i recently pulled the the motor from my 77 f150 its suposed to have the 351 but i havent been able to measure the stoke yet. anyways im planning to do some head work and ive noticed that there are no themactor bumps . i know that the heads where replaced from a merc. of some sort but i dont know what year and i was hoping that somone could tell me. i've never heard of this for a 335 series motor are they good heads anyways thanx for the info

 

Not sure about your themactor bumps, but the 335 heads are great. The 2V heads produce plenty of power at low RPMS and generally have larger ports than most intake manifolds...at least the lower RPM intake. I used the 2V heads on my truck and had to port the intake ports on my Edelbrock Performer 400 because the head ports were larger.

If you have the 4V heads, you have some great quality, high priced heads, but they are better for racing and higher RPMs, than street driving. Those are more rare than 351M 2V heads, though.

Is your engine a M or a C? That will make a difference in what heads you have. I was referring to the M heads. But I believe the C heads are ven better.

 

The only difference between the 351C 2v and 351M heads is the later M heads have A.I.R. ports for emissions and slighty larger cambers (1-3cc). The 351C would have this if it was produced past '74. I don't know if the '74 and earlier 400 head have the same heads as later ones.

Grind those bumps out of the exhaust ports on 351M/400 heads and they flow the same as 351C 2v heads.

 

The heads on my 400 are from 1971, they dont have the bumps in them. You can get the casting number off the heads and figure out what year they are.

 

what numbers and where should i look for them. also i measured the stoke and it is a 400