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I've shy'd away from stroking my 302 because of cost, but after doing some research i've come up with a way to build a 331 stroker for very little more than it would have cost to build my 302. I've finished mocking it up and have confered with a local Hi Po engine builder so now i'll share it with all the VMFr's.
The stroker revolves around using slightly longer 289 rods and a piston that does not a really short skirt and the pin in the oil ring land. I've never been very fond of the idea that the 331 and 347 stroker pistons have very short compression heights. 289 rods are 5.155 in length vs 302 rods that are 5.090.
Next I had to find a piston with the right compression height. The KB322 hyper piston came in just .015" short with a 1.405 compression height...just right for decking the block to zero deck or so. The KB322 is a 351W stroker piston with two valve reliefs and the pin is BELOW the oil ring. The compression ratio came in at 9.9:1 with a 61 cc head (351W ported heads are going to be used in this case)...it was almost too good to be true!
The rod length to stroke ratio comes out to 1.59...same as a 347 stroker with 5.400 rods. Rod length is not the end all to beat all anyhow especially for a street motor that won't see more than 400 HP and 6500 rpm.
So how does this keep cost down? 289 rods are cheap and plentiful and for about a $250 investment to put better bolts in, resize, shotpeen, hone the small end out for a .927 pin, and polish the beams, their ready to go for a mild street motor. The rod bolts clear the cylinders too. The crank was $200 from speedomotive (high nodularity 3.25" stroker crank). The pistons were about $275 but I would have needed pistons whether I did a 302 or 331 anyhow.
I actually found a set of H beam 289 rods for $299 (really good price for H beams) and notched the cylinders to clear the rod bolts. I got the rods from The Mustang Depot on .
I mocked up the engine and the counterweights just touched the bottom pin boss of the piston. I called speedomotive and they said that they routinely grind the counterweights and a lot of material can be removed from them and the crank will still balance out. The crank comes from speedomotive with plenty of material on the counterweights. I ground the counterweights down .065 where needed and the clearance is set.
So there you go...a 331 stroker for about the price of a regular 302. I'll keep you posted on how it runs when I get it put together in a month or so.
The stroker revolves around using slightly longer 289 rods and a piston that does not a really short skirt and the pin in the oil ring land. I've never been very fond of the idea that the 331 and 347 stroker pistons have very short compression heights. 289 rods are 5.155 in length vs 302 rods that are 5.090.
Next I had to find a piston with the right compression height. The KB322 hyper piston came in just .015" short with a 1.405 compression height...just right for decking the block to zero deck or so. The KB322 is a 351W stroker piston with two valve reliefs and the pin is BELOW the oil ring. The compression ratio came in at 9.9:1 with a 61 cc head (351W ported heads are going to be used in this case)...it was almost too good to be true!
The rod length to stroke ratio comes out to 1.59...same as a 347 stroker with 5.400 rods. Rod length is not the end all to beat all anyhow especially for a street motor that won't see more than 400 HP and 6500 rpm.
So how does this keep cost down? 289 rods are cheap and plentiful and for about a $250 investment to put better bolts in, resize, shotpeen, hone the small end out for a .927 pin, and polish the beams, their ready to go for a mild street motor. The rod bolts clear the cylinders too. The crank was $200 from speedomotive (high nodularity 3.25" stroker crank). The pistons were about $275 but I would have needed pistons whether I did a 302 or 331 anyhow.
I actually found a set of H beam 289 rods for $299 (really good price for H beams) and notched the cylinders to clear the rod bolts. I got the rods from The Mustang Depot on .
I mocked up the engine and the counterweights just touched the bottom pin boss of the piston. I called speedomotive and they said that they routinely grind the counterweights and a lot of material can be removed from them and the crank will still balance out. The crank comes from speedomotive with plenty of material on the counterweights. I ground the counterweights down .065 where needed and the clearance is set.
So there you go...a 331 stroker for about the price of a regular 302. I'll keep you posted on how it runs when I get it put together in a month or so.