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Post by paddymk2 on Apr 3, 2018 3:14:27 GMT
Hi Guys - I swapped the thermostat over (from 180 = 82oC) to a 170 high flow version.
After swapping Tstat and topping up coolant I noticed coolant at the radiator cap. Its a new cap but it looks defective - I put the old one in instead and no sign of leaks.
I turned the mix nut up a couple of flats (because I couldn't cope with the (rich) smoke at the tail pipe.)
I turned the idle screw down back about 1/4 of a turn - to bring the RPM down to about 700.
The vacuum increased (with the leaner ratio)
And went for an extended run to the city, (& coffee) and back.
Temp stayed below the N for most of the run and came up to N while idling at lights.
Still gotta look at compression ratio.
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Post by paddymk2 on Apr 3, 2018 8:52:23 GMT
By the way was doing some training with IR camera and had to practice on something hot. The radiator looked very uniform - nothing leapt out at me as unusually hot or wet (cold) - except shiny surfaces.    |
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Post by Penguin45 on Apr 3, 2018 15:24:23 GMT
Hi Guys - I swapped the thermostat over (from 180 = 82oC) to a 170 high flow version. After swapping Tstat and topping up coolant I noticed coolant at the radiator cap. Its a new cap but it looks defective - I put the old one in instead and no sign of leaks. I turned the mix nut up a couple of flats (because I couldn't cope with the (rich) smoke at the tail pipe.) I turned the idle screw down back about 1/4 of a turn - to bring the RPM down to about 700. The vacuum increased (with the leaner ratio) And went for an extended run to the city, (& coffee) and back. Temp stayed below the N for most of the run and came up to N while idling at lights. Still gotta look at compression ratio. Clocked this post before work this morning. As I pottered round in the Red Dog, I noticed that the temperature needle settled itself on the left leg of the N in the middle. A 15 minute bout of faster running moved the needle to exactly the centre of the gauge. I suspect that you are very close with your current settings. Chris. |
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Post by snoopy11 on Apr 3, 2018 17:58:48 GMT
Sorry if this has already been said. I haven’t time to read the nine pages of posts.
Have we taken into account that at the time of design the petrol was about 80 octane. Modern fuel is 95 octane that burns much hotter
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Post by tommydp on Apr 3, 2018 20:41:41 GMT
Sounds rather normal now, in my opinion.
As long as the gauge is in the N area somewhere, it should be fine. Mine is usually at the left part of the N, going up hill it creeps to the middle. When stopped after a drive the temp will rise, so turning ignition on after a few minutes the gauge will be at the right part of the N. However, once started the gauge falls, indicating its cooling/ circulating.
As John Twist says: The N area of the gauge is normal - it's not over heating before it boils. He mentions putting insulating tape over the gauge as an alternative to being obsessed with the temp gauge:-) Check out "MGB cooling" by University motors on Youtube.
Best regards, Tommy
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Post by dave1800 on Apr 3, 2018 23:33:25 GMT
A good result, the thermal image shows the water in the radiator is a running freely. Now time to get the mixture right, I suggest keep the idle speed up to get better accuracy across the range. It is better to check the compression after setting the mixture as if it is too rich you may well get lower readings as the oil is washed from the cylinder walls.
David
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Post by paddymk2 on Apr 9, 2018 14:31:05 GMT
Took the car in for safety check. The car checked out well - brakes, steering, engine oil, trans oil (its not possible to access the drain for the trans without removing the sump guard - so we sucked out about 2 1/2 litres from the top.) Engine oil was black - guess from running it rich while doing multiple tests etc. Had a bit of an issue with the oil filter converter (to Z9 filter) but got it sorted. Checked cooling system for pressure - all ok. But then after a short drive noticed water leaking at the top pf the radiator. Then my good man informed me that I'd got the wrong cap (both original and replacement when radiator was done ) in that it should be a Recovery type cap. He also picked out that all the grommets and plugs where missing in the boot - which could lead to fumes into the cabin (and I thought the headaches where just Above N woes). So generally good but well worth the expert eye on the subject.  Had to leave things there - had to pick up the munchkin - from the pub. Paddy |
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Post by tommydp on Apr 9, 2018 19:38:08 GMT
Hi!
The radiator cap should be a blanking cap only. If it leaks under pressure, try bending the locking "ears" of the cap, to make it seal more tightly.
Expansion tank cap should be 13 PSI.
Regards, Tommy
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Post by paddymk2 on Apr 10, 2018 5:24:34 GMT
Thanks Tommy!
That might explain something - since both the original and new were non return pressure relief type.
I'll keep an eye on it and find a blank cap. (Tridon site indicated both Return and non return both pressure relief type.http://www.tridon.com.au/PartFinder/Austin/1800/1969)
Summer has returned for this week - it too hot to be in the car...
Cheers Paddy
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Post by paddymk2 on Apr 14, 2018 13:28:32 GMT
Hi Guys
Eventually got a chance to check the compression - the results are not what I'd hoped for but here they are anyway
Engine Cold Engine Warmed Up Engine Warmed Up and a squirt of oil
Cylinder 1 100PSI 120(98)PSI 115PSI
Cylinder 2 102PSI 105PSI 95PSI
Cylinder 3 76PSI 105PSI 95PSI
Cylinder 4 120PSI 98PSI 125PSI
Among other stuff the values all seem very low.
I did have my foot on the throttle and the air filter off for all tests.
I've got the right caps on the radiator now.
Best regards
Paddy
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Post by tommydp on Apr 14, 2018 20:36:50 GMT
Strange results, as they're very low and three cylinders have a lower reading with oil in them. I can't see how the oil test can give lower readings, it just doesn't make sense.
The main thing is that the cylinders read approximately the same, however a reasonable good working engine should have 150 or more. Most 1800s I've worked on have been around 170.
First of all, are you absolutely certain the valve clearances are not to tight? It might be a good idea to press the valve down, when it's set for clearance checking, with a block of wood resting on the bonnet lock panel, let it return and then check the clearance. It may close further than when turning the engine by hand. I suppose it's down to worn guides. I've done this and have excellent vacuum, and still quiet(ish) valves.
With such low compression readings I'd also do a leak test, to hear where the air is escaping. Turn each cylinder to tdc firing, valves closed. Get compressed air into the cylinder, and listen where it goes. A leaky inlet valve makes the air escape through the carb, and a leaky exhaust valve through the exhaust. Bad rings allows the air to go into the sump (some ir is escaping here even on a good engine)
Good luck!
Tommy
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Post by Penguin45 on Apr 14, 2018 23:43:06 GMT
Knackered valve seats might be a good bet. After the head was re-worked on the red car, I got 150-155psi across all 4 pots.
Chris.
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Post by dave1800 on Apr 15, 2018 0:48:29 GMT
As Tommy suggests try a leak down test with compressed air if available to find the source of the leak (a smoke test is even better if you know anyone who has a smoke machine). Make sure the valve clearances aren't too tight. -if in doubt loosen them for the compression test. Assuming the compression gauge isn't defective then the very low readings suggest either poorly seated valves or an air leak. The lower reading on no 3 may be a cylinder head gasket leak as this is freqently the area that fails.
I assume you had all the plugs out for the test and that the battery is good and you let the engine spin until the maximum readings were obtained (typically around 5 seconds). If the engine spins too slowly you will get a lower reading. How much oil did you put in the bores - the results don't seem to make sense.
At cranking speed the piston in the carb will hardly rise at all so it is the primary restriction on the amount of air passing through, so foot on of off the throttle should make no real difference.
David
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Post by paddymk2 on Apr 15, 2018 11:06:58 GMT
Hi Dave, Tommy, Chris,
Thanks for the analysis.
Like a lot of this work I'm doing this for the first time so there's room for doing something daft.
Initially I had borrowed a little push in pressure meter with a rubber tip, I ran it with an assistant I got 140PSI on cylinder 1 but I gave up as I couldn't hold the rubber tip in tight enough to stop it squeaking (or rather squawking.)
I picked up a new inexpensive kit with screw-in adapters.
I was a bit concerned about the battery as at 12 readings each of 12 cranks I'm not sure the battery would hold up. So I did put it on charge for 48 hrs before the test. But when I tried to repeat the warm test on cylinder 1 at the end of that set I got a much lower 98PSI.
I squirted about 0.5cc of oil into the cylinders - trying to bet it into the chamber from a fat syringe.
When I did the test I was stepping in and out of the cabin. So I couldn't get an impression of how the needle was moving.
I may be able to entice my assistant to help again.
I don't have ready access to a compressor but I do occasionally use a smoke machine at work, but I've always found them difficult to follow - either too little or swamped in smoke.
Regarding the valve clearances I wont get a chance for a wee while as I've used up both my rocker cover spare gaskets.
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Other than the oil from the test above the tail pipe does not appear smokey. I would say the engine sounded quieter while I was burning out that oil. Would valve seat recession tally with the engine being really stiff to turn over by hand- even when all plugs are out? And does that lead to the engine being unusually hot?
Cheers
Paddy
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Post by dave1800 on Apr 15, 2018 13:18:12 GMT
Hi Dave, Tommy, Chris, Thanks for the analysis. Like a lot of this work I'm doing this for the first time so there's room for doing something daft. Initially I had borrowed a little push in pressure meter with a rubber tip, I ran it with an assistant I got 140PSI on cylinder 1 but I gave up as I couldn't hold the rubber tip in tight enough to stop it squeaking (or rather squawking.) I picked up a new inexpensive kit with screw-in adapters. I was a bit concerned about the battery as at 12 readings each of 12 cranks I'm not sure the battery would hold up. So I did put it on charge for 48 hrs before the test. But when I tried to repeat the warm test on cylinder 1 at the end of that set I got a much lower 98PSI. Did you re-try the rubber tipped push in gauge again to see if you had 140psi?
With the spark plugs out the battery current during cranking will only be a fraction of that when starting but it is important that it is charged to get an accurate reading.
I squirted about 0.5cc of oil into the cylinders - trying to bet it into the chamber from a fat syringe. When I did the test I was stepping in and out of the cabin. So I couldn't get an impression of how the needle was moving. I may be able to entice my assistant to help again. 0.5cc is not really enough you need the oil to flow around the rings to form a temporary seal. About 5-8 cc would be better.
I don't have ready access to a compressor but I do occasionally use a smoke machine at work, but I've always found them difficult to follow - either too little or swamped in smoke. If you can get the smoke into each cylinder in turn through the plug holes you will see the smoke from the carb (remove the air filter) if there is an inlet valve not seating, or from the exhaust after a while if an exhaust valve (more liikely than an inlet valve). There will be some smoke from the oil filler neck - cap removed - if excessive it suggests rings. Compare each cylinder and also check for leaks around the inlet manifold and gasket and all around the pipework and head.Regarding the valve clearances I wont get a chance for a wee while as I've used up both my rocker cover spare gaskets. , Other than the oil from the test above the tail pipe does not appear smokey. I would say the engine sounded quieter while I was burning out that oil. Would valve seat recession tally with the engine being really stiff to turn over by hand - even when all plugs are out? No! And does that lead to the engine being unusually hot? We need to diagnose the compression issue before being able to draw conclusions about the effect on engine temperature. We (you!) will get there! David
Cheers Paddy |
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