400 to 390 question

[Shotgun29]

Looking to put a 390 in a truck that had a 351M/400 in it. I am wondering if the 390 would bolt in where the 400 was? Or do I need to switch bell housings?

[70_F100]

Yes, along with a lot of other stuff...

[hotrodfeguy]

As much as it pains me to say this stay with the 400.

[ToughOldFord]

If it's a 351M then bolt in a 400. Valve cover tag should tell you, 351M/400 family then tell you which one it is. The 400's better, the 351M is a turd IMO.

[BobbyFord]

If it's a C6, the bellhousing does not come off.

[ToughOldFord]

Engine stands won't be right either, exhaust more than likely won't fit...

[fordman]

lets recap then. bellhousing pattern is different for both engines. the exhaust wont be the same. and the engine perches on the frame are different. if its an automatic trans c6 you have to swap the whole transmission out for one that will fit. you will also need all of the transmission accessories. kick down rod **** rod maybe a new driveshaft. or get a longer or shorted one. bolt on yoke vs slip yoke can be a problem also. you probably have a slip in yoke if its a 400 C6. the fe trucks came with a bolt on yoke on the c6.

[BobbyFord]

We don't know what engine stands are in the truck. 351m/400 wasn't offered.

[fordman]

thats true i did go on a assumption that the right ones were used to mount the 400. but maybe not. a 351m will fit in fe perches it just sits the motor in there a little off toward the front i think. or it might tip it back i cant remember which.

[ToughOldFord]

Another option if you like cubes might be a 460, you'd still need to change the engine perches, but from what I understand, (someone verify please), is the 429/460 uses the same bell pattern as the 351m/400.

Keith's engine perch page shows the 351m/400 use the small block perch. But Bobbyford's right, the correct ones might not be in there.

[fordman]

yes it is the same bellhousing bolt pattern.

[DuckRyder]

Since 67-72 ford trucks were not offered with 400's in order to properly answer this question we will have to figure out what was done to install it.

The FE engine family (the 390 is an FE) has its own bellhousing bolt pattern so the C6 will have to be changed along with the engine perches and exhaust in all probability. You will probably find a lot more stuff that has been hacked along the way..

[fomocoguy]

If it's a bump and it looks to be the original stands it may have been an original 302 truck. The perches are the same for 302's and 351M/400's...

[ToughOldFord]

I think the OP died.