Twin HS2 Carb needles

Started by Hercplt, October 27, 2019, 11:14:06 AM

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Hercplt

1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

Yeah that's an issue.  Was the head torqued properly?  Though you probably didn't think to check before pulling it.

MiniDave

#77
Also, check that head and block carefully to make sure it's good and straight - I might send it out to have it skimmed too....

Low compression completely explained now! Good that you found the problem, of course once you get the head sorted you'll have to go back into the carburetion again.

I always run the engine, then let it cool completely overnight, then retorque the head and readjust the valves and maybe do it again 1000 miles later.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring

Might be an ideal time to see what your compression ratio is and then skimming the head to raise it if it's low.  Especially if the head isn't straight.

MiniDave

#79
A good lesson here tho, any time you're trying to sort out an issue, start with the fundamentals - compression first, then valve adjustment, ignition, and carburetion last.

That head looks like it's been skimmed some already....check the block with a straight edge. If it's not flat it won't hold any headgasket. I like the composite ones better than the solid copper ones, but you do have to retorque them for sure.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Hercplt

What you are looking at is the bottom of the gasket... Looks aluminium? Yes the head has been skimmed... and looks pretty straight.  Block is dead straight as well...
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

MiniDave

#81
OK, not saying you didn't but are you certain that you have the gasket on right side up?

It's not unusual to have it fail between the middle two, but all 4 cylinders at once is not something I've seen unless the head or block weren't flat. As long as you've checked them I would clean everything up thoroughly and put your new gasket on and fire that mother up!
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Hercplt

Can't seem to upload the other pic... but gasket was black side up to the head, and silver side was down toward the block.  Not sure if that was right, but I didn't put the engine together this time, so it could be wrong I guess...
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

94touring

All 4 at once is odd.  2 and 3 are normal.  That's why I wonder if it was under torqued, though you'd probably have been leaking fluids across the whole thing.

tsumini

I'm with Da n and Dave. Looks kinda under torqued. Suggest you check stud thread height to make sure the nuts aren't bottoming out on threads giving a false torque. My engine has flat washers between head and nuts. not sure about the ones under the valve cover though.

John Gervais

I agree also - looks like it was under torqued and possibly not re-torqued after a couple of days. 

I've had good success with the genuine Unipart copper small bore gaskets, carefully torquing to 45 lbs/ft, starting the engine and running until 'warm' without coolant, letting it cool overnight, re-torquing to 45 lbs/ft, adding coolant, then re-torquing again after a couple of days.
- Pave the Bay -

tsumini

I haven't done a lot of head torquing so am not the expert however my brother used to build engine for a living. He always sprayed on a coat of aluminum paint (both sides) and swears by it. The one I took apart recently showed it made an excellent seal.
FWIW

Hercplt

Quote from: 94touring on September 01, 2020, 09:41:24 AM
All 4 at once is odd.  2 and 3 are normal.  That's why I wonder if it was under torqued, though you'd probably have been leaking fluids across the whole thing.

Thats what I thought as well... but all the water ports are great... there was no coolant mixing with anything... 
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

Hercplt

Quote from: tsumini on September 01, 2020, 01:15:52 PM
I'm with Da n and Dave. Looks kinda under torqued. Suggest you check stud thread height to make sure the nuts aren't bottoming out on threads giving a false torque. My engine has flat washers between head and nuts. not sure about the ones under the valve cover though.

Some of the head studs were loose it appeared when I un-did everything.  I presume they should be snugged into the block by hand? followed by torquing the head nuts?  Haven't checked Haynes on that piece, but any advise it appreciated.

I'm gonna use the copper gasket that I have and see how that goes.
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

MiniDave

#89
They say in the manual just to run them in by hand, but I double nut them and snug them down to make sure they don't walk out again....but first I chamfer the holes so they can't pull up the top thread above the surface of the block.

The gasket should be marked "Top"
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Hercplt

So... the saga continues.

I replaced the head gasket, with a decent copper one that I had. Torqued it down... ran it, torqued again.... ran the piss out of it around town, checked torque.. its good.

Runs the same... lack of power overall and in 4th running up slight inclines, and still regular misfire under load.

Compression check today;

1.  105
2.  90
3.  95
4. 103

Doesn't blow any oil (blue smoke) ever...

Ideas?

Question... Is there a chance that the initial timing of the cam / crank / timing chain wasn't quite right in the beginning??  Could that be an issue?  Thinking maybe if its off, perhaps not all the valves are fully closed on compression stroke...
1980 Mini 1000 (Canadian Spec).
998cc +60.  12G295 Head (ported, skimmed etc), VP7 Cam, Twin HS2.... sweet sweet 7.5" Cooper brakes!

tsumini

Still Hard to start? For that low of comprssion you probably crank and crank. Jumpering with a strong battery spins it up better too.
Sounds similar to what I had only I had only #2 and#4 low at 90. #1 and 3 were 115ish
Definitley need minimum of 115 IMO. Are you sure the head nuts weren't bottoming on head bolt threads?
Since all are the same I would suspect the combustion chamber volume too large.
Di you check the valves and make sure they are seating properly.

cstudep

I am sure this is a completely dumb question and I am not trying to hijack your thread, but I am going to go ahead and ask it anyway because I am not super savvy with these engines yet.

Is there such a thing as too much compression on these engines? Or is there anything else you can learn about a "built by someone else" motor based on compression numbers?

I get 150, 150, 140ish, 150. It jumps to about 70-75 on the first revolution and hits the highs listed in about 7 revolutions on all cylinders.

MiniDave

150 is fine. On the engine we built for Dan, it's close to 200....that's roughly a 10.3:1 compression ratio in his engine.

In theory, you can have too much compression - it will cause detonation and blown head gaskets and other internal damage - but it would be way higher numbers than even these.

Diesel engines run between 18 and 24:1 compression ratios for example
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

cstudep

Thanks for the info Dave. I was just curious what "normal" was for these engines since a lot of the numbers I have seen were quite a bit lower than what I was seeing. Didn't know where the upper end for these motors generally was or what the normal compression ratio range generally is.

All of my engine building experience in these sorts of things is on V8/v6 motors, motorcycle engines, and old diesels.


MiniDave

#95
I think the 150 range is normal for these engines, with std pistons and such, especially if done cold on a broken in engine.  They did make low compression versions of these engines too, for some markets (Canadian for example had 8:1 pistons) I'm not sure if any Mini engines were this low - but Sprites and other A series were for sure.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

94touring


tsumini

my shop manual (AKD 4935 Leyland) lists compression ratio under Engine Tuning Data for each engine and Model. Although the compression pressure listed doesn't compute very well and is also called cranking pressure.