when i hear people talk about 327ci engines, their biggest praise of it is that it has "a near perfect bore-to-stroke ratio." i understand why, a good balance of torque-to-revability (yes, i made that word up). what is "perfect" tho, talking about a SBC?

 

Bore to stroke ratio means nothing unless you're wringing every last HP out of a racing engine that spends its entire life above 8,000 RPM.

 

so, it offers no advantage to a street driven vehicle pushin around 400hp?

 

Not really.

 

Bore/Stroke ratio does matter some but like others said not much in a street engine. Thats why you don't see many people building 400+HP 305's..long stroke small bore, they aren't good at all for high RPM performance. A 327 is much better than a 305 for high RPM performance but larger displacement motors are even better especially when you want to stay streetable. It just depends on how you want to make 400HP...a 327 that spins to 7500RPM's(sluggish at low rpm's) or a 383/400 that you spin to 6000 and will have tons of low end torque. A lot of road racers like higher reving engines like 327's but for drag racing there is no substitute for displacement. Its very easy to build a 400, 383, or 377 SBC to make 400HP at around 6000RPM's and be very street friendly. While a smaller motor like a 327 will have to be more radical and less street friendly and less reliable because of the higher RPM's. If you want a higher winding better breathing motor I would go with a 377 but there would be very little difference between that and a 400 or 383 in overall power. The 377 would have a slightly higher rpm band and peak torque would be at a higher RPM.

 

i understand more cubes being better. looking at building a motor, i was thinking about maybe starting with a 400 block. or a bored 350. i was just wondering about this "perfect" ratio. my car get's used more for road-racing type driving than drag (realy, i never drag), and i'm looking for a loooooong, thick torque curve that'll rev nice.

 

how do you make a 377, btw?

 

A 377 is a 400 block destroked with a 350 crank. In a streetable application there are no benefits to be found from doing it that would make up for the loss of displacement compared to the 400.

 

400 is a good place to start but can be expensive. You will need to find a 2 bolt 400 block, idealy the 509 high nickel block. Other than that, Dart's little M block is a good place to start if your going to make some serious power. Chevy High performance did a good build with a 400 and vortec heads which made 420 horse and 525 ft/lbs of torque. This motor was a low revving set up, but would provide tons of fun on the street.

A 350 can be had for much cheaper. Just find any old good 4 bolt main block.