Boy, howdy! have I got a question for you all. My '77 400 started life as a 351
M and was converted to the 400 by previous owner. It has 0.030 over Sealed Power pistons and like most 400s, it'll knock and ping with just a little extra spark advance. I am saving up for a set of Tim Meyer's special pistons to create squish and improve the engine. Question is, $450 is going to eat nearly my whole budget for this swap. I had the engine apart right after I got it and the bores looked really fresh. I am tempted to buy 0.030 over pistons and just slip them in. But he always runs out of that size, while there are usually some 40 and 60 over pistons available right now.

The 400 block is "known" to have thin cylinder walls and I'm also nervous about taking another 10 thousandths out of mine if I don't need to.

There are quite a few 400s from cars from the early '70s and I'm wondering if anyone has used a passenger car block for a build? I understand that Ford beefed the main webs for truck service but is there really that much of a difference? Are there 400 blocks with thicker cylinders? I know about the cracking problem and I checked really well when the engine was apart because My block is one of the "bad" ones. Yet after 150K miles there are no valley cracks and no repairs to be seen.

Does anyone have experience with either larger overbores or using a passengercar block?

The real answer is to take it apart again and measure everything, but I have to ask...

Thanks,
R.

 

No .060" now. I just bought the last 5 he had and have to wait for the other 3.

 

I believe webbing was increased for strength in 77 all the blocks are the same car or truck I think. No difference in cylinder wall thickness between them.

There was a concern on some blocks about cracking in the valley on blocks prior to 77 at a specific plant.
If it hasnt cracked yet I dont think id worry too much about that

I'm .040 over now with tims pistons.

On a side note id think with the stock type pistons and the low compression from them unless some serious milling was done to the heads and block to raise compression, the detonation may be coming from something other than timing.

 

I’m running a 71 block in my 79 F350. 77ish and on block are supposed to be less crack prone but the cracks usually occurred in the water jackets of the valley. Early blocks may crack but they may also be just fine. Mine is doing just fine.

 

Going from 4.030 to 4.040 is only going to take .005 away from the cylinder wall thickness which shouldn't make or break any block. If you're in doubt just have it sonic tested. The thin areas will be where the cylinders are adjacent and usually about 1 inch down from the top of the deck. I've sonic tested a lot of 351C blocks but not a lot of 400's. The ones that I have done have been about the same and most blocks will have a few cylinders that are somewhat thin in small areas.