How do I find my target stroke?

[Driver_10]

There was an interseting thread on compression height, So someone tell me this...

I have a set of 3500 pistons with a compression hieght of 1.460 for use with 5.7l SBC con-rods. The 3500 crank will have to be ground down to 2.100 to accept these rods.

I ordered a set of copper 3400 style head gaskets with a thickness of .070 (they didnt come in any other sizes)

How do I determine how much an offset stroke)the crank will require in order to have a desirable .040 quench.

[(stroke/2) + rod legnth + piston compression hieght]
- (deck hieght + gasket thickness) = actual quench

Using the product from this equation

The actual quench - desired quench = additional -/+ stroke offset


I came up with this off of the top of my head so I dont know if the equation its correct.

[bszopi]

Plug in numbers to the site's CR Calc (link in the navbar to the left), at it will tell you your quench. Determine your optimum stroke from that.

[95Grand-Am]

deck height 8.818" -rod length 5.7" - comp height 1.460 =1.658+.03 deck height =1.688*2= a stroke of 3.376". I would suggest having the block squared before choosing a stroke. The tolerance on deck height is very loose, having it squared will make both sides the same height, then you will have to plug the new deck height into your formula to get the desired stroke. Also is .070" the compressed thickness of the head gasket or what it is before it is compressed?

[Driver_10]

deck height 8.818" -rod length 5.7" - comp height 1.460 =1.658+.03 deck height =1.688*2= a stroke of 3.376". I would suggest having the block squared before choosing a stroke. The tolerance on deck height is very loose, having it squared will make both sides the same height, then you will have to plug the new deck height into your formula to get the desired stroke. Also is .070" the compressed thickness of the head gasket or what it is before it is compressed?

I didnt give compressed thickness of the gasket that any concideration. I cant really say since its an annealed copper gasket, I know that they dont compress as much as the MLS or graphite head gaskets.

Come to think of it, squaring the block would reduce the deck-height and also reduce the need for a positive stroke offset. When I did my first crude formula, I found a maximum of .130 that I would hypothetically need to remove from the crank pin (+/- .019 of total crank machining) to get my desired stroke and crank pin diameter.

I would prefer not to enlarge the stroke if possible.

[95Grand-Am]

You could leave the stroke, and deck the block to 8.785" but you will have to have the LIM cut also, the michine shop should have a formula to determine how much.

[Driver_10]

You could leave the stroke, and deck the block to 8.785" but you will have to have the LIM cut also, the michine shop should have a formula to determine how much.

that sounds a lot cheaper

Thanks for the feedback guys. Dont know what Id do without ya.

[95Grand-Am]

Can I ask what you found for pistons and what they have for a dish.

[Driver_10]

The pistons are Weisco custom forgings. The require a .020 overbore. I dont have a berette so I cant tell you the displacement of the dish.

[95Grand-Am]

If you want a rough Idea use medicine cup a ml is the same as a cc. You should be able to get a ballpark idea.