Need to make a decision fast 5.7/6.1/340
This spring i bought a 70 duster with a tired mild 360. Now after a summer of my foot on the pedal she is real tired. Im debating on throwing a 5.7 hemi in for performance and economy. I want a street/strip car but i also dont want to pass everything but a gas station.
The guy i bought the car off wants to sell me a 340 with 9.5 pistons, steel crank, with headers and he has a set of edlebrock heads that need to be machined. He wants $4000 for the setup but the way i look at it is thats $4k for a used motor. He claims around 3k miles on the build. I also want more horse than what he claims in that motor. Im shooting for 450hp
Im womdering if someone who has done the 5.7 swap can tell me any pointers they have with problems they ran into and a round about price to do the swap. Im not looking to change the K member or anything makor like that. I PLAN ON putting my. 727 behind the 5.7
I've done all 3. I used to work in a cylinder head shop in n.j., not far from Raceway Park. Here what I noticed. The 340 with early batton w2 heads, and a .528 mopar cam, made about the same power as a 5.7 with the comp with a medium size comp cam, in the same 1969 Barracuda 727, 3.91. The difference was the 340's power was at a much higher rpm, and the 5.7 wasn't what I would call torquie, but had a much flatter curve, and was a better street engine. (That 340 with a manual trans would be more fun, but not necessarily better ) The pocket ported heads of the hemi flowed much better than the w2 race head, as a matter of fact they flowed better than a 23 degree chevy race head. The hemi's street behavior was much better for daily use. One thing nobody ever talks about is the hemi's cam base circle. The cam base circle of the 340 is about 1.310, and the hemi is about 1.615. So while the two engines might be chosen with cams that appear to be similar-numerically, in duration, and lift, the hemi cam might actually be a lot bigger, but acts smaller, Plus the rocker arm ration is 1.6, and the push rods, are a lot shorter, and lighter, which means there's less weight to move in the top end.
I put 6 years of hard driving on my 340, and eventually melted the mill down, at a grossly excessive illegal speed while racing a Porsche up the blue mountain. ( the fella was some rich guy in a convertible, holding up traffic, while on his cell phone. Once the lanes split into two, and I tried to pass him, he decided it was a race, I thought it was funny to go door to door with him since 3.91 gears at 6500 rpm's, make it tough to use a cell phone. ) When I arrived to where I was going the car never started again, the crank walked, than the motor was sold to that know-it-all from M.A. magazine. ( who stole a carb fro my garage.) The 5.7 had 7 yrs of hard driving, and eventually was sold to an off roader for a jeep, and is still running, granted he change a few internal parts for his application. The 340 holds the hearts of millions, but I think the hemi is a better engine, and your 360 might just need a rebuild, some minor head work, and to pump up the compression a bit. ( they love compression.)
