I'm slowly gathering parts for a 400 motor. I have read different opinions on which rod lenth to use. Any ideas? Was the 6.0 stock on the 400? Thanks, Bill

No it wasnt, but its the one to use for a performance engine. If you want something that will go 100,000+ then I'd do the 5.7 rod

Indeed, the 5.7 seems to be the most common choice.

The 5.7 is the most common to use due to price and its availablity. Also is said to give less side loading,and more stroke,which will increase torque some.

stock rod was 5.6 ish... they short and a lil whimpy. 5.7 is easy to do, they make standard pistons for that deck ht.

Stock 400 rods are 5.565". The side loading and dwell at TDC are pretty much moot points the difference is extremely minor (even going from 5.565 to 6.0"). What are your goals and HP level you are shooting for? They also make 5.565" H-beam rods. If you are starting from scratch I would buy 5.7" rods. If you have good 5.565" rods or pistons for them I would not hesitate to use them.

I used 5.7 rods in my 383, but if I had it to do over again, I'd go with 6.0, the reason being that it makes for a lighter piston and easier balancing. The 6" rod requires that the oil ring ride in the wrist pin opening, but that doesn't seem to be a problem. The 6" rod is pretty popular and I don't think availability and cost is much of an issue. I'm not sure of the availability of good pistons for the 5.565" rods, but my guess is that there would be fewer choices.

Originally posted by DOUG G:
The 5.7 is the most common... Also is said to give... more stroke... Just wanted to clarify that there isnt "more stroke" with different rod lengths.

Well then I stand corrected. So a longer rod does nothing? I can't believe that.

The crankshaft is what determines stroke.

I like a 5.85" rod on a 3.75 stroke.. they are just hard to find slugs for.

There's plenty of pistons for standard rod 400's, and quite a few for 5.7" rod motors... heck, you only need eight, right?

I'd get aftermarket "stroker" rods 5.7" length. Stroker rods have more clearance where the rod comes near the cam lobes.

I had a pepped up 400 with stock length rods and there was a noticeable piston noise at idle. The short rods create more side thrust on the pistons. I think the 5.7" rods would help with that problem.
David

[ 10-20-2004, 08:34 PM: Message edited by: davidpozzi ]

David I doubt the piston noise you heard was due to the shorter rod. I would bet the bores were on the loose side. I have run a short rod 383 for years and never had a problem. The engine is still together today and going in a friends Nova. I have beat on it at the track and driven it many thousand miles on the street. I had it apart about a month ago "just in case" it still looked great, bearings were still good (I replaced them since i was in there). This engine was in my street/strip car for over 5 years.

I have discussed the short vs. long rod theories with a few engine builders and it is more a matter of preference than anything else. After reading a study that was done about the different rod lengths, the difference is so minute I don't think any of us could detect a difference.

Like I said if starting from scratch I would go with the 5.7" rods. there are more piston choices and you don't have to deal with the oil support ring of a 6" rod. My blown engine is a 6" rod engine (only because I had a good set of 6" rods), otherwise I would have went with the 5.7"

Not trying to convince anyone that the short rod is "better" just not so sure it is all that "bad" either.