Hello to all! This is my first post and I am looking to get some expert opinions!

Like the title says, I have a LS7 block and nothing else. My goal is to build this engine to make around 500hp.

This engine is going into a non-GM car. I will be using a pre-built swap kit that is based on using GEN4 components.

Here is what comes with the kit and will be used on this build:

1) Reflashed GM E38 ECM

2) GEN4 58X LS wiring harness

3) LS3 MAF sensor

4) Modified wet sump oil pan

5) 1 7/8" Primary, 3" Collector headers

Ideally, I would like to use all brand new factory GM LS7 parts and build a factory LS7 copy but I am sure that will be very expensive so...

Here is what I am willing to do:

1.) This build can be a combination of any LSx parts (new, used, factory or aftermarket) as long as they work together properly and with the components listed above. I prefer to use factory GM parts new or used.

2.) This engine doesn't have to be built dirt cheap but I would like to save money wherever I can. New parts are always preferred but good used parts are OK with me as long as they don't affect performance or reliability.

3.) This engine will be going into a daily driven street car so it must be built with a combination of components that will provide a smooth power curve and/or good power characteristics that will result in excellent drivability on the street. I guess you could say "all around power" is what I am looking for. This engine is NOT for a racecar! I will probably take the car to the strip ONLY to see what it can do in the 1/4 but the lowest ET possible is NOT what I am looking for.

4.) 500 hp is not a requirement. Just a number to aim for. Anything more than that is just a bonus. I would like to have a minimum of 450hp though. FYI, the fuel system being used is good for up to 550whp so that is the limit.

I will need every part necessary to build a complete LS engine minus the parts that come with the swap kit. The accessories I won't need are the alternator, power steering pump, and AC compressor.

I am new to the LSx engine world. Trying to figure out all this stuff out on my own is overwhelming. I really have no idea where to start when it comes to building a LSx engine from the ground up especially when it comes to using a combination of things. I really don't want to spend hours and hours reading about LSx components that are not even relevant to my build.

I have a pretty good feeling many of you LSx experts reading this will know exactly what direction I should go and what combination I should use. What I am asking for from anyone willing to help me out is to just get me headed in the right direction. If you can provide some insight for a good starting point to begin some research that would be awesome. If there is any other info you need from me, feel free to ask.

BTW, for anyone that is wondering why I have just an LS7 block, I got it for free from a friend. It broke a piston badly and blew a massive hole through the sleeve and cylinder wall of the block that is beyond repair. The only option to make this block usable again is to install Darton MID sleeves. Luckily for me I have another friend that is capable of doing that and he owes me some favors so all I have to pay for is the sleeves. I know, I know, this block will be way overkill for my build after the sleeves are installed but it will be a cheap starting point for me and I WILL really like saying my engine started life as an LS7 but I am open to the option of selling that block after it is finished and re-investing in a different LSx starting point. That might actually be the best option for me financially and I would like some opinions about that too.

 

the best approach IMHO WITH YOUR GOALS specially when starting from a scratch is to go to a very simple setup which if i were in your position i will be looking for :

first choose a 427 rotating with 11.0 to 11.5 c/r end result
Gm LS3 cnc heads 1350$ for assembled pair without rockers (will change the springs to accommodate higher lift )
GM LS3 ROCKER ARMS W/ BTR TRUNNION KIT 330$
Drop in's Johnson or Morel lifters
have the Chevrolet LS3 intake package 792$ includes:
intake+throttle+rails+injectors (its really a bargain and headache free)
buy all engine covers and miscellaneous (head gaskets front rear valley covers.. etc)
melling oil pump
choose between any respectable cam vendors to have a cam package ( my choice will be btr ls3 stg 3 )

for that 4.125 bore and 4.000 stroke and 11.0 to 11.5 c/r the ls3 btr stg 3 will be a STREET friendly cam and enough to bring more than your 500WHP target with auto trans and you wont exceed 550WHP with manual. (93 octane)


Just quick thoughts to help you out


GOOD LUCK WITH YOUR BUILD

 

Dont even need all that. stock 3.62 crank, stock gen4 rod, 4.125 drop-in piston. 390 inches, add cnc'd factory ls3 heads and a decent cam and it'll make 550wheel all day long for cheap and spin to the moon.

 

I like Diet Coke's plan.

 

I would drop the BTR trunnion kit (needle bearing) for the Straub bronze bushing trunnion kit, which has proven far more dependable.

 

Lol I like it as well.... :p

And a fast mid runner intake and cam it for 7500 rpm

 

I know a person on another forum that I'm on who is selling a crank and rod set that would be a good starting point if you want to use factory components. That said. it may not be a big cost savings from going aftermarket. Just something for you to consider, he's had them for sale for a while:

http://www.lateral-g.net/forums/showthread.php4?t=53970

 

The front, rear and valley covers from GM come with new bolts, gaskets, crankshaft seals and a new cam sensor on the front cover. Since you're starting with just a block, it's less stuff to run down and the price, considering all you get, is not bad. Check out p/n 19299099 gen4 block completion kit and p/n 12639250 rear cover. I also got ICT oil pan bolt kit p/n 551680 (13 bucks).

 

Thanks guys! That is exactly the info I am looking for!!

I do have a few questions about Diet Coke's plan.

Why not use a 4.00 crank instead of a 3.62 crank? Seems like easy power to me. Are they cheap or something?

Can the CNC LS3 heads support 427ci if I use a 4.00 crank?

Any issues with a 4.125 bore and a 3.62 stroke combination? How will that affect the power characteristics of this engine?

Do LS7 pistons and Gen4 rods "play nice" with the LS3 heads? What about the chamber size, valve clearances, compression ratio, etc?

What head gasket should I use?

What Gen4 rods should I be looking for? Are they all the same except LS7 titanium?

What are some of the best online sites for factory GM and aftermarket LSx components?

Thanks again guys for all the help and insight. I have learned a lot so far with the little bit of research I have done about these recommendations. I still have a long way to go though...

 

You have a good point....

I will do the switch to Straub bronze bushing



Thanks

 

[QUOTE=LS7_block_build;19587948]Thanks guys! That is exactly the info I am looking for!!

I do have a few questions about Diet Coke's plan.

Why not use a 4.00 crank instead of a 3.62 crank? Seems like easy power to me. Are they cheap or something?

4.000 crank will give you better low end torque and better daily driven car characteristic+the engine will bring the peak hp earlier in the power band 6400-6600 rpm which is the range to all stock gm ls intakes. here comes the need for aftermarket intake if you want to peak higher than that.

+ the LS7 block is the ideal block for 4.000 stroke because the length of the sleeve being longer (5.900") than ls2-3 (5.400'') etc... so no pistons rocking or oil consumption issues.

The idea to have a stroker kit is to minimize the process and have a balanced will matched parts and save time sourcing parts from here and there just to save few bucks.
Can the CNC LS3 heads support 427ci if I use a 4.00 crank?

Yes they will work just fine either 4.000 or 3.6 stroke that wont matter

Any issues with a 4.125 bore and a 3.62 stroke combination? How will that affect the power characteristics of this engine?
I think i answered that earlier

[QUOTE=3.) This engine will be going into a daily driven street car so it must be built with a combination of components that will provide a smooth power curve and/or good power characteristics that will result in excellent drivability on the street..]

Do LS7 pistons and Gen4 rods "play nice" with the LS3 heads? What about the chamber size, valve clearances, compression ratio, etc?

What head gasket should I use?
Stock LS7 head gasket

What Gen4 rods should I be looking for? Are they all the same except LS7 titanium?

The LS7 Titanium connecting rod length is 6.064''

gen4 connecting rod length is 6.098

What are some of the best online sites for factory GM and aftermarket LSx components?

a lot of vendors on this website will help you


GOOD LUCK AND WILL BE WAITING TO SEE YOUR CHOICES AND RESULTS

 

Mahle makes Pistons for an ls3 crank in an ls7 block

 

Getting a high milage ly6 for cheap would give you all major parts needed plus extras. Crank, rods, heads and some of the little things.

 

A factory 3.62 crank will cost you all of $75 used. Maybe $150 after a polish on the journals. All gen4 steel rods are (close enough to) the same.

 

If you're new to the LS world, trying to cobble together a destroked LS7 might turn into a bit of a headache. A 4.125"+ bore piston designed for a 3.622" stroke, a stock 6.098" rod with a .943" pin, and LS3 valve reliefs is unique. It might even have to be custom made.

I would suggest keeping it simple and use a normal 427-440ci rotating assembly. It's more expensive, but it will alleviate a lot of potential headaches and you get a MUCH better overall power band. The increased displacement will help make your 500whp target without making the engine much more radical than stock.

 

Thanks again everyone! After doing some research I have given this build some thought...

I don't think I am going to use the LS7 block for my build. It's mostly a cost issue for me. I've been pricing new parts and if I build this engine with all brand new parts it will end up costing me way more than I want to spend. Used parts are not really an option because even though I haven't looked yet I'm pretty sure that trying to piece together a used 4.125 bore-4.00 stroke-Gen4 connecting rod rotating assembly will be difficult and not worth the effort. Even if I could do that I would not be comfortable putting any of those parts in a like new LS7 block with brand new Darton MID sleeves installed. That just doesn't seem like a smart thing to do...

And lastly, from what I've read, I know I don't need to start with a LS7 block to make 500hp. I could put a set of LS3 heads on a stock Gen4 6.0L or 6.2L shortblock with an upgraded cam, springs, etc and be around 500hp AND save a ton of money. If I could find a complete aluminum Gen4 6.0L or 6.2L engine without the accessories or electronics that would be ideal because that stuff comes with my swap kit. Also, I wouldn't have to buy all the other little stuff to build a complete engine and that would be a BIG time and money saver.

Even though I would be installing brand new LS3 heads on a used stock engine with a new cam, it still has to be WAY cheaper than building a brand new LS7/LS3 combo right?

I haven't tried to source a used Gen4 engine yet so any info or guidance about pricing and what to look for would be appreciated.

What got me thinking about all this was an ad that I found on my local craigslist. It was for a stock LS3 shortblock with 60k on it for $1700 OBO. It is disassembled. The cylinder walls are perfect, the pistons look great with no scuffs, and the bearings are cherry. The ad said MUST GO so I could probably get it for much cheaper.

Is this a good deal? Should I jump on it? Is this a rare find?

Doing this would save me THOUSANDS!!! Finding all the other little stuff to complete this engine is not a big deal and I feel it would be worth the effort.

One last question: What is a LS7 block with Darton MID sleeves installed worth roughly? Keep in mind the sleeves cost $1350 and the labor to install them is around $1000.

I didn't have to pay for the labor and the block was free so if I could get $2500 for it I think I would sell it. I would leave the bores unfinished so whoever buys it can make the bores whatever they want. This block should be just as strong as an aftermarket aluminum LS block AND it will be much cheaper too. I just feel like this block would be better off with someone that will use it to it's full potential. I really don't need a block like this for what I am trying to accomplish and the $2500 I would get for it would go a long way in getting there.

 

the 500 whp is possible even with 5.3 engine (high C/R, RADICAL CAM HEADS INTAKE ... but, you have to keep in mind that the smaller the engine the more attention to details needed.
''example'' more overlaping cam and or higher C/R and the list go.

what dose that mean you will be sacrificing a part from street manners and might add cost for buying gears and stall to help the smaller engine with bigger cam achieve what bigger engine could achieve with a baby cam that wont need a gear or aftermarket stall.

just my opinion

 

If your actual goal is 500+ hp an ls3 block is plently lots to do that

 

Have you considered purchasing a crate motor from GM? They offer the LS3 in a few different configurations. By the time you collect all of the parts, pay for machine work, etc, one of those may be the best path to take...

 

Guess You'll have to change your user name.