When your engine becomes a boat anchor
 

The 400 in my 66 GTO is apparently a boat anchor. The motor starts up and idles fine, but I’ve never driven it more than on/off the trailer and in the driveway. You can move the pistons front to back by hand while in the motor, and it has already been bored .60 over. Also a few of the exhaust valves are sunk in. The heads are 62’s and I think the block is a 68 or 69? The shop suggested building a spare 400 I had to rather than this one.

Is it worth keeping this block or heads? I Really know very little about machine work. I figure I will research the block and see if it is anything desirable that someone could use?

If it can’t be saved, any ideas as to what to do with it?

If it’s already 60 over unless you want to sleeve the whole block I’d say it’s time to put the old girl down

Melt it down and start stamping out 71-72 GTO hoods and fenders

The heads are a good number,you can have hardened seats installed.

Need more info. If the bores are still good, it might just need pistons? Heads, you could have hardened seats installed? Just need to determine exactly what is what first.

What is the block casting number and date>? Could be worth sleeving to someone.

That’s kind of what I figured- if it’s a GTO block or something like that then it may be worth the expense to someone

Could you have oversize custom pistons made? how much?

I would be worried about it overheating if I went .80 over

Nobody is throwing out early 400 blocks unless they are cracked right up the middle!
Some early blocks have a thick cylinder wall castings like the 67' casting I have for sale
Have the cylinder walls sonic tested for thickness....
You may be surprised and may be able to bore.

It really depends on what you want to do with it and the true condition of the block. Since it's not numbers matching because it's a 400, not a 389, using a good spare 400 standard bore would be a much more cost friendly way to go. if the block is .060 over AND worn out, custom pistons will be needed. they can be made any size you want in .001" increments, Then you need custom file fit rings. Any good piston manufacturer can make them. BME, CP, Ross, Diamond, JE to name a few. $1000.00-1200.00 range for pistons, rings, pins. IMO, this would be a much better choice vs 8 sleeves. Pontiac blocks are pretty tough to install 8 sleeves in. If it was a numbers matching Ram Air IV, or an SD-455, it might be worth it. At my shop you would be looking at a minimum of $1500.00 for 8 sleeves installed. Because you are talking about boring for the sleeves, installing them, cutting the tops, square decking the block, and line honing. Finally, it would need a proper 4-step plateau hone with torque plates to make it as good as possible. All is necessary because the integrity of the block is greatly compromised when you bore 8 giant holes in it. I agree with your machinist, start with a better block. Make a cool man cave table out of the old one.

sonic measures may show it can go .070, .080 , .090 where 400 SBC pistons are avail and work perfectly well with a 455 crank and stock rod length (927 pins)

Maybe.....I've seen few blocks that would take a .090 overbore and still have cylinder wall rigidity. I agree with Mike(mgarblik). The idea of installing eight sleeves into a run of the mill 400 isn't really a cost effective proposition. Blocks pop and crack when you install one sleeve, let alone eight.

Thanks for the info guys. Since I have a spare untouched motor I am going post up the data on the block and see if anyone thinks it’s worth keeping

Ditto on what's been said about the block, and to reiterate about the heads - some new seats will fix them up better than new.

The .060 bore shouldn't be an issue. An easy fix is .065 custom piston. Heads shouldn't be a big deal to save either. Custom bore size flat top piston can be purchased for less than $500 from the right place. I have a set of .065 over dished pistons in the classified section if you want to drop your compression to a more friendly pump gas ratio.

Where are you buying custom pistons for $60.00 each? They are cast, I assume? If forged, that is one heck of a deal no matter what alloy. Pins included? Man, I am buying from the wrong place.

Here is my repurposed block

That block looks pretty cool - that may be what happens to it..

Please note I have very little knowledge of machine work (even though I do work for a Foundry)...

So I went and looked at the engine again today. As a reminder the car is a 66 GTO and it was thought the motor was swapped due to the #16 heads (not 62 as I had thought).

The casting# by the distributor is not legible but the block code is YW.

It appears there are some odd chamfered edges in the cylinder bores- are these for the valves? The 400 I am rebuilding does not have them.

Thanks to Johns website I am now wondering if this is the original ‘66 389 rather than a ‘68 400?

The #16 heads that came off the motor look like they have bigger than stock valves? Or at least very little room between them