408 vs. 427
408 vs. 427 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?
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.
Originally Posted by cyphur_traq
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.
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?
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!! 
And they are dumbfounded and amazed when I tell them it's a small block!! Trending Topics
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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?
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?
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.
Last edited by 52172; Sep 16, 2004 at 05:16 PM.
Originally Posted by CANNIBAL
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?
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?
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.
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.
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.
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
Originally Posted by JoeDirt
Will the 427 make alot more torque under the curve than a 408 ??
As far as money per hp, a LS2 block with an Eagle stroker kit would be hard to beat!
Originally Posted by ace68
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.
Originally Posted by JZ'sTA
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.
Originally Posted by 11 Bravo
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.