Longevity & Reliability vs. Power

[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.

[blykins]

It doesn't matter...

Build it for 700hp and just don't push the gas down as far.

[Rick Parker]

In the search for reliability is is best to remove the term "Split lock washer" from your vocabulary, regardless of what component you are referring to, or your local.

[patrickt]

Originally Posted by Rick Parker

In the search for reliability is is best to remove the term "Split lock washer" from your vocabulary, regardless of what component you are referring to, or your local.

Lykins swears by split lock washers.

[patrickt]

... and I bet I can five pages or more out of a "how do you load your greasegun" post.

[CobraEd]

Originally Posted by 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.

I deleted it !!!!!


AHAHAHAHAHAHA


.

[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.

[Stentor]

Originally Posted by blykins

It doesn't matter...

Build it for 700hp and just don't push the gas down as far.

I like that logic!

[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.

[blykins]

BTW...

Don't get hung up on horsepower numbers. The best way to tackle an engine build is to build the engine to make the most horsepower for the range that you're going to run in. Also, a 450hp 408W will fit stouter than a 500hp 347.

[CobraEd]

Originally Posted by blykins

a 450hp 408W will fit stouter than a 500hp 347.

What does this mean?

A 450hp 408 only needs to run about 5500 rpm but will have about 450 ftlbs of torque.

A 500 hp 347 will need to run about 7000 rpm, but will only have about 400 ftlbs of torque.


.

[blykins]

I guess I didn't explain it that well.

My point was that you build an engine to run at a desired rpm range. A street driven Cobra doesn't run constantly at 6500-7000 rpm....you're usually between 2000-5500 or 2000-6000 and you normally cruise at around 2000-2500.

So if you build a higher horsepower engine, it doesn't necessarily mean that it's going to be a barn burner because it may not be suited for a specific street driving range.

In our case above, our 347 may make 500hp, but it's going to peak at 6500, with a very narrow powerband, and probably around 425-430 lb-ft of torque. The average hp and average torque numbers will be low.

The 408 may "only" make 450hp, but it's going to peak a lot lower, have a big broad torque curve, and have a considerable more amount of torque.

With the transmission, rearend ratio, and tire sizes being the same, the 408 will "feel" like it has more power because it has more average power/torque in the range that you're driving in.

You can even apply this same scenario to two engines of the same displacement....maybe two 408's or two 347's.

So we're back to my post above...don't get hung up on horsepower numbers, because the engine with the most horsepower may not feel powerful in the range you're running in.

[RodKnock]

Originally Posted by 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.

You're far more delusional that I thought if you think your 445 makes similar HP as my 482. Bigger cam, bigger cubes and weighs a lot less.

I would say "talk to the hand", but instead, I'll tell you to talk to Chas. He'll better explain it to you.

[patrickt]

Originally Posted by RodKnock

You're far more delusional that I thought if you think your 445 makes similar HP as my 482. Bigger cam, bigger cubes and weighs a lot less.

I would say "talk to the hand", but instead, I'll tell you to talk to Chas. He'll better explain it to you.

I conceded you have more. I would bet probably 75 more. I'm betting your 482 puts out about 525HP at the fly with the pipes and accessories all hooked up. Lykins, you agree with that?

[blykins]

Probably less.

I'd say you lose ~20% with drivetrain and exhaust losses on a Cobra.

How are you getting your own dyno numbers? On an engine dyno with Cobra headers and accessories running, or on a rear wheel dyno?

[patrickt]

Originally Posted by blykins

Probably less.

I'd say you lose ~20% with drivetrain and exhaust losses on a Cobra.

How are you getting your own dyno numbers? On an engine dyno with Cobra headers and accessories running, or on a rear wheel dyno?

I had mine broken in on the dyno and then measured with the pipes and accessories on it. I do not know what my rear HP numbers are, but I've always viewed dyno numbers on an engine that is being measured in a state that you're never going to see under the hood as being bogus. So you're in agreement that Rod's flywheel numbers with his pipes on and accessories on drop from 610 to below 525? Excellent. Take that, Rod.