What rpm power range for my 460 build

[cycleguy55]

Originally Posted by txcobra

Where should i build my power band at for a 460 for my cobra build. I am going to build it for around 500hp and just need to know if my power should be low, medium or hi end of the rpm range. I am looking for a nice tame driver, my tire dia is 25.7 inches, my rear end is a curie 9 inch Detroit locker with 2:50 ratio, and my trans is a Richmond 5 speed with 3.27 1st and 1:1 fifth so technically no overdrive. Thank you for your help.
Greg

IMO your 500 HP goal won't be attainable if you want to have "a nice tame driver" with a 2.50:1 final drive ratio. In order to have the former you'll need a mild cam, and that mild cam will keep you in the 400-450 HP range, even with good aluminum heads. A bit more cam will get you to 500 HP with a BBF, but then you'll be a lot happier with a FDR in the range of 3.00:1, even with the stump-puller 1st gear in that transmission.

Just my $0.02.

[Paul Kane]

Originally Posted by blykins

With a BBF, you'll probably save 100 lbs between cast iron and aluminum heads...

Assuming the valve train hardware between the two heads is identical, and both heads are passenger car type (ie, not A460, etc) then the weight reduction will be about 60 pounds.

Originally Posted by cycleguy55

IMO your 500 HP goal won't be attainable. In order to have the former you'll need a mild cam, and that mild cam will keep you in the 400-450 HP range, even with good aluminum heads. A bit more cam will get you to 500 HP with a BBF...

Just dyno'd an engine that made 1.05 hp/inch with a 233"@050 custom flat tappet cam, 4150 carb, as-cast dual plane, and unported Edelbrock heads, pump gas. The same results could have been fulfilled with ported OEM iron.

For a low rpm responsive 385 Series, I'd recommend stroking it. Even a little ol' 4.14" stroke 500-inch engine will meet the needs, desired hp numbers, on pump gas with a pump gas friendly compression ratio. And with the right cam the torque number will far exceed the hp number (the above noted engine made 1.22 ft-lbs/inch).

[cycleguy55]

Originally Posted by Paul Kane

Assuming the valve train hardware between the two heads is identical, and both heads are passenger car type (ie, not A460, etc) then the weight reduction will be about 60 pounds.

Just dyno'd an engine that made 1.05 hp/inch with a 233"@050 custom flat tappet cam, 4150 carb, as-cast dual plane, and unported Edelbrock heads, pump gas. The same results could have been fulfilled with ported OEM iron.

For a low rpm responsive 385 Series, I'd recommend stroking it. Even a little ol' 4.14" stroke 500-inch engine will meet the needs, desired hp numbers, on pump gas with a pump gas friendly compression ratio. And with the right cam the torque number will far exceed the hp number (the above noted engine made 1.22 ft-lbs/inch).

I note how you left out the contextual "if you want to have "a nice tame driver" with a 2.50:1 final drive ratio" from my comments. That context is an important factor in cam selection, as you well know, yet...

[Paul Kane]

Originally Posted by cycleguy55

I note how you left out the contextual "if you want to have "a nice tame driver" with a 2.50:1 final drive ratio" from my comments. That context is an important factor in cam selection, as you well know, yet...

cycleguy55 to be clear: the 500-inch engine I suggested in my post above would be a "very nice tame driver," and absolutely "will meet the needs" as I myself stated. The 460 could be, too, depending on the exact needs (ie, the 460 would still idle below 1000 rpm, for example).

It was not my intention to specifically delete that particular portion of sentence from your post. On the contrary my intention was to streamline the quote down to the matter at hand and provide the relative anecdotal advice, that's all.

The engine's would indeed be "nice tame drivers," specifically tailored for good idle, great low end throttle response, and an excellent overall broad power band.

[olddog]

My second car was a 1968 Dodge Charger (my favorite) with a 383, automatic and about a 2.50 rear end. I bought the car in March. Next morning the engine was frozen and busted. The asshole I bought it from drained the antifreeze and put water in it without telling me. I found a 400 engine (two barrel carb) and put in it, so I never ran the 383.

The torque converter makes a tall gear much easier to tolerate. In drive, it shifted 1->2 at ~ 50 MPH and 2->3 ~ 90 MPH. If memory serves, it shifted around 5500 RPM. The 400 was out of breath at 6000.

It had decent tires, but an open differential. The tires would slip a little but it hooked to the ground very well. It would beet 289 Hi Po Mustangs and 400 Firebirds. Mostly because they were burning up tires and I was accelerating away.

I put a set of 440 heads, that was ported by a local racer, on it, with a monster cam, 1000 CFM carter, headers, etc. The engine made huge power above 4000 rpm and pulled strong all the way to 8000 rpm. It idle about 1500 rpm. What a horrible combination, but I was 17 yrs old and did it all myself. By the way at 8000 rpm 1->2 shift was 90 MPH and 2->3 was 135 MPH. It would peg a 150 MPH speedometer.

Now it had no power on take off, but when it hit about 40 MPH it would melt the tires. It was no fun to drive at all. I destroyed the transmision in about two weeks, and put it all back to normal. In hind sight, I wish I had tried leaving the heads on it, go to a milder cam, and change to a 3.5 rear end gear. At 17 I had built a half dozen engines, but had no idea how to work on a rear end.

The point to my little story is: don't design your engine to fit a rear end ratio. Build the engine you want and then put the correct gears in the rear end.

[cycleguy55]

Originally Posted by olddog

The point to my little story is: don't design your engine to fit a rear end ratio. Build the engine you want and then put the correct gears in the rear end.

Amen, brother.

Merry Christmas to all!