Now I'm all for building a 9000 rpm 400+ inch LS1! Although it still probably wouldn't make for a very good street car but at least it would be crazy fast.

 

Why not a 302ci that spins to 8k rpms and a nice turbo setup?

Benefits of that over a nicely setup 346 with a turbo setup?

 

Obviously, you guys have not driven many cars and most of of you prolly havent heard of bikes. There is more to driving a car than 1/4 mile times.

 

Giving up cubic inches in favor of RPMs is silly.

But speaking of RPMs, I know of 418cid LS1 that revs to 8,000.

 

R. Gross?

 

I agree with this statement. Just b/c it has smaller cubes does not mean you are sacrificing hp. Maybe sacrificing HP where "drag racers" need it but not where road racers or even some sick street racers would need it. Building a motor like that would be pointless on the street like many of said but probably cheaper than 400+ cubic inch spinning the same RPM limits which would be a little less pointless on the street.

 

Kumar,

Unlike a lot of others on the board, I HAVE been around FAST cars and bikes and so am warning you that building what you are talking about is silly. You won't go any faster PERIOD. You'll go slower everywhere and anytime. You don't see fast street bikes either with small mini mee motors unless that's all your racing. Cubic inches aren't everything but they make it MUCH easier to make power. Who gives a crap how much rpm you're turning if your slower? Do you see F1 superbikes running smaller engines to turn more rpm or F1 cars? See any 2500 cc F1 engines? You never will unless they drop displacement back to that to slow them down again. They all run the largest engine they are possibly allowed and they do it for a reason. Road racers have even more of a reason than drag racers to run large engines and that's reliability. No one in road racing runs smaller engines than they can unless like in drag racing they get to take weight off of their car.

People turn rpm to make POWER not just to turn rpm. Anyone can do that, just make the engine smaller! With that logic why not build a 250 inch LS1 or just keep getting smaller until you have a full weight LS1 that makes less than a 100 hp at 20,000 rpm.

 

Yip that's who he's talking about. Good Ole Keith from MFBA's car.

 

Just so that no one misunderstands me, I am not against rpm but it IS expensive and if you're getting it by making the engine smaller instead of the heads and intake better you are just not gonna be happy with the results in general.

Kumar please forgive me because I didn't mean any of the sarcastic stuff for you individually or anything since everyone brings this up every few months. I just don't believe in rpm for rpms sake.

 

Yes, you are sacrificing HP - even if you make the same peak hp you will have a much narrower powerband. What exactly do you mean - where "road racers" or "sick street racers" need it? Power is power, doesn't matter the rpm it comes at. If you have more of it (area under the curve) then you are better off, period.

There really is no reason to destroke the motor, unless you just think it's fun or you are working under a cubic inch limit (as was pointed out earlier). You can get a big enough piston compression height on a stock stroke setup for anything the block can handle, and aside from that I don't think there are any other real world strength benefits from the destroking?

 

You are assuming that the peak HP will be less. I do not think that will be the case. As stated he wanted a 4.125 bore with the 3.27 stroke which someone stated will be 350". With 4 more cubes and the possibility of more RPM's I think that there would be significant peak differences. If you can keep your car at its peak HP range for most of the activity you will be doing,( i.e. top speed street racing or top speed oriented road racing) then what does power under the curve really matter if you are not spending anytime there. Yes, these are extreme examples but examples none the less. Do they represent most peoples view probably not, but is nascar everyone's cup of tea.

 

Who ever said a 4.125" bore and a 3.27" stroke was smaller than a stock LS1? I think that this particular combo would be way better than a stock cube and stroke LS1. Now if I personally was going to go 4.125 bore would I go to a 3.27" stroke...........No. Everyone is different, look at all of the Muscrat drivers revving the **** out of their 4.6's b/c that is what the little motor likes to do or rather needs to do.

 

Why compare it to a stock displacement motor? For the $$$ you are going to spend you could have a 380-430" motor. If you are limited to 350 cubic inches, then yeah, I would probably go for as big of a bore as possible - but we aren't limited to 350 cubic inches.



What exactly is "top speed oriented road racing", and how does it differ from say, a normal SCCA Road Race? Because in a typical event like that you are going to be going through a wide mph range, and if you have to shift to keep your car in a 1000rpm band you are going to be going slower than if you can just stay in gear and power through a 3000 rpm band.
I'm not sure exactly what "top speed street racing" consists of, so can't comment on that - but yeah, if peak hp is the same and you stay at peak hp then then the destroked car wouldn't be any slower. It would be just as fast. But then you would be turning 8000 rpm vs. say 6000 rpm. Which motor do you think will last longer?





You are entirely missing the point - you are comparing bore vs. stroke while keeping the cubic inches the same. Comparing a stock motor to a built 4.125" bore motor. But for the $$$$ you could have much more than stock cubic inches - the point is by going with the smaller crank you are giving up cubic inches, everything else being equal.

 

I totally agree that a 400+ motor is the only logical way to go for the price, but price was never mentioned here. If the style of racing was limited to 350" then a destroked all bore 350" would have an advantage over over engines b/c of the higher rpm potential. I agree that comparing the peak hp of a 400+ cu in motor and the one in question you would arrive at roughly the same value. I can not argue with the fact that that this way is backward logic but if seeing the brighter side of 8000 rpm gives you a rush then so be it.

As far as top speed street racing, I basically mean side by side as fast as you can go and who ever is willing to hold it there the longest. I have never been a fan drag racing so running down the freeway at top speed is what I meant.

 

ChrisB and All- Interesting article here on HP vs TQ and RPM ->http://mclements.net/mrc-PowerTorque.html#_ftn1 FWIW.
joel

 

If they both have the same cubic inches, cylinder heads, and camshaft then they are going to turn essentially the same rpm. The destroked motor will do so at a lower piston speed is all. Now if you put on significantly better heads/a much bigger camshaft it can turn more rpm, but what are we talking here? 8000rpm, 9000rpm? Plenty of people with stock shortblocks turn 7000rpm already. When you try and turn 8000rpm+ your cost has just increased greatly. Shaft rockers, lightweight valvetrain components. Plan on changing your valvesprings on a much more regular basis. A camshaft that turns that high is not going to have very nice street manners, etc.
So it's not just the de-stroking that gives more rpm, it's a reduction in piston speed that allows for a higher rpm while maintaining sane piston speeds - but you still need to alter the rest of the car to achieve that higher rpm.


I am pretty sure it was stipulated way back in the beginning that if you were class limited to a displacement or just wanted to do it for fun then go for it, but from a racing/speed/power/money standpoint it doesn't make any sense.

 

while on the subject of RPMS...

the new ls7 motor for the corvette will spin to 8k from the factory no problem gm says..this is the 6.0l 500hp motor, by the way.

u have to know GM knew that RPMs was one of the things sort of missing from the ls-blocks.

u can have a high displacement engine making 1000 ft pounds and it redlines at 4k rpm, but if u have a motor making 600ft pounds and it revs to say...8500 rpm, the torque monster has no advantage in power at all. more usable RPMs are always good.

u have to know that an s2000 that would redline at 7k rpm would not get 240hp out of that 2.0l inline 4.

 

I'm with you on the making power up top thing. Ooh, my first post.

 

I don't think you see the point that was originally expressed. This is not about new motors to come. This is about an ls1 and what the benefits would be if you destroked it. Which there are none, except as I stated before to make a certain class that has restrictions on displacement? Also ls1 strokers rev a little higher then 4K rpms. You can’t compare a inline 4 cylinder turning 7K rpms to a 8 cylinder turning 9K rpms. You really can’t compare a 4cylinder to any 8 cylinder engine because of the rotating mass involved. There is not substitute for cubic inches that’s as simple as it gets, and less expensive

 

How many people have tried this on an LS motor to know that it will not do any good?

Why would GM have gone to great lengths to make the ZR1 the high revver that it is. I think the general idea of the ZR1 was to trade off some low end torque in favor of an extended powerband and more top end needed to compete with the other supercars of the time. Sure it had 4 valve heads to help it breathe better, but I am sure a well ported set of LS6 heads could keep up with, if not outperform them. Here it is 8 years later and it seems that no one believes that todays technology can expand the envelope on that concept even further without having to mortgage your house? Why not have a motor that revs to 8 or 9K? I know of atleast one LS6 motor spinning to 8K with a solid roller cam. How many are spinning well into the sevens with stock blocks? If you look at the import side of performamce, the rule is max efficiency through high revving well breathing motors over 90 hp per liter in many cases. As someone pointed out earlier, our mustang bretheren have been exploring this concept for years. Add a turbo to the mix and you have a very versatile motor with a huge amounts of power "under the curve", an unbelievably long, broad, flat, useable curve. And the money issue is not relative, because anyone who is willing to build a very serious motor is not looking for a bang for the buck project (and stroker motors are not exacly cheap). Anyway, that's my 2 cents.