I have a 1981 F-150 how much work is involved in replacing my 300 six with a small block? The truck has a manual 4 speed in it. Do I have to change anything major or will it slip right in and one other thing what is the best small block to build 351 or a 302?

 

351 is best. You have to grind the motor mount perches off the frame, and go get ones you have ground off from a junkyard truck with a v8, and bolt them in place. Then theres little odds and ends like throttle cables and some wires, and a flywheel to match your v8 engine.

You can get a v8 from any Ford or Mercury car or truck, but you have to make sure it has a rear sump oil pan. Usually you have to go to the junkyard and get one of those too, with the matching dipstick, oil pump pickup, and the main bolt stud to hold the pickup in place.

 

Definately go with the 351 a heck of alot better of a motor than the 302.

 

If you change to a 351W, you need to change the engine brackets.

EOTZ-6028C

EOTZ-6029C

Not sure which is left or right.

I had the same idea, same truck, '81 F150 4.9L---- but.......................

sckootter578, Welcome to FTE.

 

ok thanx is there a diffrence between 351 modified and the 351 winsor and how do you can you tell the diffrence between both? getting back to the sump pump basicly I a looking for a complete engine with oil pan and dipstick attached does the year matter? I plan on a total rebuild of the engine.

 

Try this site.

http://www.fordcobraengines.com/351c%20Differences.htm

 

The 351m has 8 bolts holding the valve cover on, and the 351w has 6 bolts on the valve cover.

The 351m will not bolt up to where the 300 six was, unless you get a different bellhousing. The 351w will bolt to the 300 bellhousing. The 351w is generally considered a better engine than the 351m.

If you want an engine that fits right off the bat, then stay with a 80-up truck or bronco engine. It will have the correct exhaust manifolds, and if you get the whole vehicle, you can get the y-pipe and all the other little things too.

 

yea that y pipe is only about 300$ im gettin a 351w tomarrow guy says it came out of a 85 4x4 just like mine i have been lookin for a exhaust kit for it and stock exhaust is about 200+ with out the y pipe go with the 351w for sure

 

so the y pipe is diffrent also. I dont havent have to worry about that if I am going to run true duel exhaust right?

 

if u run true duel u dont need the y pipe but will still need cats for the trucks exhaust dont think 80 is old enuff not to have them not sure tho a cat can run 40-90$ea depends on what u get really ive been told that it would be cheaper and sound lots better then goin with stock or tryin to fab a kit your self was told by a few part guys that a exhaust shop would be the way to go if u wanted true duels

 

what about his bellhousing, and pilot bearing or bushing that he will need??

 

83 is the last year without cats to leagally pass but if you go into an exhaust shop make sure the sticker on the core support sould be on the left side of the hood catch is removed or they will not touch it because technically if it come from the factory with cats it has to always have cats so scrape it off and you can you should be fine

 

the easiest way to tell if it is a modified or a W motor is the way the headers mount holes are alined the w motor is straight across left to right the C, M motors the mount holes are diagonal across

 

the bellhousin is the same pilot bearing not sure the starter is the same flywheel is differnt its about 80$ for a new one heck i think u can even use the same bolts that are in the inline 6 for the bellhousin clutch is the same so if u got a new/very little used clutch that will work but still not sure on the pilot bearing ill do some checkin tomarrow and try to get back with ya on that
srry had to edit its only true tho if he goes with a 351 windsor the 302 300 and 351w/ho used the same clutch starter and bellhousin