Scalpel

iTrader: (4)

I, too, feel that this a huge predictor of the engine's outcome. A properly setup and matched setup dictated to the needs of the customer is the outcome we all should strive for

ace68

iTrader: (15)

sorry what I ment is I am going to have a iron block machined it is at 4.00 right now so if I get it boared to 4.06 it will cost the same amount as if it was going to go to 4.03 that's what I ment. I know I have to get it line hone deaked and all that stuff it's a given I was just talking boar diameter.

ace68

iTrader: (15)

the only extra cost is a sonic test

Scalpel

iTrader: (4)

Ok, gotcha.

However, a iron block + all that machining (everything needed) will run right near or above $1,000.00, though, correct? I used that to subtract from the average minimum cost of a Darton MID of $2500-$2800 (not including finishing machine work and line hone, etc)

11 Bravo

iTrader: (3)

You said you were going to run 427 cubes. Iron block? What stroke are you running?

JZ'sTA

iTrader: (23)

Yes I know what you ment, just throwing out my oponion.
I agree with what you are saying as a example, it just dosent work on LS1's in the higher HP levels.
There are tons of comparisions. some say that you gain 4% of your total HP per every point of compression. Another example used sometimes.
I was just stating that the lack of air geting into our motor's really hurts when you get in the higher HP numbers.

JZ'sTA

iTrader: (23)

The intake's are much improved but there is still a lack of air for the LS1.
I think that is pretty easy to see.
A 346 makinh 500 but a 427 only making 550. something isn't right.

How do you figure a 550 HP 427 will win in a race?
If the 408 made the same exact power through the whole RPM band and both cars were somehow setup exactly the same, had the same weight how ect, how can you say just because of the extra cubes the car will win?
I understand if the motor makes more power before the peak power number, but that inst what you wrote. Just trying to figure it out.
Thanks

11 Bravo

iTrader: (3)

I kinda agree, but when you have a 427 ls1 that has 550rwhp n/a, way more than 1hp per cubic inch, is totally streetable and gets 20mpg then I can't see how an intake is a major restriction. It's hard to get much better than that. But maybe I'm way off base. It would be interesting to see what kind of power a tunnel ram type of intake would do for the big cubes.

1BADFNHuggerZ

There are formulas that support these theories, but it all boils down to who knows "how" to build the best engine. Alan Futral's little 348 c.i. put 550 @ the back wheels. I think there are a great deal of 427s that are not doing this. 19 or 25 more h.p. is not worth several more thousands of dollars, just spray the house down for a cheaper price with the iron block 408.

silent1

iTrader: (3)

What is being compared here isn't a 408 and 427 with the same power output, but rather the same internal specs less the cubic inches. That is why the 427's extra cubes will make more power than the 408.

JoeDirt

Bah, the difference is one is a totaly mild , streatable setup with gobs of low end torque and the other one is high strung, high maintanence and bitchy to drive. Ill take the mild 427 anyday

texada

iTrader: (3)

If both engines had the same or close to the same setup gears, cam, heads,etc. I actually think it would probally be a driver's race How streetable and the idle are 240-248 duration cams in a 408?

11 Bravo

iTrader: (3)

Sorry, I should have been clearer. If both motors make the same peak power, and all else is equal, then the bigger cubes win because it will have a stronger powerband. You could probably search on this site and find a dyno graph of a 500rwhp 346, and a 500rwhp 408. Compare the two graphs and the difference is night and day. Same difference. In the end "there is no replacement for displacement".

slow trap

iTrader: (22)

the exhaust system will play a role also.you will need 1 7/8 headers to make that 427 breath right.the 427 will be moving more air at lower rpms.the bigger bore will unshroud your valves and help your heads flow alittle better .only the bore is different from a 408 to a 427.4.03 bore x4 inch stroke =408.179,4.125 bore x 4.0 stroke=427.650,approximately.if you put in a 4.125 stroke and 4.125 bore you have a 441 ci.if you don't have a set of killer heads the 408 wouldn't be far behind the 427.

gollum

iTrader: (1)

This makes sense. LOW END TORQUE is funner on the street.

JZ'sTA

iTrader: (23)

This makes no since.
A 240 duration cam is no problem as a daily driver in a 408. The T rex with a nice tune would be a 10000 mile per year fun car.
IT MAKES NO DIFFERENCES HOW MANY CUBES YOU HAVE, if the car is set up to be street friendly then it can be street friendly. If it is set up as a all out race car then it probally wont like the street very much.
Give you a example. Every heard of the C5R? Of course you have.
That is a 427. Some of the guys take that thing and but a big cam shaft in and rub like 13.5 C/R. Guess what that 427 isn't street friendly.
I have a 410 in my Camaro a 242/246 duration camshaft.
Makes awsome power and torque.
Drives very nice, loud but very street friendly.
Maybe you should try both with similar setup before you make your oponion.
I have. And for the money I am glad I went with the 410.
This of it this way if you save the money you would have spent on the 427 and invest it else where you could be better off.
If your on a budget you have a real nice set of heads + a 408 for the same price as a 427.

JZ'sTA

iTrader: (23)

I agree for the most part, however the dyno means **** in a race.
If 2 cars were to race and both making the same exact power from say 5500-7000 RPM's one being a 346 and the other being a 427 and both setup to run the fastest times it could with the power it makes the race would be very close. With the correct size stall converter and gear you will never see the RPM range during a race where the cubic inch whoops the stock cubed cars ***. On a dyno there will be a difference down low, but who races in the 2500-4500 RPM range?
That is why these big cam guys as going so fast. A big cam and a 4400 stall can make a car .4+ tenths better then another car that made the same exact power as the big cam car until 5500 RPM's.
I would be very upset if I had a 427 and the 346 beside me was face to face with me down the track. Way more to racing then HP.

JZ'sTA

iTrader: (23)

I agree 100%. Would be extreemly close.

A 240-248 duration cam in a 408 is very similar to a 224-230 cam in a 346.
You know its there but when tuned nicely drives real nice.

11 Bravo

iTrader: (3)

The original question was how do a 408 and 427 compare with the same cam and specs. One last time: *all else equal* and the bigger cubes win. And it will have a smoother idle. That is the answer to the question. This post kinda got off track lol.

silent1

iTrader: (3)

I'm going to have to disagree just a bit. Most "would be/should be close" races are won due to better 60' times where the bigger cube's low end will kill a smaller cubed engine. Don't you think?