Quote:
Originally Posted by bbraden
You're right, making the connecting rods wouldn't increase the stroke length, but increasing the length between the crankshaft and the connecting rod will. That's what I meant I just said it wrong. The stroke should be twice that distance. I'm not sure what that's called though. 12V P-pumped Cummins have a CR of 17.5:1, a 4.02" bore and a 4.72" stroke. A VP-44 SO Cummins has a CR of 16.3:1. Since the bore is the same in both 5.9L engines, the stroke is obviously shorter. A 6.6L Duramax has a bore of 4.06" and a CR from 17.5:1 to 16.8:1 depending on the year models. The earlier Duramaxes have the 17.5:1 and a stroke of 3.9". The older powerstrokes (7.3L's) have a bore of 4.11" and stroke of 4.18". It's CR is 17.5:1. All of these engines are turbocharged.
The older, naturally aspirated engines (generally indirect injection) have the high compression ratios you speak of. The highest I've heard of is about 23:1... not much higher than that though. If you plan on having direct injection as well as some sort of forced induction, good luck keeping headgaskets on that thing without a CR lower than 18:1. Anything lower than 15:1 and good luck starting it on a cold morning.
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Thanks for explaining what you meant there.
While I won't argue the point, I will explain my stance on static compression ratios:
If you build an engine with a static CR of 21:1, and allow the cam to hold the intake open beyond BDC, (atkinson cam design) your dynamic compression ratio will be lower. By controlling cam timing events (which I'll have to do with a custom cam anyway), you can effectively control detonation, even running high boost levels against high compression.
None of that really matters so early in the game, though, and it won't make a difference in the end-game, either, since the rods and pistons will be custom pieces.
I do know that the stock crank in a 300 is good for 500+ lb/ft of torque/around 300+ HP (was a factory setup, I'm sure it could do more), and they're already low-speed engines which are durable enough to handle extended periods at 4,000 RPM. Ford used them in 5 ton trucks for their amazing torque capabilities.
It looks like those are all pretty square engines, or very close to it, that you've mentioned there... Maybe I'll be fairly close to where I need to be, and just decking the block and custom pistons/rods will do what I need?
I'm fairly certain I'll need to do some head work, as well, to allow the engine to breathe easier, since it'll be pulling in all the air it can all the time.
Also - anyone know where I can source an injector pump/injectors for a 6 cylinder?
(Cheap, used, free, preferably.)
I'm going to call this one a career project, by the way. That means it's going to take awhile, and there are other projects WAY ahead of it, but as I have time, I'll tinker with it. Especially now, since my Father just pulled ANOTHER 300 out of a truck.