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A buddy of mine has a 351m/400 in a 77 f-250 4x4 and it has a 2brl. he has a hard time getting up to 70mph with it if he floors it but if he backs out of the throttle a little it will climb faster to 70 but he has to work at it we replaced both fuel filters timing is at 12' it's a 4speed I told him that he should pull the motor and put in a 460 he wants to but hes short on cash but for now can we put a 4brl intake on this 351m/400 with 600 edelbrock and pull this off later and put it on the 460 I know it would be cheaper just to tear into the carb and clean it but he's used to the power of my truck and would like it more like mine power wise. I just figured he could use this later anyway but I don't think that 351m/400 would be the same intake.
PSYCHO 1977 F-250 4x4 472cid race truck,PSYCHO2 19771/2 F-250 4x4 472cid and goodies to go with it!!!,1987 Mustang GT 5.0 H.O. SNAKEY2. 1988 Mustang LX 5.0 H.O. Spectator Eliminator!
Not worried about gas mileage just performance!!!
Sounds to me like either there is some junk in one of the carb jets, It is running to lean wide open, or maybe a weak fuel pump not keeping up with the engine.
I had the same problem your friend is having with the 400. The remedy came with an intake manifold, 600 carter, headers (biggest improvement), and a comp 268H. If he is going to keep the 400 for a while, he might want to invest in a split duration cam, especially if he keeps the manifolds.