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Compression Tester adapter
AlexXtreme - 12/7/16 at 06:20 PM

I am trying to check the compression on my silver top ford engine.... I have an only compression tester that worked fine for cross flows however for the zetec I realised i needed an extension adapter. Brought one from Machine Mart (down the road from me) but I can not get extension thread on the cylinder head... :-(. Feels like a stupid question but I am doing something wrong???

obfripper - 12/7/16 at 06:58 PM

The thread in a zetec spark plug hole does not start for the first 10mm and most adaptors only have 6mm of thread, if you are confident with your welding you could weld the adaptor to an old zetec spark plug body, and put an o ring in place of the seat gasket for a homebrew adaptor.

Dave

britishtrident - 12/7/16 at 08:00 PM

You need a long reach adpator (ie one with 14mm x 1.25 thread 3/4" (long )reach sparkplug thread) --- to give useable readings it should have the schrader valve at the point where it screws into the head.
No welding required.
A lot of ebay sellers incorrectly describe extra long extensions as long reach ---- spark plug reach is the length of the thread.
Similar to the plated extension screwed into the black adapter in this photo

Locost Running Compression
Locost Running Compression


This kit has one
PETROL COMPRESSION TESTING KIT - CAR VAN MOTORBIKE CYLINDER HEAD TEST TESTER

Alternative buy the rubber cone type and get an assistant to crank the engine.

AlexXtreme - 12/7/16 at 09:46 PM

Hi thanks for this... looks like this is too short then
https://www.machinemart.co.uk/p/clarke-cht748-long-reach-compression-tester-ad/
that was a waste of £14!
Alex :-(

britishtrident - 12/7/16 at 09:55 PM

quote:
Originally posted by AlexXtreme
Hi thanks for this... looks like this is too short then
https://www.machinemart.co.uk/p/clarke-cht748-long-reach-compression-tester-ad/
that was a waste of £14!
Alex :-(


That looks like 1/2" or 3/8" reach without a Schrathe lackder valve ------ apart from the thread reach being to short it will give false low readings.
because in effect it would lower the compression ratio.

benchmark51 - 12/7/16 at 10:37 PM

I had that problem when using a Draper tester on my ST170. Fortunately I still had an AM- Tech tester, which never worked from new but had an assortment of adapters. Used the appropriate adapter with the Draper tester and ' BINGO' it worked.
It was this one

PETROL ENGINE AUTOMOTIVE COMPRESSION TESTER KIT DUAL SCALE GUAGE - TWO ADAPTORS

AlexXtreme - 13/7/16 at 07:23 AM

Thanks for the advice and new kit brought. The Machine Mart adaptor had the valve in but as you said, the reach is not long enough....

Cheers
Alex