Is a 78 model 440 out of a RV a good block to build??

[69wannabe]

I picked up a 78 440 RV engine last year for a great price and later in the year I purchased a 72 steel crank, factory rods with ARP rod bolts and a set of 2355 TRW pistons all balanced and ready to assemble. The pistons are 30 over and I was wondering if the 78 block will go 30 over without any cooling system problems. I have read that the 76-78 blocks are thin wall casting blocks and are prone to running hot if bored. I'm hoping to go 30 over with it and start getting the rotating assembly together soon. Another question I have is about the main bearings, There are different part numbers for the 72 engine and the 78 engine and since I will be running the 72 steel crank instead of the 78 cast crank which bearings would be the right one's?? Just planning on a good street build with a comp XE274 cam, headers and a 750 holley carb. Should put me in the 450hp range and be very drivable and street friendly.

[heyoldguy]

There is no such thing as a thinwall block. If one can afford it, it is best to have the block sonic checked before boring, but .030" over should be safe. Order the main bearings for the year of block. The later blocks use a thrust bearing with a wider flange. You can use an early thrust bearing on a newer block but you cannot use the later bearing on an earlier block.

[69wannabe]

That'll work!!! You know you hear all kind's of different stories when it comes to the later model cast crank engines verses the early steel crank engines. Good to know about the bearings, I just knew there were different part numbers but I didn't know what the difference was between the two.

[69CoronetRT]

Here's a pretty good read on the differences in blocks: http://www.440source.com/blockinfo.htm

[myk]

Hmm...based on a cursory reading of that article, one could argue that the later the block, the better...

[Cooter]

Wonder why did Mother Mopar NOT recommend boring over more than .020???
I'm all but certain that THIS is where the "thinwall block" story got started. Could it have been because of metal urgy with the later blocks being made of a softer metal?

[firefighter3931]

Wonder why did Mother Mopar NOT recommend boring over more than .020???
I'm all but certain that THIS is where the "thinwall block" story got started. Could it have been because of metal urgy with the later blocks being made of a softer metal?

It's more to do with core shift than hardness. 

Lots of late model blocks out there making big power and surviving just fine. 

Some very good reading on BB engine blocks : http://www.440source.com/blockinfo.htm



Ron

[Cooter]

My brother back in 87 bored a 69' 440 "HP" block .030 and one cylinder. Went into water.

[69wannabe]

Wonder why did Mother Mopar NOT recommend boring over more than .020???
I'm all but certain that THIS is where the "thinwall block" story got started. Could it have been because of metal urgy with the later blocks being made of a softer metal?

I have read this same thing in a big block rebuilding book and that's why I asked the the question about the thin wall casting's. Either way i'm gonna send it on and get it bored and hope for the best!! According to the article there is no difference in thickness between any of them so that clears up my thin wall casting questions.

[flyinlow]

My 440 is a '76 Block similar to your "78.  Bored .030 over no issues. 32K. miles so far.  Latter blocks have stronger motor mount ears.   

[68CoronetRT]

78' Motor Home cast crank 440 here. Mild build and so far so good. If you search my name you can find my write up and all the motor specs. Runs real good thanks to Firefighter! 

[ACUDANUT]

Imo, find a 440 with a forged crank, I have never liked the cast cranks. But, To each his own.

[69wannabe]

Imo, find a 440 with a forged crank, I have never liked the cast cranks. But, To each his own.

I have a steel crank to go into this block already balanced with forged pistons too!!