I also posted this in the FI forum...

I've thought it over again and again, this time I know officially what my plan is. I'm going to build a motor first, that's ready for boost, then with a small savings I'll make in the next few months get the trans rebuilt along with a good clutch, then it's off to the rear end. Eventually maybe by next year I can buy that FI kit. I'm going to be looking for a motor build starting now. Two weeks I'll have the funds.

My goal for the motor build will be forged internals, small blower cam, probably stock 317/LS6 heads. I don't know if I want to buy a 347 ($2800), 370 iron ($3300), or 408 iron ($3500) forged shortblock from a sponsor. I want a safe, reliable, long lasting daily driver, 600+ RWHP, on about 8-12 PSI. Which dished pistons should I get? Mahle, Wiesco, or Diamond? I heard Mahle last longer, and Diamond puts up better numbers? And what compression do I need to be making? I heard most turbos around 8.5:1 or 9:1 and EPP recommend 9.5:1 for the supercharger.I haven't decided if I want a turbo build or a D1 or F1 build, probably which ever of those systems are cheaper & I can rely on most.

The car is a m6. I have all LS1 stuff from two longblocks I have. My budget for the motor is $4000. I know if I went with a 347 I could have a little extra money to buy the other supporting mods (like cam, or heads, clutch, etc). Also I could save a little money if I bought the shortblock from another member. Would taking that chance to save a couple hundred be worth it?

 

Don't mind me...just lurking.

 

subscribing.....I am looking for the same thing

 

I know most are going to say there's no replacement for displacement. But to extend further on this, if I had the same mods (same cam, intake, etc) for a 347 and the same mods for a 408, I should expect slightly bigger numbers from the 408? My best bet for this answer is to probably look at dyno sheets and see if the extra horsepower is worth it or not.

But I'm still wondering about them pistons.

 

I am glad to see your first post includes a thought out list of your goals. I cannot stress enough that the first thing to sit down and think on is what the intended application entails. I want a safe, reliable, long lasting daily driver, 600+ RWHP, on about 8-12 PSI. Definitely doable. As you know, the larger the displacement the easier it will be for you to see those 600hp numbers, but instead of saying "there is no replacement for displacement" think of it instead as "there is no replacement for CFM". Also know ahead of time that a 600 rear wheel horsepower motor is a 690 flywheel horsepower motor in front of a 4L60E, a 720hp 4L80E and about a 650 flywheel horsepower motor in front of a manual. Simple parasitic losses at work there inside the transmission.

I think you're off to a great start. You know what you want, what it takes and how long you'll have to wait to get it. As we all know, iron blocks are by far the best platforms for boost. Simple answer; metal fatigue. An iron block 370 would make for a great start with a twin turbo setup. Figuring out your static compression ratio via dished pistons, heads, head gasket, ect ect is a task left to figure out AFTER you've determined the amount of boost you're after, the size and efficiency of the compressor, the size and efficiency of the intercooler(s) and the type, the cooling capabilities of the engine bay (mostly engine materials, fan CFM and radiator), the fuel octane level around your area and last but not least, your wallet. There are many other variables such as timing, electronic safety controls and spark plugs that go into your ideal compression ratio, but those aren't the major factors. To give you a rough guestimate (I hate that word but it's useful sometimes), you're looking at a minimum of 543 flywheel horsepower and a rough maximum of 760 flywheel horsepower with a twin turbocharged 370 at 12psi. Twin turbos are a basic necessity once displacement reaches over 350cid.

My question to you though is why 600 rear wheel horsepower? If I can better understand the reason behind this, I might be able to make more sense of the build.

 

^ I agree, but also think of how high you wanna rev. If low revs like 6300 and less, then I would go for twins on a 408. If higher revs then single on a 370. APS system comes to mind as they are a phenominal kit for a twin 408.
That will make 600 without a blink on premium gas without meth just ATA cooled.

 

I would have to agree with PREDATOR-Z already to be honest. It's getting late and this slipped my mind. A reliable boosted motor making 600+/- rear wheel horsepower as a daily driver will definitely need forged internals. Since your stock crank will be tossed anyway, a forged 4" crank would be the better choice over a forged 3.622" crank to increase displacement (and thus CFM). However, the real bennefit of increased crankshaft throw will require fewer RPM's (saving on the overall life of the motor and related components) and less boost to make the same power goal, therefore allowing an increase in static compression ratio accordingly to better your throttle response and low RPM torque. Also, higher compression usually means less fuel consumption due to the more efficient burn of gases within the combustion chamber.

All in all a smart move I think.

 

wow. awesome information! I hadn't got into reading all the techs & specs of the FI systems but man sounds like I've got a lot to learn about them. 600rwhp & 408... mainly because I'm looking for one of the fastest & wickedest street machine around here. but I read a GREAT thread about some similar setups...

https://ls1tech.com/forums/forced-induction/763698-stay-d1-go-f1.html

and it's got me thinking about traction. from reading that, sounds like a 347 might be best for me. one of the locals (ChevyChad) is running near 700rwhp on a 347, DD, & a D1SC. he said there's no PURE traction on the street with his setup. so then I question myself why go bigger cubes (& money) for more power when the extra would be near useless on the street? perhaps I could just turn the boost down a little on the 408 and be safer? I'm not planning on making power over 5500, basically cause I'm a mentally cautious driver and don't take it up that high.

 

hmm, very good point.

 

I can sit and spin aggressive 35x13" tires with my pretty much stock 4.3L V6 but that doesn't stop me from putting in a 370.

Traction will be your main enemy. No doubt. Wider rear tires and throttle management will help out a lot from a stoplight. I've had more experience with leaf sprung suspensions so I'm not sure if coil sprung cars such as yours will have any traction assist bars like Cal-Tracs/Slide-a-links. Someone else can chime in about traction.

The real question is why not 500-550 rear wheel horsepower? Is there another car in your neighborhood making more power that you'd like to dust? Is there a local drag strip near you where you'll put 600 rwhp to good use? On a daily driver, I simply see that much power being a lot more hassle than it's worth. That is my opinion, others are surely entitled to their own. 500rwhp is a lot easier to obtain AND maintain. By maintain I mean it wont require a stroker crank, nor a forged crank. Just a good turbo or two along with lightweight forged dished pistons. You'd require less boost, less strain on the motor, less fuel consumption (and we all know gas prices aren't going down any ), ...less of just about everything. The cost of the total build would drop by half I'm willing to bet, with a 500-550hp motor simply because after 600+ major components such as the rotating assembly need critical consideration, along with many other things.

 

I have a FI setup in the works for my C6
Stock block (LS2 364), nitrated stock crank, forged rods, pistons and Hellfire rings. Stage 1 317s (by Bo White), my cam design (215/230 115+1 LSA- XE lobes) and D1SC (10psi on 94 octane and ATA).
Nothing drammatic as boost is concerned. I expect close to 600rwhp

But that thing is gonna be friendly, reliable and Stealthy
(unless you pay attention to the whine, but all vettes sound like that )

That is how I plan on reaching that goal for a street only setup.

 

this is a good thread and a whole lot of information, gotta love tech.

 

makes me think again if I'm only shooting for 500+ RWHP I could do that with the 408 stroker, heads, cam, and Fast 90 and save even more money. The only downside to that is I'd have to go with a bigger cam & more expensive heads and would definitely decrease my fuel mileage & make it rougher as a DD than it would with a baby cam & FI. when building a hot rod fuel mileage should be your last concern. but I think there is a significant difference between those two setups, so is it really worth the extra money for this FI setup if I'm only shooting for 500+?

 

Oh yes it is, just gotta have the $$ but pleasure wise, boost and V8 is sommething else.

 

In your first post you said you're not sure if you'd like to buy a 346, iron 370 or iron 408. Which motor do you currently have to work with and/or why is it not on your project list?

 

I've never ridden in a boosted v8 but I've watched some videos, in the car & outside the car and it's insanely fast! I've had a 410rwhp NA LS1 m6 before and I felt like I wanted to go faster. So I probably should build for FI though since I'd love to have something like that.

The motor I have. Actually I have two. One in the car, 146k miles on it, and has a bad block. The other is a longblock LS1 in good shape that has 100k miles on it. It came with the car as a getting back on the road motor. I've checked and it'd cost near the same to have the shortblock on it rebuilt as to buy a NEW 347 from a sponsor. As of right now I don't have any supporting mods.

 

I'll probably end up building a 347 for boost or a 408 stroker. Both would be at near maximum ability for a DD & street. Most likely end up going 347 since the motor build is cheaper & it keeps the same type of motor in the car. Any opinions?

 

Boosting the 'spare' LS1 is a great idea. It'll keep costs low and save you the hassle of finding other major motor parts such as a block and rotating assembly, ect. Of course an iron block will make for the most reliable platform, but an aluminum LS1 block can still handle a good bit of abuse so with keeping the goals within reason, I'd wager the block itself will last just as long as the iron block does. The obvious advantage the aluminum block has will be weight savings and since it's 75%+/- aluminum, you'll have an easier time with cooling/detonation.

With this decrease in mandatory expenditures, you'll have more funds for a great forced induction system while cutting no corners. I would however limit your amount of boost to below 10psi to save the motor's stock integrity. Under or around 10psi of boost will still yield a 90% motor life. You're still looking at a low flywheel output of 408hp and a high of 604hp (there are those guestimates again based off a simple formula) at an honest 8psi of boost. Those formulas I use are about as accurate as desktop dyno with no relation to parasitic loss or other outside factors within the engine build, so you'll probably fall right in the range you're looking to be at with 500-550rwhp. Intercooled and electronically controlled will still mean you can run off of 93 octane with a compression ratio around 8.8-9.0:1 so as to not lose throttle response and low end. With how gas prices are lately I'd want the most amount of boost while sticking with high grade gas found at the pump.

It's getting really late even by my standards and I've been trying to concentrate on writing this post now for an hour or more but I keep getting side tracked. My question to you is, where would you like to improve power over the rev range? Low? Mid? High? Somewhere in between? Also a specific RPM range would be nice to go off of.

 

Inchup, your info has been awesome and I'd like to thank you for your time.

I can't find 93 octane around here anymore. I think the state has something to do with that. about emissions or something. so at best I can only run 91. I came to a conclusion that I'm going to use the factory GM crankshaft. but I'm still not sure about the 100k motor. I'd just really hate to detonate it and have to do everything over again. By leaving the pistons stock, which I can easily see detonation with them, would it even be possible to get around 9.0:1 with the 72cc heads & a thicker head gasket? Haven't decided where I want to pick up more power with the RPM band. If it was low I'd probably spin the tires all day out here. So I'd assume mid range.

 

I guess this is where the aluminum blocks show their downfall, machine work. With the iron sleeves you're very limited to how much clean up you can do of the cylinder walls to prepare for new pistons. I think GM said they recommend less than .010" bore/hone to avoid machining the iron sleeves too thin. This is where a tear down of the 'spare' motor will help to determine your direction. If, upon inspection, the LS1 blocks are not deemed suitable for a machine shop quality rebuild, you'll have a choice to make; put the LS1 back together and just run it, re-sleeve it, or start looking for other blocks. Chevy Silverado's and the like are all over junk yards and finding a 5.3L can be very easy, but I did a quick search around your 74075 area and found outrageous prices. The average complete motor for a 99+ 5.3L V8 was around $1000, lowest $650+/-. Around here the motors are so cheap I can get them for under $200 all day long, everything included. So perhaps sticking with the LS1 is a cheaper move, just hope the cylinder walls aren't gouged out from 100k miles of use.

Seldom will a cylinder block need special attention JUST because a turbo enters the scene. A good stock block will serve most applications well. If the LS1 block is good to re-use, take the bare block and rotating assembly to a machine shop where will a simple over bore and hone to .010" will remove 100k miles from the block. If one characteristic of a block could lend a hand to the turbo application, it would be the rigidity of the deck surface. Decking the block and heads will ensure a tight head gasket seal, which is very important to avoid detonation. At 8psi, the pistons don't have to be expensive. You'd be amazed at how many novice builders will will rush to the forged piston store every time a turbo engine needs building. Any T6 hypereutectic piston would be my choice over forged simply because the silicon alloy allows for a lower thermal expansion and reduced heat transfer, plus they're often much cheaper than forged. The type of dish in the piston to look for will better be discussed with your machine shop, after they've determined how much block and head material to remove during the decking process.

So you don't reduce this motor down to a low compression lawn-mower engine, try putting a cap on the boost to 8psi. This isn't all bad though because it will still make for a happy daily driver while keeping costs low. A mid-to-upper range turbo is a good choice for a sports car. I can assist in selecting a turbo with you, but first tear down the long block to see if you have a motor worth building. In the mean time look through other boosted F-body builds to see what other enthusiasts are using for turbo's and their opinions.