Cylinder Block Drain plug thread

General Chat About Cooling & Overheating

Moderator: phpBB2 - Administrators

Post Reply
vanquishspirit
Newbie
Newbie
Posts: 24
Joined: Sat Jan 12, 2008 6:18 pm

Cylinder Block Drain plug thread

Post by vanquishspirit »

Hi Guys, I am just trying to it a new cylinder water drain plug in an early Range Rover, 1971 and the threads need cleaning out. I note the new plug I have is tapered and was wondering what thread it is in the block? It looks like it may be a 3\8 NPT but just a guess. If anyone knows it would help me along my way. Also, I will need to buy a tap if it is NPT would it be a standard tap to only clean the thread not take any metal out? thanks in advance. Andrew



User avatar
ChrisJC
Top Dog
Top Dog
Posts: 5039
Joined: Mon Nov 20, 2006 1:13 pm
Location: Northants / Cambs
Contact:

Post by ChrisJC »

If I were guessing, I would go for a BSPT thread. No idea what size though.

Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8

vanquishspirit
Newbie
Newbie
Posts: 24
Joined: Sat Jan 12, 2008 6:18 pm

Post by vanquishspirit »

thanks for the feedback. I was thinking NPT as its a US engine, but of course they would be blanks when machined, but perhaps Rover kept with all the tooling from the US? perhaps someone else has a view as well. cheers

unstable load
Top Dog
Top Dog
Posts: 1278
Joined: Mon May 04, 2009 6:53 am

Post by unstable load »

Take the old plug and using a hacksaw, cut diagonally across the threads to make a groove. that will clear the hole of debris.
Cheers,
John

vanquishspirit
Newbie
Newbie
Posts: 24
Joined: Sat Jan 12, 2008 6:18 pm

Post by vanquishspirit »

Another great idea and certainly something I can do if I cannot find a tap. I am a bit worried that the block is alloy, the plug is brass. I could see a right cock up occurring which is why I really want to do it properly with a tap. I have used your method before where I cannot find a tap, my Dad taught me that one! :D

DaveEFI
Gold Member
Gold Member
Posts: 4603
Joined: Fri Feb 26, 2010 4:27 pm
Location: SW London, UK

Post by DaveEFI »

vanquishspirit wrote:thanks for the feedback. I was thinking NPT as its a US engine, but of course they would be blanks when machined, but perhaps Rover kept with all the tooling from the US? perhaps someone else has a view as well. cheers
Interesting point. Most of the threads into the block etc are Unified Coarse. Are the Buick versions that or American Coarse? I realise the two are similar.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y

vanquishspirit
Newbie
Newbie
Posts: 24
Joined: Sat Jan 12, 2008 6:18 pm

Post by vanquishspirit »

Same thing is it not? UNC and UNF are US threads, where as the UK used until after the Second World War, BSF and BSW (fine and course) and a variety of other threads BCY ( cycle threads etc etc) . I am fairly confident the threads will be the US pipe thread, i.e NPT as opposed to the standard UK BSP. I have ordered a tap so will await to see whether its correct. thanks chaps

User avatar
SimpleSimon
Knows His Stuff
Knows His Stuff
Posts: 620
Joined: Mon Apr 25, 2011 10:36 pm
Location: East Sussex

Post by SimpleSimon »

Dont be surprised if its BSPT 8-)
Last edited by SimpleSimon on Tue Jun 21, 2016 8:33 pm, edited 2 times in total.
TVR Chimaera RV8 Mods & Megasquirt

DEVONMAN
Top Dog
Top Dog
Posts: 1440
Joined: Sat Dec 13, 2008 2:46 pm
Location: Croydon UK

Post by DEVONMAN »

As far as I can remember it's 1/4" NPT.
3/8" NPT would be too big. 1/8" BSPT too small.

Pipe threads sizing is not based on the thread diameter but is based on the bore of the pipe you are connecting. So the overall diameter of the thread would be the diameter of the pipe bore plus twice the wall thickness of the pipe. This applies to both English Imperial and US pipe threads.

JUST NOTICED THAT THIS IS AN OLD THREAD AND ALL MAY BE SORTED BY NOW
1950 A40 Devon Hotrod with 5.0 twin turbo RV8.
EDIS8 wasted spark, Holley Injection.
Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!


Image

Post Reply

Return to “Cooling Area”