Datsun Roadster Forum-311s.org

Hi everyone, still making slow progress on my car and last night I was installing my new petcock drain on the engine block and did a mock up of the header and it hit the drain plug. Is this normal? My first thought was that I didnt screw the plug in far enought but it dont want to force the plug in since the thread diameter gets larger up at the end. Anyone else experience this? Do I need to dent in one of the header tubes to make it fit? I also thought if I double up on the manifold gasket, it may leave enough room. Anyone do this or recommend using two gaskets? Thanks.

it shouldn't touch or at least doesn't on mine but also what header are you using the stock one?

Have you tried an Allen wrench type plug. Should be almost flat. Put some pipe thread compound TFE paste on threads in case you want to remove it some time.

Richard

It shouldn't hit. Is it possible that when you mocked it up, the manifold bolts weren't fully tight, and it was "hanging" a little, in toward the petcock?
You should not need to dent the headers.

Thanks for the replies. I have one of the standard headers from the vendors. The petcock I am using is from Rallye so I assumed the fit should not be a problem. I didnt tight it all down so maybe I should tighten it down before I jump to conclusions. Thanks.

Heck, do you really need the thing? Don't have one on my 2 liter. I think they are only used when you want to fully flush out the system to replace with water or anti-freeze. In the old days I think they thought that anti-freeze was for the winter and water for the summer?

The early cars had a petcock like on the early radiators - the one with a T handle of sorts to drain it. Then the cars had one with a huge slotted head screw to open it. Finally they just put a plug in it. I suspect you have the first type as it sticks out more. You need one of the others.

While doing a search on radiator servicing, I stumbled onto this thread, & since I am on my third header ( actually 2nd, since the stock manifold the blew apart on an "epic" backfire, was not really a header ), I thought I had better check my block drain-plug/petcock for clearance. What I have is a small ( 3/8"-1/2" ) solid plug, with a hex head. I don't recall ever removing it when flushing the radiator, or re-building the engine, but perhaps the machine-shop removed an original petcock, & replaced it with a plug. VIN is SRL311-08559, so this may be the original stopper.

Since the threads appear to be male pipe, I hesitate to attempt to remove it ( 49-1/2 years in place, is practically "permanent" ). I am thinking, that since the cooling system has always contained 50/50 water & antifreeze, there shouldn't be a ton of loose rust in the block, & I might get by ok by jacking up the rear, & hosing the block out through the water-pump port, before installing the new water pump.

Any comments or cautions from any cooling system Gurus?

Garry S

Originally the petcock looked like the petcock on the bottom of the early radiators - a hex with a wing bolt screwed into it. Then they changed to a drain which looked like a bung for a wine barrel with a large screw slot on top. Later cars just had a hex plug. The first one was discontinued I suspect due to the interference possibility. The discontinuation of the second I believe was just a cost saving measure.

That makes the best sense. I think I will put a pan under the water pump port in the block, jack up the rear, and see what runs out, before I try to remove the plug. I don't like to screw around with pipe threads, particularly those installed with lead pipe dope. Any time I tried to "unscrew" any of the 1" pipes from my 89 year-old ex avocado orchard, the fittings always broke off, so I ended up cleaning up the field for other uses with a sabre saw.

Garry s