Drain Back From Head to Crankcase
Greetings to All:
I'm just a little reluctant to address this issue. I've researched the archives and learned a lot about high volume oil pumps (I'll assume here that high pressure pumps will also likely kick out additional oil volume, but my situation is a high volume Melling pump), some from this forum and elsewhere.
However, I'm still learning and hence I'll dive in with a question, which may explain, as I'm still learning, my reluctance to pose this issue on the forum. It is certainly far from uncommon for knowledgeable people to question whether a high volume Melling pump would flood the area atop the head with sufficient oil to enter the combustion chamber via the stem guide. I'm not taking sides and I tend to agree with those on this forum who state that more than likely excess oil put out from a high volume pump will flood the head and cause oil to be drawn/sucked down the intake guide (some even through the exhaust guide and burned on the valve head underside?).
But here's my question. I'm in possession of two 1966 blocks, one cast in October 1965 and the other in April of 1966, although I'm doubtful if the casting information as noted is relevant. Both these engines have the heads attached and hence a little of what I'm asking is perhaps a mite on the conjecture side. I have looked at numerous photos on the internet of small blocks for sale and assume that the 1966 blocks were (almost had to be) cast the same. In particular, I cannot see the area in question on the two 1966 blocks I have. On the internet photos I've seen, in the area right below (and in line with the head gasket hole) the drilled drain hole in each corner of the head is a, as cast, depression area in the block which would serve as a drainageway for the oil to flow into and down the lifter valley. However, on my blocks when I peer down the drilled hole in the head all I see at the bottom is a machined block deck surface. This would certainly severely restrict flow into the lifter valley. [I've tested these engines by pooling oil at the rear end of the head and in fact it does drain down but very slowly and instead easily cause oil to drip/flow on the exhaust manifold and down onto the floor]. Although shadows cast down the drilled passage in the head do make it somewhat difficult to see, there is apparently a SMALL opening which does lead into the as cast "trough" in the block.
Here's my question, and I'm thinking it is rather obvious: if my blocks are not REALLY atypical this would seem to guarantee that a high volume pump would undoubtedly cause excess oil to be backed up atop the heads and lead to significant oil consumption. No? I fail to see how there could be any doubt of this! And yet recently I've seen for sale on the internet VERY few standard volume pumps, in admittedly my somewhat limited searches all I can find are high volume pumps, with few exceptions. Almost without saying, my 1966 327 has a M-55HV pump. At 83 years of age I'm not real keen on crawling under the car to replace it with a standard volume pump but my "research" tends to make this a no-brainer. However many "Chevrolet people" would question the need for this, as noted earlier.
I'd certainly like to put this issue to rest!
I'm just a little reluctant to address this issue. I've researched the archives and learned a lot about high volume oil pumps (I'll assume here that high pressure pumps will also likely kick out additional oil volume, but my situation is a high volume Melling pump), some from this forum and elsewhere.
However, I'm still learning and hence I'll dive in with a question, which may explain, as I'm still learning, my reluctance to pose this issue on the forum. It is certainly far from uncommon for knowledgeable people to question whether a high volume Melling pump would flood the area atop the head with sufficient oil to enter the combustion chamber via the stem guide. I'm not taking sides and I tend to agree with those on this forum who state that more than likely excess oil put out from a high volume pump will flood the head and cause oil to be drawn/sucked down the intake guide (some even through the exhaust guide and burned on the valve head underside?).
But here's my question. I'm in possession of two 1966 blocks, one cast in October 1965 and the other in April of 1966, although I'm doubtful if the casting information as noted is relevant. Both these engines have the heads attached and hence a little of what I'm asking is perhaps a mite on the conjecture side. I have looked at numerous photos on the internet of small blocks for sale and assume that the 1966 blocks were (almost had to be) cast the same. In particular, I cannot see the area in question on the two 1966 blocks I have. On the internet photos I've seen, in the area right below (and in line with the head gasket hole) the drilled drain hole in each corner of the head is a, as cast, depression area in the block which would serve as a drainageway for the oil to flow into and down the lifter valley. However, on my blocks when I peer down the drilled hole in the head all I see at the bottom is a machined block deck surface. This would certainly severely restrict flow into the lifter valley. [I've tested these engines by pooling oil at the rear end of the head and in fact it does drain down but very slowly and instead easily cause oil to drip/flow on the exhaust manifold and down onto the floor]. Although shadows cast down the drilled passage in the head do make it somewhat difficult to see, there is apparently a SMALL opening which does lead into the as cast "trough" in the block.
Here's my question, and I'm thinking it is rather obvious: if my blocks are not REALLY atypical this would seem to guarantee that a high volume pump would undoubtedly cause excess oil to be backed up atop the heads and lead to significant oil consumption. No? I fail to see how there could be any doubt of this! And yet recently I've seen for sale on the internet VERY few standard volume pumps, in admittedly my somewhat limited searches all I can find are high volume pumps, with few exceptions. Almost without saying, my 1966 327 has a M-55HV pump. At 83 years of age I'm not real keen on crawling under the car to replace it with a standard volume pump but my "research" tends to make this a no-brainer. However many "Chevrolet people" would question the need for this, as noted earlier.
I'd certainly like to put this issue to rest!
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