I threw a rod in my 540 so I have to buy a new rotating assembly (block looks to be OK). I had a 6.385 rod in it but am debating if a 6.535 would be a better choice. The only thing I don't like with the idea of the longer rod is having the wrist pin higher in the piston and interfering with the ring lands. Thoughts?

This is a low deck block (9.800).

Personally, short deck no, tall deck yes.

I run 6.385 rods in my 588 short deck. Wrist pin is in the oil control ring land and has no issues. Pushing to rod length an addition 0.150 may be acceptable but I think it moves it up too high into the ring land.

How many piston options are there for the longer rod?

quote:

Originally posted by AlkyIROC:
Personally, short deck no, tall deck yes.

I run 6.385 rods in my 588 short deck. Wrist pin is in the oil control ring land and has no issues. Pushing to rod length an addition 0.150 may be acceptable but I think it moves it up too high into the ring land.

How many piston options are there for the longer rod?

Your combo has a longer stroke so it limits your options a little bit more. There arent as many piston options with the longer rod but I might end up going with a custom piston anyway depending on the bore size to get the one banged up cylinder cleaned up.

The wrist pin up into the 3rd ring is well scienced out and not an issue. Most of the ring packs are the metric type now which are pretty thin/light and have no flutter problems like the "old" days. I would put a .400" long rod in it. But I've always been a fan of longer rods...
That would leave you with a relatively easy to find "off the shelf" compression distance of 1.120" piston..

Good luck with your project...

Lighter piston

Better ring seal

Yes, but it's usually offset by the extra weight of the longer rod..

I have been running a +.400 rod in a "semi" short deck (9.855) Dart Big "M" 582 for two years. Very happy with the results.

Bob

We have 6.535” in our 540 and (2) 555s, all short decks. Larger rod to stroke ratio. Here’s an article from Oliver: https://oliverracingparts.com/...tandingRodRatios.pdf

quote:

Originally posted by 183N:
We have 6.535” in our 540 and (2) 555s, all short decks. Larger rod to stroke ratio. Here’s an article from Oliver: https://oliverracingparts.com/...tandingRodRatios.pdf

Good read, thanks for posting

4.600 bore x 4.250 with a 7.000 Oliver rod

Screamer BBC

Me being a non engine guy thinks that if your not interested in rotating the earth, go with the longest rod possible. My tall deck 540 with 6.700" rod was a revving beast and it's still going strong today very reliably.

I have a long rod and think it is better than a short one.

One of my SBC has 6.250 rods(454)and the other has 6.4. (408 Cu.In.)

Rod ratio, man that's a flash from the past. I've always run long rods.

Stick with the +250. +400 is a huge compromise on piston and ring stack.

Here is my experience

565 with +.400 rods
584 with +.400 rods
Both in a 9.800 deck block

The 565 was faster with the exact same cam, heads and intake and carb.

Some friends have had similar experiences comparing 565's to 582's....565 made equal or maybe even slightly more power than a 582

In my case I believe my heads/cam are the limiting factors and the added stroke magnified the issue.

One of my good racing friends is a big believer in the +.400 rods with the longer stroke is worse than a shorter rod with less stroke...

I don't accept that and just think every combo needs the right components to make the best power....

Engine builders learn from their experience what components work best......Trail and error....The dyno and the ET slip doesn't lie....

Longer rods comes from the ancient days of high revving Small Blocks......Longer rods reduce side thrust loads on the pistons.....

Big blocks have way lower rod to stroke ratios than old small blocks but generally aren't turning real high rpm's like SB's did....and they all pretty much work....

Callies Ultra I beam #U15111 6.535 rod in my Firebird's engine

In the words of one of the best engine builders in pro stock history, and one of the winningest drivers as well, Warren Johnson:

Pick your ring package, pick your stroke, connect the two. Rod length isn't nearly as important as many make it out to be.


I run a 7" rod in my 665. 10.7" deck, 5" stroke....I could have fit a longer rod but I wanted the ring package I have and deck clearance.

1.300 -1.325 @ 0 deck??? OR 10 in. Still stable for sure.

My ring pack is a 1.20", .020 below the deck

.250-.400-etc as said pick your stroke, pick you ring package, and connect the two. The WIN light in bracket racing does not care about rod length and I have run 6.135,6.385,6.535, as it may change the piston speed to cam events(very little) the win slip only cares about vehical reaction time and who crossed first with out breaking out. Any rod length can go .000 and dead on the dial so pick as needed and for longetivity.