[70geeteeohh]

I was looking at a 1967 428 engine and noticed something that looked odd to me. It seems to me that the block was drilled and tapped for some reason on the back. There is a plug installed in the hole now.

Is this done from the factory? If not, why would somebody do this.

I am not very familiar with Pontiac engines.

[Stuart]

Pontiac blocks typically have a plug in that area that goes into an oil galley. It's a convenient place to hook up an oil pressure gauge. I'm guessing that one has been removed and replaced before, if I remember correctly the original plugs had a square drive instead of hex drive.

[77 TRASHCAN]

That might be a good sign. Engine may have been re-built by a legit shop. Those plugs are seldom removed by engine remanufacturers. It means the engine oil passages were likely thoroughly cleaned upon reassembly...it also means it may not be a standard bore block. Depending upon the current bore size, it may or may not be able to re-bored......if it needs it...
428's are awesome engines!!!

[70geeteeohh]

Originally Posted by 77 TRASHCAN

That might be a good sign. Engine may have been re-built by a legit shop. Those plugs are seldom removed by engine remanufacturers. It means the engine oil passages were likely thoroughly cleaned upon reassembly...it also means it may not be a standard bore block. Depending upon the current bore size, it may or may not be able to re-bored......if it needs it...
428's are awesome engines!!!

What is the safe ovebore for a 428 and what is a maximum overbore?

[77 TRASHCAN]

.030 or .040 over are usually safe over sizes for MOST classic Pontiac engines. Many will go .060, all should be sonic checked to make sure for .060

[sdbob]

Some have 4 bolt main caps others have 2 bolt caps. All the 428s I've seen are drilled for 4 bolt caps.

[PunchT37]

All the `67`s and `68`s should have 4 bolt caps.

[sdbob]

My 68 428 is a 2 bolt ,drilled for 4 bolt. I do have extra 4 bolt caps I've accumulated over the years.

[PunchT37]

I always thought all 428`s were 4 bolt main except the common `69, YH, 360hp with small valve 46 heads and press in studs.

But, as they say, the only thing for certain is, nothing`s for certain.

[beemergary]

Originally Posted by PunchT37

I always thought all 428`s were 4 bolt main except the common `69, YH, 360hp with small valve 46 heads and press in studs.

But, as they say, the only thing for certain is, nothing`s for certain.

I have a yh. 2 bolt caps but drilled and tap for 4.

[lust4speed]

Originally Posted by 77 TRASHCAN

That might be a good sign. Engine may have been re-built by a legit shop. Those plugs are seldom removed by engine remanufacturers. It means the engine oil passages were likely thoroughly cleaned upon reassembly...

So true. Sellers claiming block was inspected and cleaned by a professional shop and rusted 4 sided pipe plugs show that the shop never pulled them. Good to see a hexagon pipe plug in place. Non-Pontiac aware shops also miss pulling the inner passenger side rear gallery plug and that pretty much means about 3" of debris in the gallery on the other side of the plug that didn't get cleaned out.

421/428 Blocks usually don't have much core shift and are thick. A .065" overbore wouldn't concern me at all. Probably go more without a problem but cylinder walls should be sonic tested before going over that.