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Blanking off the bypass is a must, as long as you have 1 or 2 1/8" holes in the rim of the stat.

The larger pulley will increase the fan speed but the extra pump speed won't help, few things online saying the pump is most efficient at around 2000rpm (Pump shaft speed?).

Was there any signs of head gasket issues? Coolant loss?

Are you checking the ignition timing with a strobe light? Is the pointer accurate?

Hipwell wrote:The larger pulley will increase the fan speed but the extra pump speed won't help, few things online saying the pump is most efficient at around 2000rpm (Pump shaft speed?).

Surely the other way around? A larger water pump pulley will have a slower speed than a smaller one, given that the crank pulley is bigger than both.

Hipwell wrote:Blanking off the bypass is a must, as long as you have 1 or 2 1/8" holes in the rim of the stat.

I plugged the head bypass thread, and changed the water pump to MiniSpares Evo no-bypass version. Both are reversible changes. I’m using a thermostat blanking sleeve initially, but yes will drill the thermostat rim when I switch back.

Hipwell wrote:The larger pulley will increase the fan speed

Other way around - am changing to the smaller, non-S pulley so it spins the pump and fan faster. i.e. more flow at low revs.

Hipwell wrote:Was there any signs of head gasket issues? Coolant loss?

It was a copper head gasket. Looked ok but am changing to Payne composite instead. Some coolant loss yes, when it boiled over after a hot run

Hipwell wrote:Are you checking the ignition timing with a strobe light? Is the pointer accurate?

TDC and cam timing was checked using a dial gauge on #1 piston and inlet valve. Ignition timing I did originally with a set-back strobe light, but I found using a vacuum gauge to give better results as the curve on the repro distributor was a bit hit and miss.

For the new (refurb original) distributor, I have the actual calibration curve measured on the dyno, so I can set up with static timing and know exactly what the advance is.

smithyrc30 wrote:

Hipwell wrote:The larger pulley will increase the fan speed but the extra pump speed won't help, few things online saying the pump is most efficient at around 2000rpm (Pump shaft speed?).

Surely the other way around? A larger water pump pulley will have a slower speed than a smaller one, given that the crank pulley is bigger than both.

Yes other way around, misquoted you.

iain1967s wrote:

Hipwell wrote:Blanking off the bypass is a must, as long as you have 1 or 2 1/8" holes in the rim of the stat.

I plugged the head bypass thread, and changed the water pump to MiniSpares Evo no-bypass version. Both are reversible changes. I’m using a thermostat blanking sleeve initially, but yes will drill the thermostat rim when I switch back.

Hipwell wrote:The larger pulley will increase the fan speed

Other way around - am changing to the smaller, non-S pulley so it spins the pump and fan faster. i.e. more flow at low revs.

Hipwell wrote:Was there any signs of head gasket issues? Coolant loss?

It was a copper head gasket. Looked ok but am changing to Payne composite instead. Some coolant loss yes, when it boiled over after a hot run

Hipwell wrote:Are you checking the ignition timing with a strobe light? Is the pointer accurate?

TDC and cam timing was checked using a dial gauge on #1 piston and inlet valve. Ignition timing I did originally with a set-back strobe light, but I found using a vacuum gauge to give better results as the curve on the repro distributor was a bit hit and miss.

For the new (refurb original) distributor, I have the actual calibration curve measured on the dyno, so I can set up with static timing and know exactly what the advance is.

Can we actually get some clarification to what the thermostat blanking sleeve does? Surely it’s there to blank/ restrict the bypass port in the head hence why some people find an advantage to running one with a thermostat. I would run a 82 degree stat or 74/5 if you prefer, climate dependant.

Don’t get how you can check the timing with a vacuum? Static timing is not accurate enough. Another thing, The graph you have may be totally made up(it’s hand drawn) his machine maybe inaccurate. Having the distributor in the engine is very different to having it tuned by a little motor on a distributor tester, it’s subject to much more torque, resonance and temperature changes. I know this from using a distributor tester many times, it was more useful for using to set the points gap on that adjusting an advance curve, again could have been a poor machine, there is no easy calibration.

All the vendors say to use the blanking sleeve to avoid hotspots in the head when running without a thermostat. But anyway I do not plan to use the thermostat blanking sleeve long term, I just want to prove that the ‘new’ cooling system is able to keep the engine cooled when run hard. If it looks ok, then I will reinstall a thermostat with the appropriate holes drilled, and see how it behaves then.

Regarding the ignition timing, when you don’t know the characteristics of the distributor curve, or have no reference for what the dynamic advance should be with modern fuels, a timing light isn’t going to help and all you can realistically do is set the timing for best behavior of the engine. For example the Cooper S 1967 data sheet says 2 degrees before TDC on 100 octane fuel and 3 degrees after for 97, both leaded fuels. That has no relevant to modern unleaded. See the discussion here: viewtopic.php?f=3&t=20434

Using a vacuum gauge to set the timing is fairly straightforward; advance the distributor to find the point of maximum stable inlet vacuum and then back off until the gauge drops one inch Hg.

IMHO the function of the blanking sleeve is obvious from its design.... Its there to stop water taking the path of least resistance; in from the pump and straight back out via the top hose... bypassing the engine ... Nothing at all to do with the bypass hose.....

The holes in the thermostat top plate are there to compensate for the lack of a bypass hose - should the thermostat fail closed...

Cheers, Ian

iain1967s wrote:All the vendors say to use the blanking sleeve to avoid hotspots in the head when running without a thermostat. But anyway I do not plan to use the thermostat blanking sleeve long term, I just want to prove that the ‘new’ cooling system is able to keep the engine cooled when run hard. If it looks ok, then I will reinstall a thermostat with the appropriate holes drilled, and see how it behaves then.

Regarding the ignition timing, when you don’t know the characteristics of the distributor curve, or have no reference for what the dynamic advance should be with modern fuels, a timing light isn’t going to help and all you can realistically do is set the timing for best behavior of the engine. For example the Cooper S 1967 data sheet says 2 degrees before TDC on 100 octane fuel and 3 degrees after for 97, both leaded fuels. That has no relevant to modern unleaded. See the discussion here: viewtopic.php?f=3&t=20434

Using a vacuum gauge to set the timing is fairly straightforward; advance the distributor to find the point of maximum stable inlet vacuum and then back off until the gauge drops one inch Hg.

Agree about the distributor curve, hence the advantage to have a vacuum advance fitted. I don’t see a reason to have the timing that far retarded at idle or static as long as the engine doesn’t run on.

I will do some more research on the blanking sleeve, did Mini’s come out the factory with a bellows type thermostat upto a certain date? Or always the wax stat we are used to? Is there any difference in the castings in the thermostat area on say a 1950’s Minor that did use a bellows type stat.

Captain Darling (Blackadder): I put a note in my diary today. It simply says…”bugger”

iain1967s wrote:this was 2/3 of 50:50 antifreeze with the other 1/3 topped up with a mix of water-wetter and distilled water i.e. aiming for around 1/3 antifreeze.

I just noticed in my amazon history that the last delivery was antifreeze concentrate, not the 50:50 premix I normally use. Annoying the label on the bottle is almost exactly the same. Grrr. So for that last road test (after draining the CLR) it was running 2/3 antifreeze.

this behaviour suggests to me that there’s no problem getting the heat out of the block/head and into the coolant, and the real problem is getting the heat out of the coolant and into the air

which I guess could easily be the case running on 70% antifreeze.

there seemed to be quite a lot of green salt crystals attached it, presumably from the CLR. Am hoping those will dissolve again over time.

When I removed the radiator and water pump last week, I noticed the ‘new’ coolant was cloudy when drained, yet the car had done less than 100 miles in between. I guess CLR crystallises in the water jacket when it cools, and only dissolves back into solution under heat/pressure. i.e. it wasn’t completely flushed out by cold water from a hose pipe.

After I put the engine back together, I’ll run a few heat cycles on plain water and drain it down while still warm.

Hipwell wrote: Can we actually get some clarification to what the thermostat blanking sleeve does? Surely it’s there to blank/ restrict the bypass port in the head hence why some people find an advantage to running one with a thermostat. I would run a 82 degree stat or 74/5 if you prefer, climate dependant.

The Blanking Sleeve covers over the port in the head under the Thermostat that leads to the By-pass Hose. So, in effect, fitting a Blanking Sleeve blocks off the Bypass System, though it doesn't 100% seal it off in the same way as removing and plugging it. The Port in the Head can be seen here;-



Removing the Thermostat won't achieve anything if there's an Overheating Issue, only that the coolant may take a little longer to get to the Overheated state. Fitting a Blanking Sleeve may assist in the case of Run Hot issues, but it won't cure Overheating Issues. I think we are all on the same page with this.

Hipwell wrote: Don’t get how you can check the timing with a vacuum?

With stock engines, this can be done, along with a host of other engine diagnosis, however, really, all this may give is a bit of a guide for items to check and look at, I wouldn't take Manifold Vacuum readings as gospel. If the engine is modified, then this is all well out the window.

There's been some debate in regards to which fan pushes the most Air and is best to run with.

While looking for the Factory's take on the Blanking Sleeve, I found this late document, which contains info on the Blanking Sleeve (though quite light on) and down the lower part of the page, the info which I recalled reading many moons ago in regards to the Fans, including the Plastic Types;-

Thanks Spider.

That document is actually where I started my diagnosis from, before first posting on this thread

i.e. running a tropical 6-blade fan, cooler 75°C thermostat, and the 3-row larger capacity 'S' radiator.

At one point I even took the driving lights bar off the front of the car for “better airflow” - it made absolutely no difference

I only use Evans waterless coolant in my classic cars,never any problems!

+1 for Brian as above. Been using it in both my 69 S and 2000 RCS-5 for a few years now in the hottest summers. Never had a problem of any kind. No pressure cap (except to keep the liquid in of course) so no pressure to load up the system and hoses. My pal also uses it now in his temperamental Dolomite Sprint too. Now if there ever was a car that was coolant critical, it's a dolly

I would like to get back on Evans eventually, for the long-term corrosion protection and ease of maintenance. If I can get to the point that it doesn’t overheat on water, and then behaves on 30% antifreeze mix, I’ll be more confident to flush it all dry again and switch back to Evans next year.

I am sure as others have said, that what this old engine really needs is an acid bath to clean out the internal crud. Next years project may be to send it out for a rebore to +40 and rebuild with new S pistons, in which case it can be dipped then.

My gut feel is that the CLR did its job of cleaning inside the waterways, and that it was just my mistake of running 2/3 antifreeze that skewed the result. Am pretty annoyed with myself for missing that.

But the head is off at the moment due to me replacing valve guides on #3 cylinder, and the weather has not been cooperating with me putting it all back together at weekends - I only have a rented garage to work in, half a mile from my house with no mains electricity so no light or heat...

Hopefully I’ll have it running again this weekend, and we will see what’s what before the big freeze. But for now, I just want to complete my checklist to ensure the cooling system is at least in proper condition, and take it from there - not sure if I'll get around to fitting the new distributor this year.

[ Plain distilled water, 82° thermostat, fast idle until engine is warm to allow the new head gasket to seal. That should also dissolve whatever remains of the CLR crystals, so drain while warm and refill with distilled water when cold. Re-torque head, run to temperature and drain again, fill with 50% antifreeze and pack the car away for winter... ready to be continued in April ]

All good fun and games...

Got the head back on, valves set, and filled with straight distilled water then took it for a local drive for 15 mins or so. Thermostat opened but temperature never got above half way to normal. Drained out the already very rusty water while hot - so the CLR was obviously working.

Unfortunately I didn’t have time to do a second fill and flush, or to use the chemical flush that I bought off Amazon. Those will have to wait to Spring as the forecast calls for -6°C this week, so I just refilled with 50% water and antifreeze mix ready for winter.

One thing I did differently when reassembling the new radiator, water pump etc. is to omit the metal fan spacer. I noticed with the spacer fitted the blades were positioned well inside the cowling, whereas for most efficient airflow the tips should be running directly in the aperture.

Can’t say I noticed any additional airflow at the wheel arch, but the noise level of the fan certainly increased! Might revisit that next year, but for now at least things are behaving better.

Early days yet, but it does sound like you're making some progress.

I tend to run the 6 blade fans without a spacer, just making sure I have 1/2" between the fan and the radiator fins so I can slip a new belt in there if I have to. The fit, along with the 52 mm, 4 tube Radiator is 'cosy' to say the least. The fan will work best when most of it is within the cowling.

Very minor point Iain but your heater cable looks toooooo long. Is it from another car?

Agree with you and Spider about the fan and cooling. In the back of my brain Venturi (Prof Venturi's law or theory) says that air disperses at 29 degrees outwards. So if the tips of the fan blades are within the cowl, all that air MUST go to (and through(?) the rad

Peter Laidler wrote:Very minor point Iain but your heater cable looks toooooo long. Is it from another car?

Left hand drive Peter, so the choke and heater controls are reversed locations on the panel, hence the standard Mk1 cable is ‘too long’ being on the same side as the heater valve, rather than having to cross the engine bay diagonally.

Two more fast runs since re-re-build, and it’s behaving itself. Of course, ambient temperatures are down in the 40’s°F now, so it’s not a sure thing. But I see the thermostat doing its job rather than having to stay open all the time.

The car is tucked up for the winter now. But before I put the new water pump etc. on I took a photo down into the water jacket. The CLR seems to have done a great job scavenging out all the rust and calcium buildup that was in there. Just the slightest trace of it left at the top of the photo - previously the whole block had an orangey-yellow layer of that junk.

I will say, if you do use CLR my advice is don’t run the engine too hard because it seems to crystallize after if cools if the fluid has boiled. Flushing it out again then needs several cycles of clean water, and drain when warm so the stuff is still in solution. Doesn’t come out if you just flush cold. But once it’s out, so is all the junk.

Thanks to Spider for the CLR suggestion.