whats going to be the pros and cons to this setup? I am gathering parts for a fully forged rebuild and need some insight on this topic.

 

Pick the kit that is cheapest.
There is no difference in either one except maybe piston weight. That won't matter to a street engine.


"A rod is a good thing to connect the piston to the crank"

 

This is JUST the rods I am talking about. I have the pistons already on their way but I need to know whether to go with a 5.700" or 6.000" rod. Whether there will be valveiston clearance issues.

 

I think what I am going to post here is correct, someone correct me if I am wrong.

A 6" rod requires the stubby piston machined for a 6" rod.
A 5.7" rod requires the standard piston machined for the 5.7" rod.

You can not interchange these.
What pistons did you get, ones for 5.7" or 6"?

I used 6" rods with Mahle forged 6" pistons.

 

If your pistons are on the way, your decision on rod length is already made.

Good luck.

 

The rod length doesn't change the length of the stroke.

You either use pistons for 6" rods of 5.7" rods.. since your pistons are already on their way you will need to use the proper rod that the piston was designed for.

 

Rod length is actually a very important part of designing a motor. Ideally you want a 1.7:1 or so rod length to stroke ratio. The longer rod puts less pressure on the cylinder walls and provides a longer moment arm for the piston to push on the crankshaft.

The above posts are correct, if you've ordered pistons, you're choice has been made. Find out whether the pistons are for 5.7 or 6" rods and buy the correct ones.

 

Just about everyone I know is brought up to believe this. The GM engineers believed it to until we proved it to be false. In 1995 Reher Morrison conducted an R&D project funded by General Motors to once and for all prove the Rod ratio theories that everyone subscribes to. In a tall deck small block Chevy the rod ratio was changed from 5.550 to 6.650. The difference in ratio was 1.59 to 1.91. The difference in power? NOTHING, not one single horse power difference. The dyno sheets looked identical in every way all the way up to 9000rpm. That is why I now say its a fallacy.

Now, I once again want to clarify my point on Rod Ratio so nothing I said is taken out of context. The test we did was from 1.59 to 1.9:1. I never stated that above or below those points that there may or may not be daemons lurking. From what I have seen with the older 265 engines with ratios in the 2.15:1 range and the extreme 500+cubic inch small blocks in the 1.3:1 range I can safely say that there are problems with induction system lag above 1.9:1 and frictional power losses, parts damage and decreased component life below 1.5:1. Evaluating the differences in power output from 1.3:1 to 2.15:1 would be impossible because of all the other variables that must be changed in order to achieve that task. I think its a mute point any way because in each case they used what they had to as far as block and deck height as is the case today. We now have the Aurora block with 8.200 decks so we don't have to put up with 2.15:1 rod ratios. What I am trying to get across, is that trying to build an engine around an "ideal rod ratio" is a losing proposition. Design the piston with the ring package properly compacted and spaced , put the pin as high as possible so as to not intrude on the oil ring groove, and connect it to the crank what ever stroke that may be. The rod is dictated by the piston design, stroke and deck height not a preconceived "ideal " rod ratio.

Before you blast me with obscure engine combinations I must say, NO I am not condoning sticking a 4.750 stroke in a 9.8 deck block with a 1.2 compression height piston. A little mechanical common sense has to come into play here as well.
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Daren Morgan