Engine rebuild question

[banks]

I have stock 302 at the moment and i want to build the bottom end while i have it out of the car. I would like to make it a stroker and I have been looking at a lot rotating assemblies. I would like to stroke it to a 331 using a forged crank with a 3.25 lift and a forged rods as well with 5.4 length. I know a stock 302 has a 3.00 lift and uses a 5.090 length rod.

My question is this. I'm am new to actually building motors and i was looking at the distance between the piston and the top of the block where the heads would go. (this is called the deck right?) I notice that the distance is very close to the top of the block and if you stroke it how does the piston not actually go higher then the top of the block? is the excess stroke made up for by moving the location of the wrist pin further up in the piston or is it done differently?

sorry if this sounds like a dumb question, but i'm trying to learn as much as i can before i spend the money.

thanks for the help

 

[85_SS_302_Coupe]

Part of it is the pistons, but most of the extra stroke happens at the BOTTOM of the cylinder, not the top. The piston actually comes further down in the cylinder, making more cubic inches....basically the same thing Ford did to make a 302 out of the 289.

 

[347HO]

It's in the compression height of the piston.
What changes is the distance from the centerline of the pin to the top of the piston.
With more stroke and longer rod, you need less CH.
You're good to go with a 331 setup. A 347ci setup depending on which route you go will put the pin in the oil ring lands.

 

[banks]

thanks for the help guys, the CH thing makes sense, i didn't really think about this. I definitely understand now. I've gotta do some more research at the moment. I'm trying to decide between a scat forged rotating assembly and an eagle forged rotating assembly.

Would it be necessary to upgrade the kit to h beam rods or would the forged i beams be ok? my plans are to keep it n/a and if that isn't enough i might throw a 75-100 shot on it but not more than that.

 

[347HO]

With a stock block... a forged crank is a little overkill, but as my camshaft maker always asks; "can you ever build an engine too good?".

I suggest you look into buying lightweight Probe rods and pistons for your build. a Probe cast crank with a 28oz imbalance and an aluminum flywheel (if manual).

You'll be very impressed with the engines acceleration when tuned correctly and the correct top end as a combo.

I have a distributor who probably will beat any price on the Probe stuff and a bad ass camshaft maker... if you're interested.

 

[banks]

thanks for the suggestions, i'm going to do a little more research and i'll let you know