XFlow Pressure

[cskip]

Just done a compression test on my 1994 1600 Xflow. The readings are (PSI):

 

1. 90

2. 106

3. 88

4. 95

 

I have a Xflow manual (Haynes) and it says that the readings should be 156 to 184. Obviously the difference is very worrying. Also the difference between 3 and 2 is greater than 15 PSI, could this be an issue?

 

What readings should I be getting?

 

HELP!!!

 

Clive.

[oilyhands]

The first thing to do is to ensure that you are taking the test correctly, the two main areas people get wrong are

 

i) they test on a cold engine

ii) they dont open the throttle fully when cranking

 

If you are sure that the test was taken correctly then you need to try a 'wet' test to see if the compression improves, put a teaspsson full of engine oil in each bore just before you run the test and give it time to run into the cylinder (2 mins), then take the test, if the compression figure improves notably over the normal value then your rings are liklely at fault, if the figure doens't improve then its more likely the problem is connected with valves/seats. Check your valve clearances to ensure none are too tight. It's not unknown for a worn out cam to seriously affect compression readings, but its usually not so uniform across the bores. They sure look low.. with figures this low, discrpanices between cylinders are the least of your problems.

 

Two adjacent cylinders with very low readings can often suggest a blown gasket between the two but your reading dont indicate anything like that.

 

Take the test again on a hot engine and then try it again 'wet' and publish the figures.

 

Oily

 

[Roger King]

Bet you didn't open the throttle when you did the test!

 

You can ignore the figures in the Hayne manual. Assuming that your engine is running twin 40s, this means that your induction system is totally different to a standard engine.

 

Reasonable figures for a 1600 would be around the 180 - 190. Be aware that compression gauges are notoriously variable from one example to another, but reasonably even figures are a must.

 

It is not unusual for a worn cam to increase the figure because of lower than standard duration which works well at very low revs.

 

If your 1600 has been modified, especially with a higher compression ratio, you may see figures up to 220.

 

 

[cskip]

Oppppps! You spotted my deliberate mistake. Need to open the throttle! How silly do I feel now?

 

I will do the test again.

 

Thanks,

 

Clive.

[cskip]

Thank God!

 

1. 193

2. 190

3. 192

4. 193

 

Clive.

 

 

[David Jackie Ford]

Hello all. Clive I hope it is OK to jump on the back of your thread. Does anyone know what the ideal PSI should be for my 1991 1700 Supersprint X-Flow? (the one with the "spitting carbs" thread of a few weeks ago - they are still spitting but I think I am getting there and will let you know when resolved).