Kawboom

I think you misunderstand what I meant, and I was a bit unclear. A longer stroke will give more power on cubic inches, but if you had a 400ci engine that was 4" bore by 4" stroke, and another that was 4.125" bore by 3.75" stroke, and another that was 4.25" bore by 3.54" stroke, with everything else equal the torque and horsepower produced will be the same. Cubic inches are cubic inches. This has been tested over and over again. The "leverage" of the longer stroke doesn't matter because the larger bore engine has that much more pressure on the piston pushing down on the rod. It all equals out.

Think about it this way. Two hypothetical engines, on has a 4" bore and a 1" stroke, and one has a 1" bore and a 16" stroke. These engines have the same displacement. The 4" bore engine has a piston area of 12.56 inches square, the 1" bore has 0.78. Thats 16x larger area for combustion pressure to push down on. The long stroke engine has 16x the mechanical advantage but only 1/16 the pressure on the piston. Everything else being equal difference is nothing, but in practice larger bore shorter stroke engines tend to breathe a little better and a shorter stroke is easier on your rods.

KCS

iTrader: (20)

So far, no problems with my 4.250” stroke 6.0L block. Still no metal in the oil, no smoke out the tail pipe, and no crazy oil consumption.

https://ls1tech.com/forums/generatio...ld-thread.html

The 4.250” stroke crank is a little tricky to get to work in a standard deck height block, but it’s not rocket science. Wiseco has a good skirt design, we just made some compromises to the rest of the piston to make that much stroke work. The piston cleared the counterweights but needed a little clearancing for the reluctor wheel. We found a set of stroker profiled rods that cleared the cam and needed very little clearancing at the bottom of the cylinders. I compared the piston rock at BDC to a 4” stroke 408ci and they were the same.

The 4.1” stroke combos I’ve built were a lot easier. With a good set of rods, like Callies compstars or K1’s, only a little clearancing will be needed at the bottom of the cylinders, and as always, a good deburr of the bottom of the cylinders is needed as well. Wiseco makes shelf pistons for this which are usually cheaper than the custom pistons the longer stroke combo requires.

Jimbo1367

How common is using a smaller rod journal? I think I seen one of Tony’s builds were he used a smaller rod diameter

any input on that?

Kawboom

It works, and comes and goes as a bit of a fad in the car world. There is a small but real amount of power to be gained by having a smaller main and rod journal, but it's pretty minimal, and probably not enough for a hobbyist to worry about. Competition areas like NASCAR and others where they are fighting for extra horsepower in 1 and 2hp increments are where it becomes relevant.

KCS

iTrader: (20)

I used to do it all the time with a 2.00” rod journal. Callies Compstar cranks and rods can be ordered with the 2.00” rod journal. It hurts the strength of the crank a little bit by reducing journal overlap, but with a stroker it helps the rods clear. IIRC, a 4” stroker may not even need the cylinders clearanced for the rods with the Compstar 2” journal connecting rods.

CamaroSS22

iTrader: (1)

I would be more worried with the rod hitting the lobes on the camshaft. If you pick the right pistons and crank it will be fine, the compression height on the piston will make up for the the sleeve length. I have built plenty of DD strokers for people with no issues. Just build the engine for it's intended use and it will run forever......with decent oil

Utinator

That's what I was hoping to hear. I would prefer to work with the 4.1" crank. The only one I could find is the Manley Pro Series Crankshafts 190124, Part Number: MAN-190124. They are a bit pricey, but that's all I could find. I'm not considering Pro-Comp Electronics. I haven't heard anything good about their product. I might check with K1. They have every other size crankshaft, I don't see why they wouldn't make a 4.1". I believe I was already looking at the Wisco "shelf" pistons you were referring to. Also expensive, but it costs to be the boss.

KCS

iTrader: (20)

You may be better off with the 4.125" crank. There are more options for crankshafts in 4.125", such as K1's 58x crank (PN 012FAE41358), which is about $400 less than the Manley cranks at Summit Racing. Wiseco's pistons are closer to zero deck with that stroke versus the 4.100"..

KCS

iTrader: (20)

With all else being equal, you're right that there may not be any difference in power or torque, however, over square and under square engines offer different advantages when the rest of the engine is tailored to the bore/stroke ratio. Smaller bore engines tend to be able to achieve better combustion efficiency and can sustain more cylinder pressure for a given fuel, so they have the potential to make more torque per cubic inch. This has been tested as far back as the 80's at the Sloan Laboratories of MIT and most recently at the Engine Masters Challenges, where most winning combinations were under square because points were based on power/torque per cubic inch within a given RPM range.

Double06

iTrader: (1)

They just finished up my 455 CID ls motor with a 4.19 bore and a 4.125 stroke. Previous motor had piston rock issues after 35,000 miles, thus oil consumption. I have a 5.80 inch sleeve length so not too short. On new build the machinist worked with piston maker on a specific taper for that long of a sleeve so my issue did not happen again. The taper is important as when you measure piston it is like .275 from bottom but that does you no good if your piston sticks out .500+ from bottom and what was a .004 piston (.275 from bottom) to wall clearance is now .008 or more as it pops .500+ out the bottom. Also don't cheap out on the rings that is also very important on a stroker motor.

getnit

iTrader: (6)

I have a nice Scat Superstock series 4.125 stroke crank I would sell. Let me know if this interests you. I will be posting it today.

QwkTrip

iTrader: (23)

I had a gen IV 6.0L with 4.125-in stroke. It was a dirty engine, oil turned black pretty fast. Lots of windage in the crankcase, PCV system was not sufficient. LS1 F body oil pan had to be clearanced for one of the rod bolts. The rods are crammed up against the oil pan, it's a recipe for oil aeration and general PCV problems. Also, the engine was finicky about cam selection.

Results will vary but that was my experience

Later got an LS7 with a deeper pan (whole pan is deeper front to back) to add more volume in the crankcase. Also enabled me to have room for a windage tray and crank scraper. All the issues went away.

grinder11

iTrader: (1)

Even at the 800+hp level, with/without FI, it's hard to beat a Callies crank. Excellent quality....

Kawboom

I wonder if because the Engine Masters Challenge gives so many contest points for torque and for numbers far below the torque peak, the under-square (small bore big stroke) engines have an advantage because of how the combustion chamber isn't as big around, like a sphere instead of an oval-shaped (this shape is called an oblate spheroid, a 3d oval). That could give a more complete or easier to control combustion at low RPM. Over-square engines with bores often much larger than the stroke are the standard in all performance high-rpm applications from motorcycles to Pro Stock to Formula 1, and I believe the reason is due to simply how these engines don't have an artificial RPM range and when run are run past the torque peak for most if not all of their duty cycle.

I still assert that all else equal cubic inches are cubic inches, they won't make more torque per cubic inch at peak head efficiency with the same combustion chamber, but may have advantages when you pull the engine way down below what even the worst torque converter possible could hold back. The Engine Masters Challenge used to start their dyno pulls and points system at 2500rpm, today that's a typical starting point for a turbo DIESEL on the dyno. If you have a hot rod with a torque converter and you can get it to flash past 2500 just by foot brake you need a different torque converter.

grinder11

iTrader: (1)

IMHO, what you've done is a win-win. Not only have you increased oil capacity, but increased bay-bay breathing. Hard cornering, the engine will benefit with more oil covering the pickup, and extra power no matter what g-force, due to better bay-bay. Don't know if you've seen my posts, but when I had a stock internals LS1 in my C5, best run I ever made was when I was coming back from the timing shack, and the low oil light went on!!!!! DOHHHHH!!!!!! I attribute that to having better bay to bay breathing, but doing it the wrong way!!!

Utinator

Would the LS7 oil pan even fit in the 4th gen f-body? I had planned on keeping my LS1 oil pan no matter what engine I swap in.

Utinator

Are you talking about the windage tray? I figured it would need spacers to clear the crank. Did you have to notch the tray out too?

QwkTrip

iTrader: (23)

#2 rod bolt literally scraped the oil pan. I had to grind out a depression in the pan for rod clearance. This can happen depending what rod bolts you use. Stock F body pan is so shallow that it has a partial windage tray because a whole one won't fit.

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01CamaroSSTx

iTrader: (3)

And easily remedied with a Moroso 21150 pan and Milodon oil filter adapter 21566 but it's not cheap.

Utinator

Wow. I wasn't expecting that. Which rods and bolts were you using?