What's the ideal rod length for a 4.1 stage II with a 3.625 crank?

[turboclam]

Block has the stock deck height and will be used primarily as a street car.

 

[Buickrat]

My choice would be a 6.300 long rod this will give you a rod ratio of almost 1.74 I believe anything thing higher than that does not really benefit a boosted set up. A NA set up would benefit with the 6.500 rod. I am currently going to run 6.500 long rod only because the engine I purchased had them in it.

 

[bison]

6-6.3"

 

[turboclam]

What are the downsides of running a 5.960 rod? Thanks

 

[Cme2fly]

There are no downsides to a 5.960 rod..if you have them I would use them. There are plenty of affordable H beam 5.960 rods available, Scat, K1, etc.. What are your HP goals? 700-800 hp?

 

[turboclam]

Yes about that HP range. Thinking that the 6.3 would be less stress. 5.960 would hurt my RPM wouldn't it?

 

[Cme2fly]

Are you using a solid lifter? I shift out at about 7000 rpms with a 5.960 rod. My car make plenty of power to 7000. If you have problems acheiving the rpms..your going to need more spring.

 

[turboclam]

Hydraulic roller. I was wanting a 6.3 rod for a better rod/stroke ratio. Less side load friction I guess. You know your piston specs by chance?

 

[Cme2fly]

I'm running a Diamond piston, I don't have the specs in front of me. I'm running a 3.820 piston which won't do you any good but, I'm sure Diamond can spec out a piston for your needs. If you plan on running a hydraulic lifter, look into a shimmed lifter to acheive the rpms your looking for.

 

[Buickrat]

The only advantage of a long rod in a higher rpm application is dwell time over TDC but, for drag racing application it will not make much of a difference.

 

[turboclam]

Thanks for the comments.

 

[49-blues]

I have a new set of 4.00" je pistons and a set pf carillo 6.5" used rods I could make you a deal on if interested.

 

[turboclam]

No thanks, the block is around a 3.970 bore and the crank is a narrow journal. As stated above I would REALLY like to stay with a 6.3 rod.

 

[Mike Licht]

Do some math and figure out the difference in ACTUAL rod angle, you will find that is is very small. Which means the difference in side load is very small. It has been proven that longer rods do not make any more power and in fact in boosted application some builders like to get rid of the extra piston dwell time since they think that is causes some detonation from extra cylinder pressure. The 6" rod with a .927 pin is my choice.

 

[turboclam]

So will the 5.960 be OK to run?

 

[Mike Licht]

If you already have the 5.960 rod or the piston for it then run it will work fine. I like the smaller lighter .927 wrist pin that is Chevy size since there is so many choices. If you need to buy them I would go that way

Mike

 

[turboclam]

I think the .927 pin was used. Thanks for the info Mike.

 

[turbobitt]

You can get away with a 6.5 but it will limit your choice on the ring pack. 6.3 rod gives you more room for ring selection.
Allan G.

 

[marleyskater420]

No thanks, the block is around a 3.970 bore and the crank is a narrow journal. As stated above I would REALLY like to stay with a 6.3 rod.

If you need, I can always do you a favor and take your rods off your hands so you won't have this horrendous issue to deal with. I mean, what kinda friend would I be if I just let you run this rod length when something else would work better.

I don't wanna, but I guess I'll just have to take your forged rods off your hands.

I know, I know...I'm a great guy. Its hard being this amazing.

 

[turboclam]

Tyler....you're not touching my rods, I don't care how short they are. I don't ask to play in your curtains! All kidding aside, I thought that I would be stuck with a 5.960 but they're looking into fitting the block with the 6.0s. Pistons are already done for the 5.960s, so let's hope. I know it's just (.04). I originally had a lead on some 6.2s but my motor got shipped 1600 miles away accidentally. Long story, just short rods. Thanks for the input and stupid comments.