Tired 383 Head Gasket

[EngineerDoug]

Hello all,

I am in the throes of tearing apart - and deciding what to fix - on my '68 383 2BBL. I am the guy who has been asking about main bearings and what not. After going through the bottom end, I decided I had better pull the heads and have a look-see. The engine was running OK before I tore it apart, and the compression test results were decent, with acceptable variation between the cylinders.

So now I have the heads off (906 heads), and the bores are scary worn. No scratches or gouges, but a lot of ridge at the top of the cylinders. I am about to mike the bores, but I'd say those ridges are at least 10 thou deep. So I may go against my vow to NOT put much money into this motor, and bore/hone it for new slugs and rings. I have to remove the pistons to properly clean the block anyway, given the carbon and sludge that was circulating in this engine.

Here's my question of the day - I don't know which head gaskets I will use yet, but I am looking at the water passages that go from the block into the head. There are three that sit up near the valley side and pass through the 'V' between the cylinders. The passages are maybe the size of a dime. I see that these are clogged with who-knows-what. Looking at photos of both the steel shim and composition head gaskets, I see there are only narrow slots in this area. My stock gaskets had much larger openings - can anybody shed light on this? Why such a small opening?

 

[Cranky]

I have a stock set of steel shim gaskets on the wall that I use for mock ups and they too have the slots....

 

[moper]

The holes were too large, so the more modern gaskets have a smaller passage to allow the coolant to pick up more heat as it passes through the block and head passages.
If you decide on a full rebuid - due to an gravity accident I need a piston and rod combo... for the one I'm doing a ring-an-bearing on. I'd be happy to send you mine if you're going to have the piston pressed off my old rod instead of yours and you send me yours. I'll pay shipping...
Let me know.
thanks,
dave

 

[EngineerDoug]

OK on the gasket openings; I just wanted to be sure there was nothing I had to do, like open up the holes.

As for the bores, I mic'ed all the cylinders with a snap gauge and a micrometer. It turns out the best cylinder is 0.010" over, and the worst is 0.019" over. So my estimate of a 0.010" ridge was fairly close. Hopefully my machinist will be able to bore it 0.030" over and be good. If I go with hypereutectic pistons and moly rings it won't be too expensive to get the cylinders done right. And if the crank polishes out OK then the long block will be in decent shape with all new bearings.

The next step will be evaluating the condition of the heads. I'll be disassembling them soon.

Dave, are you asking if you could have my old piston(s)? I'll be happy to donate one or more once I have them pressed off the rods. They are stockers - flat top with a shallow dish. Underneath I see a part number of 2863115, if that helps.

 

[moper]

Hi Doug,
You have the right piston... but the engine I have is not getting new pistons. It is very difficult to press one off and have it still be usable. So what I'm proposing is I can press off my piston and send you the rod. You use that rod in your build. Then Put your piston and rod in the box as one unit so the piston remains usable. I will pay shipping all the way around.

I've sent a reply on a local complete shortblock too, as I'm looking to get this problem solved asap.

 

[Rick62]

Hello all,

I am in the throes of tearing apart - and deciding what to fix - on my '68 383 2BBL. I am the guy who has been asking about main bearings and what not. After going through the bottom end, I decided I had better pull the heads and have a look-see. The engine was running OK before I tore it apart, and the compression test results were decent, with acceptable variation between the cylinders.

So now I have the heads off (906 heads), and the bores are scary worn. No scratches or gouges, but a lot of ridge at the top of the cylinders. I am about to mike the bores, but I'd say those ridges are at least 10 thou deep. So I may go against my vow to NOT put much money into this motor, and bore/hone it for new slugs and rings. I have to remove the pistons to properly clean the block anyway, given the carbon and sludge that was circulating in this engine.

Here's my question of the day - I don't know which head gaskets I will use yet, but I am looking at the water passages that go from the block into the head. There are three that sit up near the valley side and pass through the 'V' between the cylinders. The passages are maybe the size of a dime. I see that these are clogged with who-knows-what. Looking at photos of both the steel shim and composition head gaskets, I see there are only narrow slots in this area. My stock gaskets had much larger openings - can anybody shed light on this? Why such a small opening?

People get confused about the difference in size between the holes in the head face of the block and the gasket. In addition to cooling the holes in the block are there to remove the sand after the casting process. They are large by design as there's no way to make a very small slot as part of the casting process.