408 vs 427 strokers

fastcoupe68 · Jan 29, 2008

skywalker said:
You understand how to build an engine and have done so for 25 years. I fail to see how that changes how metal reacts to stress. And I said that using a Dart block fixes reliability issues and I also said that anytime you overbore you reduce reliability (true) and that you drastically reduce reliability at max over-bore (you do.)

Let say we are using a good after market block with a 4.00 inch bore and lets say we over bore this .030. How much strength did we lose? Percentage wise 1% 2%
10%, hardly a reliability issue.
Do you lose reliability at max overbore? absolutley, I could not agree with you more.
If you use a stock factory block and your worried about cylinder wall thickness have it sonic tested, this measure the wall thickness. There are safe overbore limits. Just dont go over them and you will not have reliability issues. All TRUE!

fastcoupe68 · Jan 29, 2008

I was in no way saying that the 427 won't hold up: it will. But It has a much higher likelihood for failure than a 408. I've heard of several 427's blowing under heavy load at the track. But that likelihood goes down a lot with a Dart block or any block for that matter with a siamese bore.

If you are using a Stock block application the 427 is pushing the limit compared to a 408 ci engine using a stock block
Using an aftermarket block, this rational goes out the window.
On some applications you can go as high as 460ci with an aftermarket block, and I have seen larger, which is really pushing the envelope.
TRUE!
Just take this into consideration, There are small block fords out there using aftermarket blocks that are making in excess of 2000hp. Just look at the Pro 5.0 Class. Those cars with small blocks are making insane numbers and are quite reliable
TRUE!

fastcoupe68 · Jan 29, 2008

5.0Torx said:
skywalker, its great to talk to a fellow engineer. im a junior at UM-Rolla and i follow right along with what youre saying. The truth of the matter is that both you and fastcoupe68 are right, just looking at it from different perspectives. I am fine with doing AFR 185s or 205s with a modest cam so that the shift-point is between 6000 and 6500. I want a real ground pounder with lots of torque down low. I know that, for that objective, deciding between a 408 and a 427 is like deciding between a sledgehammer and dynomatie for killing flies, but like i said earlier, i mainly just want the 427 so that i can say 427 lol. Im going to go check the bore sizes for the 408 and 427 stroker kits and decide what i think is best.

Of the two, which one would have a higher max engine speed? I want to cam it so that my shift-point is around 1000 rpm before the thing explodes.

thanks for the help guys. keep it civil.

PS will it fit in my cougar?

Using a stock block I would go the 408 route, with good internals 6500rpms wont be a problem. but make sure you use very good main studs and good bearings! These are a must as your rpm's increase, also alot of engine builders recomend a main stud girdle in which they claim reduces cap walk. I myself have never used one. I just use good old ARP main studs and have never had a problem, but to each his own on this. My only recomendation on this is if you choose to use one make sure you use a steel main girdle and not an aluminum one. Your main caps are steel and if you use an aluminum type girdle they expand and contract at a different rate and this just doesnt sit well with me.
I hope this helps you
If you def want to go with the 427 and your going to beat the snot out of it I would recomend an after market block.
With the 427 using a stock block you will need to increase the stroke to achieve this cubic inch size as opposed to the 408 4.00 stroke

skywalker · Jan 29, 2008

Loss of strength and therefore reliability is exponential with regards to cylinder wall thickness. Frankly, yes you can run for years on a stock block at 2000hp. I'm not denying that. I'm simply saying that the more you over bore a cylinder wall, the less reliable it is. I had (until my house burned down in June) a 15 year old hard drive that still worked, but I've seen hard dive fail after 3 months. Because strength and reliability are based on a normal distribution (like most every other real event.) Something will take beatings and just never quit. Others will fail the first time you get into it, all other things being equal, it comes down to cylinder wall strength. The distribution of the molecules in the block is a random variable. You you can't know the strength of the cylinder wall unless you test it until it blows. So without that knowledge you can't know how much reliability decreases except that it is reduced on an exponential basis with reference to the thickness of the metal.

In short, you make an engine with a thinner cylinder wall, you increase you chances of blowing the wall. And a Dart block over bored 0.060 may blow quicker than a stock block over bored 0.060. It's a lot less likely, but it's possible because the strength of the metal is a random variable. The manufacturers do everything they can to increase the strength but in the end, they can not tell you where it's break point is. They can only tell you that mean max over-bore is x with a (most likely) 95% confidence and that the cylinder wall should hold to y hp and torque with z compression ratio and w cylinder pressures at that over-bore with that 95% (most lieky 95% anyhow) confidence.

70vert · Jan 29, 2008

My decision is for the 408

I plan on doing a 408 - for the simple reason that, reading all the threads and all the opinions, I would rather let someone else do the bleeding-edge 427 than the less-drastic, in terms of rod angle, 408. Stroking is already putting more stress on the engine than normal and making it peak lower in its' rev range, I don't see a need to make it more of a mutant motor than a stroker already is.

It's a good practice, in general, to leave the bleeding edge to someone else. Let others buy version 1.0 of a product. Let others push the absolute envelope of performance and reliability. The true "bang for the buck" is usually one or two steps down from the most extreme/newest/most expensive option.

Then again, if you have money to burn, want the fastest/lightest combo, and reliability is not a huge issue, do the 427. It's your money to do with as you will.

5.0Torx · Jan 29, 2008

decisions, decisions

Dart says at a 4.125" bore, their siamese blocks still have .250 inches of wall thickness. that sounds pretty good to me. arent the 5L Cammers and the LSx strokers alot less than that?

Right now i have to take care of getting my ass through school and doing the bodywork and paint. maybe a junkyard 351 efi for the short term while i save up the huge amount of money itll take to get the 408 or 427. By the time im ready for it i think the 427 will be my choice.

thanks

skywalker · Jan 29, 2008

427 is a good choice, what do you plan to use it for?

fastcoupe68 · Jan 29, 2008

skywalker said:
Loss of strength and therefore reliability is exponential with regards to cylinder wall thickness. Frankly, yes you can run for years on a stock block at 2000hp. I'm not denying that. I'm simply saying that the more you over bore a cylinder wall, the less reliable it is. I had (until my house burned down in June) a 15 year old hard drive that still worked, but I've seen hard dive fail after 3 months. Because strength and reliability are based on a normal distribution (like most every other real event.) Something will take beatings and just never quit. Others will fail the first time you get into it, all other things being equal, it comes down to cylinder wall strength. The distribution of the molecules in the block is a random variable. You you can't know the strength of the cylinder wall unless you test it until it blows. So without that knowledge you can't know how much reliability decreases except that it is reduced on an exponential basis with reference to the thickness of the metal.

In short, you make an engine with a thinner cylinder wall, you increase you chances of blowing the wall. And a Dart block over bored 0.060 may blow quicker than a stock block over bored 0.060. It's a lot less likely, but it's possible because the strength of the metal is a random variable. The manufacturers do everything they can to increase the strength but in the end, they can not tell you where it's break point is. They can only tell you that mean max over-bore is x with a (most likely) 95% confidence and that the cylinder wall should hold to y hp and torque with z compression ratio and w cylinder pressures at that over-bore with that 95% (most lieky 95% anyhow) confidence.

Never argued this point with you

Haha, You can put it how ever you want but when you start breaking it down the way you are anything is possible, can a aftermarket block blow up because you over bored it .060 sure! can a stock block 351w bored .060 live for 100,00 miles? yes it can. Anything is possible.
In real world experience with as many engines I have built, Worked with many top engine builders all around, and raced, built many cars and still doing it. I'll go buy my experiences with what works and what doesn't. Never needed an engineering degree to tell me what works and what doesnt. I'm certainly not claiming I know more then anyone either.
there are so many variables and the blanket statements about this one being better then the other one is just ridiculous.
I thought we were here to help one another not get into a pissing match, and I apologize if I insulted you but until you have 25 years plus experience building engines racing and so forth dont come out swinging a big d--k when you dont know how to use it!
REAL WORLD EXPERIENCE is the best education you could ever get.
PEACE

skywalker · Jan 29, 2008

You were the one who came out swinging. All i said is that as you over-bore you decrease reliability. It's a an irrefutable a fact.

Bosscat · Jan 30, 2008

I just bought a 427 for my 69 block, but I tend not to rev the crap out of my engines. Live to fight another day mentality

Shooting for around 5800rpm limit, do you guys see any issues with this, also a 150 progresive shot, 228/228 550/550 114 cam, 205 AFRs, Long tube headers, Vic jr intake, 11:1 comp ratio. Any issues with this set up?

mo'factor · Jan 30, 2008

engine

Yes, a 351 stroker will fit in a '68 Cougar. I have a 351 in mine.

Hack · Jan 30, 2008

Bosscat said:
I just bought a 427 for my 69 block, but I tend not to rev the crap out of my engines. Live to fight another day mentality

Shooting for around 5800rpm limit, do you guys see any issues with this, also a 150 progresive shot, 228/228 550/550 114 cam, 205 AFRs, Long tube headers, Vic jr intake, 11:1 comp ratio. Any issues with this set up?

I believe that the '69 351W has a shorter deck than the later years, but as long as you mock everything up and make any required adjustments you will be fine.

Bosscat · Jan 30, 2008

Yep, I figure a thicker head gasket should do the trick As long as the quench is not out of tol.

5.0Torx · Jan 30, 2008

skywalker said:
427 is a good choice, what do you plan to use it for?

Spending money i dont have to modify a car i dont need to impress people i dont know. HAHA

I dunno, general all around hooliganism, and a few track days. Maybe a road trip, depending on how reliable and solid-running it becomes.

fastcoupe68 · Jan 30, 2008

Bosscat said:
I just bought a 427 for my 69 block, but I tend not to rev the crap out of my engines. Live to fight another day mentality

Shooting for around 5800rpm limit, do you guys see any issues with this, also a 150 progresive shot, 228/228 550/550 114 cam, 205 AFRs, Long tube headers, Vic jr intake, 11:1 comp ratio. Any issues with this set up?

Sounds like a solid combo, you should have nothing but fun with it!

10secgoal · Jan 30, 2008

5.0Torx said:
Spending money i dont have to modify a car i dont need to impress people i dont know. HAHA

Pretty much sums up the sport

5.0Torx · Jan 30, 2008

haha yep

Bosscat · Jan 31, 2008

fastcoupe68 said:
Sounds like a solid combo, you should have nothing but fun with it!

Great! I guess I will press on with the build

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