Longevity & Reliability vs. Power

[zrayr]

for a street driven FE 427, at what point do power modifications begin to seriously degrade longevity & reliability? 500 HP, 550 HP, 600+ HP ?

Z.

[blykins]

For an engine of that displacement, it's not hard to get 500hp with good cylinder heads, hydraulic roller cam, etc.

When you start approaching 600hp, you need to start using the larger, rowdier cams, little higher compression, etc. Peak horsepower rpms go up, better valvetrain components are necessary, etc.

Of course the larger the displacement, the easier to make more horsepower.

The 428FE that I built for my own Cobra used Edelbrock heads, a Tunnel Wedge intake, a solid roller camshaft, and it was about 11:1 compression. Peak horsepower was about 550 @ 6500. If you were running this car hard, you would need to shift at about 7000. A solid roller cam needs a little more attention than a hydraulic cam and the lifters don't live as long. I would consider that a minus in the longevity department.

Where reliability starts becoming an issue is if you're drag racing with hard launches, spinning the engine really high, etc.

[Tom Kirkham]

At about 5,500 RPMs

[zrayr]

Originally Posted by Tom Kirkham

At about 5,500 RPMs

then, is it too much of a generalization to say that keeping the rpm under 5500 will do more for reliability & longevity than limiting horsepower ?

thanks for all the (mostly) serious answers.


Z.

[patrickt]

Originally Posted by zrayr

then, is it too much of a generalization to say that keeping the rpm under 5500 will do more for reliability & longevity than limiting horsepower ?

thanks for all the (mostly) serious answers.


Z.

... or you could do like RodKnock and keep it at zero RPM and it will last forever. I will add that revving your FE up in the 6000+ range is fun, regardless of whether it is necessary or causes extra wear on the engine. It really is fun, and it sounds great.

[RodKnock]

I might go one step further and say to over build it with quality components and limit the RPM to 5,000-5,500, but 5,500 should be max for reliability.

I think my hydraulic roller cam poops out about 5,600-5,800 RPM and my engine dyno'ed at 605 HP. I think. It's been a while since I reviewed the dyno sheet or driven my car for that matter.

I will say Patrick is right. Zero RPM does wonders for engine longevity.

[patrickt]

zrayr -- dyno numbers can be sneaky. It might sound like Rod's 605HP is a lot more than my 450HP... but it might be closer than you think. My 450HP is with the pipes on, air cleaner on, and water pump churning. Pull all that stuff off and you can get a dyno well in to the 500's. Now if Rod's 605HP number is with open pipes, and maybe a few "adjustments' factored in on the dyno, he could be well down in to the low 500's with an "apples to apples" dyno run like mine. You can play a lot of games with dyno numbers... a lot of games.

[blykins]

Originally Posted by zrayr

then, is it too much of a generalization to say that keeping the rpm under 5500 will do more for reliability & longevity than limiting horsepower ?

thanks for all the (mostly) serious answers.


Z.

It's all related to each other.

A 427 ci engine is never going to make 550-600 hp without spinning it up. So keeping it under 5500 is going to limit your horsepower itself.

Don't use 5500 as a magic number.

There are plenty of engines that peak at 6000 or 6200 that are perfectly reliable.

The easiest way to go about this would be to say:

What combination of parts would I need to get to xxx hp? I can answer that question very easily and provide information on reliability and longevity.

[Wbulk]

“5,500 RPMs”, I agree.
The higher the RPMs the greater the cost to build and the longevity goes down. It’s literally diminishing returns.

[blykins]

I wouldn't call it diminishing returns since rpms make horsepower, but in terms of reliability, I would say anything over 6400-6500 would start to see a decline.

[patrickt]

Originally Posted by zrayr

for a street driven FE 427, at what point do power modifications begin to seriously degrade longevity & reliability? 500 HP, 550 HP, 600+ HP ?

Z.

If it's street driven, you will not notice the difference between 600 and 500 horsepower. Plus, any of the FE builders on this forum can build you a 500+ HP FE that will last your lifetime.

[CobraEd]

If you put Royal Purple oil in it with a ZDDP additive, it may physicaly break, but it will never wear out!




.

[patrickt]

Personally, for a predominantly street-driven car, I think the "sweet spot" is mid to upper 400's in horsepower at the flywheel, measured with all accessories and pipes attached.

[RodKnock]

Originally Posted by patrickt

Personally, for a predominantly street-driven car, I think the "sweet spot" is mid to upper 400's in horsepower at the flywheel, measured with all accessories and pipes attached.

And this is based on...............................personal experience with one engine?

(just giving you a hard time).

[patrickt]

Originally Posted by RodKnock

And this is based on...............................personal experience with one engine?

(just giving you a hard time).

Awwww, man. In a Cobra, I guess that's true. But, I always try and get my engine running at its tippy-top right before I put her away in her seal-a-meal bag for the winter (which I did last week). I took her out for the last drive of the year and it was in the 50's (which is arctic weather, in my book). With the cold air, and the cold tires, I could not safely push the throttle more than half way to the floor for more than a second or two. I don't know how an additional dose of horsepower would do a thing for me. And, if there was the slightest bit of "streetability"* taken away by the horsepower fairy that wanted to wave her magic wand and give me a magic extra 100 horsepower, I would politely decline the gesture.

EDIT -- *streetability, longevity, or increased maintenance. (I need the last one like a I need a hole in the head.)

[Tom Kirkham]

So, it all boils down to:

Performance, Reliability, or Cost.
Pick any two.

[Hotfingrs]

But it did conclude that anything over like 525/535 HP, even in racing conditions, was of no help.

So Donohue didn't really need 1400 horse in his 917-30 ??

[patrickt]

Originally Posted by Hotfingrs

So Donohue didn't really need 1400 horse in his 917-30 ??

One has nothing to do with the other -- you know that. If I could find his post, I'd paste it here, but I think it may have gone down in one of the crashes we had a couple years ago. I bet Ernie remembers it, though. I have a vague recollection of him discussing it in that thread. I'm sure there are others who might it recall it.

[Stentor]

Originally Posted by Hotfingrs

So Donohue didn't really need 1400 horse in his 917-30 ??

Hotfingrs,

Per Pat's supposition, are you able to run in the 9s in your car with 525 HP?

[patrickt]

Well I've spent a half hour searching every way I know how and can't find it. I can find threads where a reference to his thread is casually mentioned, but not the thread itself.