ssfast99

iTrader: (3)

okay i was thinking about something that i cant figure out.

if you have a rod and piston combo that from the center of the crank journal of the rod to the top of the piston, does it matter if you use a tall piston and short rod compared to the long rod and shallow piston. what i am getting at is if they are the same length, what is the advantage. how does horespower or durability react to the setups. say a 6.1 rod attached to a piston that overall has the same length as a 6.0 rod attached to a piston.

i hope my question makes sense because i am getting ready to build a lq4 and want to know the trade off.

also, is a longer stroke with a shorter rod better than a short stroke and long rod setup. i noticed that the new ls9 has a sub 4" stroke and yet makes bad *** power. does this change the rules as far as big stroker motors being the way to go, or is that for NA motors.

thank you in advance for helping me out.

Schwanke Engines

iTrader: (1)

These are design questions that have different answers for different situations. You need to fist specify what your application is going to be and then we can give you a better direction. There will be no right or wrong answer, there will only be different answers from different people that have had different results.
So, give us a little background about your project and we will help out the best we can.

ssfast99

iTrader: (3)

well i was thinking about my 408 build i am starting and was wondering if a 6.00 rod is better than a 6.1 rod. also is a 6.1 rod with a 4.00 stroke going to give the same cubic inch as a 6.0 rod with a 4.1 stroke. what is better.

Schwanke Engines

iTrader: (1)

Rod length has nothing to do with displacment. It's main function is simply to connect the piston to the crank. The longer the rod, the shorter the piston compression height will be.

Are you planning on doing this yourself, or having one of the engine builders here do it?

ssfast99

iTrader: (3)

I Havent Decided Yet. I Have A Lq4 Block That I Want To Biuld To 550 Rwhp Na ( Wishing For 600na Rwhp W/tf 225cc). I Want The Motor To Rev Well And Be Reliable. People Told Me My T-rex 346 Would Not Live Long And It Has Worked Flawlessly. I Can Build Motors On My Own But If The Price Is Right, Who Knows. Just Curious Why People Use A 6.125 Rod Instead Of A 6.000 Rod Or Like Lt1 5.700 Rods.

ssfast99

iTrader: (3)

Schwanke, Can You Pm Me A Price On A Stroker Kit And What Manufactor Of The Parts You Use. I Have To Piece This Motor Because I Dont Have Bulk Cash To Buy One Already Done Yet.

Schwanke Engines

iTrader: (1)

Well, the one reason to use longer rods on these engines is because the deck height is .035" taller than a standard SBC.

I will have to get back with you on Wednesday, that is when I will be in the shop.

blackz93

iTrader: (2)

Couple good things about long rods is a lighter piston and less side loading on the skirt. Besides that, the most important thing about a rod is whether or not the bolts are torqued.

Schwanke Engines

iTrader: (1)

Our complete 402 stroker shortblock is $3200.00.

Comes with Eagle crank and rods, Mahle forged pistons. I would have to come up with a pieced price I guess.

grinder11

iTrader: (1)

I may be wrong here, but doesn't the traditional "small block" Chevy have a standard nominal deck height of 9.025", while the standard LS1's (GenIII's) come in at 9.250" If correct, and I know this IS a bit off topic, but want to make sure I have MY facts straight, wouldn't subtracting 9.025" from 9.250" leave you with a difference of .225", NOT .035"?

grinder11

iTrader: (1)

As RPM's increase, so does friction and side loading of the piston skirt against the cylinder walls. The shorter the rod you use for any given stroke, you increase this side loading of the piston skirt against the cylinder walls, thereby increasing friction, heat, and piston/cylinder wall wear. Also, at higher RPM's, a longer connecting rod tends to "dwell" longer at the top/bottom of the stroke (i.e.-it has stopped moving at bottom dead center for a few micro seconds longer than would a shorter rod). This has advantages in certain applications where you are trying to fill the cylinder at higher RPM with a later closing intake valve, like if the piston were moving upwards ever so slightly at, say, 7,000 RPM's, it would be fair to assume that the piston which remained "at rest" longer (However slight) would allow more complete cylinder filling. However, in a low RPM "torque monster" engine, the short rod accelerates away from TDC more quickly, thereby exerting a more powerful "draw" on the intake charge sooner than a "lazy" longer rod would. You will almost always find engine builders favoring the longest rod they can reasonably fit into the engine. But the longer the rod, the shorter the piston skirt must be, and that allows for the piston to "rock" in the cylinder more due to less support of the short skirt against the cylinder wall. Hope this helps-some!!

RE AND CHERYL

iTrader: (31)

There are a lot of variables involved. But for most applictions, the longer the rod the better. It reduces cylinder wall loading and increases piston dwell time at TDC. I think NASCAR motors use like a 6.5" rod or close to it.

Re'

SincalT/A

iTrader: (16)

Just want to confirm something I already believe to be true.If the longer rod has more dewel time doesent that also increase an engine chance to detenate as opposed to a shorter rod.

GrannySShifting

iTrader: (10)

connect the correct piston and crank with whatever rod fits... Doubt anyones motor here is close enough to right to matter even a little bit in .100 of rod length. there are lots of other things worth thinking about.

1997bird

iTrader: (2)

GM says 9.240" on the deck height. As a side note a 351W Ford has a 9.250" deck height and they were trying to adapt the LSx heads over to work. There was a thread here in this part of the forum about this with a link to the Ford website.

Schwanke Engines

iTrader: (1)

You are correct, sorry, must have been sleeping there. The as delivered deck height on a LS series is 9.240".

GrannySShifting

iTrader: (10)

Did I read that right, youll give someone an assembled 408 for 3200? Im scared to ask what parts are in it and what machine work is actually done? Yuo can give most of the engine "builders" $4000 and they dont do anything to em except bolt parts together!

Schwanke Engines

iTrader: (1)

Actually, it's a 415, and these are the parts, eagle crank and rods, mahle pistons. If you would like, I guess I can charge you $4000.00 for it, I don't have a problem with making more money. We do a very good job of shopping part costs here and we pass the savings on.

If this is the general thought as to not buying a shortblock, then I guess we better raise our price.
You have to remember that is just the shortblock, no covers, cam, lifters, nothing but the block, main caps and bolts, crank, bearings, rods and bolts, pistons, rings and cam bearings with assembly.

Sorry for the thread hijack

1 FMF

iTrader: (1)

the LS9 may have < 4" stroke but don't forget it's supercharged which is a big reason it makes more power.

i agree with what grinder said, only thing else i can think of is a longer rod will have more mass for a given material but that may be a mute point depending on the material you use a lighter material to begin with such as titanium.
and I don't know if a difference in rod length would have any affect on balance of the rotating assembly regarding reciprocating mass vs rotating mass... whether a shorter or longer rod is beneficial or detrimental.
For longer vs shorter pistons, would a longer piston be more durable from a heat standpoint but worse because it would be more massive?

check this out http://rustpuppy.org/rodstudy.htm

ssfast99

iTrader: (3)

wow, if was a dead topic for awhile but then got some good stuff. i know i should think about other things also, just curious. those are some good prices 3200= short block. i just want to build it myself, stupid pride.