Horsepower Estimate?

3RD Duster said
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.

Sorry, but in my humble opinion, we don’t have enough data, and you said that some of it was second hand. J heads can accept 2.02 heads, but I believe they came with 1.88 intakes. It could be anywhere between 250 and 300HP.

4mulas said
250-260 ish

Probably pretty close, maybe a bit higher.

273 said
Mid high 300's.

I kind of doubt that. With low compression and unknown valve sizes

273 said
So it's got less than stock ?

Probably; with low compression and smaller valve J heads.