some questions on a 340 challenger

[Chryco Psycho]

factory single plane ?

[71chally416]

The "M-1" that MP sells. It's probably more $$$ than the Victor though but is just as good. Definately DON'T use the old ED single plane manifolds like the old Torquer. They were horrendous and the prices they sell for used reflect that. I think they have a newer better design now but I have no experience with that.

And generally speaking about SB Mope intakes, the old dual plane LD340 is only 5hp off of the Performer RPM and has bigger internal passages. It's a very good Intake for being an old design and it has a heat crossover for those that drive in cold weather that can be blocked in the summer. If you're building a motor from scratch and you can pick one up for $50/75 at a swap meet (that doesn't have stripped out threads) I would say to buy it and invest the $150~ you saved not buying the RPM on something else that gives you more than that 5hp you lose vs. the RPM. A cam & lifters for instance or a better carb. You can even paint it and have it look like a stocker. It works a hell of a lot better than it looks!

[PlumCrazyChris]

I know this is probably late in coming, but I noticed no one mentioned checking your fuel pressure.  The reason your falling down near the end of your run could be that your carb bowls are running dry.   Try to spray a motor like that with low fuel pressure and your gonna burn it down.   Go pick up a pressure guage at Harbor Freight for $15 and make sure your getting enough fuel. 

Also, MP makes a decent (cheap) 2500 stall converter for about .....$250?.  Well looks like they doubled in price since I bought mine several years ago. 

I hope it worked out for you.

Chris

[72hemi]

I was at a Mopar Drag racing event this past weekend and talked to a guy with a 70 Challenger that was consistantly running around 12 flat in the quarter. He had a 340 with 10:1 pistons, stock rods, stock crank, gasket matched X heads, harland sharp roller rockers, weind single plane manifold, Mopar .528 purple mechanical cam, demon 750, mallory ignition, headers, 4 speed, and 4.56 gears. The only lightening of the car was the removal of the back seat and passenger seat. No spray, no nothing else, just a mild 340. hope this information helps some, figured since this combo was in the ET range you are looking for.