Thread: Coolant in cylinders; fresh 400 sbc build

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No I did not. The block is in stock form

It's not the block that gets drilled, it's the heads. Did you look at the link I provided for you?

Originally Posted by techinspector1

It's not the block that gets drilled, it's the heads. Did you look at the link I provided for you?

No sorry haven't had time. Here are my compression numbers...

#1 = 175 psi, 3 = 150, 5 = 140, 7 = 170

#2 = 142 psi, 4 = 168, 6 = 166, 8 = 157

#4 is the one that water flows out of. 1, 6, and 7 only have a little when I turn it over.

The heads were done by a machine shop before I got this mess. I can only assume that they are fine.

Originally Posted by Bigbzc

No sorry haven't had time. Here are my compression numbers...

#1 = 175 psi, 3 = 150, 5 = 140, 7 = 170

#2 = 142 psi, 4 = 168, 6 = 166, 8 = 157

#4 is the one that water flows out of. 1, 6, and 7 only have a little when I turn it over.

The heads were done by a machine shop before I got this mess. I can only assume that they are fine.

Not if they don't have steam holes drilled in them.

Originally Posted by NTFDAY

Not if they don't have steam holes drilled in them.

so with no steam holes I can have coolant going directly into the cylinders?

Well – here’s my two cents worth on what may be your problem. The 400 block starts life with a 4.125 bore (verses a 4.00 for a 350). You didn’t say if the block was bored but if it was, the bore would now be between 4.155 and 4.185. In any case, the head gaskets for a 400 typically are sized for a larger initial bore size and they have steam holes. The 400 block requires specific head gaskets with matching steam holes (Fel-Pro PN 17031).

The 350 heads are intended to be used on a smaller bore and they do not (in their stock form) have steam holes. 350 head gaskets do not have steam holes. Many well intended hot rodders have put 350 heads on their 400 blocks in anticipation of upping the compression ratio with the smaller chambers only to have a real disappointment in a very short time if steam holes were not drilled and proper gaskets not used.

When using heads without steam holes, the pressure immediately builds and more often than not, compromises the gasket. When that happens, water in the cylinders is common. I think you’ll find the gaskets have been compromised – as evidenced by compression being significantly lower in #2 cylinder.

I’d recommend pulling the heads, making sure you have steam holes and correct gaskets and reassembling.

Good Luck,
Glenn

I said the block was stock. Never been machined.

Originally Posted by Bigbzc

I said the block was stock. Never been machined.

You seem to be fixated on the block. We're not talking about the block. It has steam holes already in the decks from the factory. As Glenn told you, the heads and the gaskets must also have steam holes to match up with the holes in the block decks.

Originally Posted by techinspector1

It's not the block that gets drilled, it's the heads. Did you look at the link I provided for you?

I just skimmed through your post and remembered that they said that they tried to rebuild the stock 350 that came in this truck. (78 K5 Blazer) They found that the 350 block was cracked and then found a 400 to build for it. The heads were already done and I think it could be possible that the heads were off the 350. So, with that in mind and the compression specs I posted, is it possible that my problem is that water is entering the cylinders through these non-existent steam holes??