273 needs new heads, suggestions

JBurch said

While the thumb over the spark plug hole netted you little or no pressure, a leak down on that cylinder will tell you volumes more about the condition of the cylinder. Do a leak down on the whole motor; it might not be a head issue at all.

Eddy's will bolt down, and they come loaded with valves, etc. HOWEVER, you must notch the cylinders for valve clearance.

Click to expand...

I agree with JBurch. A leakdown test is a much better diagnostic tool than a simple compression test. The leakdown test is great for helping you pin-point where the cylinder is losing pressure from: intake valve; exhaust valve; rings; head gasket; or a combination of them.

Notching the cylinders is required when putting the big valve head on the 273 because of its small 3.63" bore. A notch has to be machined into the top edge of the bore to clear the large intake valve. It's not as simple as just swapping heads as the engine will have to go to the machine shop to have the notches done.

There is also the issue of port size. I don't know what intake or exhaust manifolds/headers you have, but the 273 ports are a lot smaller than the Eddy or 340/360 heads. Having the ports of the head and manifolds mismatched will create flow velocity and turbulence problems.

Also don't know what year heads are on your 273. If you have 64-65 stock heads and intake the intake bolts are at a different angle than the 66 and later ones and you wont be able to bolt up the early manifold to the Eddy or 66 and later stock heads.

Since it sounds like you are looking for a stop-gap fix to hold you over until your 360 is ready, I would first do a leakdown test to pin-point the problem. Assuming it is a leaky valve, I would pull the head and fix JUST that cylinder's valves. If everything else looked ok, I would then put it back together and drive it until your 360 is done and ready to install. Just seems like the most economical way to go about it.