OK Chas, See If You Can Tell What's New...

[blykins]

Your heads must perform horribly. To peak at only 5000 with the cam that you have says something for how efficient the heads and intake are.

I use similar durations on engines that are 40 cubes bigger than yours and peak 1000 rpm higher.

[patrickt]

Well, it is what it is... and my side pipes drop it all down to 475 or less. I had custom pipes made to be a little quieter than the average, with the understanding that it would take some power away. I still set off car alarms, but it doesn't hurt my ears. In fact, it sounds exactly how I want it to sound. I sat in somebody's Cobra a few years ago that was so loud that I had ringing in my ears for the rest of the day.

[RodKnock]

Originally Posted by patrickt

Well, it is what it is... and my side pipes drop it all down to 475 or less.

...or less. Typical drivetrain HP loss is 15-20%. A 50 HP loss would only represent about a 10% loss.

[ERA Chas]

Originally Posted by RodKnock

...or less. Typical drivetrain HP loss is 15-20%. A 50 HP loss would only represent about a 10% loss.

Rod-he means the loss of FWHP on the engine dyno. A chassis dyno loses 15% (or more) from drivetrain friction and tire contact.

[patrickt]

Originally Posted by ERA Chas

Rod-he means the loss of FWHP on the engine dyno. A chassis dyno loses 15% (or more) from drivetrain friction and tire contact.

Yes, my true, honest, no-fibbing horsepower numbers are between 450 and 475 at the flywheel. I get a little extra for the Ersons and the fact that it is nicely broken in and carefully tuned. But still, when people ask, I tell them it has 450HP because that's the truth. BTW, my valve sizes are 2.09 and 1.66. You know, if I just wanted to test out a bonus 50 to 75 horsepower I could bolt on shorty straight-outs and then put on some ear plugs.

[ERA Chas]

Originally Posted by patrickt

You know, if I just wanted to test out a bonus 50 to 75 horsepower I could bolt on shorty straight-outs and then put on some ear plugs.

No you couldn't-they'd have to be tuned length around 37" plus a proper length collector.
Honesty is the best politics as Stanley used to say. A 447 that makes 475 is a rebuild-period. That's been my beef all along and it's a shame (even) you got hurt for a performance build price.
At least you know Brent and the current crop of builders won't hurt you on price and it's cake for them to deliver a pump gas, mild 1.3 engine these days.

[patrickt]

Originally Posted by ERA Chas

No you couldn't-they'd have to be tuned length around 37" plus a proper length collector.

I'm pretty sure we have a set of these at the local club. These would not work?

[ERA Chas]

Originally Posted by blykins

Your heads must perform horribly. .

That's why I'm hounding him (you) to do a Stage II, III or 1000 (), on them and get them near 300 cfm-at least. He never said valve sizes so that wouldn't hurt either. I think he has enough bore for 2.19s.
Maybe the BT dual plane is OK but the heads / cam don't work with it.

[Bernica]

Originally Posted by ERA Chas

That's why I'm hounding him (you) to do a Stage II, III or 1000 (), on them and get them near 300 cfm-at least. He never said valve sizes so that wouldn't hurt either. I think he has enough bore for 2.19s.
Maybe the BT dual plane is OK but the heads / cam don't work with it.

Yep. 325 CFM or so will do the trick.

[patrickt]

Chas, do you remember the erudite thread from Steve Sunshine a few years ago, that concluded, after a detailed and thoughtful analysis, that 535 flywheel horsepower was the maximum usable power in a Cobra under almost all conditions? Do you buy in to that?

[ERA Chas]

Originally Posted by patrickt

Chas, do you remember the erudite thread from Steve Sunshine a few years ago, that concluded, after a detailed and thoughtful analysis, that 535 flywheel horsepower was the maximum usable power in a Cobra under almost all conditions? Do you buy in to that?

Yes I do remember and NO I don't subscribe..
Speaking in absolutes is a fools errand in any context.
I always strove to maximize power and be smart enough to apply it effectively. Bruce's #3170 is an example and so is Morris' KMP. Both make well in excess or 535 HP. Those guys are light-years ahead of me certainly and 98% of the forum. But I go to school on their work.
Sunshine always wants to exude authority in the 'correctness' of his car and any pronouncements (such as your example) he makes. Lack of an open mind is like living in a dim room.

[patrickt]

I can't find his thread -- I think it got eaten during one of the server crashes. I do remember there were some pretty smart guys on both sides of the argument.