RonA

iTrader: (1)

Why no 3.27" stroke aftermarket crankshafts(custom only)?

KCS

iTrader: (20)

Probably not much of a demand. Less stroke is counterproductive for making power.

Sales2@Texas-speed

iTrader: (5)

Stock cranks handle quite a bit of power as they sit. It just wouldn't make since to make them for the couple guys that might buy them.

RonA

iTrader: (1)

And yet every shop I talked to told me to avoid 4" cranks like the plague.(and everyone carries them).

redtan

iTrader: (5)

When people don't know how to do a certain thing they tend to talk crap about it so potential customers stay away from something that they can't do.

Most if not all of the top end engine builders in the country give the option for a 4" stroke with good reliability.

KCS

iTrader: (20)

Most of the manufacturers even have trouble keeping them in stock.

Why would they recommend avoiding the 4" stroke cranks?

LS1MCSS

iTrader: (18)

Sounds like you are talking to the wrong shop.

2000PewterT/A

^^^^ x2

garygnu

^^^^^^x3

wildcamaro

iTrader: (15)

Xxx4...had to lol

Sales2@Texas-speed

iTrader: (5)

GM put a 4" stroke crank in the LS7 as a stock piece. I have no idea why a shop would say to avoid that.

RonA

iTrader: (1)

I guess I will have to expand my search. The quotes I got for the builds were both from shops highly recommended on this site. Both machine shops I use agreed with the logic too. Funny how much conflicting data there is in this regard. If 4" is good to go, I'll admit I'm wrong. My apologies.
I'll continue to look for a shop that is better informed.
RonA

redtan

iTrader: (5)

You don't even have to look far, like someone else said GM themselves put a 4" crank in a mass produced engine that they warranted for tens of thousands of miles.

If that isn't enough evidence for you, I don't know what is.

crash41301

iTrader: (1)

I'm going to go out on a limb and guess they were worried about the rod stroke ratio when going with the larger crank. Does an ls7 have longer rods to offset its longer stroke to keep side load to a minimum?

nobreaks254

iTrader: (50)

I believe ls7's have a shorter rod than any other ls engine. 6.067 I believe

KCS

iTrader: (20)

Correct, they are shorter.

96capricemgr

iTrader: (1)

The logic that places can't keep a long stroke crank in stock means they are a great option is deeply flawed, you know how many idiots out there still believe displacement is the biggest factor in power and will buy a longer stroke crank before wanting to even port heads.

In other engine platforms the Eagle cast stroker cranks are still very popular even though they are outright fragile, they break at less port than guys expect from a heads/cam stock shortblock, but guys buy them because "there is no replacement for displacement". They don't even look into the fact they break at less power than guys expect to make with heads/cam on stock shortblocks.

Far as the LS7 block again flawed logic as a quick search tells me the LS7 sleeve is half an inch longer than the LS2 and LS6 sleeve. No small detail to be considered. and there is probably a reason they added sleeve length.

I am not saying a 4" stroke is good or bad. I am saying at least make coherent arguments to support your opinion rather than cherry picking random info that sounds so long as you don't actually things through.

Blowerman

So many things to factor in when going beyond the original stroke. Engine mock up and clearances must be done.
You also have to realize piston speed and dwell at tdc which influences cam profile and tune beyond the standard cam and header bunch.
Rod ratio which was mentioned earlier is something that is well worth learning about.
As far as long stroke crankshafts being no good. I say bullshart.

Jenson

iTrader: (32)

He probably told these shops he wanted a high revving engine therefore they tried to steer him clear of a long throw. And yes the LS7 revv's pretty high and the piston speed is up there but they also used Ti valves and rods.

KCS

iTrader: (20)

Displacement is as much, if not more of an influence on power output than just about anything else, which is why almost every competitve NA class (in drag racing) has limits or weight breaks for cubic inches, but not necessarily valve or port sizes. You would have to be an idiot not to understand that.

If there was something wrong with using a 4" stroke, there wouldn't be much of a demand for the crankshafts. More crankshafts are purchased through engine builders (ERL and TSP are the big buyers) rather than the average Joe, so its not "idiots" buying up all the cranks. The majority are professional engine builders.