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Mate of mine has a 307 chev that he wants to retain (for external appearance & engine number reasons) but wants more cubes.
How big can the 307 be safely bored to?
It currently has a 40thou over bore on the original 3 & 7/8 bore, but can these be bored to the 4.000" bore of the 350?
He's hoping to be able to bore it to 4" and drop in a 3.48" stroke crank from a 350 - to round the capacity up to 350.
I know it would probably be simpler to get a 350 short motor, but he's stuck for the reasons listed above.
Cheers,
Mick
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Cheers,
Mick
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Hi Mick.
I've seen many 307s bored to 4" (= 327ci). I've even seen one succesful at 4" + 0.030" but I wouldn't recommend it.
I wouldn't bother with the 350 crank, all that extra for 23 more cubes, stay with the 327.
Dr Terry
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Boring to 4.001 is not a problem, same for using 350 crank.
Large Journal Crank changed in 1968 from small diameter journal. Rods 2.10" Mains 2.450"
I would strongly suggest drilling to accommodate 4 bolt mains caps.
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Bugger the 3.48" stroke. Put a 3.75" stroke crank in it, 400 rods and suitable 4" pistons for 377 cubes! A 3.75" stroke crank with 307 size mains are about $325 ground ready to go. |
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In theory it's nice to add the extra cubes by stroking with the 400 crank and rods, but then you run into the extra cost and troubles of having to change the cam and re-jetting the carby. You can't only half do the job, it still has to be drivable.
Jus
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Well here's an update....
He started ringing around chasing a 3.8" stroke crank (for 383 cubes in a $ inch bore) but was rather surprised at how much it was going to cost.
He's been offered a reco 350 short, stamped with his existing engine number, |
Cheers,
Mick
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Fair enough. If he wants to keep 'revability' simply boring to 4" and using 327 pistons will do this better than any other combo.
The 3.75" crank and 4 inch bore gives you 377 cubes not 383. And these things rev like crazy if you use 5.7" rods and have s |
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