i have a 71 400 out of a 72 mercury (pulled the heads and checked, definitely a 9:1 compression motor) and i was wondering if anyone has a dyno sheet of this motor with an rv cam, edelbrock dual plane intake, 600cfm carb, and long tube headers. this is pretty much the build i plan and i want to know what most of them run with no overbore and no regrind on the crank.

 

I have a build that's similar, except mine has a .030 overbore. It has a 9.3:1 compression, mild CompCam 255DEH, Edelbrock Performer intake, Edelbrock 600cfm and long tube headers.

 

damn them are some pretty good numbers! did you have to run 93 octane or could you get away with running midgrade without predetonating? also, how's the gas mileage with it?

 

Thanks, the engine builder and myself were pleasantly surprised with the outcome.
I have to run 93, even before the 351M was rebuilt I had to use premium fuel to keep it from pinging. I'm now getting 12.5 - 13 mpg, before it was getting around 10 - 11 mpg on a good day.

 

not bad. i was thinking of getting a summit cam with a slightly higher lift and slightly longer duration. do you think it would hurt the mileage much? i know these aren't exactly gas sippers, but if i end up driving the truck longer than expected, then i'd like to at least keep some money in my pocket haha.

 

It might hurt fuel consumption a little, but I've said before if you're concerned with fuel mileage, you better not drive these old trucks very much. With the price of fuel nowadays I just use my truck to pull my boat occasionally or haul some dirt , lumber, etc. when needed. It's to costly now to just get out and tool around in anymore, especially @ $80.00 a tank full.