The Garage i am working with to rebuiled my 400 states, that it has been bored .040 over ( note: engine block is true, straight and heades and intake fit good ). Everthing looks good. Is this going to be a problem being 40 over? Build up is as follows: 650 cfm 4bbl eddelbrook carb and intake,extreme energy 268 degree cam. forged pistions,3 angle valve grind w/stainlees valves. and headers. Going into a 1979 f-250 4x4,c-6,np-205 w 4.10 gears and 33" tires.
Thanks for the input.

 

.040 is normally the max recomended over bore on the 400. anything over that and you start running into over heating problems from what i've heard. although others on this site have gone up to .060 . i would suggest rebiulding at .040 unless the block has to have another over bore. your set up sounds pretty much like what i've got, except my 400 is .030 . mine runs great and has plenty of grunt. hopefully some of the guys runnning .060 will drop you a line and give you some suggestions.

 

you have pretty much the same set up as me, except my 400 is .060 over. i have a edel. 600 cfm, edel performer intake, flat top pistons, mild cam..stainless valves, the 3 angle grind as well, hardened seats...crank ground and polished .020, no hedders yet, in a 79 250 4x4, 4.10's amd a little under 32" tires, Np-203 case with doug nash 2 part time kit...

gets me 10 MPG...pleanty of power, no overheating problems, although i have to re route fuel lines away from repositioned exhaust,

fed by a carter elec. fuel pump. Its a good set up. where i am, i run 75 MPH at 3000-3200 rpm, and have had it up to just about 5000 rpm a few times.

Im looking into a holley carb now though, the edel has the cfm i need, but isnt the carb for my build...with a holley i think there would be a decent increase in my power.

Hope some of this helps for a comparison. Let me know if there is anything more you would like to know.


---JOHN

 

The 400 has the material in the casting to go 0.060 over with no problem with core shift or out-of-line bores, etc. As posted, the problem arises with it trying to overheat. However, if push comes to shove, companies like TRW and Perfect Circle offer sleeve assemblies for the 400's. Any good and competant machine shop can install them, no problem. With the usage of varying diameter sleeves, one can get several lifetimes out of a 400.

 

Thanks for the info and help