Have I made the right choices?

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Hey X, dealing with Islanders huh? Well, if I was in your shoes, I'd be feeling OK as well.
The builds not bad at all. Have fun with it.

Wheres the Hunny from? (town)
 
Glen Cove originally. Her entire family moved down here in the early 80's. As a matter of fact her brother in law pitched for the Yankees for a short period of time, Mike Armstrong. He moved here also. As far as the motor goes I am going to have to run it as is and see how it does, If I don't like it I'll change it.
X
 
Xstream_1 said:
As far as the motor goes I am going to have to run it as is and see how it does, If I don't like it I'll change it.
X
Click to expand...

I think you will be very disappointed.

The Sealed Power 285n piston that you mentioned is a flat top with 4 valve reliefs. The compression height is listed as 1.720". If you add that to 6.123" rod length and 1/2 of the stroke (3.31 / 2) 1.655" you get a compression height of 9.498". If your block has not been decked, and it is near the 9.600" blueprint dimension, then these pistons will be 0.102" down in the hole. Add the .039" compressed head gasket and your quench distance is 0.141". So quench is non existent.

Using these numbers:

Bore = 3.940"
Stroke = 3.31"
Head Volume = 63cc
Gasket bore = 4.180"
Gasket Comp Thickness = .039"
Deck Clearance = 0.102"
Piston Volume = 12cc

I get a calculated compression ratio of 7.35:1. And to be honest, I am guessing that is on the high side because the four valve reliefs are probably more like 14cc's. Couple this with the aluminum heads and the compression will feel even lower.

I hate to tell you, but I think this engine will be a dog... unless you install a turbocharger or supercharger. Then it would be perfect.

If you don't plan on forced induction, then you need to bump the compression up. I would suggest milling the block and/or heads a combined .080" and then use a Cometic head gasket with a .020" or less compression thickness. This would at least get you in the 9:1 range.
 
I agree with you to a point, that the block is less than spec., my stock block without machining is .070 below with stock pistons and the rest, as produced (78 vintage) I also agree with you on the heads, as the smaller runners will help. If you use the mopar performance gaskets @ .020 thickness you should end up some where around 9:1 compression or just under. Even with the valve reliefs as they are only 4 -6 ccs as they aren't deep. But you should still have a very good running engine.


BJR Racing
 
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