318 Head on a 340 Question

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jefflock

jefflock

69 Dart 408 10.08 best pass so far
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How bad will a set of 318 heads hurt a 340????? Thanks
 
it will be torquey on the botton end but lose it early and then fall off fast.....
 
The 318 and 340 are the same engine in terms of airflow. At least for most of the low and mid rpm ranges. There is .130 more bore, so the valves would have less shrouding. Otherwise, identical. Cammed and built similar, the 318 respondsto the same stuff. I think you will notice your throttle response is way better, and the 318 heads will make more torque below 3000. I think by 4500 or so the ports will become a restriction.
 
For what little i know I would think if you are running the .444 340 cam you would definately be restricting the air flow at all rpm's. But I'm just an auditor. Pick up a set of 70's 360 heads with the 1.88 intakes. you should be able to find a set for 2 to 3 hundred. I have an extra set of J heads. Where are you located? I think I remember reading in a mopar engine rebuild book that you would smother the engine. YOUR MOPAR BROTHER WALT. :coffee:
 
I managed to come up with a set of X heads. It will interesting to how much difference it makes on the strip and the seat of your pants. Thanks for the replies. Jeff
 
Mr Goody,
X heads on a 70 model 340 with flat top pistons need to have the chambers milled down? Are the chambers bigger than J heads? Thanks Jeff
 
oops, sorry i was reading 340heads on a 318! it'll be pretty torquey on the low end. Top end will bottleneck pretty good with those heads however.
 
Jeff what cam and are going to zero deck the pistons ? I think the stock 70 340's pistons came out of the block a few thousands. Someone on here will know. I think you need the compression and right cam to get the most out of those heads. walt :salute:
 
thanks dartman, right now i am putting the drivetrain together. She is still flying the slant under the hood. I chose to do the body and interior first as the car only has 43K on it and I can run it when the sun is shining. My son in law who has built a few novas suggested to do it that way as some guys try to do too much all at once and burn out on it. I still take it to car shows, just don't open the hood, still gets alot of attention. thanks again walt. :salute:
 
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