Help: SBC Crankshaft clearance!

[WolfLMM]

Hey guys, long story short, I ordered a sledgehammer Crank from Lunati that had been discontinued, so Lunati put me in a racer series crank for the same price, Great Right? Well here is my question, I have 5.7 inch rods, the orginal Crank was a 3.75 Sledgehammer that works with the 5.7, this new crank I'm not sure about, it is still 3.75 inch stroke, but I am not sure if it is clearanced for 5.7 inch rods? Summit says it needs 5.85 on the website, and lunati's site has no info on it?

BTW, this was all ordered throught summit. Lunati suggested the Racer series crankshaft, that I will have tomorrow? I just hope that nobody goofed up, I'm ready to put this engine together.

 

[Stingpuller]

Crank

It depends a lot on the piston. Most of the time you would need a 5.85 rod with a 3 3/4 stroke. Is the crank internal or external balance? External will have a shorter counter weight and possibly work with a short rod. Jeff

 

[WolfLMM]

It is internal, I am going to call Lunati in the A.M. Dang looks like I need to find another crankshaft. I already have Crower Sportsman rods (5.7) and KB pistons, let me find the info on those.

Thanks Jeff, I was hoping you would chime in.

 

[WolfLMM]

Here is a link to the pistons.

http://www.summitracing.com/parts/UEM-KB135-STD/

 

[voltage]

As long as you have the right pin height and the piston skirts clear the counter weights 5.7 rods will be just fine. I ran them in my motor for years until I built a 434 stroker which uses a 4 in stroke so I went with 6 in rods.

 

[SHOTZY]

The piston link doesn't tell you if they're for a 3.48 stroke or a 3.75 stroke. Or 4.00 for that matter. If they are for 3.75 you should be fine with 5.7 rod. Just be sure you have minimum .060 clearance between counterweight and piston when assembled.:thumb: Having similiar issues with bbc right now.

 

[SHOTZY]

Well I was wrong on that. I was curious so I called lunati. Tech said those cranks are ground to clear 6.00 rod only. Counterweights need to be clearanced for 5.7 rod. If it were me I would sell the 5.7's and go 6.0. That's just me though Good luck with the build!

 

[WolfLMM]

Well I was wrong on that. I was curious so I called lunati. Tech said those cranks are ground to clear 6.00 rod only. Counterweights need to be clearanced for 5.7 rod. If it were me I would sell the 5.7's and go 6.0. That's just me though Good luck with the build!

I just talked to Lunati, My crankshaft was custom made for 5.7, so I'm good to go. My pistons are for 3.75 stroke and 5.7 rod, so if anything was going to change it would be the crank. But that doesnt matter mine is ready to go.

 

[SHOTZY]

Good to hear man! Should be a runner.