Already in the works? Go for it.

 

If you are ok with it lasting only 1 season then I say go for it. I just really think you should adjust your power goals. Also a 4.1 stroke is just going to make the problems even worse. But again if you are ok with getting 1 season out of it, why not.

 

Joe, it is in the works, but I do not HAVE to turbocharge it, that part is up in the air still.

 

I figure if I got a season out if it, i could save up and then over the winter send the block to ERL for sleeves, and go even bigger. I do not have an unlimited budget, so I can't do that now. However, again, I am not looking to drive over my crank at 150 mph.

 

I don't think you will be driving over the crank. Eating up main bearing... more than likely. One of the major issues you need to solve will be lifting heads. You will torch the heads and block and be left with scrap. Look into doing a fire ring or something.

 

Would better main caps help?

 

It won't help with the other problems associated with the 4.1" crank, or the 4 bolt heads on an aluminum block @ 1500 HP.

An iron LSX or Dart block is cheaper than an ERL LS3 block.

 

Yeah, Just want to keep it light! Maybe I should scrap the 4.1 crank idea. Is a 4.0 any better for this combo?

 

You said you had a 2600-2700 lb car.
Looks like you have 100 lbs to play with.

The iron block weighs.... you guessed it.... 100 lbs more.

 

LOL, shooting for less, but I hear you. I'll go on a diet!

 

If you don't have the crank yet I would go stock stroke or 3.9 at most. I really think the stock stroke would be best though, you don't need the extra cubes with boost.

 

One thing it is hard for people that have not worked with turbos before, is to get over the idea that more displacement is better. The "there is no replacement for displacement" really doesn't always apply. I'm relatively new to the turbo idea myself, and I think I can speak well of this because I've been recently understanding this better.

You can have a turbo set up on your 427, working ok, blow the 427 up and replace it with a smaller displacement engine, like a 365(4.005" by stock stroke) or such, and actually go faster sometimes because the turbos are working more efficiently on that smaller displacement engine. The turbos can only move so many lbs of air in a given time frame, there is a limit to how much they can move. On a smaller engine there is more resistance to intake flow and the turbos are able to build more boost. Because of the design of the compressor wheel, it is often more efficient at the higher boost level and will move more lbs of air at that higher pressure level. Compressed air weighs more, so you get more mass of air at the same turbine rpm. More air mass = more power. This is counter to the conventional thoughts about engine displacement, normally more displacement means more power, and that is often not true on a turbo car.

I would contend that 427 is too many cubes for 1500 hp. The Honda guys are making 600whp on the B18, 1.8 liter engines, reliably. I hate those buzzy little things, and the punks that build them, but if you look what they are doing, you can learn something from them too.

The other thing that you need to dismiss is the idea that a 427 at low boost is more reliable than a smaller engine like the 365 I referenced above, at higher boost levels. Considering the same quality of internals the 365 will be more reliable at the same HP levels as that 427. Consider why GM backed off to the 6.2 for the LS9 rather than continuing to boost the LS7 at 7.4L? Here is why the smaller engine is more reliable.

1) consider they will use the same rod, at the downward thrust limit of that rod, it doesn't matter the size of the piston above it, it can only transmit so much force, so it is a wash there. On the way up, the rod and wrist pin needs to stop a heavier piston, this is an advantage for the 365 with a lighter piston. It is also easier on the rod bolts.

2) The cylinder walls with be thicker on the 365, the block will flex less, and withstand more side thrust load against it, it will also make a larger surface for the head gasket, and cylinder head to seal against, advantage 365.

3) The 427 will have a longer stroke. This will make more of a side load on both the main bearings, and the cylinder walls because the rod journals will be more off center. Think of the mid point of the power stroke, and how it is wanting to twist the crank out of the bearings, and how the additional leverage works against your block. This will also put more stress on your crank. It will also lower the skirt of the piston out of the jug, which the stock 3.622 stroke won't, and the piston will be less supported at the bottom of the stroke, this will put more side thrust load on the cylinder wall, because the piston will not be as strait in its jug at the bottom of the stroke.

4) This longer stroke pushes the wrist pin up higher into the piston, which places the top ring higher, which exposes it to more heat, it will fail sooner normally under these conditions. This can be overcome to some extent with steel top rings, but this could also be done on the 365, which would also give more reliability to it. The higher wrist pin also weakens the piston because it potentially makes the top surface of the piston thinner in some designs.

You might have guessed I'm building an iron 365 as my next short block. I'm a little too cheap to buy an aftermarket block, but have a new 6.0 iron factory block. I'm using a Lunati crank(3.622 stroke) and rods(6.125") with L19 bolts, Weisco 2618 pistons (-11cc), ARP main studs. I'm not going to bore it at all, only hone it for piston fit, to keep cylinder walls as thick as possible. I'm going to use ARP 12 pt head studs, and LS9 head gaskets. I believe it will be an affordable combo, I'll not have much in it because I have most of the parts already. While I know this won't match billet builds with the aftermarket iron blocks, I'm confident it will be really stout. I would sleep better at night with it, than I would a 427 cid build on an aluminum LS3 block.

Don't get me wrong, I'm not judging you. I've never built the combo you are, so I don't really have experience with it. I wouldn't tell you not to build it because I don't know. It may do more than we think it is capable of.

 

This is a great post. My only "problem" is I have the ls3 block already. I can change the stroke, but the bore will be 4.070 no matter what.
I guess when starting this build I saw all of the fastest cars with 427+ cubes, so I figured that would be my starting place, not really thinking that all the fastest cars are owned by guys with deep pockets, and $5000 blocks. this was going to be my "poor man's" version. Now I need to start rethinking....

 

just do a stock stroke motor? run what you have.

 

I read something some time ago, from a reputable LS builder, the LS3 factory block, built to stock displacement, with forged internals and ARP main studs is very reliable up to about 1100hp. I don't remember who it was, it was someone like Mast or Nelson, one of those type builders. Knowing these guys there is probably a little safety margin in that too. Now those guys are usually talking crank, not wheel HP. You can still make quite a beast from what you have. Like I was saying, I'm not saying you can't make 1500, simply because I have no personal experience at power levels that high, but I wouldn't say you can either.

 

 

What JoeNova said and I'm surprised it took so many comments.

People who know what they're doing with a bit of margin, run 408-412 maybe touch more, never 427 because you're pulling skirts out the bottom. Hell or GM wouldn't have needed to make an LS7 block for only 427 and everyone else would run 427 LS3s... nope.

So watch that stroke. I'd just buy an LSA, sell the supercharger and turbo it, stronger than LS3 and built for boost already with lower compression. Leave it as is, stock stroke for now. Won't get 1500hp (not many non aftermarket LS setups do for a long time) but it'd last a hell of a lot longer than an LS3 trying to destroy the bottom of the bore and mush the skirts.

Iron block also you might want to look at..

as someone who has an LS3 and looked into boost for a while and know someone who was running close to 1khp on one in a heavier car, one issue (probably helped by studs) is the heads will lift and or warp if you really push stuff. This is why the LSA has rotocast heads, they're a bit stronger again, more rigid, made for boost, piston cooling forged crank stock and the rest..

Those guys went to ironblock TT setup and never looked back.