New engine problems...

[aspira]

Hi

Thanks to the support from many on this forum I built my first V8, replacing the 1800 MGB engine. I almost finished the build about 3 years ago but fell ill so couldn’t continue. Now fully recovered, I’m back to it , spending the last 3 months or so welding in new floor for the MG, refitting the inside and trying to remember where I got to with the engine & everything else.

I do have some engineering experience but the V8 was a big project for me, but I took it slowly and was very careful and got a lot of support from here. It’s a standard Rover 3500 block. I had the crank and block machined, fitted new pistons and all other parts. It runs an Edelbroke carb and a Mazda MX5 gearbox. Brakes are refurbished Princess 4 callipers.

Last week I ran it for the first time in over 4 years and it sounded really sweet. Ran it up to temperature and all was looking good.The brakes need a bit of bleeding but that shouldn’t be too difficult to sort out.

Today, I took it around the block for the first time. Got a few issues.

The prop shaft is rubbing on the chassis. I remember it was a very tight fit, but I think I should be able to drop the gearbox a little with some spacers, assuming it’s rubbing on the top of the floor plan.

The biggest concern, unfortunately is the engine. It’s started to create a lot of smoke and when revved a little higher started to make some bad noises from the engine. I’ve added a video below that will give you some ideas. I don’t have enough experience to fathom out what the root cause is and the step I need to start running through. Oil pressure remain steady at about 30psi and I haven’t taken any compression tests yet.

I've added a video link below so you can hear and see what's going on.
https://www.dropbox.com/s/7rflhppujmxfr ... 7.mp4?dl=0

Obviously feeling a little despondent and worried what could have done wrong, so any help much appreciated.
Stephen

[ratwing]

I suppose you could try running it without the fanbelt to see if the noise is anything to do with the alternator or water pump?

[aspira]

Some feedback...

I think the problems have occured because of overheating. I wanted to test that the electric fan thermo switch was working. It didn't kick in at about 80º so I assummed it hadn't reached that temperature. After further investigation I found the switch to be faulty so I suspect I've been running it hotter that I should probably causing the high pitch noice, as suggested.

I took some compression tests. Engine cold, with a good battery on the starter.

Not good news...
Cyclinder one reading 75-80
Cylinder's 2-8 all similar at about 125 but that seems a little low to me for a newly rebuilt engine?

I tried Cylinder 1 with a little oil, didn't make any difference.

I'm guessing this probably means there's a problem with #1 piston or the rings.

Any further thoughts?
Thank you

[ratwing]

I haven't used one myself so don't know how good they are but what about trying one of those endoscope things to have a look inside the cylinder?

[GDCobra]

I tried Cylinder 1 with a little oil, didn't make any difference.

I'm guessing this probably means there's a problem with #1 piston or the rings.

Any further thoughts?
Thank you

My understanding is that adding oil is supposed to give a bettter reading if the problem is due to the piston/rings, if that is the case this would make me suspect valves or head sealing (warped head or blown gasket - Or both). Having said that I'm not sure how well the 'oil test' works on a V engine, I'd have thought all the oil would migrate to the low side of the piston.

Worth checking again as it is also possible the result was a false negative.

If still bad I'd say the next step is a leak-down as this should help identify where the compression loss is.

[GDCobra]

I think the problems have occured because of overheating. I wanted to test that the electric fan thermo switch was working. It didn't kick in at about 80º so I assummed it hadn't reached that temperature. After further investigation I found the switch to be faulty so I suspect I've been running it hotter that I should probably causing the high pitch noice, as suggested.

Based on what you've put regarding the temperature readings I'm assuming you have a temperature gauge in the car? If so what did this get up to?
80° seems a bit low for fan coming on, I don't think your thermostat would even have opened at that level, I'd expect into the 90's for fan trigger.

[aspira]

Yes, I do have an endoscope, not used it much tbh - but I'll give that a go. I guess it would identify if I've put a hole in the top of the piston. That should be easy to spot.

I've checked #1 a few times and it displays the same low reading everytime with the compression tester.

The leakdown kits aren't that expensive to buy (I don't have one), but I also don't have any air, so would need to take it to a local garage.

I guess, if the compression is low it can only be the head gasket or warped head, inlet or exhaust valves or a piston - all of which requires the head to come off. So not sure if doing a leakdown test is worthwhile? I suppose once the head's off you cant test it, and if it's not obvious then how would you identify the problem. I might have answered my own question here, unless I've missed something.

Regarding temperature. It creeped up to just over halfway. My 15lb reseviour cap was already starting to complain and the fan still did't kick in so I shut it down. I did try turning the temp down to 70º whist it was still running - nothing. Once it had coolled down I tested the thermo switch and found it wasn't working. Therefore my assumption was that I overheated the engine which was the cause of the high sqealing sound you hear on the video, coming from the water pump (I think) and probably the cause of the low compression in #1.

If that's the wrong assumption and I didn't overheat it (as per GDCobra's point) then I guess I'm back to the drawing board to understand the low reading.

Without wishing to compliciate things further, I spent a long time working out the best way to route my water flow - slightly different to usual aparently. I used a method by an engineer called Bill Mccullough who ran a V8 a wrote a long paper on this. Anyway I've attached my diagram - just in case anyone thinks this could have been part of the problem.

[scudderfish]

The belt below the alternator looked to be flapping about a bit. Is it tensioned enough?

[GDCobra]

I guess, if the compression is low it can only be the head gasket or warped head, inlet or exhaust valves or a piston - all of which requires the head to come off. So not sure if doing a leakdown test is worthwhile? I suppose once the head's off you cant test it, and if it's not obvious then how would you identify the problem. I might have answered my own question here, unless I've missed something.

Personally I'd always rather diagnose a system before taking it apart as it's too late by that point, this is why a leak-down test would appear to be the next base to cover, at least then when you do go into major surgery you'll know what to target.
If you don't have air couldn't you get a garage to do the test. OK, you'll have to pay for this but it would seem to be better than thrashing about blindly.

Regarding temperature. It creeped up to just over halfway. My 15lb reseviour cap was already starting to complain and the fan still did't kick in so I shut it down. I did try turning the temp down to 70º whist it was still running - nothing. Once it had coolled down I tested the thermo switch and found it wasn't working. Therefore my assumption was that I overheated the engine which was the cause of the high sqealing sound you hear on the video, coming from the water pump (I think) and probably the cause of the low compression in #1.

I'm a bit confused by this one minute you are talking about temperature in °C the next you are talking about 'half way', do you have a gauge which gives you an actual temperature reading or just a pointer on a scale?
Even if it is just a pointer on a scale surely 'half way' shouldn't be anything to cause a problem and whether or not the thermo switch was working I still think 80° is too low for the fan coming on (although that's better than too late!).

[ratwing]

I use a very similar cooling system except that I've an unpressurised overflow/return catch tank and no heater - Turner Engineering put temperature warning stickers on their blocks and mine hasn't gone over 88ºC in the 9 years I've had it so I wouldn't have thought that's your problem (assuming all the system components are working as they should).

[aspira]

Re the belt tentioning - I originally thought that it might have been too tight. About 1/2 inch movement? I think the crank pulley and water pump are aligned but maybe the alternator pulley isn't - I don't think I've got that aligned spot on.

I'm just looking around for a good North London garage that can do a leakdown test for me or possibly a mobile mechanic with a compressor. I agree, I'd like to have some idea what I'm getting into. I'm also going to try the endoscope this evening - see if that gives me any ideas.

The main concern, is the root cause. If the problem was not caused by overheating, which perhaps now seems likley, I still need to identify why a newly built engine had a sticky valve, damaged piston or whatever the problem turns out to be.

Thanks for confirming the water flow diagram. Re the components, I guess I should pull out the thermostat and check it's working. I'm sure I did when I built the engine. The water pump was a new short nosed version but the engine's has sat for almost four years. I'm not sure how to test the water pump.

[GDCobra]

The main concern, is the root cause. If the problem was not caused by overheating, which perhaps now seems likley, I still need to identify why a newly built engine had a sticky valve, damaged piston or whatever the problem turns out to be.

I assume you mean this is the 'main concern' after you've found what the problem is .
There's not too much point in working out what can cause a problem before you know the cause unless it is to work out if there is anything which can be done in the way of diagnostic before you manage to get a leak-down test.

What can cause low pressure in one cylinder? Choices to me seem to be
Damaged piston, possibly hole. Unlikely but if you can get hold of an endoscope this may help identify.
Damaged rings - Not a much you can do to check that.
Damaged bore - May see it with endoscope but unlikely that it can be scored enough to cause high compression losss so early in life

Head to block seal - May give crank case compression and combustion smell in breather, possibly hard to identify beyond 'normal' aroma though.

Sticking valves - May be worth flipping off the valve cover and seeing if any evidence of a sticking valve, are the rockers loose when on compression stroke? If you are running (standard) hydraulic lifters they should never be loose.
Are they (particularly the inlet) opening on induction? No or limited induction equals nothing/little to compress.

Can't really think of anywhere else you could be losing compression, at least in one cylinder.
I'm assuming you are doing the test with throttle wide open? Not that this would only affect one cylinder.

[aspira]

Thanks for those pointers... and yes you're right, I need to find the problem first and this will help me understand whether I can get away with just pulling the head or whether I have to take the engine out. I'm still hoping this will just be a sticking valve - so it's definatley worth pulling off the valve covers - thank you. I tried using an endoscope but it was difficult to see anything useful, although I don't think there's a hole in the piston.

I'm still hoping this will be isolated to that single cylinder. However, whilst cylinder #1 is the problem - low at 75psi, the others are all reading at about 125psi. Reading other posts on here, it sounds like those other cylinders are also quite low.

I didn't run the compression tests with the throttle wide open so I'll re-run the tests again and see if that pushes the other readings up a little. I'll check the valves as well (yes im using std lifters) see if I can isolate the issue just to #1 or if I have a bigger problem.

All the plugs were black so that could also point to low compression but apart from one trip around the block, I've only ran the engine on the drive, so that could also be the reason for the black plugs.

I think ultimately, as suggested I need to run a leak down test so I can better understand the extent of the problem.

[GDCobra]

I'm still hoping this will be isolated to that single cylinder. However, whilst cylinder #1 is the problem - low at 75psi, the others are all reading at about 125psi. Reading other posts on here, it sounds like those other cylinders are also quite low.

I wouldn't worry too much about the numbers on the others if they are all even, some people chase big number and, as with many things in life, think bigger is better. From memory mine were all about 150 when I tested them but all even so I'm not concerned, I put it down to the cam which is, possibly, running more overlap hence not getting a complete cylinder fill at cranking RPM.
Your readings could be a little low simply due to your cranking RPM, camshaft, or even just the tester you are using and possibly other causes.
Not having WoT may give you lower readings although this usually means it takes a few more revolutions to max out, I'm assuming you did keep cranking until the reading went no higher?
Not sure if I mentioned in ealier post but when you take the valve covers off check for equal lift on #1 valves as well as no loosness on compression.
Also, as someone mentioned earlier, worth taking that belt off, briefly, to check if the sound becomes better.

[aspira]

Thanks for detailed and clear response. A few things to work on over the weekend. Much appreciated