[DAVID GAGNARD]

Troy;

Actually a single plane intake is better for top rpms and a dual plane is better for low to mid range rpms,(I'm running a dual plane Edelbrock Performer Rpm),either of the ones you have should work just fine.... My setup is very similar to yours,timing about the same,I think I have a top end of 34 degrees and run a Holley 600 double pumper,but have had everything from that 600 to a "built"750 on it and two or three in between. I'm running more compression but I would not think that would matter that much.... Something seems way out of wack with your dyno #'s,dropping off too soon for your cam.... Also,ask about how the cam was installed,straight up/advanced/retarded,this could also have a big efect on top rpms....

As for as spring pressure goes to get to 6000 rpms you would need a minimum of around 120lbs. on the seat give or take 5 pounds or so....I'm running 125lbs. seat pressure and have no problem with 6500 rpms,once while doing a burnout at the dragstrip and not paying attention to the tach I had it would up to 7100rpms in second gear.....

Something surely seems off for your motor to fall off that quick at that rpm. Seems that cam should pull strong thru 6000 rpms.... Mine is only 272 duration and 484 lift,a lot smaller than yours and pulls good to 6000rpms,after that it falls off but I do not think near as fast as your motor did....

Hope you find the trouble and keep us posted....

David