Why go forged?
Sorry I wasn't clear. I meant honing out a ls1 to 3.905 not boring. I was referring to the ls1 when I said I won't stroke it.
It does make a lot of sense to aim it for more of a daily driver rather than a track car. I totally agree with that and I wasn't sure how drivable this car would be.
The problem with ls7's is that they aren't cheap and they don't come up very often at all. Unless I'm completely off my rocker.
What could I reasonably achieve with a ls1/ls2 block since they're cheaper? If I were to stick with just a hone? I think a 383 would be pushing it for side loading..yes?
It does make a lot of sense to aim it for more of a daily driver rather than a track car. I totally agree with that and I wasn't sure how drivable this car would be.
The problem with ls7's is that they aren't cheap and they don't come up very often at all. Unless I'm completely off my rocker.
What could I reasonably achieve with a ls1/ls2 block since they're cheaper? If I were to stick with just a hone? I think a 383 would be pushing it for side loading..yes?
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.
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.
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.
You do give up displacement if you go to a larger bore and then destroke it. Just a larger bore alone would be more displacement (say 364ci?), but you're suggesting going the extra effort and destroking it too so that it stays at 346ci. That's giving up displacement.
The point I'm making is why high RPM when you can make the same power at a lower RPM, and more of it everywhere with a larger engine? An over square engine is the ticket for high RPM, but is it really worth it? For gearing?
The point I'm making is why high RPM when you can make the same power at a lower RPM, and more of it everywhere with a larger engine? An over square engine is the ticket for high RPM, but is it really worth it? For gearing?
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.
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.
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?
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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.
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?
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?
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.
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.
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
https://ls1tech.com/forums/new-produ...l#post14005147
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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.
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.
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
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
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?
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?
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.
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?
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?
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
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...
I'm looking at making a road racer/DD out of a Ls engine in a porsche 944. Due to the tranny I can't break 500rwhp. But I'd like it to turn up to 8,500rpm. So is there any point in going forged? As long as I replace the rod bolts I think I should be good? Would the stock pistons handle that kind of rpm and power? What do I have to loose by going this route?
Also, what would it take to get that kind of power....550hp from a ls1? I'm not stroking but I could bore it out to 3.905. What heads, cam, valvetrain, and I think I'll be running a ram air. This is not a drag car so I need this to be able to run daily and on the track.
Also, what would it take to get that kind of power....550hp from a ls1? I'm not stroking but I could bore it out to 3.905. What heads, cam, valvetrain, and I think I'll be running a ram air. This is not a drag car so I need this to be able to run daily and on the track.
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...
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...
Also, 2618 is the stronger alloy used for big power engines. The 4032 is more brittle, but expands less and is typically lighter.
