texada

iTrader: (3)

Hello, I see Scoggin Dickey has the new 6.0 block for 1k. With a 408 build up of a 236-248 duration stage 3 heads etc. how does a 408 stack up against a 427(4.125 bore) with the same cam and specs?

cyphur

iTrader: (10)

well um a 427, if built right, will make more power. where did you see on their site the new block? i must be blind/not paying attention. plus the new darton-sleeved blocks can withstand some crazy power.

Hysteria

Overall bang for the buck engine is the 408, and within a couple of numbers in the power department.

texada

iTrader: (3)

They are taking orders. It is in the LS2 section.

texada

iTrader: (3)

I know that the 408 is the best bang for your buck. I am talking apples to apples as far as the same specs from the engine, transmission and rear end how much more would a 427 make over a 408?

Trojan T/A

iTrader: (1)

What about a 421 using a 4.125 stroke? The should be about the same price as the 408s but you get an extra 13 cubes.

nitrorocket

iTrader: (12)

Cube to cube you will probably only gain 15 hp and 20-25 lbft. with everything else the same. Not much to justify any kind of large price difference. The fun part of having a 427 though is everyone at shows asking "It's a 427 bigblock??" And they are dumbfounded and amazed when I tell them it's a small block!!

52172

iTrader: (2)

427 will make more power heads will flow more on a larger bore so why not step it up with a resleeved block from race-engine-developement?

Scalpel

iTrader: (4)

Just some quick math.

427 - 408 = 19 cubic inches.

Using the general 1.45 HP/CI we get 19 CI x 1.45 HP/CI = 27.55 HP (engine HP)

This is a general rule of thumb. So, the 427 has at least a 27.55 HP greater potential just based on the increased cubic inches.

The Darton MID block is about $2500-$2800 and that doesn't include the rest of the machining, like a line hone and a finish hone, etc.

A fully machined and ready to go iron block (4.030" bore) for is about $1,000.

So is the minimum of $1500-$1800 worth the potential of at least 27.55 more HP at the engine for you?

52172

iTrader: (2)

great answer!

52172

iTrader: (2)

for some they will pay 5000 for 20 hp but thats crazy! Now that you can get an ls2 aluminum block for 999.00 408 is the way to go unless you are power hungry and wealthy. Anybody that has built an iron 408 in the last 6 mos was not thinking of the future.

JZ'sTA

iTrader: (23)

Great answer except we have a intake that just cant support the air the extra cubes need's to make your example right on the money.
You go from a 4.030 bore to a 4.125 bore which will help the heads flow better.
The problem is the intake restriction. Even using a 90MM setup it still dosen't produce enough air to make the full 1.45 HP per cubic inch. It will defentially make more power however I honestly believe it would be closer to 1 HP per cube. Now if you can find a way to get more air then you will see a bigger difference.
Notice the stock cubic inch LS1 guys with real aggressive setup's are now making 500 HP with a M6. They are at 346 cubic inches.
If the above theory was correct on the LS1 then a 408 should make 590 to the wheels (1.45x62)+500 and a 427 should make 617.5 (1.45x81)+500to the wheels. We all know this isn't happening.
I am not saying this theory is always wrong, however on the LS1 it becomes very hard to prove with are shatty intake/air induction setup's.

11 Bravo

iTrader: (3)

A 90mm setup seems to gain an average of 25rwhp on a 427 over a LS1. I don't think it's really a big restriction anymore, though I'm sure it could be better. As far as a 408 vs a 427, there is more to the comparison than peak dyno hp numbers. All else equal, a 550rwhp 427 will kill a 550rwhp 408 everytime. Most of you know that, but people get too hyped up on peak #'s here. It's all about how much money you are willing to spend. For some, a $1500 difference for the block isn't worth it, for some it is. I have to admit, 1K for the LS2 block is a killer deal.

JoeDirt

Will the 427 make alot more torque under the curve than a 408 ?? I dunno why Im stuck on a 427 . . . it just sounds soooo kewl

ace68

iTrader: (15)

well you don't pay extra for a larger bore say from 4.030 to 4.060 if you go right to 4.060. when i drop off my block they arn't going to charge extra to go to 4.060 from 4.000. so it dosen't cost more to get a bigger boar.

I'm just going to go with 427 and if the block crackes oh well I'll just get a ls2 block later

11 Bravo

iTrader: (3)

Yes. Alot more? That is subjective. Everything equal, in a race it will win. That's all that matters As far as money per hp, a LS2 block with an Eagle stroker kit would be hard to beat!

Scalpel

iTrader: (4)

I don't understand what you mean with that statement. Why don't you pay extra to bore and do a finish hone? You can't just bore it and leave it at that. You bore to "x" spec and then do a finish hone so the rings will seat. This doesn't include having the block main bores line honed, either.

VINCE

iTrader: (1)

The biggest thing is all being equal... My 408ci dyno's like a 427ci. Hp/Tq is about the same. I think it really depends on who builds the setup.

Scalpel

iTrader: (4)

That's why I prefaced it with a general rule of thumb and a as a potential increase in power. It was just a general comparison to give an idea as of what one could potentially expect if they wanted to spend the $. I didn't say that they'd reach that, just potentially using a general rule of thumb calculation. I should have made it more clear, though, honestly.

Scalpel

iTrader: (4)

Exactly. Well said.