1970 455 coolant loss / compression test pls advice

Thanks Chris and Schurkey.
No idea whatsoever about the lifter brand and/or the cam timing.
I have an overflow tank and I see the coolant level drop in both the overflow tank and the radiator itself. Cap has 2 seals and seems to work fine.

Certainly I have no intention to induce any further damage to a matching# stage1 engine, so I make up my mind now on how to get rid of the knocking at WOT and go from there.

 

A few things. First, don't allow the knocking to go on. Don't do WOT unless and until you address the knocking.

Second, does the engine run hot or hotter when the coolant seems to drop in level and does the level keep dropping? Losing coolant from both the radiator and the bottle says there is a problem. The bottle is there to contain the coolant that would normally be lost to the ground if and when the system saw an over-pressure situation and vented coolant. It goes into the bottle. When the engine cools down again, a vacuum or low pressure develops in the cooling system and draws coolant from the bottle, back into the radiator. The prior suggestions to pressure test the system should find that leak. If you don't have coolant in the oil or the transmission, there is an external leak. Don't be afraid to put pressure to the system. Run it up to 3-4 psi above the rating on your radiator cap (or bar equivalent) and get a bright flashlight. You probably won't hear anything, but you should see where it is coming from. Multiple times I have found small leaks that evaporate before they hit the ground. The seam between the radiator core and the tanks is a good place, the weep hole in the water pump was mentioned. Be sure to look over that #8 exhaust port too. Look at the freeze plugs in the sides of the block. Hate to put a jinx on you but all that pinging and knocking COULD have led to a crack in the exhaust port leading to the coolant passages in the head. Keeping my fingers crossed that this is not the problem.

Last, Before you hit WOT throttle again, be sure you are running good gasoline. It will probably require the highest octane fuel you can find. If you are already using the best petrol you can find for your car, you need to go through Larry's timing thread again. As Larry said earlier, pinging or knocking at WOT is really bad for an engine. Blown out head gaskets, hammered rod & main bearings, cracked pistons and bores, broken rings. All of these can result from this.

 

Thanks GS464. Temperatures seem stable but I cannot say whether the coolant level ever continues to drop or not. I'll do a pressure test, waiting for the equipment to be delivered.
Agreed, no more WOT. Highest grade gas is given.
Probably need different pistons in order to bring the CR down. Rebuilding an exotic engine like a BBB here in Germany is very costly, and brings a risk of someone doing it 'not right'.
So I started a discussion with Jim Weise about a replacement 455 from him. Would then put the original motor in storage. Let's see.

 

This isn’t the main problem it seems, but if your balancer has slipped and the timing marks no longer read true, you could be putting 40*, 50* or more advance into your engine when of course it really only wants 30-34* at WOT.

 

For the loss of coolant, check engine oil for contamination. Possible leak from intake manifold into crank case.
If using paper intake gaskets there is a possibility the gasket deteriated and coolant is pushing past the sealing surface.

 

Have pressure tested the sytem and there was a leak at the heater hose clamp at the water pump. Don't ask - I checked many times before and have no idea how I managed to overlook it.
So now with new heater hoses and new clamps the coolant system seems to be really tight, no more external leaks.
Will have to check regularly how much of the coolant loss still remains.