340 Horsepower? • The Dodge Challenger Message Board

by **shatar4** » 11 May 2004 23:26

Can anybody take a educated quess how much horsepower a 1971 balanced 340 with 10.5 x 1.00, steel crank, cam with 570 lift, 340 j heads with triple angle valve job, bronze seats , six pack set up would be? Thanks

by **dave-r** » 12 May 2004 7:26

Would need to know the cam duration. The duration determins where in the rpm range the engine makes it's peak torque. The higher up the rpm scale the more HP it has. Although I could make a rough guess it would be better if you could supply that information or the make of the cam so I could look it up.

by **shatar4** » 12 May 2004 8:10

sorry, forgot that. It is 296/296 .050 duration

by **dave-r** » 12 May 2004 9:09

I will plug the numbers into Desktop Dyno tonight.
(unless someone can do it before then?)

by **shatar4** » 12 May 2004 12:08

Thanks dave-r

by **dave-r** » 12 May 2004 20:12

That is a pretty wild cam for the street.

Anyway. The desktop dyno came up with power in the region of 400hp @ 6500rpm and 370lbs of torque at 5000rpm.

A lot depends on how good the heads and general machine work are.

You would have to rev it pretty hard to make the most of the power but having said that it makes some torque lower down the rpm scale too. It will have a rough idle and little manifold vacuum though.

I think torque will drop off a lot faster on a real engine than it does on this chart which would pull the power off faster after 7000rpm.

by **shatar4** » 12 May 2004 20:35

Do you think I should put a little less wilder cam in it? what would you suggest?

by **dave-r** » 12 May 2004 20:40

What are you going to use it for?

Will it see much track action or is it just fast street you are wanting?

by **shatar4** » 12 May 2004 20:47

Just street action. I might take it to the track once or twice but thats about it. Just to see what it will do.

by **dave-r** » 12 May 2004 20:51

Give me 10mins.

by **dave-r** » 12 May 2004 21:07

OK try this one.

Hughes Engines Cam HEH-3742-AL.

The cam you have seems impressive but compare the torque curve with this one. Look how much more torque this one has.

Also although peak torque seems a lot less these two cams are making about the same power in the rpm range you can actually use i.e. below 6000rpm.

by **shatar4** » 12 May 2004 21:13

That one does seem better. Thanks Dave. I'm ordering right now.

by **dave-r** » 13 May 2004 7:09

Hell. You don't hang around do you?

The limiting factor here is the heads. With ported heads you could use a smaller cam and still make the power. You would loose a little torque though in the idle - 2500rpm range.

Bare in mind that you gave me the bare minimum of information on your engine. The more detailed the engine (esp the heads) and cam spec the better the results from the desktop dyno.

by **72 Challenger (Hans)** » 13 May 2004 16:26

Port the heads, throw in a 9" converter and you're ready to hit the streets too. You know, there are lots of variables out there! All depends on how do you want it to drive around town.

Start up first time, good fuel consumption, low end torque, shift @ 5k or start up 3th time, poor fuel consumption, top end, shift @ 7k...

And how about rear end gear ratio's here... don't expect to fly the 60ft with that cam and 3.23's but put in a 4.30 instead and it's a blast. Need more specs of the car to give some proper advice. For example I have 242@050 duration with 528 lift and I think it doesn't have enough top end power, but throw in a 3.23 gearing and it will seem to have to much top end...

by **shatar4** » 13 May 2004 16:47

After I pulled the heads off of the engine, I found that it was bored .60 over. As far as the rear end goes, I have 3.91, 3.23, 3.55, 4.10 gears in 489 cases to choose from. The trans was rebuilt with a B&M shift kit. The intake, I could have either the six pack or a 750cfm Edelbrock with a Torker 2 intake. So I do have some other things to put on the car if it helps improve the performance on the street. That was going to be my next Q is the torque converter, What stall is best?

by **72 Challenger (Hans)** » 13 May 2004 18:45

As far as the trans goes, the B&M rebuilt is just fine. You rebuild it by street/strip specs or what? For converter, first decide the rest of the combo. With top end power in mind I would go for something like an 9" I have a 10" but somehow I'm not satisfied with it (sorry Graham - other people --> I picked the rpm and so myself so nothing to blame graham) But do pick a bigger trans oil pan for heat. The B&M alu pan is a good one.

If it was mine I would leave that cam you have, but adjust the rest of the combo. So with this cam you have lots of power up top, so better use the following; pick the manifold with the best upper rpm range power (torker 2 I believe), install 4.10 gearing, flow the heads, port match the intake. It will be the most expensive choice I guess but also the most street/strip. But with a good converter you can safely play with it on the streets too. Use roller rockers too with that cam, but I think you already have them? Shift point for the optimum results (read strip) will be around 6500-6600 I guess. And fit a bigger oil pan... with HV pump. Don't aske me how I know. Easy 12's should be on your way!

by **shatar4** » 13 May 2004 19:14

I have everything (8qt oil pan, HV pump, gears, intake) so it won't be that expensive. I've never had heads ported and matched so I have no idea how much that is. Thanks for your suggestions. They sound very do able.

by **dave-r** » 13 May 2004 21:51

That cam i gave you the spec of will like a 3000 - 3500 stall convertor. 3.91 gears will be plenty for the street too.
It will really wake up with ported heads. Ported iron heads cost about $800. Edelbrock ally heads work great right out of the box but cost about $1300. They are great though.

The cam you had first works at too high an rpm for a mainly street engine.

Sorry to hear the block is 60thou over. that means it is very likely the bores will flex a bit which will loose some power. It will still make plenty for the street though.

by **72 Challenger (Hans)** » 14 May 2004 9:19

Oh wait a minute, missed something...

296 dur @ 050 ?? :shock:

Must be a misstype as this will be around in the 340 adv. range. NEVER saw a cam with that much duration and 'only' 570 lift.... Let alone for a SB. My new hemi cam 'only' has 283@050 and already a shiftpoint towards 7k rpm. Something's not right.

When I plug in 296 adv. / eddy head flow (same as well ported irons) single plane manifold / 750cfm / 10.5 CR / Headers is gives me the following peaks; 484#6500rpm HP & 433@5000rpm TRQ This way I would get an around 4000rpm converter.

Should be a screamer when adding 4.10's, that said, better get some dragradials pretty soon...

Hmm, Dave, doesn't happen that often we have such a diff. opinion ;-)

by **dave-r** » 14 May 2004 14:33

If he was doing a lot of racing I would agree with you Hans but his words were;

Just street action. I might take it to the track once or twice but thats about it. Just to see what it will do.

Up to my eyes in work and other stuff at the moment so couldn't give this problem my full attention. That must be 'advertised' duration yeah?

I need to look at it again.

by **dave-r** » 14 May 2004 16:54

Yeah I did take it as 'advertised' (seat-to-seat) duration. I must have realised it was not at 0.050 lift.

That cam I picked is the modern version of the cam I use in my 440. I honestly would not like a wilder cam than that in a street car.

by **72 Challenger (Hans)** » 16 May 2004 12:35

Shatar, is the cam a hydraulic or solid one? The numbers I came up with were with the solid version.

Just street action. I might take it to the track once or twice but thats about it. Just to see what it will do.

That's the same way as I use my car, street action & 3 times at the strip. But I definetly would like a bigger cam... It's just a matter of how Shatar wants his 340 to act up. For me, it has to run fast but sounds nasty too. I like to rev it. Don't forget it's a 340 which liked to be reved too. When all components match eachother it will always be faster then a low rpm machine but there are things that much be taken care off when turning rpms. (high volume everything, roller rockers, converter, gearing, fuel lines, valve springs means more wear, head work, high cfm fans and so on)

A little off topic thing; Andy (Yeah, I know Dave) is running a 340 with a 8800rpm shiftpoint... :shock:

Man would I love that! If I ever built a light A-body or similair... watch out!

by **dave-r** » 16 May 2004 18:07

And as long as Andy does not touch anything on it it will run fine! :lol:

You seem to have Andys warped idea about what constitutes a STREET driven car Hans. :wink:

I know you said years ago you never drive very far in your Challenger.

Andy thinks Street legal is the same thing as street capable. In his head if he can drive to the end of his drive or down the street for a few hundred yards that means it is street drivable. None of his cars will drive 300 miles to an event like mine has to. None of them will take him to work and back. None of them are any good for going to the shops or having a nice drive out to the beach with the wife.

That is to take nothing away from his Hemi Dart and whatever else he has right now (what has he put the small block in?). Ted Evans did a FIRST CLASS job of building that Dart for him. Ray Barton does a FIRST CLASS job of building his engines for him.

But NONE of them see much in the way of any action either on the track or off.

So when you finally get this hemi in your car you had better drive it over here under its own power and prove to me your car is streetable Hans!

I will buy you a BIG drink if you can do it!

by **dave-r** » 16 May 2004 19:09

Just remembered the small block will still be in "tweety" the RHD Barracuda. He was going to ProCharge that engine last I heard. He had taken all the NOS stuff off in preparation.

by **72 Challenger (Hans)** » 17 May 2004 15:27

No way he said his are streetable Dave as ours are. But ours won't run down the strip putting down high 9's with a SB in it, and N/A uh! Just told me 8800rpm shiftpoint and HOPE to be able to run it on the streets, for a mile or 2 he told me. Nothing more then that.

He his very short in time since a couple of months as, don't know if he likes it if I tell this, his wife got into a VERY serious accident with their regular car. Has been on the IC and everything else. Already some months ago, but still VERY busy trying to recover. Hard times for him these days.

Yep, this 8800rpm SB will go into Tweety and a pro charged Nascar SB in some station car :shock:

Looks like fun.

And oh yeah, when the hemi is in it sure will be capable of being driven to the Nats. If I supply the fuel... So guess it will be trailered anyway. Not because of the engine but of the fuel it wants! What MPG would you think, 528, BIG lumpy cam, 1150 dominator, 4.10's w/ 28" tires...

by **dave-r** » 17 May 2004 15:42

Yeah I know about Sheri's accident. I sent him a message when it happened. She was lucky not to be killed. I hope she continues to recover and I hope she makes a full recovery.

She is a totally mad driver! So is he!

He was demostrating the power of his Subaru to me when we were over there. Doing 95mph down the country lanes.
Fair enough you might think?
Yeah well it was the end of December in Upstate New York and the road was covered in snow and ice!
He is a good driver though. Just a bit too reckless for my nerves! :roll: