BIS compression testing.

[Gadge]

Just a quick question I'm gonna try and give my car a compression test tomorrow but I can't seem to find any info on what pressure reading I'm supposed to be getting? Has anyone ever done one on a BIS?

[Gadge]

Ok I managed to kind of do one. I say "kind of" as I couldn't do the number 2 cylinder (gearbox side) as my compression tester won't fit past the carb but I was able to do the rear one and I got a reading of 125psi (9.5bar) so because no one has done a compression test on a BIS before I hit the Internet for some typical compression test figures and found out that your supposed to do the test with the engine hot AND with the throttle wide open both of which I didn't do so with that in mind I reckon that 125psi in fact probably higher so I'm happy with that...... Just wish I could've done the other   

[Xylaquin]

Compression ratio is listed as being 8.6 bar (plus or minus 0.15 bar)

[Gadge]

8.6 bar  wow it's got a good seal then 

Incidentley where did you find that I searched around and couldn't find anything?

[drcdb15]

A friend was doing some compression testing on his Lotus recently and got figures ranging from under 100psi to around 125-130, so your 125 sounds healthy enough. The main point is not the absolute figure but any discrepancy between cylinders. The closer the two are the better. I'm afraid your rear cylinder reading isn't very much value (other than saying at least one cylinder is OK) without the reading for the other one to compare with. Given the space constraints and your well-demonstrated engineering expertise can you not make up some angled adapter tube thingy to get into the space?

[Xylaquin]

Incidentley where did you find that I searched around and couldn't find anything?

1. Haynes sheet in the subscriber section
2. Page 12 of General Information in the workshop manual

The problem with your engine Gadge, is you've modded it. So how can you tell what you're meant to get 🤔

[Gadge]

While that is true I'm only looking for a rough idea. I run a standard BIS block and a cinquecento head so I guess I'm after either a cinquecento 700 figure (if there different) or a BIS figure. What I should have asked originally is what is everyone else getting but I didn't think a lot of people would have done one. I'm
Not suspecting a problem with it I'm just st curious

drcdb15 Yes I really do need to do that front cylinder. I don't have the materials to make an adapter although the simpler solution would be to remove the carb but it can be a fiddley job on a BIS

[drcdb15]

How about something like this little gadget? Under £25 and seems to be flexible and adaptable, if you'll pardon the pun.

https://www.tradecounterdirect.com/product/sealey-petrol-engine-compression-test-kit-8pc-set_engine.html?gclid=CPSKye6_rdMCFUu3GwodYdgIaA

You might even pick up a used one on fleabay for less.

[Gadge]

Ahh yes that would be a better one. I have a gunson one and it has an unusually long threaded end on it - about 5 inches I'ld say

[drcdb15]

about 5 inches I'ld say

Five inches? Well don't feel bad about it Gadge, size isn't everything ... 

[Gadge]

It's a cross I have to bear bud