Standard bore?

[TokyoJoe]

Just wondering if this is a standard bore measurement? Looks like 10.16ish.... a 030 over is 10.2x right? This motor was sold to me as a "347" yet somehow I'm skeptical, how else to tell?

I've never cracked a 302 before so just to ask, these are aftermarket at the least aren't they?

 

[5spd GT]

Put one of the cylinders at the bottom of the bore. Then get a tape measure out and measure from the top of the piston to the block deck.

You should get 3.4 inches.

 

[TokyoJoe]

Okay then, looks like 3.4. Hmmm

Thanks

 

[5spd GT]

The pistons look aftermarket, because they have an extra intake valve "lip" valve relief.

Also, you can have a stroked 302 with the stock 4.00" bore. It would be a 342 cubic inch engine.

 

[Fast63]

yeah, don't listen to when people say they "bore it out to a 347" you have to stroke and bore it, but almost all the added cubes are from the extra stroke. Those look aftermarket pistons cause of the extra valve relief for the intake valve like 5spdGT said. They are dished somewhat so compression is probably fairly low depending on your cylinder head cc chamber. I think normally too if a piston is oversized, it will be stamped with ".030" or 4.030 somewhere on it in the middle. Don't worry that it's a 342, those extra 5 cubes wouldn't do much. Rejoice that you have thicker cylinder walls instead.

 

[5spd GT]

And to answer your other question, 10.16 centimeters is equal to a stock 4 inch bore, and 10.24 centimeters is equal to a 4.030" overbore, rounded up.

Where are you measuring at? At the top ridge may not be the most accurate place. Maybe try a couple inches down in the bore. You may just have a stock bore though, with the "347" crank, with a 5.315" or 5.400" rod.

I agree with Fast63. Do not worry about the extra 5 cubes

 

[TokyoJoe]

Thanks for the help, I measured as far down as the calipers would go, maybe an inch. I need to go measure my pushrods also I guess just to be certain.

 

[5spd GT]

Your pushrods are not going to matter. I was talking about your connecting rods. That is something you will find a hard time measuring without removing the oil pan at the very least

I would be willing to bet you have the 5.4" rod. That includes the 1.090" compression height piston.

The 5.315" rod includes a taller piston at 1.175" compression height.

They both can make a 342 or 347 (depending on bore size).

 

[Fast63]

you should measure at the very top of the cylinder bore too, because the bore is always bigger at the bottom, it is tapered.

 

[Jack's95gt]

They are after market pistons. Many manufactures will have the parts number and the size right on the top of the pistion. Clean then up and you will see. I bought a new SVO block and kept it standard bore and I have a 342.

 

[TokyoJoe]

LOL, I feel dumb. Yeah, would be a feat to measure the connecting rods without pulling the shortblock haha. Thanks for the help everyone.