400 Chevy small block 5.7" vs 6" rods

[BillK]

Hey guys,
Just curious of your opinions / experiences. I have an aftermarket 400 block I cant seem to sell so I think I am just going to build something out of it. Probably in the 500 hp range nice street or mild bracket engine. 3.750 stroke. No crazy rpms etc. Is there any real advantage in that type of engine to use a 6" rod over the 5.7 ? One reason I ask is I have never been a fan of oil support rails.

Just curious what you guys think,

[F-BIRD'88]

You can get 500 hp using either.

[TomCombo]

My ‘opinion’ is there is no power difference for what you are doing. I would choose the 5.7 in order to avoid the support ring. Engine Masters tested rod length on a 478 cid BBC 800 hp and saw 10 hp gain at 7400 with the SHORT rod (6.8 vs 6.135).

[Gregory]

There are pistons out there that do not require a support rail with a 6” rod.

[swampbuggy]

Employ the longest rod you can put in it without getting into the oil ring/s groove. Mark H.

[Alaskaracer]

Pick a ring pack and connect the piston to the crank.....rod length is so overrated it's stupid......

[F-BIRD'88]

Maybe in order to find the right buyer you need to
build confidence in the quality of the block fir sale.
Machining dementions (measured).
So the buyer knows what he is paying for.
OR adjust the price a bit.

If you cannot sell the block how are you going to sell the finished engine (without a bigger $$$ loss)?

If I see just a sbc block for sale I wonder. why is it being sold off VS being built. Is it dimetionally correct ???? ready to rock...

[steve cowan]

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Click on photo for clear picture

[Geoff2]

Read the Isky Tech Tips on rod length.

[swampbuggy]

Mark G., I do agree that Connecting Rod Length is over rated and can be argued both ways, however it can not be denied that for a given stroke the shorter the Rod the more side thrust there will be and vise-versa . Mark H.

[skinny z]

Mark G., I do agree that Connecting Rod Length is over rated and can be argued both ways, however it can not be denied that for a given stroke the shorter the Rod the more side thrust there will be and vise-versa . Mark H.

This was going to my comment as well.
Also is not a longer rod engine mechanically quieter?

[Alaskaracer]

Yes, there are thrust issues depending on rod length....but I'll revert back to Warren Johnson once again regarding this matter. He very clearly stated the same thing I did. Pro Stock is the epitome of performance. If it was that big of a deal, they would go to any length to optimize it, yet they don't. Granted, there is a ton of info posted on the subject.....however, in reality, if it made that big of a deal then it would be a primary consideration for a build, which it's not. Rod length will make virtually zero difference in his build. Unless he's willing to optimize cylinder head, camshaft, intake, etc and design his engine combo around the rod length, it's not going to change it. I'd go with the 5.7" rod, done a few of those builds and it makes it easier to find parts.....

[skinny z]

I'd always intended to go to a 6" rod for the next SBC that was in the works. Whether it was 350 based or 383. As it turns out the 357 that's just been shortblock assembled ended up with 5.7" rods. That came about as a matter of circumstance and I was a little disappointed that it ended that way at first.
Much like the OP, I had explored and solicited opinions on the subject.
The responses in this thread (and elsewhere) have sort of calmed the waters so to speak.

[bigcam406]

It is my understanding that rod length has an effect in restricted induction circumstances (ie. 2bbl classes).

[bobmc]

there is a real difference in 3.75" SBC cranks, 6" rods allow for internal balance, run of the mill 5.7" rod rotating assembly uses external balance? has anyone ever checked crank rotating breakaway force differences between long vs short rod setups?