Rebuilt 340


#1

Hey everyone, I just bought a 340 that has been professionally rebuilt, I am wondering if there is anyone out there that can possibly give me an estimated HP on it. I will tell you everything that i know about it, it has been bored 70 thousanths over stock, roller rockers, high rise cam(I cant remember the numbers of how much longer it made the intake and exhaust valves stay open or for how many degrees of the complete rotation they are but it is quite a significant ammount compared to stock), I have a set of Hooker Headers for it weather or not that makes much of a difference in the HP im not to sure. I bought an Edelbrock Intake Manifold that is quite a bit taller then the one that was on the stock 360 i had in the car to begine with. so thats about all the information i have on the engine if anyone can estimate roughly what I might have it would be much appreciated. Thanks, Colin


#2

Sorry, but there is no way in the world to determine this and especially without knowing the cam specs. There are going to be so many influences on it (ignition timing, advance curve, carburetion, heads ported, oversize valves, etc. that even a wild guess may not be too close.

If you get an honest 1 HP per cubic inch (rated at the flywheel) then you’re doing fine.
Many HP estimates are often overblown anyway. I’ve watched some of these television drag race shows (Pass Time) and got a chuckle or two out of some of those HP estimates the car owners give. “Yeah, it’s about 400 HP” and then they proceed to rip off a 15 second plus run.

That being said, the 340 is one whale of a motor and will run like a bat out of…
Many years ago a friend of mine had a Dart Swinger 340 and he would trade that car to me for my Roadrunner for the evening with the promise we would not hammer each other’s car. Ha, from both sides.
We’ve got a local guy with a 'Cuda 340 that runs mid 10s in the 1/4 and it’s a tagged, street driven car with legal exhaust.


#3

Thanks alot for the info man, i guess the only way i will find out is to take it to a dyno…untill then i will just tell everyone its somewhere in the 8-900 range, hahahaha ya i wish. Thanks again
Colin


#4

Took a look at one of my books and it shows the early pre-smog 340 as being rated at 275 HP at the flywheel. The better figure was the most important one to me - 340 ft. lbs of torque stock.

It would seem to me that with the cam, intake, headers, etc. that both numbers should climb considerably.
The torque numbers are always more important to me than the HP numbers. Torque makes it more pleasant to drive and gives that nice “pulling forever” feeling.

I’ve got a performance small block Ford here that has a beautiful torque line on the dyno sheet. It hits maximum torque at about 1700 RPM and stays straight as a rail all the way to 5800 RPM before it starts to taper off.
Unusual, but nice.

Just curious. What kind of Mopar is it going in?


#5

Tell us more about that Ford…


#6

The builder of the last blueprinted high -performance engine I bought had produced so many simular engines (in all aspects)that he gave me his dyno results. What does your builder say,does he ever dyno his work? His name is Quincy Purcell out of Orange Texas.


#7

I bought an Edelbrock Intake Manifold that is quite a bit taller then the one that was on the stock 360

You bought an intake without knowing the cam or header specs? Dude, slapping performance parts onto an engine without any regard for matching them to the engine and intended application is one way of wasting lots of time, money and HP.

Since you already have the motor, the next step is to get all the information you can from the builder. Then decide how you plan to use the motor and check to make sure the parts you bought match that application and the motor specs. Just trying to save you some $$ and disappointment. Can’t tell you how many times I’ve seen people do it this way and end up wondering why it doesn’t perform as expected…


#8

its going in a 1966 Barracuda


#9

I can tell you one modification you may need to make right now unless it’s already been done and that’s the rear axle.
The '66 Barracudas used a 7 and 1/4 rear axle and a healthy 340 is probably going to twist the rear end out of it if you hammer it often enough and hard enough.

It will take a little hammering, depending on tire size, but if you flog this car a bit the rear axle won’t last.
Many years ago an acquaintance of mine had a 65 Barracuda with a 273/4 speed and he knocked the rear out of that one.
(Granted, he kind of beat on this car a lot though)


#10

And I would just second TwinTurbo’s comment about trying to match things up a bit. He’s exactly right and sometimes more of something is not always better.