# Stroker crank?



## Nightmare2003 (Jan 4, 2010)

I just realized the title sounds kind of funny. Anyways odd question. My wife and I both have GTO's, both '06 and A4's. Mine is modified (engine internal wise) with a Livernois stg 2 cam and heads. Her is pretty well stock, mainly just a CAI, exhaust and nifty speaker system. 
Amongst my searches online for stroker kits and whatnot, I had a strange thought. Brian Crower sells a stroker kit adaptable for an LS2 without oversize pistons, retaining the same bore size. I assume this wouldn't be highly beneficial however that is merely an assumption. So would this be basically an add on part without the need for machining, and if so would the benefit really even be there? I have the itch for more power with my GTO, and the wife wants hers to sound meaner, and my possibly hairbrained solution would be to add a stroker crank to both of them. I suppose it would be a smarter idea to just machine and bore them higher with the engines already torn apart, however this is something that's confusing me. 
Thanks anyone for any help!

P.S. How much power would a 6.6l stoker kit add, in general?


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## BearGFR (Aug 25, 2008)

More cubic inches = more air capacity = more torque, and it doesn't matter whether the additional inches come from increased bore, increased stroke, or both. Lengthening the stroke also adds additional stresses to the rotating assembly due to mean piston speed and side loading. Bore can only be increased so much before the cylinder walls get "too thin". Usually, you can gain more inches via longer stroke than you can via larger bore.

Bear


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## Nightmare2003 (Jan 4, 2010)

Alright so either way there's a positive and negative. I know Chevy engines typically run larger bores and shorter strokes comparably to Ford Engines. My engine only has 60k so I would assume it's nowhere near any point of needing to be refreshed, however having a 6.6L with forged / higher quality internals does sound rather attractive. The kit I'm looking at retains the 4" bore however the stroke is increased to 4", making it "square" as a few friends called it. Would the drivability suffer from doing this?


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## BearGFR (Aug 25, 2008)

Nightmare2003 said:


> Alright so either way there's a positive and negative. I know Chevy engines typically run larger bores and shorter strokes comparably to Ford Engines. My engine only has 60k so I would assume it's nowhere near any point of needing to be refreshed, however having a 6.6L with forged / higher quality internals does sound rather attractive. The kit I'm looking at retains the 4" bore however the stroke is increased to 4", making it "square" as a few friends called it. Would the drivability suffer from doing this?


Nope, shouldn't. Be aware though that things can "snowball" on you... To take full advantage of the increase in inches, you might have to revisit the fuel curve and might need larger injectors, more fuel pressure, etc. Also might need to reprogram the ECM so that it "understands" it now has a larger mouth to feed  You might find you need to open up the air supply - remove restrictions in the intake tract (filter, housing, etc) to meet the demand for more air. More inches also changes the VE (volumetric efficiency) curve so you might need to play with valve lift, timing, duration to put peak VE where you want it --- that means a cam change. And, getting more air INTO the engine means now you've got more exhaust you have to get OUT of it, and that can lead to exhaust system upgrades.

Don't ever forget that an engine is a "system" and all the parts have to work together and be optimized for each other to get the best results...

Bear


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## Nightmare2003 (Jan 4, 2010)

Ah yes, absolutely. It would be more involved than going to a local shop and say "Hey, throw this in." I do have the livernois Stg 2 cam (.232 @ .050, .595 I & E lift, 114 LSA) and Stg 2 heads. Do you think that's large enough to feed the increase in stroke that I'm looking at? I'm going to be looking into a FAST 102mm, improved fuel system (not sure of what make yet), better headers and whatnot. Thanks for the help! These are the things that keep up tossing and turning at night.


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## BearGFR (Aug 25, 2008)

When you start getting down to specific parts and specs on LS's, I get out of my element pretty quickly. I generally work with "old" Ponitacs 

So I'll defer to folks who have more experience with specific LS combinations than I do.

Bear


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## EN3DVED (Oct 14, 2010)

Nightmare, 

Bear was pretty spot on with everything for the internals and motor parts. I have an LS1 5.7 that is stroked out to a 395. This is literally the ragged edge that you can go with this motor. As for the air flow your heads and cams should/seems to be aggressive enough to handle the stoker part. 

There are two other main concerns that have to be monitored as well. With the longer stroke you need to make sure that your piston to valve reliefs are clear. If you retain the stock pistons and stroke it you might not have the clearance for the stroke to cam valve lift clearance so you might need relief cut pistons. The other problem is the stroke to the side of the block clearance. I have a 4.125 stroke in my motor and it required notching the block so the rod bolts would clear without smashing into the windage tray or side of the block. I did not have much of an issue with stroking out mine. 

One other point to keep in mind is if you are going to leave it NA or forced induction later down the road. A 4.00" stroke is about the max with a stock ls block with no increased deck height to allow for the thicker crowns on the piston and not run into issues with FI. I have the 4.125" stroke and it in turn pushed my compression ratio to 12.5:1 so I run race fuel to prevent det. Run a nitrous setup as well but will have to completely redo the motor to go forced induction. 

Just a few other things to think about and hope this helps. The FAST 102 intake would be a good upgrade regardless to help out the heads and cam so it will help one way or another.

Ed


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## danfigg (Sep 27, 2009)

*re*

Nightmare what your talking about here is rebuilding your engine. Only a machine shop can tell you what size piston you need. He has to machine the block first and then determine if it needs an over bore. If this is what you want to do you really need to look into this further who is doing the work who is going to pull the motor who is going to rebuild it. THis is in no way just an add on part this is serious business----Danfigg


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## dustyminpin (Jun 19, 2006)

:agree X 100


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