Freefallin

Thinking of a 61mm twin turbo setup to reach goal...

Goal:
Over 1,000 rwhp
Streetability
Least lag
Low end torque
Drag strip weekends / DD weekdays

What would be a better candidate for the above: a 408 or 427?

stevieturbo

Small turbo = smaller motor.

Huge turbo = bigger motor.

I'd say 408. Lag wont be an issue on either.

If low rpm torque is really essential ? 427. But you will be ringing the life out of the little 61's at the top end.

Of course the other query...which 61's ? there are many variations.

Freefallin

I haven't really decided on which 61's. Open to suggestions.

Main concern atm is if an LS2 based resleeved 427 would be as solid and reliable as an LQ9 based 408 under that much power.

Guard dog

When you say over 1000rwhp, how much over? A 370 with twin 6266s will get you a very streetable 1000rwhp.

redtan

iTrader: (5)

What's the 427 based on? LS7 block or sleeved LS1/2/3?

If it's the LS7 block forget it, won't handle that sort of power. If it's a sleeved aluminum block then definitely go with that. Will be just as strong as an iron block but weigh less and more displacement.

Freefallin

Its LS2 based. Where would i see the advantage of a 1000rwhp 427 over a 408 making the same power?

Granted the 427 will be lighter but if i, hypothetically, were to add a few more hp to the 408 to compensate for the weight difference...what would be the difference between the two in terms of streetability, 60ft, 1/4 mile...etc.?

stevieturbo

With small turbos I would see the larger engine of no benefit at all to making power, as it will just work the turbos harder and make them even less efficient at doing the job you're asking of them.

Heavy H.P.

I would think it would be longevity as for as how long the engine lives. Think that would be the main difference if there is one.

redtan

iTrader: (5)

Thar:

Streetability
Least lag
Low end torque

All else being equal, a bigger displacement engine making the same power as a smaller one will have better streetability, less lag and more low end torque.

Now the difference in your case won't be as big as an N/A setup between a 427 and 408, but it will still be there. A 427 will take less cam and boost to reach those levels making it easier to drive and easier on the components, and those cubes will spool up a turbo quicker.

Yeah but in terms of streetability and low end torque, a 427 with smaller turbos will be much better than a 408 trying to spool up big turbos with more boost.

stevieturbo

Unless it's a mega heavy truck....realistically how much low rpm torque do you need, and can the drivetrain and tyres handle ?

And he isnt looking to use large turbos from what Ive seen.

Freefallin

Im assuming you are saying the iron block engine will live longer. But why is that if the resleeved one is "said to be" just as strong.

stevieturbo

Iron blocks are inherently strong.

Aluminium can be very strong too, but just wont match iron when designs are the same.

Re-sleeved....you hear good stories and bad. Make sure you choose somewhere with a top reputation before going down that road IMO.

For 1000hp though, alloy is fine and no weight penalty to pay.

redtan

iTrader: (5)

Idk but he said that's on his list of must haves, so that's why I suggested something like that.

Exactly, so a 427 will require smaller turbos to reach 1000rwhp than a 408.

stevieturbo

Stick the small turbos on and you'll just overspin them, run them very inefficiently and end up breaking them.

So if going down that route, make sure a robust turbo is chosen ( that could rule out Precision it would seem from others doing the same and breaking them )

Freefallin

So if a 9sec slip in a very streetable and reliable GTO that wouldn't cost more than the other (LS2 based 427 or LQ9 based 408, not considering the cost of the block itself and the sleeves or labour or machine work) to build is what im after...what do you suggest i go with?

stevieturbo

I dont get the whole "streetable" comment.

What aspect would there be that you might think would make it anything other than streetable ?

You can easily make 1000hp with a turbo setup with impeccable street manners. You dont need huge cams, you dont need loud setups, you dont need anything aggressive in that respect.

The main thing that will make it unstreetable, is the 1000hp when trying to put it to the ground.
But normal day to day driving, no problem at all.

Now as for reliable, that's a massively loaded query. Almost any well built LS2, LSA, whatever based block with decent heads and studs will be reliable IF BUILT AND TUNED CORRECTLY.

Those two things are the most important over any individual component. And thats not mentioning your drivetrain.

Your biggest hindrance to a 9sec slip will be the manual transmission, and getting it down the track reliably. The engine side will not be a problem.

I personally would not go for iron because of the weight. I currently use an LS2 block at 5 thou, and have another LS2 block I'll be swapping soon with oil squirters and billet/pinned mains. Retaining LS2 so I dont need to change pistons so it's a simple block swap really.

No real reason other than I want to, and I'll be seeking more go in future ( I've just changed to twins )

So I'm around 382 with a 3.825" crank. My previous use of my current LS2 block was 403 and I downsized. I just seen no reason or benefit for the larger motor when traction was almost non existent on the street anyway. More torque was the last thing I needed.

So I would neither go for a LS2/427, nor would I go iron. I dont trust re-sleeved blocks and I dont want the weight of iron

I would go for whichever is deemed the strongest factory alloy block.

Whether that's LS2, LS3, LSA I'm not sure.

Obviously others will have different ideas and experience, but that's just my opinion.

Freefallin

Alright! In order for it to be reliable...does it have to be resleeved by ERL. Im getting Darton sleeves, if i go with 427, and getting it sleeved at the local machine shop since we don't have ERL here.

I know it depends on how good the machine shop is but generally thou, is resleeving a block to handle 1000rwhp usually done at the local machine shop? I've seen them frequently resleeving blocks, including truck and trailer motors...would the process any more different in my case?

stevieturbo

Unless the machine shop has a 100% proven track record sleeving whichever block you chose for a high performance application.

No way would I be using them

But you can buy blocks from many shops and have them shipped to you if you insisted on a sleeved block.

Freefallin

I hear ya!
I already got the block so yeah, would rather use the money somewhere else, UNLESS, there will be a huge difference between the 408 and the 427 and reaching my goal will be unlikely or difficult with the 408.

F110Mech

iTrader: (2)

If i was putting a sleeved block into my car with twins my goal would be much higher than 1000rwhp. I hope to hit that number on C16 with stock cube forged bottom end when i want to lean on it.