the original gaskets are. You want about .035 to .065 clearance between the piston and head. If you use the composition gaskets that come in most common sets, you should be at .040 to .050 with zero deck.


Lawrenceville, GA

Charlie   I appreciate all the info.  I guess I'll start with the block and have that bored and zero decked. Do you know what the difference in thickness is between the old style steel gaskets and the new compostion gaskets? I assume that difference is the minimum amount that needs to be removed from the block and heads to be equivalant to the original compression.  Thanks  Dave V

SE Wis

You don't have to figure dynamic but that's really the only way to get it dead on. Shoot for low 9s for compression.

You should be able to achieve that by zeroing the deck and milling the heads. You may not even need to mill the heads if the bore required to clean it up is on the larger side.



I'm using a repro of a blower grind. Low end is not as strong but is still sufficient for light duty truck work. After about 1500rpm it is real nice. It gets 16.5mpg on the highway with my combo and I think it can get better with some more tweaking. I've never calculated the city economy but I can go a whole week doing my regular stuff between fill ups. It should work out to somewhere around 11 in city driving.


Lawrenceville, GA

Charlie   I went thru the links on dynamic compression. It's quite involved. I do think that I will zero the deck at least. Does anyone out there have a similar setup that can tell me what cam is working good for you while still using 87 to 89 octane fuel or will I need to go to 91-93 octane.  Dave V

SE Wis

I don't think there is really a right or wrong way.

You can gain a fair bit by zeroing the deck of the block. If you're not familiar with that terminology, the piston top is usually lower than the block surface at top dead center. If you remove enough material so that it is flush the compression will increase and detonation resistance may also increase. This alone may not require a change in the grade of gasoline. Zeroing will require the thicker head gaskets that come in most gasket sets because the shim gaskets will now place the piston too close to the head.

Milling the heads is another option. Domed pistons are another. If it were me, I'd zero the deck and go from there.



I think Ted has said that with G heads every .0065" removed from the surface reduces the volume by about 1cc. Some quick math indicates about .1 point of compression per cc. Take time to actually do the math when you are figuring this all out, though.



I'd shoot for 9.3ish (you may be thinking "well it's 9.7, stock." That's advertised. Forget that, it's not 9.7) and if you really want to get fancy, make a decision on the cam and then figure out which static ratio is required for a dynamic ratio which is suitable for the grade of gasoline you wish to run.



Some links about dynamic compression:

http://www.y-blocksforever.com/forums/Topic57116-3-1.aspx?

http://www.y-blocksforever.com/forums/Topic46641-3-1.aspx?

http://www.y-blocksforever.com/forums/Topic44558-3-1.aspx?

And much more is available by using the search function.


Lawrenceville, GA

Charlie  What is the right way to increase the compression on a Y block. I understand that the replacement head gaskets are thicker than the original steel gaskets which would lower the compression. So how much would be needed to mill off of the heads to raise the compression enough to make a difference?  Dave

SE Wis

You can get a clue about that cam by measuring the lobe with a caliper.



Increase your compression. That helps with economy and power. The gas required will cost more per gallon but the efficiency increase will negate that increase in cost. With compression, the cam is less critical, within reason. You can have a cam that provides a nice sound and reasonable mileage if you wish. I think that, to a point, how you drive is more important than the cam profile when were talking about better mileage.


Lawrenceville, GA

Oldmics    Thanks for responding. There are no other letters on the cam. It does have a #75 and #82 on it. I guess if we can't  ID this cam I will have to consider a different one. Thanks again.  Dave V

SE Wis

I have had good experience with the '57 Blower cam. Regrinds or repo's are available. Good street cam.

What is after the EDB ?

There should be an "A","B","C","D" or an "E" on the stick

Oldmics