longer connecting rod

[K-Star automotive]

rods

Oh yea i forgot, some times you need a longer then stock rod to keep the skirts off the crank throws....


Keith

 

[Anonymous]

Mahle has 400 pistons for 6" rods #SBC125165F05 that number is for .040 over. They also have pistons for 383's. Nice tight ring package and no ring supports the pin is just under the oil ring! I've used them in a 383 for a customers motor and in my 408. Great piston/rings/pins and graffle coated. It's like having your cake and eating it too.

 

[gmachinz]

Wow-I'm late on this one but awesome reading! I'm running JE pistons in my 400 with Ford 4.9 rods (6.235). I built a duplicate of the motor that HR built back in 1996. I used a LG 327 crank though so crank clearance was a no-brainer. I just had to sonic check the block for a little notching. My main focus was to reduce cylinder wall loading because I wanted high RPM's with a lot of torque. The result with Vortec heads was about 11.75 comp. ratio and it ran great on pump gas. I thought about running nitrous oxide and I'm sure I can dial in my digital box to compensate for the longer dwell time but that's down the road some. Not to change the subject but a little more interesting topic is what rotating architecture is more stout-V8 or inline? I got into a conversation about this when thinking about a turbo-charged V8 build and comparing formulas from a TT Supra. . -Jabin

 

[Robert1320]

An L-6 is more receptive to a turbo than a V motor. Mostly due to the crank offset. Tycipally a turbo like most stroke too.

A single 88mm turbo on the sbc can make over 1000 and destroy a stoke block in no time.

 

[Goob]

Re: rods

Without opening up a box of worms,

short answer is "no".

like Supe said.........no
but if you do want to run 6" rods get ready for doing alot of clearancing to block..

There is NO clearancing necessary because of the rod LENGTH, the only adjustment is to the pin height of the piston.

The problem with clearancing is because of people using stupid, cheap, H-Beam rods when all they need is a decent I-Beam rod with cap screws instead of bolts and nuts.
There can also be an issue with ANY 5.7" bolt and nut style rod hitting the #2 and #6 cam lobes with the LARGER (3/8") rod bolts that come in factory 5.7" rods versus the 11/32" bolts that stock 5.565" 400 rods were equipped with.......that is why the stock 400 is generally considered inadequate for hi-po use. It isn't the length, it's the size of the big end and bolts.

Now, for high performance, if you can't see the benefits of a higher pin position, in a smaller, lighter piston with a shorter skirt, with a slightly longer dwell time at TDC and BDC, with a slightly quicker piston speed through the intake/exhaust sweep as a result of the longer rod, you'll never understand it.

 

[Anonymous]

I think the long rod vs. short rod is of little or no real world relevance to us. None of us are designing an engine from scratch so we have to work within the parameters of the block designs we're given. We have a specific deck height to work with and have to compromise between stroke, rod lenth, and pin location. Decide which of those three are more important to you and build accordingly. For most of us I think rod lenth is least important and the small differences in rod lenth options available aren't going to make any noticeable difference.

 

[Goob]

This is the kind of discussion that will go on until the end of time. If you ask 10 different, knowledgable, people, you will get 10 different answers. All I can say is when you have professional engine builders such as David Reher saying that it doesn't matter, you kind of have to start to lean towards their way of thinking.

Here's a good article he wrote on the subject. http://www.rehermorrison.com/techTalk/10.htm

I wrote to Mr. Reher and asked him why there are NO engines or rotating assemblies offered in their product lines with stock length rods.
No answer = no credibility to that theory.

 

[Mistah]

Now, for high performance, if you can't see the benefits of a higher pin position, in a smaller, lighter piston with a shorter skirt, with a slightly longer dwell time at TDC and BDC, with a slightly quicker piston speed through the intake/exhaust sweep as a result of the longer rod, you'll never understand it.
I wrote to Mr. Reher and asked him why there are NO engines or rotating assemblies offered in their product lines with stock length rods.
No answer = no credibility to that theory.[/quote]

Well put Dave.

 

[Goob]

My disclaimer to the Reher beef........if I were running a big bore, short stroke Pig-Block and buzzing it 9500, and rebuilding it at about 20 passes or so, I'd choose the lighter weight over the rod length.
His theory may hold water for a Pro Stock engine, but none of us has one of those.

There are physics related benefits as well as performance benefits to a longer rod in most cases, just like SHE said......

 

[Autometer]

Goob, any concerns about a wristpin in the oil ring for a street car?