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Nailhead water pump question


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I sold a water pump (the correct pump) for a 1963 Riviera with 401 engine to a hobby guy in Australia. Upon receipt, he has informed me that the pump I sent is too wide to fit the timing cover of the engine in his Riv.

However, he and I both now suspect that his timing cover was changed over the years and may have come from an earlier nailhead. It seems possible that the engine is indeed a 401, but that the timing cover might have worn through, and was replaced with whatever nailhead cover was available there.

Does this make sense to any of you....and can you shed some light on when the nailhead timing covers may have changed in design? Both the fellow in Australia and I thank you! John

Edited by Jolly_John (see edit history)
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I left it too late to check today but will have a look tomorrow. The 59-61 timing cover and water pump is definately different but is easily interchangeable with the later 62-6? setup. I have done this change myself. I just need to double check that the later one is the wider of the two, memory tells me that the early housing is different around the radiator hose area but otherwise very similar. The bolt pattern to the block is the same- I fitted a 62 housing and pump to a 61 block no problem which is probably the opposite to your situation. Good housings are very hard (expensive) to find now.

Rick (Perth WA)

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Thanks for taking the time to help, Rick and Leif. The water pump parts book information is nothing short of amazing.

Another helpful Buick guy has messaged me that the 1959-1961 water pumps have a 2" longer "snout", compared to the 1962-1966 nailhead water pump. He noted that putting a 1959-61 timing cover and water pump on a 1962-1966 nailhead engine will likely result in the 1963 Wildcat's cooling fan hitting the radiator (or at least being much too close to it). He also said fitting the earlier timing cover and water pump to the later nailhead would result inl the accessory drive pulleys not lining up (because of the longer snout on the earlier water pump).

So, the plot thickens. I have asked my friend in Australia, who is having this problem, to email me some photos. I'll share them here, and hopefully we can get him going in the right direction. Thanks again, Guys. John

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Have made a rough measure of my 2 pumps. The early pump 59-61 off the car against the later 62-66 pump on the car. Measurements are thus approximate only.

They both appear to share the same bolt pattern but the later pump has a longer extension that the radiator hose attaches to. The housing/ gasket is about 1" longer at this point so a late pump on an early housing has an opening at the back and so will not fit.

As stated above, the early pump has a longer shaft to the cooling fan flange about 1.5 to 2". To compensate, the early pump has a deeper pulley and a shorter aluminium adaptor to the cooling fan. My rough measurement shows the total difference being about .5" so if an early housing/ pump/ pulley and adaptor are used on the later block the cooling fan would be about .5 inches closer to the radiator but the pulley grooves do seem to line up okay.

Seems to me to be a lot of work/ replacement parts?

If the complete engine was replaced for the early block (engine number would confirm this, second letter should be J?), it is not simple either as the oil pump is not interchangeable without drilling new mount holes in the block. I have had to do this on my car so I have an early (1961) block with later oil pump, sump, water pump and timing cover housing fitted.

What state does your friend live in?


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