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DJW32
07-07-2006, 10:39 AM
This is what I'm thinking about
I'm looking for 750-800HP

How about an aluminum LS2 with a 4.8L crank, 6.0L heads with crane cam springs, edle. intake,forged internals, and a twin turbo setup (2 hi-fl 61 turbos, this is subject to change for whatever will work in the most efficient manner)
Questions:
1. How many cubic inches is that(364 cubic inche LS2 with a 4.8L crank)?
2. What will I be giving up by destroking the motor?
3. How high can I spin the motor?

Thanks, David

Nine Ball
07-07-2006, 12:36 PM
I gotta ask why when considering destroking an LSX engine.

1. Any gains you hope to achieve in with making it more oversquare would not exceed the potential limits of the block itself, when speaking of a boosted setup. You will lift the heads under enough boost (around 900 rwhp or so) even with a stroker crank.

2. You aren't really concerned with the higher revving characteristic of an oversquare engine, since these LSX engines can pull past 7000 rpm no problem with a hydraulic cam. My LS2 in the Corvette pulls to 7000 rpm with a 230/230 114 cam and stock unported heads.

I'd leave the stroke alone, and just let the turbos do the work. You can even run a cast Eagle crank and save some bucks. The block will be the limiting factor in that combo, not the crank.

DJW32
07-07-2006, 12:44 PM
Tony,
The post is only a theory, I should've mentioned that...
Thanks for the feedback...I'm always looking for opinions

Kenova
07-07-2006, 06:52 PM
Assuming you use the standard 4" bore: 328.23 cu.in. If you want or need a 5.3L engine this combo would have a slight advantage over the factory 5.3L when it comes to breathing. The larger bore will help unshroud the valves and/or you could use bigger valves.
The 4.8 con rods are longer to make up the difference in the shorter stroke so you could probably use LS2 pistons.
Yeah .... I've given it some thought too.:idea:
Ken

rocketman
07-08-2006, 08:46 AM
I built a destroked LS1 for a guy in town,it came out to a 302.i don't rememeber I think it made 575 hp,It's a very high windy engine.I know we turned it 9g onn the dyno.he did it for the 302 combo in a z/28 think.

DJW32
07-08-2006, 10:48 AM
rocketman,
Do you have any pictures or a dyno graph...

rocketman
07-08-2006, 06:14 PM
When I get back to the shop next week I will look.

gEtyOpAPiOn
08-12-2006, 09:07 PM
hmmm i did a search on a destroked ls1 to make it into a 302 for a z28 that i wanted to build but i came up empty handed ...what crank and rods did you use rocketman ?

SLED28
08-13-2006, 08:00 AM
This is what I'm thinking about
I'm looking for 750-800HP

How about an aluminum LS2 with a 4.8L crank, 6.0L heads with crane cam springs, edle. intake,forged internals, and a twin turbo setup (2 hi-fl 61 turbos, this is subject to change for whatever will work in the most efficient manner)
Questions:
1. How many cubic inches is that(364 cubic inche LS2 with a 4.8L crank)?
2. What will I be giving up by destroking the motor?
3. How high can I spin the motor?

Thanks, David

I would stick with a 347 motor or the 364 LS2. Turbo's like stroke, a 3.900 stroke or 4" stroke would be even better. It helps them spool. Many years ago I built a 347 with a single turbo and it made 815rwhp. So either way you are good but I would not de-stroke it.

rocketman
08-14-2006, 08:22 AM
hmmm i did a search on a destroked ls1 to make it into a 302 for a z28 that i wanted to build but i came up empty handed ...what crank and rods did you use rocketman ?


Callies 3inch stroke crank
sleeve block to 4inch bore
i cant find my file on that motor,i dont recall what rod we use,it was a billet rod i dont recall length.

it was copy of the yearone 302 ls1 they did back in 01.

the motor had i did had 12.1 comp and a solid roller with ls6 heads.

when i find the file i will give you all spec's.

DJW32
08-14-2006, 12:19 PM
Rocketman,
I have thrown the turbos out of the equation.

Was that 575 horse to the wheels?
Do you remember the torque curve?

rocketman
08-14-2006, 01:40 PM
No that was motor,tq was only 400 if that,it's not a tq maker.I for the life of me can't find that file.It has no bottom end to it.

rocketman
08-14-2006, 01:42 PM
If you want a nice ls1 i would build a 393.make's nice hp and tq.

Diognes56
08-30-2006, 11:23 AM
Example of destroked LS1 :look: .

http://www.ultimatecarpage.com/frame.php?file=car.php&carnum=1147

David

DRCE
09-05-2006, 08:50 AM
Turbos like stroke plane and simple. I have always followed the plan of building the largest engine possible for a turbo application provided it was within the efficiency area of the turbo/turbos still.

A like doing 408's in iron form fairly often for boosted stuff, coupled with an 88 or a pair of 63's your in good shape and it will make a boat load of power.

chuntington101
09-06-2006, 10:58 AM
looking at a few vettes and cameros, i would go with a stock inch LS1 with good internals and go for it! :)

you should beable to make 1000bhp easlily (as easy as it is to make 1000bhp! lol).

thanks Chris.

Fuelie Fan
09-06-2006, 12:05 PM
Turbos like stroke plane and simple. I have always followed the plan of building the largest engine possible for a turbo application provided it was within the efficiency area of the turbo/turbos still.

A like doing 408's in iron form fairly often for boosted stuff, coupled with an 88 or a pair of 63's your in good shape and it will make a boat load of power.

I think that should read "driver likes stroke." EVerything being equal, more displacement equals more power, and that's always good! But, there's nothing about stroke itself that makes turbo matching difficult. You can match a turbo to a 327 just fine even though it's got less stroke than a 383. HOWEVER, if you're reducing stroke with the goal of drastically raising an rpm limit, then you have a bit larger challenge on your hands. Centrifugal compressors have limited ranges within which they will work well (I trust most of us have seen turbo maps), so asking a turbo to be responsive from 2000 to 8000 rpm is much more difficult than getting response from 2000 to 5000 rpm. This is NOT just a stroke thing, this is an entire engine combination thing (stroke, cam, intake, heads). So, what it should actually say is, "turbos don't like extremely large variances in airflow rates."

RobM
09-06-2006, 03:56 PM
destroked engines are built to work in a narow powerband any way. if you want an engine that makes power below 5k dont waist your time. your building the wrong tool for the job.

Fuelie Fan
09-07-2006, 06:50 AM
Yeah, in the context of this thread I'm not disagreeing with DRCE. At the same time, engines with "short" strokes can ALSO make huge power with a turbo and still be very streetable. It's all relative; the 327 is a stroker compared to a 302! I just think there was some oversimplification that I thought I might elaborate on. If somebody is starting out with a 327 which isn't already set up for high rpm performace, (maybe it's their numbers matching 275hp motor?), I don't think they should feel compelled to stroke it to 383. I take that back, I would endorse it, just as DRCE does simply because it's easy power...but my point is that such an increase is due to DISPLACEMENT, not stroke.

Put another way: Is a 307 a better turbo platform than a 302 because it's got a longer stroke? (i know...the tiny bores shroud the valves, but if that weren't an issue...for the sake of conversation)

It reminds me a little bit of the 377 vs 383 debate, and the ensuing hot rod article (which now I can't seem to find) in which the two performed almost identically, going against all pre-test speculation. Had they turbocharged them, I suspect the result would be the same.

Anyway, my original post and this post are both probably not of interest to original poster who was interested specifically in destroking his engine, to which the correct response to question #2 is along the lines of DRCE's. removing displacement reduces the amount of possible peak torque, whether it be through a reduction in bore or displacement. To compensate for this and still make the same horsepower, you need to increase engine speed (hp ~ T * RPM, so if T goes down rpm must go up). Because reducing the stroke reduces piston speed, this approach is the most viable (as compared to a small bore long stroke) for raising the engine's rpm potential. But in order to match that, you need to time the valve events differently (in other words, run a more aggressive cam). Doing this will cause a FURTHER reduction in low end torque. PLUS, now you've made your turbo matching more difficult, and if you match it for top RPM/peak HP numbers, you'll have more lag down low, making the engine fell even weaker yet off the line. All of this adds up to not removing stroke if you don't have to in order to meet the rules of some sanctioning body.

SLED28
09-07-2006, 07:07 AM
It is true, STROKE drives the turbine faster. Look at the 449 fords out there, all stroke, running 6's on 10.5's!!!

RobM
09-07-2006, 03:05 PM
stroke has alot to do with mechanical advantages, high rpm stability, and piston dwell. cant forget about these!.... discuss... man i love this stuff

Fuelie Fan
09-07-2006, 04:44 PM
I'm wondering if you can elaborate on what you mean by high rpm stability?

RobM
09-07-2006, 07:49 PM
We a shorter stroked engine generally has less rotating mass than a longer stroke engine, and this mass is generally closer to the axes of the crank than a longer stroked engine. This in turn makes the engine less sensitive to imperfections in the balance of the rotating assembly. Any engine builder will tell you they balance to “0” but it is impossible to balance any thing entirely perfect. How ever the hole in my theory is that the benefit if this concentrated rotating mass can be canceled out due to the higher rpm capabilities of a de-stroked engine. A shorter stroke also makes for slower bearing speeds. which frees up power

Fuelie Fan
09-08-2006, 07:50 AM
Once again we need to clarify whether we are talking purely about a change in stroke, or a change in stroke in combination with an increase in redline to achieve comparable max piston speeds.

For the former, then yes you've decreased rod bearing speeds, but crank bearing speeds are the same and all accessory speeds are still the same. That's all well and good, but I guarantee you that the minor rod bearing friction reduction won't offset your loss of displacement! You're better off running different bearing diameters (see nascar running Honda bearings) than reducing stroke if you're looking to reduce friction losses.

If you increase engine speed, your rod bearing speeds will be basically the same as they were before. Meanwhile, you've INCREASED speed of the crank bearings, resulting in a net increase in friction. You're also driving your pump and all accessories faster. And, probably most importantly, your crank is cutting through oil at a much higher rate. You will experience increased losses as you increase engine speed.

RobM
09-09-2006, 12:21 AM
i agree with what your saying, i was just bringing some other factors into the mix. this conversation could become endless but thats ok. I mean if you throw rod length into the mix it opens up even more doors of conversation

68ls1wannabe
09-10-2006, 09:26 PM
Why the high rpms. V8's are about torque. Longer stroke = more torque. That is what move's the car right. Where can you use 8000 rpm on the street. That high winding motor would get it's ass handed to it by a properly setup turbo motor in a useful powerband. Say 2000 to 6500. I thought the whole idea of the turbo was to pack maximum amouts of air into the cylinders without having to turn the piss out of the motor. Check out ls1tech.com. They argue these ideas constantly.

Kenova
09-11-2006, 12:48 PM
:hmm: I normally try to stay out of discussions like this one, but sometimes I just can't help myself :banghead: . I haven't had much experience building engines, and I've never seen the inside of a dyno cell, but I have done a pile of reading over the last forty years. What follows is merely what I think I have learned.
First off, torque is primarily a product of displacement. I've seen more than a few tests over the years where different bore and stroke combinations of the same displacement were tested. The torque and horsepower readings are usually within one or two percent, sometimes even closer.
A shorter stroke with longer rods reduces strain on the rod bearings, rod bolts, rods, and wrist pin. The friction from thrust side loading is also reduced. Does this result in more power? Usually not, but if it makes life easier for your engine, why not do it?
Just because an engine has a short stroke and big bore doesn't mean you have to wind it up to the moon. Lord knows there are more than a few Ford 5.0s (3.00s x 4.00b) lugging a variety of trucks and land barges around. How far you wind an engine up depends on how big of a cam you have (and the size of your gonads).
With the advent of modern fuel injection and turbocharging, large displacement engines are not always necessary. Although it will always be easier to get the same torque and horsepower out of a larger engine.
Now for my personal preference. If I were building a turbo engine for street duty, I would use a 4.125" bore so the heads can breath more freely. The crank would be in the neighborhood of 3.25" with 6.125" rods for a displacement of approximately 350 cu.in. With a good turbo system it would make plenty of power for the street and I would have a slightly higher comfort level due to the short stroke and long rods.
Needless to say, all this goes out the window if you must conform to racing class rules.
Ken

nancejd
09-11-2006, 05:20 PM
Don't forget that their is a difference between engine torque at the flywheel and torque at the wheels due to gear multiplication. The chief disadvantage I can see with the smaller displacement higher winding motor is that you'd need more gear in the differential to overcome the torque disadvantage, which would result in a higher rotational speed for the driveshat. You'd potentially be a lot closer to the driveshafts critical speed. On the plus side, how much torque do you really want to make a t a low rpm anyway? Can you really hook up a big block on the street? Or most turbo small blocks for that matter? I think something that came out of the hole soft and just kept going could be interesting on the street.

68ls1wannabe
09-12-2006, 07:37 AM
I believe one of the best motors to build is the 6.0 LQ4. It's an iron block so no issues with strength. Stpck bore at 4.00. Get a forged eagle rotating assembley, 4.00 crank, rods, pistons. Keep compression at 9:1 for turbo or 11.5:1 NA. Port the stock heads and use comp 921 springs. Lightweight valves "like the LS6". New cam. LS6 intake or if budget permits the FAST 90/90. More power than u know what to do with and getting the job done under 6500 rpm. :cool: Say goodbye to those new rear tires.

Colvindesign
09-20-2006, 01:41 PM
If this was to go into a very light car, then I'd say go for it and forget the turbos. A LS302 would be sweet.

If this is going into a middleweight to heavyweight car, then forget it, and go for a stroker LS1 or LS2 and your choice on the turbos. I think they have 396 Cube stroker kits, which would also be a sweet displacement number.

However, if you are seriously looking into the destroked LS, I'd do some research and try to get Dyno graphs on the ones that have been built (destroked LSxs that is), this will tell you exactly what you will need to do (gear, trans, etc). If you build something that revs to 9000 rpm and makes 400 peak torque, you need to know what the off idle torque is. If it's 100 off idle, that's a lot different than 200 or more. This means you will need to take it up to 2500 to get moving. A well balanced rotating assembly and a lightweight flywheel will throw the revs up and down faster than you would think, plus if you are going for those high of revs, I would suggest a dry sump, or something more extreme, if you are building it let me know and I'll let you know a secret good for up to 10% increase in power on a high winder.

Anyway, finding out where the torque is, is pretty important. Because if it makes none down low, you can go test drive an S2000 to see what it'd feel like to drive. But if it makes a fair amount down low, regular driving will be fairly normal.