What's the diff between 5140 Machined Beam Rod and 4340 Ultra Light Weight I BeamRod?

[Pokageek]

Does it make the car rev any faster? Significantly?

Are molly rings better than ductile iron? Better for boost? Better than stock?

What about Clevite H series race rod/main bearings vs king rod and main bearings?

What does this mean in english? Any experts out there?

 

[Grn92LX]

The probe ultralight I beams are lighter and come with better hardware. 3/8" through bolt vs a 7/16" cap screw. I run the ultralights in my n/a 347. They are a good higher rpm n/a light weight rod. Its not really a rod you put in a big p/a engine. I got a bunch of light weight tricks in my rotating assembly, the lighter the better

 

[Pokageek]

The probe ultralight I beams are lighter and come with better hardware. 3/8" through bolt vs a 7/16" cap screw. I run the ultralights in my n/a 347. They are a good higher rpm n/a light weight rod. Its not really a rod you put in a big p/a engine. I got a bunch of light weight tricks in my rotating assembly, the lighter the better

Cool. Thanks man.

 

[mo_dingo]

Does it make the car rev any faster? Significantly?

Are molly rings better than ductile iron? Better for boost? Better than stock?

What about Clevite H series race rod/main bearings vs king rod and main bearings?

What does this mean in english? Any experts out there?

The 5140 and 4340 are two different alloys of metal. 4340 is slightly better than 5140, as far as durability is concerned. How much, I can't say. It really depends on the manufacturer of the alloy, since not all 4340 alloys are the same.

They are still steel based and I would say the weight difference is negligible, unless the specific rods you are speaking of are smaller volume wise. The masses are about the same. I would assume the ultra lights are smaller, thus lighter.

If you are keeping the car under 6k rpm's, stick with the regular 5140's. Otherwise get the light weights; less rotating mass is a very good thing for high reving motors. But that is the only reason I would get them. JMO.

Moly stands for molybdenum and is a element that is added to the rings for strength. They are a PITA to break in (being much harder), but once they do, they are extremely good. Racers that rebuild their engines every week don't use them since they don't have time to allow for the necessary break-in time. But I think there is some confusion, since most combos use a ductile compression ring and a moly ring (middle ring).

I cannot speak about the different bearings. I have no experience with them. Hopefully someone else will chime in.
Scott

 

[Pokageek]

Thanks mo_dingo. How does break in affect drivability? How long is the break in? I think for break in all you have to do is not run it hard and regular oil for...??how long?

 

[mo_dingo]

Thanks mo_dingo. How does break in affect drivability? How long is the break in? I think for break in all you have to do is not run it hard and regular oil for...??how long?

The break-in period will vary. Everyone has their opinion and I am not about to say which one is right, since there is no complete "hard" data to support anything specific.

The popular rule of thumb is 500 miles with regular oil, then drain and add whatever you want (syn or regular). In the first 500 miles, one needs to keep the rpm's varied as much as possible. When put-putting around town, keep it in a lower gear and change your speed constantly.

Moly rings take longer to break in. But fwiw, I started romping the crap out of the motor after 200 miles and have put 8k more on since the new shortblock.
Scott