How's the Mini coming along?  Is it fixed yet?

As you already have the 12G940 cylinder head and not the AEG163 head you have probably blown the head gasket between #3 and #4 cylinders.

Thanks for your input...Here is what I found on my motor notes which I assume are correct?

1275 cc cooper s block, crank ,rods, adjustable timing gears, double row timing chain, cooper s forged rockers on thick wall shaft, 12g940 cylinder head , 35mm inlet  29mm exhaust valves, distributor number 23d4 40819h

Yup, something's up!  But cheer up, a Mini head can be off in half an hour!

Did you notice if it has the AEG163 head?  If so your 10 good years have been good service. A nicely done 12G940 will look more original, but a big valve aluminum head will work great for you high compression ratio.

Don't throw in the towel yet though, could still just be a head gasket.  Usually the common crack for the 163 head is between the valves of one cylinder, but you have something affecting two....

Ok so finally got around to check the compression and "Houston, We have a Problem"......not sure acuracy of gauge but let's assume it is close....I held throttle wide open for each test....

Cylinder 4 - 65 psi

Cylinder 3 - 80 psi

Cylinder 2 - 195 psi

Cylinder 1 - 200 psi

Sick to my stomach!  Off to fridge to get a few Hop Knots and kill the pain!!!!!  My baby done blowd up!!!

Thoughts?

Spitting back through the carb can indicate too lean a mixture; I would check the manifold flange is flat at the intake ports, and the gasket there is still intact.
It is easy to bend the alloy flanges if the nuts are over-tightened.
Also check the gasket against the manifold- if it's been ported out a lot you may need to use the `big port' gasket.

Thanks for the input...can't remember head details but I have them somewhere...I will do a compression /leak down test....waiting to borrow compression tool...I will report back on compression test....

Mile:

Does your engine have the original AEG163 Cooper S head or the 12G940 head?

I ask because your description sounds like what I went through when my AEG163 head cracked.

The crack was between the valves on Cyl 2.

Exhaust blowing past the exhaust valve at the crack burned a "V" shaped gap in the side of the exhaust valve head.

The valve head looked like it was cut with a cutting torch.

I checked everything that you checked, but I did not have a compression tester.

The engine was running well but when I started up a hill, the car acted as if it had power on only three cylanders.

No misfire, no smoke, nothing unusual except much less power.

Now, I carry a compression tester in my tool box and the engine has a 12G940 on it.

Russ

Thanks Pat..Hope all is well..When can I get you to swing by the house and take a good look at the mini???  thinking of towing it over to joe's shop and having Kevin turn a few wrenches on it...Kevin knows his shizzle....normally I would dive in but my back is shot....would really appreciate all your thoughts or help....how the hell is Simon doing????

Best,

Mike

Pommie lives up in Portland.  He visits the message forum now and then.  Will probably see your post and respond.

Thanks for all the thoughts and well wishes....L5 S1 distectomy and lapendectomy....4 days in and 4 weeks to go of just chilling out....then 4 weeks of basic rehab then finally back spinning on the bike after 2 yrs off....Tell me I won't be suffering my arse off those first few months of riding!! Lots of base miles....Bored as hell but feel awesome...May have to dig into some of the old slot car collection and do some resto work...I will keep everyone posted to the final outcome of the Mini repair...

Pete, glad to hear you are alive and kicking!!! Been a while...If anyone knows the whereabouts of Ex AZ Simon have him track me down....

Best!

Rabbit

Peter

Mike get well soon! if its not your daily driver take some time to recover and then have a look. You ll be more focused and observing.. 

i am fairly certain (99.9%) its not a spark/electrical related issue...excellent arch on points and at each plug....I am nervously thinking the intake valve may be the issue per Lankford...it makes a strong "pap pap pap" noise when you blip the throttle...This noise seems more through the exhaust than under the valve cover?? Had back surgery Friday so I am out of pocket bending over that motor for atleast 8 weeks to check compression and float bowels etc...I think I will tow this one in for the pros, particularly if something broke on the top end...Probbaly take a few more pain pills and a valium as well...Not sure which hurts worse, the back or the fact the mini is injured??  Dam thing died 2 days before surgery...has run t\like a top for 10+ years....it was almost like the damn thing wanted to be down and out with me.....

(A) This sounds like intake valve for 1 or 2 is not closing properly, worn ,stuck ,etc, and is "regurgitating."  But why sudden change?

This is where a vacuum gauge would really help, but of course configuration of intake manifold or runners or lack of vacuum port would prevent that usage. 

(B) On the other hand, is the carb somehow stuck rich (but not long enough to darken the plugs) and the fumes you see is "standoff" . Ordinarily, this only happens at high rpm or WOT, so that gets me back to A

the car would only be able to idle at high rpm and wouln't start without half to full throttle.. 

Would a failed intake manifold gasket cause that symptom?  It would certainly cause a lean condition if the gasket has failed on one of the two intake ports.  It's easy to check to see if you have an intake leak on the cyl 1/2 intake runner - with the engine idling (if it will) spray some carb cleaner around the intake manifold flange where it bolts to the head.  If the engine runs better or RPMs increase then you likely have a failed intake gasket.

Rev the engine to create the problem then switch the engine off.  Remove the float bowl lids from each HS4 and see if one of them is low or empty.

Did you check the compression?  Head gasket?