Drain Tap on side of block

[John S Bradley]

I have a problem with tightening the drain tap on the side of the block below the carburetor.The thread form on the tap compares favorably with a thread gauge so it seems that the thread in the block is at fault. My favorite option is to drill and tap the hole 1/4" BSP and fit a different tap to suit .I do have some pipe seal which I am told might work but there is still the possibility for the tap to leak . Any advice would be welcome.

[Mikeg7210 _+[]]

John
I had the same problem with my 12/4,taping the thread did not work.I seem to remember it was 1/4'" BSP and I obtained the tap frpm Paul Beck Services. You can look up his range of products on his website
Regards
Mike Gibson

[drocke]

The drain tap i believe should be 1/8 BSP.
I used a 1/8 BSP helicoil type thread repair to fix the same isssue on my 12/4. You will need to take the carburettor off to get access to fit the helicoil making sure you get it in square to the block.
The drain tap has a very small hole that is useless if you have any crud in the block that needs to be flushed out. It is well worth properly fixing the thread in the block so that you can unscrew the entire tap whenever you drain the block to allow the crud to run out.

David

[Martin27]

I agree with drocke. However I have a slightly different take on this as I use my car (20/4) slightly more than average. I tend to go for reliability first but with an eye on originality and make sure I don't do anything irreversible. Drain taps are a constant source of problems and prone to leaks. When you actually need to use them they are usually bunged up with crud and you end up having to remove them to sort them out. If you have to remove the tap to get the block to drain why not just fit a plain plug instead and eliminate the leaky tap. Non original maybe but easily reversible when needed. It is, of course, essential to have sound threads in the block and I agree helicoils is the way to go.
Martin

[drocke]

Totally agree Martin. I did actually order a blanking plug but it took longer than expected to arrive, so I ended up putting the old drain tap back in. Maybe I will swop it for the plug next time I drain the block.
Regards
David

[Mike01]

I used a compression tap blanking plug and that worked. Its still in place and not leaking, although I did make sure a fibre washer was in place also.
Mike

[Mike01]

Sorry. This was on a heavy 12/4.
Mike

[John S Bradley]

Thanks for the advice , but I tapped out the block a 1/4"BSP and fitted a different drain plug which I had in my toolbox . The envelope dimensions are only slightly larger than the original and it is not noticeable when in situ under the carburetor. Later I found a 1/4"BSP 1/8"BSP reducing bush to enable me to fit the original. The problem was the thread in the block was stripped and I didn't have an helicoil of the appropriate size.