415 vs 427
This is a discussion on 415 vs 427 within the Internal Engine forums, part of the LSx Technical Help Section category; Looking at short blocks because a bearing might have started to spin in my motor. Im debating between a few ...
12-30-2010, 07:47 AM #1
415 vs 427
Looking at short blocks because a bearing might have started to spin in my motor. Im debating between a few right now but my main question is what are the advantages/disadvantages of having a lager stroke then bore. The stroke on the 427 is 4.125 and a 4.065 bore. 415 is 4" stroke with a 4.065 bore.
I plan on going fi in a couple of years and wanna be up there in the hp numbers. But for now just going to slap some used 317 heads on it and a decent sized cam
I know the larger the stroke the less you can rev it up but what else?
12-30-2010, 09:53 AM #2
- Join Date
- Apr 2010
- Fairfax, VA
- 98 TA WS6/ 01 C5 Corvette
12-30-2010, 10:29 AM #3
they are lq9 blocks
12-31-2010, 12:37 PM #4
You have the same bore on both engines.
I'd rather do a 427 with a 4.250 bore and 3.75 stroke or something along those lines for several reasons.
More stroke means more piston speed, which means more stress on pistons and piston pins, rods and rod bearings. It also means more friction. And friction robs HP. Then there is piston ring thicknesses, ring tensions, etc...where you can find some of that HP. There are plenty of aftermarket parts now that can withstand anything you can throw at them, just costs more money.
Larger bores make more HP because they unshroud the valves. Which is why when looking at cylinder head flow numbers, you really have to pay attention to the bore diameters they are testing them on.
The strokers also vary with rod lengths. Longer rods offer more dwell time at top dead center, but you need a good cylinder head to take advantage of that. You'll also get into situations where stroke and rod length get to a point where the piston pin is actually up into the oil control rings because the block deck height isn't tall enough. Some like it, some don't.
See what I mean? You can go on and on with theories, methods, etc...there are tons of ways to find HP in a shortblock, and every engine builder has their own recipe that they like to think is better than the others.
The generally accepted rule of making HP is starting with at least a 4" bore. Since that seems to be what you are going to work with it's a tough call. Your cubic inch difference really isn't enough to sway me either way.
Your 427 choice would rely on several things for me. Rod length would either have to be shorter or the pin is moved up very high in the piston, probably requiring custom made pistons that up the cost. Since that is an unknown here I'll leave that alone.
You'll have more piston speed, more friction, more wear. All for 12 cubes??
It's up to you, I'd need more cubes to sway me towards that direction.
12-31-2010, 01:40 PM #5
Longer stroke means more TQ and less RPM's.
I'd choose 427 in a heartbeat.
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