Compression Test Results BT7

[Brian N.]

Since the igntion is out of the car for cleaning and refurbishing, it made sense to run a compression test.

The test was done with no spark plugs installed, the throttle mostly open, and the cylinders dry (not oiled through the spark plug holes).

All cylinders tested with eight full revolutions each at 195-205 PSI.

How does this fit expectations for a 29D H engine?

 

[Dave Russell]

Hi Brian,

Check this topic;
https://www.britishcarforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=001253

195 - 205 is suspiciously high for a stock compression ratio engine. It could be caused by carbon build up in the chambers or a bad gage.
D

[ 10-28-2003: Message edited by: Dave Russell ]</p>

 

[Brian N.]

Dave,

I dug through the factory service book and found a reference on page 10 to "cranking pressure". It is stated as 175 for this motor.

Perhaps the high and consistent readings are due to the cylinder overbore on the rebuild. This same sort of high compression showed up on a Ford Kent motor I build a few years ago for my Consul Capri.

There was no indication of carbon build up on the plugs. They all looked normal.

 

[Jerry]

Before you worry too much, I had a head that was shaved so far, (almost 1/4 inch), my compression was 245 lbs. Ran very fast but needed racing fuel.
Jerry
Bn4