Valve lifters…solid/hydraulic/roller tappet/flat tappet?

[xb-60]

I would be quite OK with spinning up a 289 or 302 faster and 'compromising' on torque. And if my proposed gearing doesn't work adequately - and I agree, it would be very much a compromise - then a diff change isn't the end of the world. The way I see it, there's so much more to a Cobra/replica ownership than just bare hp or torque numbers, or acceleration figures (or even max. rpm figures!). There is so much that has to be a compromise because the basics of these cars comes from a design rooted in the '50s and '60s. These are cars that don't have a roof even....the driver is so much more in contact with the noise, the smells, the feedback. To me, speccing an engine for torque on a Cobra replica is like speccing in power steering and air-cond. and a really quiet exhaust.
I'm on somewhat of a learning curve here and I am actually sponging up most of what I'm reading, and I appreciate all comments even if I don't automatically agree with everything presented.
Cheers!
Glen

[blykins]

I agree. You don't need as much torque in a lightweight car. I will encourage you to get some common Cobra curb weights, as everyone tends to think that a Cobra weighs about 2000 lbs. Some of the kits, especially when you add in a full tank of gas, driver, etc, will hit closer to 3000 lbs.

Let me remind you that I've never stressed a high horsepower or high torque engine. What I have stressed is that you forget about picking a random rpm number that you want to achieve and concentrate on making the car usable in the rpm range that you will be in the most.

You can not have a 289/302 that will have great manners and power at 1500 rpm and still make peak horsepower at 7000 rpm. It's just not going to happen.

An engine that makes peak horsepower at 7000 will not only require a 7500 (or higher) shift rpm, but the camshaft required to make peak horsepower at that rpm will pretty much insure that you won't have much at off-idle rpms.

Again, I'm just trying to help.

[zrayr]

Originally Posted by blykins

"................. You can not have a 289/302 that will have great manners and power at 1500 rpm and still make peak horsepower at 7000 rpm. It's just not going to happen.
An engine that makes peak horsepower at 7000 will not only require a 7500 (or higher) shift rpm, but the camshaft required to make peak horsepower at that rpm will pretty much insure that you won't have much at off-idle rpms. ......."

not trying to be constantly argumentative, but........ you don't need much power at 1500 rpm in a lightweight car. A stock Hi-Po flat tappet cam in a 289 K code engine will be quite happy idling at 900 rpm and pull cleanly to the maximum power rpm which is 6000 to 6500 rpm. With just a little head work you can get usable HP beyond 6000 easily, and up to 7000 (or more) is not difficult to achieve.

If the OP wants a 7000 rpm engine, then it seems that once opinions are voiced in the negative, it's would be helpful to set aside any reservations we might have and offer concrete ideas on how he might proceed.

That's why I suggested earlier that he should build a 289 FIA dead-on replica, and then drive the snot out of it. Once he's done that, he will know what, if anything. he will have to change in order to have the car he envisions.

Z.

[blykins]

Z,

It's not all about how much power you make down low, it's about how easy the engine will run and cruise down that low too.

From his description, he's wanting an engine that will cruise around right off of idle but then make peak horsepower at 7000.

There is a difference between making *some* power at 7000 and making *peak* power at 7000. If you just make *some* power at 7000 and the peak is much lower, then there's no use at all in straining the engine and putting undue stress on it at that rpms. Just because you can see 7000 on a tach doesn't mean that you haven't lost 50-75 hp by the time you get there.

I've given many concrete options for him in previous posts. And again, I'm not trying to be negative, but I'm trying to offer advice that comes from experience.

I agree with you 100%. I think it would be more worthwhile to put the peak down lower, say 6000 rpm, then see how the car behaves that way. If it's not suitable, then parts can be swapped.

[undy]

600 rpm idle, 1000 rpm cruise, tremendous off idle power, 7100 rpm rev limit & spins up faster than an aluminum rod destroked 283... sounds like he needs a LS7...

It CAN be done... (given enough $$)

[xb-60]

Originally Posted by undy

600 rpm idle, 1000 rpm cruise, tremendous off idle power, 7100 rpm rev limit & spins up faster than an aluminum rod destroked 283... sounds like he needs a LS7...

It CAN be done... (given enough $$)

A what? What's that?

[undy]

Originally Posted by xb-60

A what? What's that?

Sorry, it's a Chevy Z06, my daily beater. 10.80 @ 130 in street trim, 509 RWHP, 22 average mpg, combined w/ 28mpg on trips. My grandma could drive the thing. It's 427ci though... Ask our friends across the pond about the engine. Unfortunately, in the states it's Cobra blasphemy

Until the Coyote 5.0 came around Ford had lost it's ability to make any normally aspirated horsepower with the intro of their mod motors.

[xb-60]

Originally Posted by blykins

Z,

It's not all about how much power you make down low, it's about how easy the engine will run and cruise down that low too.

From his description, he's wanting an engine that will cruise around right off of idle but then make peak horsepower at 7000.

There is a difference between making *some* power at 7000 and making *peak* power at 7000. If you just make *some* power at 7000 and the peak is much lower, then there's no use at all in straining the engine and putting undue stress on it at that rpms. Just because you can see 7000 on a tach doesn't mean that you haven't lost 50-75 hp by the time you get there.

I've given many concrete options for him in previous posts. And again, I'm not trying to be negative, but I'm trying to offer advice that comes from experience.

I agree with you 100%. I think it would be more worthwhile to put the peak down lower, say 6000 rpm, then see how the car behaves that way. If it's not suitable, then parts can be swapped.

Max revs, or change up revs, or 7000, and max power at ....whatever...6500?....
And at the bottom end, able to take 3.08 gearing at 1500prm ideally. That doesn't mean real grunt at 1500, it means at steady speed, level ground, no driveline snatching. If acceleration required, or slight hill encountered, the a change down to third. Oh, and the weight I'm anticipating is 2350lb
Thanks for your continuing interest guys, I though this one might have died a while ago. I AM actually learning stuff here. Appreciated.
Cheers,
Glen

[blykins]

Originally Posted by xb-60

Max revs, or change up revs, or 7000, and max power at ....whatever...6500?....
And at the bottom end, able to take 3.08 gearing at 1500prm ideally. That doesn't mean real grunt at 1500, it means at steady speed, level ground, no driveline snatching. If acceleration required, or slight hill encountered, the a change down to third. Oh, and the weight I'm anticipating is 2350lb
Thanks for your continuing interest guys, I though this one might have died a while ago. I AM actually learning stuff here. Appreciated.
Cheers,
Glen

I think I know what you mean by driveline snatching....we call it "bucking". You would have that with an engine cammed to make horsepower at 7000 while trying to cruise at an off-idle rpm.

Ok guys.....listen up.

I'm not saying that it's not possible to make horsepower at higher rpms. I'm not saying that torque rules the roost.

I am saying that with this particular car, this particular transmission, and this particular rearend, an engine that peaks at 7000 isn't a good match.

If you'll look at some of the engines that I build for myself (when I have time), you'll see that I like them a little on the revvy side. Most of my engines peak at 6400-6500. I like that. HOWEVER, I don't pair them up with rearend gears that will make them total turds... I normally have at least 3.70-4.30 gears. This goes for my Mustang, my Cobra, etc.

I've also owned some of the modular 4.6L engines that Olddog was talking about. Sean Hyland doesn't need large durations and large lifts because the engines are very small. The 4.6L started out as only 281 cubic inches! You don't need 350 cfm flow numbers to support that. However, these engines made decent horsepower, but they had no torque. My '02 Mustang with the 4.6L was a complete turd at lower rpms, even with 260hp and 305 lb-ft of torque. It received a 4.10 rearend. My dad has a '97 Mustang Cobra with the DOHC 4.6L. It was a turd at lower rpms with the 3.27 rearend. It too received a 4.10 gear so that it would have some lowend grunt and pull to 7000. The 4.6's will also rev easier because they have no pushrods....everything is overhead, so you don't have to worry about valve float, etc. They also have extremely small bores and strokes so the rotating assembly is light. Not really an apples to apples comparison here.

That is what I'm getting at.

You will not find a 302 that makes power at both extreme ends of the powerband. That's not the way engines operate.

So if you want to go that route, you need to make sure that the rest of the car's combination will help you in the best way that you can.

Also, if you have an ERA FIA car, you will find that it will weigh closer to 2600 lbs, plus driver, plus fuel.

[RICK LAKE]

Blykins Brent You can lead a horse to water but will not drink. Let it go. This guys needs to run either a 6 speed trans, change the rearend ratio, build a bigger motor or go fishing. 10 pages of info from guys that have tried the same thing. If he want to have the motor not lug at 1,500 rpms he will need a heavier flywheel and dampener to absorb the firing of the motor under this kind of load. This will damage the motor over time, something will break. He want to turn 7,000 rpms with a stock block, without it being filled in the coolant passages for strength, no main cap support or 4 bolt main. Cast crank pistons and off the self rods. Good luck, it will be a short fairy tale. I REALLY hope that Glen or his friend in the pass seat don't get hurt from flying debrie when this thing breaks. Bell housing only partial protect from flywheel, they do nothing for engine parts. My thinking is a mazda rotary motor with 3 rotors and a turbo. 600 hp and will lug along too. I'm done Rick L.