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First time engine builder question, water leak??


Active member
Jan 16, 2002
Austin, Texas
First time engine builder with a question.

I am rebuilding a 350 4 bolt main with original heads, came from a 70 Vette, anyhow, its nothing fancy, only performer package (cam, intake, carb). My problem right now seems small, but I need input. Even though I know the answer but I will still ask (for future reference):

(facing the engine) The right side where the head meets the block at the bottom of the head there is a small water leak. By small I mean two three dots of water minutes apart. Turned the engine on for about 20 minutes. Leak was still small. No water in oil.

I took the head off and made sure it was clean and no obstructions, gaskets (fel-pro) looks good, put it back on, toqued it to correct specs (65 pds, in 20 pd increments), leak is less, you can see the water shine at the corner of the head bottom, just the corvette not along the edge. This is just filling the radiator with water. I haven't turned on the engine yet. I had the heads worked on (valve job and surfaced) checked for cracks.

Two questions:

the gasket? or

head wasn't surfaced right (not level)?

Just bench rodding here so any suggestions, Sorry for the long post, a detailed explanation makes it easier to visualize. Thanks
You did not mention if the block was decked/surfaced ... have you verified that the block is level?

Did you put a small dab of silicone on the headbolt threads as is routinely recommended?

I guess this is a stupid question, but what do you mean? I ordered a complete Fel Pro gasket set. Can't remember part number, or specifics. Are you asking about thickness, metal, etc?

Thanks guys!

No such thing as a stupid question. I was going to suggest Fel Pro standard series gasket if you mentioned any other brand.

Is it possible your head is cracked? Did the machine shop magna flux it?

Was it ever run hot?
FelPro HG part number

FelPro makes several different Head Gaskets for the sbc 350. Maybe you still have your FelPro gasket KIT box? On the box is a listing of gaskets ... EACH gasket has a unique FelPro part number. Maybe an invoice/receipt will show the gasket KIT number ... from kit number the specific HG gasket number can be derived.

Is the block-head mating surface clean? I like to wipe them with lacquer thinner just before mating. Are you using a a gasket sealer? ... sealer is NOT recommended with many HG's.

Could it be possible that the block or a head was bumped while apart ... raising a corner? If so, sometimes it can be fixed with CAREFUL & CONSERVATIVE use of a KNOWN straight edge & flat file.
Ive built a few motors and maybe this will help. First, I would "always" use a new "head" Gasket if the old one has been torqued, regardless of how it looks.
Also I only use a tad of clean motor oil on the head bolts, because sealants can make it difficult to get a correct torque down! please Research that though, Im not sure what the manufacturers recomendations are.
Maybe someone will suggest a better gasket that may compensate for a very slight warp somewhere..
Sounds like your close to getting your heads sealed, I would do it again rather than live with even a slight water leak. To Dangerous
and may just get worse(corrosion).
Good luck..
I agree, some manufacturers recommend that the head gaskets be put on dry. However, I was taught by my ol' man when I was a wee lad to use a little K&W Copper Cote on my head gaskets and nothing but Nev'r seize on the head bolts. I have yet to have a leaker. Make sure to use the Copper Cote around the bolt holes, both sides of the gasket. Use the same on your intake gaskets . . . as long as the surfaces are flat, you won't have a problem.

Maybe I missed it, but what type of Fel-Pro head gaskets did you use? OEM-replacement steel shim type or composition type? The steel shim gaskets are bad news unless you use them on a freshly-decked block. In any event, thread sealer is essential on all the head bolts to keep the deck dry - I always use ARP thread sealer (and ARP bolts, with their Assembly Lubricant under the bolt heads), have never had a leak.
I was asking about the gasket type to make sure you got the right one, and preferably a Fel Pro brand.

Are you sure you don't have a warped or cracked head?
Need to check the head again, also the block. If all is fine, use new gaskets. And same as rpounds copper cote my dad did this and I do also. No leaks yet.....

Also make sure you have the correct torque specs and order.

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