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Please give me your advice!
A very good friend of mine is offering me a new (less than 20 miles) LS7 engine. It's the engine that comes with the new 2007 Z06 vette. I think it's rated at 500 HP. Everything is included....just pop the old one out an drop in the new one with all the lines/hoses/cables/wires included. He'll even transfer my performance chip over to the new engine. The asking price is $14,000...he'll have one of his guys install it for me at a significantly reduced price. I wonder if I should go for it....what do you guys say?
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RE: Please give me your advice!
If you have 14k to spend... why the hell not?
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RE: Please give me your advice!
Believe me if I had the cash I would have already done it. If you have the extra funds available to do it I definitely say go for it. Not only is it one hell of an engine, but how many C5's can say they have a LS7 in them. Talk about a conversation piece.
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RE: Please give me your advice!
But what about the price guys? Does it sound like a good deal? Is it a good idea to change engines like that? Besides, I just spent some serious $$ on a new paint job......I don't know guys........
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RE: Please give me your advice!
$14,000, heck is that all.
go for it. Of course on the other hand, why not just invest in 1 bad ass supercharger for yours. |
RE: Please give me your advice!
Well I just did a little research for ya and you can buy that engine brand new from GM Parts Direct for $12,494.99 which includes the following items:
intake manifold with injectors fuel rails throttle body dry sump oil pan exhaust manifolds flywheel & clutch harmonic dampener water pump and pulley coil packs spark plugs and wires engine sensors LS7 crate engine does not include: injector wiring harness dry sump oil lines dry sump tank engine beauty cover engine processor air filter/air box accessories or accessory drive So if the one your buddy has includes everything then it sounds like a good deal, because I think it might cost you a little more that $1500 to buy the rest of the things needed when buying the engine new. |
RE: Please give me your advice!
What about your clutch, presure plate, transmisson, and rear end. Isn't the Z06 (C5 and C6) beefed up in those areas?
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RE: Please give me your advice!
Yeah I didn't even think about that, I sure you would have to upgrade that transmission. I'm starting to think you might be better off just using that $14K to mod you existing LS1 or replace it with a 402 stroker and a supercharger or turbocharger. You gotta realize $14K spent the right way can have you producing more power that a stock C6 Z06.
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RE: Please give me your advice!
Ooooh, Pece,
After reading the last few posts by Pay2Play, it sounds like there are a whole lot of things that could go wrong. Besides, $14K is a bunch of money and I think buying the "bad-a$$ supercharger" as someone suggested makes more sense. Just IMO :) Take care, stay safe. Rita |
RE: Please give me your advice!
If the price includes labor and some sort of warranty that the work is done right (and the engine has a warranty, even if only 90 days) it sounds like a good deal for the engine ( but for you? -- see below: but be prepared to spend more and I would only do it if you view this engine as a starting point to go up over 550 RWHP.
First, make certain the shop doing the work knows what it is doing: I would only do this if you can talk to two or three satsified owners that have had this same conversion done. The C6 engines (LS2 and LS7), use a different engine computer with a higher clock speed than the C5, etc., and it is not just a "drop it in and we simply reprogram the ECM" job: it's a "drop it in and make lots of mods and do a lot of re-programming" job. I would also investigate several problems, all solveable with money (more to the point, your money): 1) will there will be an exhaust manifold fitting problem? The LS7 has different heads than any other vette engine and I do not know if the stock exhaust manifolds from it will fit to a C5 exhaust (stock or aftermarket) without lots of modification (which could be expensive, frustrating, or both), or better, if headers meant for a C5 will fit the LS7. I doubt headers made for the LS7 in a C6 will fit well in a C5, period (you can always hope). You will need to switch out to a big cat back to realize the engine's potential. That's another grand there. The LS7 has a dry sump. You will have to modify the C5 underhood to fit the tank and pipes and extra oil pump (it has two, the normal one and another). From having looked at converting mine to a dry sump, it looks like the best bet here is to move the battery to the trunk to gain underhood room and then put the tank, etc., there, but it will be a tight fit and cost some money. Against all this, you have to consider what you will have at the end, 450 RWHP. With that same $14,000 you could easily buy more RWHP (I'd guess to nearly 550-575 RWHP if spent well) through any of several routes. The only reall advantage the LS7 would have is: a) if, like me, you just have to have a full 7 liters (427 cubes), or if, after you got all this done, you plan to spend another $15,000, so you can have around 600+ RWHP, without the cubes and the LS7 heads its starts getting difficult (i.e., really expensive) to get more than that out of anything but a 427 cubic inch C5R or LS7 engine: that is why Lingenfelter and MTI and Mallet never go over about 550 RWHP without going to one of those two big displacement engines. |
RE: Please give me your advice!
IMO, Lee is right on!!! Take that 14g's and push some serious hp out of what you've got.;) Or......buy a new '07.:eek:
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RE: Please give me your advice!
Thanks Lee.....that's what I needed from all of you....some good common sense advice.....and I got it!!! :)
After careful consideration....I think I will stay put with what I have right now....maybe in the future I'll consider making additional power modifications.......but for now......I better give my bank account a rest! .......for now :D Thank you all for your input....it is much appreciated! |
RE: Please give me your advice!
[sm=icon_rock.gif]
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RE: Please give me your advice!
A 346 ci engine is more than enough displacement to get 700+ rwhp reliably. This is with turbocharging not naturally aspirated of course. I say turbocharging and not forced induction in general because for the same boost level a turbocharged engine will make more horsepower than a supercharged engine. The problem is, however, the LS1 wasn't specifically designed for running a serious turbo (or supercharger) setup. To do it "right" you need to lower the static compression ratio to about 8:1, use forged internals, ceramic coat the exhaust ports, and use sodium-filled exhaust valves. Obviously it is easier to get hp out of a 427, but 5.7 liters is not small by any stretch of the imagination. If you don't want to use a turbocharger or supercharger to get high horsepower then a larger displacement engine is the definitely way to go.
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RE: Please give me your advice!
I was talking with a bud of mine and he suggested twin turbos on my 454. 9.5:1 comp, and forged internals,
rated at 400 hp now. Opinions anyone? |
RE: Please give me your advice!
ORIGINAL: C3 Starship I was talking with a bud of mine and he suggested twin turbos on my 454. 9.5:1 comp, and forged internals, rated at 400 hp now. Opinions anyone? |
RE: Please give me your advice!
I'm letting my ignorance hang out here, I don't really understand the relationship between the boost and the compression. I just figured that the turbos mean you can pack more into the cylinder. I'd like to get straightened out on this, so let 'er rip.
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RE: Please give me your advice!
this is long but worth saying.
A 346 cubic inch engine is capable of producing 700+ HP - correct. But a stock LS1 (346 cubes) or LS2 (366) engine cannot - not for long anyway. I have not seen a durable turbo, SCr, or NOS application on a stock LS1 or LS2 block at over 550 RWHP. By durable I mean one that will last at least two years when the HP is used occasionally, say about as often as you would if you ran five runs at the drags once a month and exercised it on the street for a second or two once in a while. And I have seen "heavily used" turbo and SCR stock blocks bite the dust with a bit less than 500 RWHP - at least four, with a variety of problems, a bent crank and rods (not sure which happened first), a cracked piston, and cracked blocks. A strong aftermarket short block is not that costly: the one in our Camaro cost about $3700, is 408 cubic inches, and just bulletproof as an LS series engine will come. You can order it your way, including the compression ratio lower for your planned boost (8.5 or 9:1 wqorks well) or a compromise (my vette is only 10:1, so it can take about 9 lbs), or astronomical if you are not planning boost (the Camaro is 11.62:1, a good NOS ratio), and with the pushrod clearance cut out for extreme rocker angles, etc. Before getting into my own rules of thumb, it is worth remembering that it is the torque that destroys the engine (twists it apart) and not strictly speaking HP. Suppose we set an upper limit of 525 RWT for a LS1 (I would never go higher): 525 ft lbs at 5000 RMP is 500 HP, but at 6500 it is 650. Basically, by choosing the right cam, you can move the torque peak around the RPM range. So you can actually gain a good deal of HP while still staying durable (sort of durable, anyway) but making it a high-reving engine: pick a cam that pushes the torque peak up to the red line. Just realize that pushing the torque peak up to 6500 means the engine idles and drives around town like a sick pig. that said, my own rules of thumb are: - stock botom end is good for about 475 RWT (if abused) and about 525 (if not) - the stock aluminum block and heads are a good basis up to about 650 RWT - use an iron block above that or go to a C5R or LS7 block if you have the money and need the light weight. - at somewhere south of 1000 RW the stock heads are too weak even if re-worked - need AFR or other heavy deck heads, and O-ring gaskets (getting expensive now) - at around 1300 RWHP the LS engine just is out of its range, it does not have enough head bolts and strength. Its time to go aftermarket everything. A really good turbo or SCr application should have the compression ratio lowered: my C5R is a compromise with 10:1, but ideally 9:1 or 8.5:1 for heavy boost applications. The problem with lower compression is that you don't get much power without the boost, and as a result, driveability (a sharpness in resonse) and economy suffer. That's not important in a racing engine but I picked 10:1 as the lowest I would go, even though I knew it limits me to about 8-9 lbs of efdfective boost, because the engine has plenty of power and driveability around time without ever getting into the boost. A rough rule of thumb is about 25 RWHP per lb of boost which means 7 lbs on a stock LS6 (350 RWHP stock plus 175) is about at the limit. All in all, you can buy complete engines from various aftermarket companies with everything built to last and work well together, including tubos, etc. That';s really the way to go unless, like me, you just love to engineer it yourself more than even drive the beast. |
RE: Please give me your advice!
I don't really understand the relationship between the boost and the compression. I just figured that the turbos mean you can pack more into the cylinder. I'd like to get straightened out on this, so let 'er rip. Also, if you let the turbo do more of the compressing (and then run it through an intercooler), the final amount of heat generated after it is compressed will be less than if the piston was allowed to do more of the compressing. So actually, you can have an even a higher final pressure with the lower compression/high boost setup vs. the higher compression lower boost setup. |
RE: Please give me your advice!
No doubt people can figure I I love this stuff: I used to design these things for a living.
I view it a bit differently than the cylinder only handling so much pressure. The basic LS engines can take only so much cylinder pressure, but a rebuilt one can take much more, yet there are still limits to a combination of high compression and high boost. When you get down to it, an amount of power, say 650 HP at 5000 RPM, will take the same amount of cylinder pressure upon combustion regardless of how the power is made: turbo on non-turbo, high or low compression, etc. Once rebuilt, the LS engine can take boost up to about 28 lbs at 8:1, or 1300 HP. The real issue with high compression and high boost has to do with the speed of combustion inside the cylinder and the pre-disposition of the fuel-air mixture in the cylinder to pre-ignite (i.e., explode when it wants to, not when you want it to). When things work like they should, a lot of air-fuel mixture makes its way into the cylinder and then explodes when the spark tells it to. The explosion may look and feel instantaneous to the naked eye, but it actually takes a split second, about 1/3000 of a second, to move outward in a wave of flame from the spark plug down through the cylinder. As it do4es it produces a steady pressure, for the entire power cycle, on the top of the piston: torque. And the more air and fuel you can cram into the cylinder, the bigger the bang and the more pressure and the more torque and the more HP. But air-fuel can misbehave. If you boost too much air into a cylinder (high boost) and then "squish" it too fast (high compression), it does not explode outward from the spark plug in 1/3000oth second, but instead all of it explodes simultaneously througout the cylinder in 1/50000th second. This is detonation, or pinging, or knock. It produces next to no power (there is no wave of steaqdy pressure and torque) and will, sometimes, blow a motor apart (the sharp bang caves in the top of the piston). You can avoid this only through any of four methods (unless you can re-design the basic engine, then you have other choices, too). First, you can adjust the timing, firing the mixture before it explodes itself, but to do this effectively you have to advance the timing so early (before the mixture detonates, as to where you get little power: this is self defeating, and sometimes does not work at all. Second, you can use higher octane fuel, which won't detonate until a higher temperature-pressure level. This is why people use race gas in really hi-po cars: its higher octane permits more compression ratio or more boost or both, hence more power (the gas itself produces no more power unless you do one or both). Or, you can push less air into the cylinder (lower boost) and still have your high compression. Or, you can lower the compression ratio and go ahead and cram more air with with the SCr high boost. If you do this last approachr, you get about half what you give up: lowering compression ratio cuts power but it permits more boost -- enough to more than make up for what you lost. So, an engine with say, 6:1 compression ratio can take gobs of boost (50 lbs) whereas one with 11:1 can take only five. It is always a compromise. High compression means high efficincy: good economy. But it limits the boost you can get. My compromise was the following. I built my C5R with 10:1 compression ratio, giving up a bit of around town fuel economy (about 2 mpg) but with a target of one thing: at 10:1, my engine can take enough extra boost that no stock, LS7 C6, with its 11.5:1 ratio, would be able to SC enough boost and beat it in RWHP or the 1/4 mile: the LS7 stock compresison ratio does not permit enough boost. An LS7 will have to be rebuilt - rather a costly effort, to match or beat me. A rather childish goal, perhaps, but that's why I did it. |
RE: Please give me your advice!
ORIGINAL: Lee Willis No doubt people can figure I I love this stuff: I used to design these things for a living. I view it a bit differently than the cylinder only handling so much pressure. The basic LS engines can take only so much cylinder pressure, but a rebuilt one can take much more, yet there are still limits to a combination of high compression and high boost. When you get down to it, an amount of power, say 650 HP at 5000 RPM, will take the same amount of cylinder pressure upon combustion regardless of how the power is made: turbo on non-turbo, high or low compression, etc. Once rebuilt, the LS engine can take boost up to about 28 lbs at 8:1, or 1300 HP. The real issue with high compression and high boost has to do with the speed of combustion inside the cylinder and the pre-disposition of the fuel-air mixture in the cylinder to pre-ignite (i.e., explode when it wants to, not when you want it to). When things work like they should, a lot of air-fuel mixture makes its way into the cylinder and then explodes when the spark tells it to. The explosion may look and feel instantaneous to the naked eye, but it actually takes a split second, about 1/3000 of a second, to move outward in a wave of flame from the spark plug down through the cylinder. As it do4es it produces a steady pressure, for the entire power cycle, on the top of the piston: torque. And the more air and fuel you can cram into the cylinder, the bigger the bang and the more pressure and the more torque and the more HP. But air-fuel can misbehave. If you boost too much air into a cylinder (high boost) and then "squish" it too fast (high compression), it does not explode outward from the spark plug in 1/3000oth second, but instead all of it explodes simultaneously througout the cylinder in 1/50000th second. This is detonation, or pinging, or knock. It produces next to no power (there is no wave of steaqdy pressure and torque) and will, sometimes, blow a motor apart (the sharp bang caves in the top of the piston). You can avoid this only through any of four methods (unless you can re-design the basic engine, then you have other choices, too). First, you can adjust the timing, firing the mixture before it explodes itself, but to do this effectively you have to advance the timing so early (before the mixture detonates, as to where you get little power: this is self defeating, and sometimes does not work at all. Second, you can use higher octane fuel, which won't detonate until a higher temperature-pressure level. This is why people use race gas in really hi-po cars: its higher octane permits more compression ratio or more boost or both, hence more power (the gas itself produces no more power unless you do one or both). Or, you can push less air into the cylinder (lower boost) and still have your high compression. Or, you can lower the compression ratio and go ahead and cram more air with with the SCr high boost. If you do this last approachr, you get about half what you give up: lowering compression ratio cuts power but it permits more boost -- enough to more than make up for what you lost. So, an engine with say, 6:1 compression ratio can take gobs of boost (50 lbs) whereas one with 11:1 can take only five. It is always a compromise. High compression means high efficincy: good economy. But it limits the boost you can get. My compromise was the following. I built my C5R with 10:1 compression ratio, giving up a bit of around town fuel economy (about 2 mpg) but with a target of one thing: at 10:1, my engine can take enough extra boost that no stock, LS7 C6, with its 11.5:1 ratio, would be able to SC enough boost and beat it in RWHP or the 1/4 mile: the LS7 stock compresison ratio does not permit enough boost. An LS7 will have to be rebuilt - rather a costly effort, to match or beat me. A rather childish goal, perhaps, but that's why I did it. |
RE: Please give me your advice!
Hey, thanks Lee!!!;)
Those are the lines I was thinkin' along, but wasn't sure. So....... with 8 lbs. of boost, and 9.5:1 comp, I'm lookin' at right around a 200 horse gain. No need for twin turbos, right? I'd just pay twice the money for the same results, and only runnin' 4 lbs. of boost off each turbo, or 8 lbs. to each bank with a split intake manifold. ( I can see where this would be a nightmare to tune) Am I on the right page here? |
RE: Please give me your advice!
Very true, the final compression ratio of the mixture plays a role in the power output, but it goes much further than that. You will always be able to get more power out of a turbocharged low-compression engine compared to a turbocharged high-compression engine. The final compression ratio is not why correctly turbocharged engines can make extremely huge hp increases with only relatively small increase in peak chamber pressure. A simplified explanation: When the mixture combusts in a high-compression NA engine, it makes a quick big push on the crank. When a turbocharged, low-compression engine combusts, the explosion is slower and it pushes longer on the crank. A turbocharged engine can generate 4 times the pressure on the crank after 50 degrees of crankshaft rotation. This longer period of high-compression is what is making the huge power increases.
Think of it this way (again simplified for the sake of discussion), we will say there is a static limit to the amount of pressure a cylinder can hold (be that because the head will lift, or the rings will let the mixture by, etc.). A high-compression engine will only be able to take in say 10 units of air/fuel because it will compress that say 4 times to arrive at the same final pressure that a low compression engine takes in 20 units of air/fuel compressed 2 times. They both have the exact same final pressure now, but one of them has twice the amount of air/fuel in the cylinder. Which is going to make more power here? Obviously the low compression engine with the larger amount of fuel/air. Also heat plays a factor in the combustion process. As you described, pre-detonation occurs when the heat generated by compression reaches the heat needed for combustion (again not this cut and dry, but generally speaking this is the case). Not only do people use high-octane race fuel to combat this, but water injection is also used. Another way to reduce the amount of heat in the intake charge is to use a larger turbo. The smaller turbo's compressor wheel generates a lot more heat to compress the air to say 20psi than does a larger turbo with a larger compressor wheel. This is because there is a limit to efficiency of the turbocharger itself. At a certain point to increase the boost it takes a huge magnitude increase in energy to do so. It's not uncommon to use very large turbochargers and spray to get them spooled. Compressing the air outside the combustion chamber (especially when using an intercooler) also reduces the chance of pre-detonation as the heat caused by compression is dissipated outside the combustion chamber. This also gives you more oxygen per volume unit. So for the same amount of pressure, you not only have more air, you have more oxygen. You must also watch out for running too lean a mixture when using forced induction, while a leaner mixture can help spool the turbo early on, you can easily melt a head gasket, or piston at higher boost. Reactor2. |
RE: Please give me your advice!
So....... with 8 lbs. of boost, and 9.5:1 comp, I'm lookin' at right around a 200 horse gain. No need for twin turbos, right? I'd just pay twice the money for the same results, and only runnin' 4 lbs. of boost off each turbo, or 8 lbs. to each bank with a split intake manifold. ( I can see where this would be a nightmare to tune) Am I on the right page here? |
RE: Please give me your advice!
I'd give you guys a tip, but my cd port won't accept bills.:D
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RE: Please give me your advice!
This thread is a keeper for sure. Buying a C3 with 454/4speed. lots of good stuff here. "build your own beast" great idea. Can't wait to get it. I got the fever now and there ain't no antidote but raw HP.
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RE: Please give me your advice!
The major advantage two small turbos have over one large one is resopnse time -- the two can spool up to boost faster. One is simpler and easier, but will have more lag before coming on boost. If I only wanted a bit of boost I would try a SCr instead (less hassle) but if you have carbs on the engine you need a "Pressure box" approach.
By the way, a point about all I said before: aluminum heads are worth about 1 full point of compression ratio. An aluminum block doesn't have any affect, only what the heads are made of. Aluminum conducts heat so much more effectively that the coimbustion chambers run cooler and the air fuel mixture can be denser. If you are going to use iron heads on that 454, Starship, you need to subtract one full point (9.5 becomes 8.5:1) from the ratios I spoke about above. Your 9.5:1 would be good for somewhere around 5.5-6 lbs max, which would give you, I think about 200 extra HP (you'd get a bit more than 30 HP per lb boost on a displacement that large, I'd hope). |
RE: Please give me your advice!
Got it Lee, Thanks for all the info.
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