vineman

I bought a 302 from a guy for $20 mainly for the block but it had heads, intake, oil pan etc. I got to rebuilding it and pulled the pistons out and noticed they had .040 etched into the top of them. I measured the cylider width and sure enough its a 302 bored .040. I asked the guy about it and he said it had been rebuilt and had only 20,000 miles on it since rebuild. My question is...do i have a power bank here like a 347? I dont know the bore for a 347 so... if so, what parts should i get to make this at least a moderate beast? just lookin for a cruiser mustang really.

tyler72

You dont have a 347. a 347 is a 302 block with a crankshaft that has a stroke of 3.4 inches instead of the factory stroke. A 331 is the same deal with a 3.25 inch stroke. Hence why these engines are called "strokers." To make a beast out of it with out messing too much with the block, I say put in new rings and bearings and hone the block. also, check and make sure there isn't a wear ridge at the top of the cylinder bore. If there is you may need to take it to a machine shop and get it ridge reamed. You will want to put in ARP wave lock rod bolts (like $50 in jegs) and maybe even ARP main bolts ($20). Then add the Edelbrock performer RPM top end kit with about a 600-650 CFM carb and you will have a pretty mean combination that is dependable and very streetable.

ky

if i were you id try to find a new block. i just took my 289 out of my car a few months ago and it had been .040 over. i had no clue. its ok to just hone it or even go to .060 over but thats SUPER risky. not even worth it. i found my standard bore 302 block for $50. it came with heads, a front cover, and a fan. the guy just started giving my old parts to take lol.

kalli

here's the maths.

volume = diameter*pi*height
pi=3.14159265
diamter=bore
height=stroke

from this:
bore stroke vol/cyl total ci for 8 cyl
4.00000 3.00000 37.69911 301.59289 (302ci)
4.04000 3.00000 38.07610 304.60882 (305ci)

Kalli

my77stang

wait, a .030 302 is a 306, how is a .040 302 a 305?

PReal

That equation doesn't include the volume of the combustion chamber.

urban_cowboy

With a stock block, .30 over is pretty normal on the first rebuild. I know a lot of people will go .40 at some point. I am not sure if it is on the first machining or a second rebuild. In stock blocks, .60 over is getting pretty thin and probably will not last long. .50 would probably be ok, but there do not seem to be very many piston options for .50 over. In aftermarket blocks like the Darts and Ford Racing, your can bore upto .125 over, I think. The problem with going too much in the bore is finding pistons, and getting the engine to run cool. You get heat problems the thinner the cylinder walls get. My point is, if you are already .40 over, you are approaching the limit of what should be done to a block, but more may be possible.

On a side note, you can always sleeve the block, but that runs into money.

67mustang302

.040 is a 307