questions

[Mopar Monster]

....

[Topcat]

I have a 340 bare block needing a crankshaft.  I'd like to build it to rev 7000 rpms or higher.  I will be using light weight Oliver rods, hydraulic lifters, I forget the pistons but there good too.

Someone told me to find a 273 forged crankshaft and use that for my build.  Is this possible to use or am I better off getting a new one from Eagle?

I'm not on a tight budget so that's why I'm confused about the suggestion for using this crank.

If you're not concerned on budget, why are you going LA block?

No replacement for Displacement.   

Rpm power and torque are sooo much better. You won't regret it.

Go stroked 440 or join the Elephants.   

[jhaag]

Someone told me to find a 273 forged crankshaft and use that for my build.  Is this possible to use or am I better off getting a new one from Eagle?

Ah the infamous someone. They told you to use a 273 crank because the shorter stroke equals higher revs. Think Boss 302, 302 z28, etc. I would definitely recommend an aftermarket crank, they can build you whatever you want. Why do you want a 7000 rpm small block? There are much better choices for a street motor. Torque is king. Lower rpm stump pullers are the way to go. High rpm = more maintenance, and more temperamental tuning. JMHO

[RzeroB]

Actually the 273 and 340 share the same stroke of 3.31".

Years ago I picked up one of those "coveted" 273 cranks for a 340 build. If I remember right, I think it was the old DC engine manual that suggested the idea of using the 273 crank in lieu of the 340 one. If I recall correctly, the rationale was that the 273 crank was supposedly stronger than a 340 crank because the rod throws didn't have a lightening hole through them, or something like that. In actuality, there probably isn't much difference in strength between the two.

For a 7,000 + rpm screamin' small block you need a lot more than just a great crank - you need an "engineered" system of complimentary components that will allow the engine to live up top without self-destructing. As jhaag said, "torque is king" on the street, so a stroker small block would give you a lot more of the good "bang for the buck" than a rpm monster that just might go "bang" as you are winding it up north of 7,000.

[Chryco Psycho]

412 CI stroker LA works very well but I agree max the torque & limit the RPM  you cam make a lot of power & not beat up the parts staying around 6000 , LAs will often spin 5/6 rod brg with oiling issues

[barnett468]

I have a 340 bare block needing a crankshaft.  I'd like to build it to rev 7000 rpms or higher.  I will be using light weight Oliver rods, hydraulic lifters, I forget the pistons but there good too.

I'm not on a tight budget so that's why I'm confused about the suggestion for using this crank.

Those rods are killer and the light weight ones come in 2.00 and 1.889 journal size . They are a few thou wider than the 273 and 340 rods so they can widen the journal when they turn the crank down . There are a couple ways to reduce the potential for bearing failure and using those rods are one of them because you will be reducing the bearing speed a little with the slightly smaller journals . A good crank shop will also put a fairly smooth finish on it, then you can have it rem finished then hav it and the bearings coated with tungsten disulphide . You can also use 1/2 groove bearings.

Also, always use good oil . I use oil with between 1250 and 1400 ppm of ZDDP or ZDDB and change it frequently because the additives get used up over time.

I would also use high quality lifters with tool steel bodies for that app . Morel makes a nice set for around $750.00.

As was mentioned, you will need accompanying parts that can take the abuse like good push rods and valves and springs etc . You can also have 2 bolt steel main caps with dowels installed . This will totally eliminate cap walk and cap breakage, so if anything breaks, it will likely be your block at that point.

[barnett468]

I'm not looking to make torque with my 340.  I think some of you got me mixed up with those little Nancy's over on slant 6. org who want their grocery getters to drive well in traffic.

They could easily stroke their engines but that seems to be outside of their budget and ability to do . They all have the same reply to people that want more power out of their 6, which is, "Increase the compression" and they all seem to like repeating what others have said over and over again, but perhaps that's because people that only own a 6 cylinder don't catch on very well, I just don't know for sure.

Other mods you can do to reduce the chance of bearing damage is to have someone whom knows how to bore an engine, bore it for you . The bores should be bored square to the crank, however, some shops bore them square to the block surface which can be slightly unsquare to the crank . Doing this will also give you the exact same volume in each cylinder which equals out the compression.

You can also increase the size of the oil hole leading from the lifter galley to the main journal by one size then enlarge the hole in the bearing slightly if need be.

You can also use a Mopar Performance oil pump with a high pressure spring.

Mopar performance oil pump drive and Crane cam gear.

Set the crank clearance to 2.6 to 2.8 on the mains and 2.5 on the rods.

Unless you drive it in 20 degree weather, use at least 10w-40 oil or 15w-40 oil.

High volume baffled oil pan . They make stock looking racing pans if you don't want the traditional big racing one which I am not a fan of except on race cars.

Radius the sharp 90 degree oil pump outlet and main cap where the pump bolts to.

Have the lifter bores trued then have bushings installed with a .030" hole in them.

Check the oil pick up to pan clearance . It should be around 5/16" - 3/8" . If i does not have spacer tabs on the bottom, you can tack a 5/16" nut to it to prevent it from getting to close to the pan.