KCS

iTrader: (20)

You could get an LS1 to make 500whp, it's just that you will likely be sacrificing a considerable amount of torque from the lower RPM and shifting it in the higher RPM where it will make more horsepower. An LS2 would be that much easier to make power with since you would already be starting out with a 4" bore and 364ci with the same stroke. Not to mention, the LS2 is supposed to a considerably stronger block.

A typical rotating assembly for a 383ci LS1 uses a 4" stroke as well as a 6.125" rod. An LS7 uses a 4" stroke as well, but with a shorter 6.067" rod. Most people that concern themselves with sideloading look at the ratio of rod length to stroke. After dividing rod length by stoke, the higher the number, the less angularity the rod makes and therefore less sideloading.

A stock 427ci LS7 has a rod/stroke ratio of 1.51:1.
A 383ci LS1 would have a ratio of 1.53:1.

A 383ci LS1 should have less side loading than a stock LS7, so as far as sideloading is concerned, if an LS7 doesn't have issues, neither will a 383.

Brief Encounter

iTrader: (6)

If you are truly worried about side loading, then why not go forged piston with a longer rod?
Last time I checked there wasn't a law stating that you HAD to run a 6.125 rod. If I were to be building an ECONOMICAL street/track engine, I would opt for a 383 with the longest rod I could cram in there. Sure, you are more than likely going to have to move the pin boss into the oil control ring groove, but since you aren't going to boost or spray it, you should be just fine.

IMHO, unless your diving abilities are that of Michael Schumacher's, You are gunna wont some torque and what better way to do that then with a 383.

Darkman

iTrader: (2)

The reduction in displacement notion focuses on destroking and ignores the increase in bore size. My original post envisioned both albeit an expensive option. It is axiomatic that if you start with another engine with a larger bore, the decision whether and how much to destroke changes.

With rsepect to RPM the answer is yes - in road racing, which is much different than drag racing, RPM is king and low end torque is considered meaningless. In a road racing sedan, an LSX engine would rarely (if ever) see rpms below 4,500 rpm outside of the pits.

KCS

iTrader: (20)

That is because it is the destroking part that reduces the displacement. Like I already said, considering that the increase in bore size alone will bump displacement up, destroking gives up that displacement you would have already gained from just the increase in bore alone. You're suggesting taking out stroke to reduce the displacement closer to what we began with.

Read my comments as to preparing a daily driver for track use. Doing double duty as a DD and track car, it will spend 90% of it's life under 4500RPM. Again, is it worth it to optimize an engine for an RPM range which it will only see for maybe 10% of it's life, while disregarding the RPM range in which it will spend 90% if it's life?

AnnivSS

I still fail to see why a solid built 346 with a good set of heads and a custom grind cam isnt the best idea. The custom grind will get your powerband where you need it and get you the power youre looking for. Which honestly I think 550hp for a road racing porsche is being a little greedy. I dont think alot of people understand what a car is really capable of at what hp levels.

Darkman

iTrader: (2)

All else being equal a shorter stroke motor is more reliable for high rpm operation than a longer stroke motor. I will stop now- as I believe we have cluttered up this thread enough and are not helping the OP with his inquiry. This is after all a forum primarily of drag racers and road racing is a different world.

KCS

iTrader: (20)

That's not even the point. The point is that the engine doesn't need to be a high RPM engine because it is not limited by rules or air restrictors, not to mention it will also have to serve as a daily driver. Since you're familiar with the "road racing world", I'm sure you can imagne the misery of having to drive an engine optimized to run at high RPM, like a NASCAR or Indy V8, to work everyday.

Since we're stopping here, I'll leave with a quote..

"The 7.0-liter engine combination allows us to run relatively low rpm to maximize fuel economy and reliability while producing extremely high torque numbers that make the cars very ‘driver-friendly' on a road course," explained GM Racing engineer John Rice.

Gordon0652

iTrader: (4)

You should go billet! With Callies new crankshaft and some Ti rods! Make it like a 2.00-2.50" stroke and spinn 12,000rpm all day! Have a nice size bore like a 4.00".

https://ls1tech.com/forums/new-produ...l#post14005147

eray

LS3 bore it to what you need and leave the stroke alone. cheaper than a LS7

FastKat

iTrader: (10)

Probably the most fundamental reason go with a forged rotating assembly is engine speed. Sure, forged pistons will take a lot of abuse from power adders (forced induction, nitrous) but the rods and crank... not a lot of threat from power adders there (say, up to 500hp) as long as engine speed remains close to stock.

Loads on the pistons, rods, and cranks are (by far) highest at top dead center (TDC) and bottom dead center (BDC) - not during the downward power/thrust stroke of the engine... which is where power adders make their presence felt.

There's a lot of good discussion in this thread! What it really comes down to is defining the purpose of the engine in the car and the qualities you want the engine to have. After you clearly spell out what you want the engine to do for the car, approach the design and build with an open mind and find the best way to achieve your goals... probably balancing optimal design and budget.

cam

iTrader: (9)

With <500 whp LS1 builds the last thing you have to worry about is the bottom end so long as you upgrade the rod bolts. Soon as you crest 7000 RPM valve control will become your challenge. After 8000 RPM you are really entering into lunacy territory with valve control on ANY push rod engine. At 8500 RPM you may even be as low as 500 miles per set of valve springs let alone the oiling system you would have to build to handle those RPM's without failure.

Long and short of it is? If you want an LS engine to hang together and be reliable AND make great power?; Just keep the limiter to the 7000 RPM range and you'll be happy for thousands of miles without worry or without overly exotic parts required.

But hey if you want to spend 20+k on an 8500 RPM de-stroked screamer thats reliable? Go ahead it aint my dough

bp944

iTrader: (4)

Thanks for all the replies.

I actually have a set of 383 stroker pistons and rods. The rod is a 6.200 rod so that should be fine to avoid too much side load and its all forged. I bought them awhile back without thinking it through and at the time it was a bad decision. But now I'm thinking that will give me the best of both worlds. Long rod to prevent side load and stroked to give me the extra cubes. I just have to get the block notched for the extra length

Darkman, This banter is actually quite useful since it gives me more than one perspective so I know I'm not getting a bias opinion. So keep on going please.

Annivs, I am being very greedy especially for a 2700 lb car. I just know if I overshoot, I'll hit somewhere below.

I think in general aiming for a lower rpm is probably by best bet since this will be my first/only vehicle for the next 4-5 years. If I go with a ls6 intake, custom grind cam, a set of good heads, with a light valvetrain.....I think I should be sitting alright

Does a stroker engine actually dip deeper into an oil pan? The oil pan I'm using for the conversion has to be very shallow to fit but I'm not sure if it'll be deep enough if the stroker needs more clearance?

What are the best priced heads as in dollar for flow? I don't want to spend an extra grand to get 5 more horses of flow but I don't want to go cheap either.

Any recommendations on springs?

KCS

iTrader: (20)

The dfference is less than .200" and with the deep skirt design of an LSx block, the crank doesn't protrude into the oil pan very much.

soundengineer

iTrader: (16)

anything that is going to be higher rpm's for extended durations should be a double spring...
you need to find a spring that suits the needs of the cam and the engine...
Manley, Comp, PAC, just to name a few

as far as heads go.. Patriot makes some great budget heads... but then again you can get a better for more money.. it just depends on your budget...
$2500 gets you some dam nice heads that will outdo most of the field.. $4000 gets you serious heads that will be on top of everybody...
how thick is your wallet?

FastKat

iTrader: (10)

I fully understand the concept of side loading... but I don't think building a stroker motor will alleviate side loading. Sure you're using a longer rod, but I think that just compensates for the longer stroke... unless the wrist pins are recessed a lot farther into the piston? I know aftermarket wrist pins are often offset, but I don't think that fully solves the problem.

Also, since you're not using a power adder, you have a great opportunity to pick your piston material. Typically the 4032 alloy is used for power adders because its characteristics are better for that application. However, i think the 2618 alloy is easier on your piston bores. I could have them mixed up, but it's definitely worth looking into if you're that concerned about side loading and scuffing the cylinder bores and piston skirts. So is coating your pistons. I wish I would have knew about the two different types of alloys before I build my engine...

ShevrolayZ28

iTrader: (4)

I'm not expert but I think you'd end up spending quite a bit on valve train parts that could survive spinning that fast. Titanium valves, fancy assed valve springs, linkbar lifters, etc. An LS motor will make that thing fly, no need to rev it like that, If you want something fast and NA - displacement is the answer!

KCS

iTrader: (20)

You can look at the rod/stroke ratio to get an idea of sideloading. I'm not saying sideloading is even going to be a big deal or that you need to be super **** about what the rod/stroke ratio will be, but with a 6.125" rod the rod/stroke ratio is better than a stock LS7 and the same as just about every 402/408 stroker out there. A 6.200" is even better.

Also, 2618 is the stronger alloy used for big power engines. The 4032 is more brittle, but expands less and is typically lighter.

ls1 1990 VN

If you're going to spin that high, forge the bottom end, Heads & cam will make the power, bottom end will hold it together, otherwise your going to be sorry.