Engine Overhaul

[tdefur]

So my 77 waggy has the original 401 in it. I am certain that this vehicle has seen several owners and the engine appears to be pretty ready for an overhaul. I see where a rebuitl 401LB would run me 2k. Any comments on whether doing the rebuild is worth doing or simply fork out the money to have one done and ready to put in? I would also take the turbo 400 out and send it off to be rebuilt as well (i have never done a tranny and don't plan to do one). Time is not really a factor as it is not my DD but would like to think I could overhaul in 2-3 weekends depending on how long the machine shops take to clean parts and do the head work/cam work.

Tom

[tgreese]

So my 77 waggy has the original 401 in it. I am certain that this vehicle has seen several owners and the engine appears to be pretty ready for an overhaul. I see where a rebuitl 401LB would run me 2k. Any comments on whether doing the rebuild is worth doing or simply fork out the money to have one done and ready to put in? I would also take the turbo 400 out and send it off to be rebuilt as well (i have never done a tranny and don't plan to do one). Time is not really a factor as it is not my DD but would like to think I could overhaul in 2-3 weekends depending on how long the machine shops take to clean parts and do the head work/cam work.

Tom

The main issue with a 401 is the thin walls of the bores. The 401 bore is about as large as can be fit into that block, and the material available for boring oversized is very limited. Due to normal variability in the block casting process, the alignment of the core passages will be different from block to block.

So you need to measure your bore diameters to check if your block has been bored or not. An engine that is bored too much will overheat, due to hot spots at the thinnest parts of the block wall.

You can have your block sonic checked to see if it will withstand boring oversized.

If it were mine, I would probably do an old-fashioned overhaul (rod bearings, rings, valve job) instead of a rebuild, and reuse my pistons. Then there would be no issue wrt the bore diameters - assuming it does not overheat now.

[FSJ Guy]

So my 77 waggy has the original 401 in it. I am certain that this vehicle has seen several owners and the engine appears to be pretty ready for an overhaul. I see where a rebuitl 401LB would run me 2k. Any comments on whether doing the rebuild is worth doing or simply fork out the money to have one done and ready to put in? I would also take the turbo 400 out and send it off to be rebuilt as well (i have never done a tranny and don't plan to do one). Time is not really a factor as it is not my DD but would like to think I could overhaul in 2-3 weekends depending on how long the machine shops take to clean parts and do the head work/cam work.

Tom

The main issue with a 401 is the thin walls of the bores. The 401 bore is about as large as can be fit into that block, and the material available for boring oversized is very limited. Due to normal variability in the block casting process, the alignment of the core passages will be different from block to block.

So you need to measure your bore diameters to check if your block has been bored or not. An engine that is bored too much will overheat, due to hot spots at the thinnest parts of the block wall.

You can have your block sonic checked to see if it will withstand boring oversized.

If it were mine, I would probably do an old-fashioned overhaul (rod bearings, rings, valve job) instead of a rebuild, and reuse my pistons. Then there would be no issue wrt the bore diameters - assuming it does not overheat now.

Good advice there. And if you buy a long block, I don't think they guarantee the overbore. You don't want to go more than 0.030 over. If time is not an issue, pull your motor and check the bores and do it yourself. It's fun!

[tdefur]

Thanks for the advise. It is fun to do so I will get all my parts gathered and start after the new year. Doesn't overheat now so here's hoping a few cases of beer and some parts will keep it going for a while longer

[Cecil14]

You'll be lucky to actually get a 401 if you go for a long block. From what I've seen most shops try to pass off 360s as replacements for 401s.


aa

[tgreese]

If your block is used up, you always have the option of having it sleeved. This will bring it back to factory spec. Not cheap, at ca $100 per hole.

Or, you can make a 360 stroker with a 360 bare block and your crank and rods and custom pistons. The 360s have conventional cast iron blocks and should go 60 over without issue. A 360 with a 401 crank is a 390 at 30 over and 396 at 60 over, so you won't give up a lot in displacement.