playtoy

Is there any reason that most engine builders go with longer stroke engines (4" and longer) vs using the stock stroke? I realize that the longer the stroke should improve the torque but I can't see it being that big of a difference in most street motors. Does piston speed become an issue with a 3.622 crank and forced induction. I'm about to have a new short block built and will be reusing my heads that require a 4.125" or larger bore just trying to make a decision on what stroke length to run. Would like to build a 387 (4.125 bore x 3.622 stroke) to keep the piston more stable in the cylinder and run a smaller blower or should I build another 427 ( 4.125 bore x 4.000 stroke). I'm also not building another 1000+ rwhp motor. Shooting for around 800 or so. Let me know what you think and why.

Unreal

I wouldn't do another 427. Big bore short stroke is a winning combo.

Nosferatu333

Please elaborate as to why. Thanks

CI GS

The added benefit from being able to keep the rod length to stroke ratio where it needs to be to avoid excessive side loading of the piston and bore and to decrease piston speeds at TDC and BDC, not to mention avoiding pulling the piston partways out the bottom of the bore on LS motors, far outweighs any gain from the few additional cubic inches you can gain from increasing stroke.
Other gains from decreased windage, etc. are just icing on the cake. And for boosted guys, all they need to do to make up for the loss of cubes is pulley it down a tad anyhow. There's your replacement for displacement: Boost.
That being said, the <4.03" bore motors apparently tend to take boost better too, so I'm not so sure that you should waste the effort on building a short-stroke LS7, although I seriously doubt you would crack the block at that level, unless you experienced some heavy knock.
If you're "only" shooting for 800hp, just do a forged bottom-end 6.2, or use a stock LSA/LS9 bottom end, with good heads, and you can get there easily with just about any centri kit and a little meth, for much cheaper.
Why try to reinvent the wheel? Just my 5 cents, FWIW.
Good luck with whatever you decide to do and make sure that you do a build thread on it regardless.

Unreal

Less stress, stronger motor, better piston support, less piston speed. Extra low end torque is not needed. A 6.0 with a blower will kill any tire down low, so it is added torque at expense of reliability for no real advantage.

lt1z

The large bore allows you to use good heads with larger valves and keeping the shorter stroke adds to longevity as well as rpm potential. It's a win/win in that regard, the downside is the larger bore often requires an aftermarket block and custom pistons. A 388 is one of my favorite engines 4.125/3.62.

Pekka_Perkeles

So, you have to use at least 4.125 pistons.

And a tiny boost (for 800 rwhp).

Now wondering how much cubic inches?

Right?

playtoy

Thamks for the replies. That confirms what I was thinking. Think I am going with a 3.622 or a 3.750 stroke.

Correct. I have a 427 now making above 1000rwhp and I am tired of the constant attention. I want to get back to enjoying my car. When my car had 700 rwhp I would drive it any where without a care in the world. Now that it's above 1000 I don't like making the long cruises from the house for fear of braking something and having to have it towed home. Going to sell the F2 off my car now and get a F1C or F1R and put it on a 388 or 400 cu/in. I even thought of going back to a D1SC.

Unreal

Why downsize though?

I've thought same thing. 700rwhp is SOOOOO much more fun than 1000+. I'm not going to change anything besides maybe throw a 3.4" or big pulley on to kill power, and then its only 5 minute swap for a race/event.

playtoy

I already have a 4" pulley on it so I would have to have one made because I'm running a cog setup with a sprag pulley and I'm pretty sure that would be expensive. I would like to get back on a 8 rib because belts are cheaper and easier to change. I don't really race anymore except for the occasional Friday night at the track and the only event that I want to run is the Texas mile but my wife keeps putting her foot down on that one. Also the F2 takes so much just to spin the blower and with the 50mm cog belt it puts a side load on the front mains. Could probably solve that issue with an iron block but I don't want to take the chance again. If I had a F1X I would probably just pulley up.

Unreal

Yep. 10 rib works good too. After next 1/2 mile going to put a 3.3" on it and just beat on it nonstop which I do now, but at least it will hook up better.

lt1z

I love the 850whp level personally in a C5/6

Nosferatu333

For street or strip?

Unreal

In any RWD vette. I would even say 750-800.

realcanuk

I really don't see the difference. I doubt I ever see even 800 driving on the street.

Nosferatu333

I usually run out of road or ***** with my 617 to the wheels. Shooting for 750 for no reason other than sh its and giggles. 800+ seems like a death wish for me. No reason to believe 750 won't kill me either. It's just feels safer. Ignorance is bliss.

realcanuk

Yeah. I meant don't see the difference in 800 or 1000. Just push the pedal as far as you want to.

inspector12

James, Piston speed doesn't have any real effect with a 4" crank as most aren't turning enough RPM to even get close to an issue. Big blocks running a lot longer and bigger CI turning more RPMs with out issues. As far as why ppl buy a 4" over a stock stroke etc... Cost is the main reason same price and your picking up more CI mainly. I recently built a Callies 3.625" with a 4.125 bore for a CTSV cause he's still running the smaller blower and wanted to turn more RPM's for the mile. With that setup it was way better to limit CI for the small blower etc... But normally if you have a properly sized blower or turbo for your goals then the extra CI doesn't hurt you really. The piston support can be argued, but its been done for so long now without serious consequences that its a moot point. But with that said If you want to build a smaller motor then I don't see a reason not too. Do I think its going to help reliability. Meh not really. Reducing HP will for sure. GL!

lt1z

Just for the chassis in general , especially with a manual. Its a much more usable car. The 4 digit C6s pretty much need an auto swap which kind of ruins the car beyond the strip.

playtoy

Jeff I really think a smaller blower is more suitable for what I use my car for. Big cubes and a big blower is fun but we don't race every weekend like we used to so there's not any reason to build my car back the way it is now. Anything I can do to make the car more reliable is what I'm looking to do this time.