info greatly needed. any body out there bored their 400 60 over ? or is this going to far on a 400m thanks.

 

The max overbore is .040" but people have gone .060" and some of them have run OK, others haven't.

FYI, no M in the 400. The 351C/M/W engines were identified by letter suffixes.

 

I saw a 400 go .080 over once but don't know how long it lasted. Don't take a chance going .060 without having the block sonic checked. There's no other way of knowing about core shift or if the cooling system was maintained properly over the last 25-30 years. It's not that expensive.

 

My 400 is .060 over. No overheating or vaporlock problems after it got worn in. Its worked for me, It cools fine, and i live at 9118'...

Have the block checked first though, just to be safe, and take it to someone who knows what theyre doing.

 

I bought a NAPA short block that was .060 over. It was the first engine I ever assembeled, and still runs great 30k miles later. Doesn't overheat, and has full fan shroud.

 

I recently took apart a 060 400 that had unsolvable heating problems according to the mechanic- didn't know it was 060 until we broke it down then he said 060 often leads to heating problems-lack of metal or something.

I'm not real comfortable with 040 but thats what i'm building. theres too many blocks around to build a 060 imho.

 

Roger, did you check to make sure the head gaskets were on the right way as you took the problem 400 apart? i just don't buy into the "bored too far causes a hot engine" concept.

 

When i did my last 2 400's they were both .060 over. both still goin strong. What we did notice when it was bored was that we had to use the head gasket as a guide so the firing ring on the head gasket would not overhang into the cylinder . We used the largest bore head gasket felpro makes. The cylinders had to be bored slightly off center. I recomend always using torque plates as well.IF sonic testing is availble definetly have that done. Saves alot of guess work. I will add also that the engine shop i worked in a few years back, routinely bored 400,s .060 with no problems i knew of in the 7 yrs i was there.

 

grclark; wasn't my motor- i got it after it was out and stored for a while so I don't know what they did except put a bunch on silicone down two jackets in the block- ended up being water jackets I think. lol....mechanic didn't know that...maybe the builder didn't like the customer. funny how my memory fades...not

 

Boring the block to match the gaskets is NOT a good idea. Find a set of gaskets that fit properly. Gaskets can be way off at times. If you guys only knew how they were made... The bores must be aligned with the crank and thrust bearing.

 

Author George Reid says a 351C, 351M, and a 400 can go 0.060 over.
Make sure your block isn't susceptable to water jacket cracking above the lifter bores.

 

thank you all for your very helpful info. i took it down to the machine shop today and they said that it would clean up .040 over and be fine. even with a crank case full of mud & water this 400 still had a ton of power. these motors ROCK!!! thanks again...