Horsepower Estimate?

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3RD Duster

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Anyone want to give me a horsepower estimate? This is all I know about the 340.
1973 block
Bored 30 over
J Heads (probably not ported)
New pistons and rods (no idea what they are)
New lifters (?)
8.5:1 compression (could be higher...not sure about head gasket thickness)
474/280 purple cam
RPM Air Gap intake
Holley 650
Hooker Headers

I probably won't be able to answer any other questions until I can find the guy who built the engine. Thank you.
 
Run a full comprehensive compression test for us and see if he knows what the cam degreed in at. That will let us get a halfway guesstimate of your actual compression ratio as well as overall engine health.
 
Here's a video on basic mods to a low cr 360, give you an idea what each mod will do.

 
290 hp at the crank. I think compression is the limiting factor.
 
Thanks for the responses. A lot of the information I collected was 2nd hand. I have written a letter to the guy that built it. Hoping he responds with better info. I was mainly hoping it would be at least somewhere near 70-71 stock numbers. It does run pretty strong for my needs.
 
3RD Duster said:
Thanks for the responses. A lot of the information I collected was 2nd hand. I have written a letter to the guy that built it. Hoping he responds with better info. I was mainly hoping it would be at least somewhere near 70-71 stock numbers. It does run pretty strong for my needs.
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At the end of the day it's bout seat of the pants and if it does what you need, the HP number wont change that :)
 
3RD Duster said:
Thanks for the responses. A lot of the information I collected was 2nd hand. I have written a letter to the guy that built it. Hoping he responds with better info. I was mainly hoping it would be at least somewhere near 70-71 stock numbers. It does run pretty strong for my needs.
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If you're happy with, don't worry about the numbers. That'll drive you insane. Just drive it and have fun.
 
I think everyone with a performance car kind of likes to have an idea, does it really matter if it's 340 or 360 hp or whatever on a dyno under ideal conditions, probably not, which translates to who knows what in the car, especially if not tuned, geared, stall etc.. to get the most out of it. Yes ultimately it matters more how enjoyable it is.
 
Just do like everyone in the 80s did... if it has headers and a intake (not even cam) it makes 500hp.
 
273 said:
I think everyone with a performance car kind of likes to have an idea, does it really matter if it's 340 or 360 hp or whatever on a dyno under ideal conditions, probably not, which translates to who knows what in the car, especially if not tuned, geared, stall etc.. to get the most out of it. Yes ultimately it matters more how enjoyable it is.
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This.
It’s your car to make it what you want…
If you are happy with it that is all that matters.
 
I don't understand all the hemming and hawwing. How much power it makes, might not be important to you.... but maybe it's important to the OP.

Here's the way I'd approach the question.

First, how much did the original car make in all its smog era glory? (About 285 HP, GROSS NOT NET).

Second, how much might each of the modifications add to that?

Intake: 10, headers, 10, cam...20? Added displacement of going 30 over... another 10?

So if guess around 285+50=335.

You can bump that up a bit more with a decent tune.

Also do we know for a fact it's still running low CR pistons? Do us a favor and run a compression test.
 
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Mean416 said:
I don't understand all the hemming and hawwing. How much power it makes, might not be important to you.... but maybe it's important to the OP.

Here's the way I'd approach the question. How much did the original car make?
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There is no way to know.. being a 340 people will say the factory lied about the power... so it could be 265hp or 750hp and spins to 8000 all day...
magic.gif
 
Icetech said:
There is no way to know.. being a 340 people will say the factory lied about the power... so it could be 265hp or 750hp and spins to 8000 all day...
View attachment 1716286848
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You can know based on an abundance of readily available data and published dyno tests. @273 posted the holdener tests which to me prove that even a 360 smog motor can make some good power with simple mods.
 
Mean416 said:
I don't understand all the hemming and hawwing. How much power it makes, might not be important to you.... but maybe it's important to the OP.

Here's the way I'd approach the question. How much did the original car make?
Click to expand...
I find It's generally one of the usual questions someone will ask me about my car. What is it, what's in it and how much power ?.
 
Mean416 said:
I don't understand all the hemming and hawwing. How much power it makes, might not be important to you.... but maybe it's important to the OP.

Here's the way I'd approach the question.

First, how much did the original car make in all its smog era glory? (About 285 HP, GROSS NOT NET).

Second, how much might each of the modifications add to that?

Intake: 10, headers, 10, cam...20? Added displacement of going 30 over... another 10?

So if guess around 285+50=335.

You can bump that up a bit more with a decent tune.

Also do we know for a fact it's still running low CR pistons? Do us a favor and run a compression test.
Click to expand...
I generally go by the heads for the engines power potential and look at the rest of the combo to guesstimate how much (%) of that potential is probably being used.
 
Make a pass at the track and see what Wallace says.......
 
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