1961 Mark II. 3.8/9.1 w/ auto
About 60K miles showing.
Sitting for as long as anyone alive can remember.

Although at one time I did a lot of really intensive work on vehicles, including Jaguars, it has been a Very Long time since then.

Engine turns but only #1 has 150 (dry) / 167 (wet) - the other five cylinders are 0-8 wet and dry. Cam covers off to peek and found only #6 intake appears sticky; just slow to close: not stuck open.

That's the known-so-far - but my question is:

After the head comes off will I be able to leave the engine/trans in place, drop the oil pan, and pull the pistons out the top? Somewhere in my (very dimly lit these days) memory is a picture of working on some engine on which the pistons had to come out the bottom - because the big end bearings were larger than the bore. It doesn't seem possible on a 3.8 or 4.2 - but, as I say; that was a Very Long time ago. Maybe it's just the valves - but with the head off anyway . . . .

Hmmm . . . . wait a minute - maybe I'll rework the valves and then use the old gasket to temporarily replace the head. Check the compression then and make a decision about going further. And a look at the bores can help make a decision.

But anyway: the front suspension has to come down - to pull the engine out. But can I leave the engine in to do a 'cheap & dirty' rebuild? I ask, for one thing, because I have extremely limited facilities here: no garage or lift and so forth. Hell; I barely have a tree! <g>

CJE
---------

 

Yes, the pistons can be pulled from the top - how could one compress the rings and install the pistons from the bottom _ on any engine ???
Don't over hone the bores, if there is a ridge then you will need to re-bore and go with over sized pistons.
If you hone it out to get rid of the ridge, then the bore will be too big and not parallel, this will cause piston slap and excessive blow-by.

The engine can be pulled from the top too, and having the head off makes that much easier.

There's a chance that just doing a valve job may be enough, but the increased compression may force combustion gasses past a worn bottom end _ even if the bottom doesn't look worn.
If it were me I would find a way to pull the engine and do things properly.
If you have 150 dry and 167 wet, then the bottom end probably needs doing.

 

It was just like putting them in from the top - except that the crankshaft had to be out of the block.

Would you expect to find a deep ridge at the top of the bore on a 60,000 mile engine?

What would be considered normal compression pressures on a 9.1 3.8 engine ?

CJE
-------

 

Have you got no undercover facility at all ? Doing a proper rebuild will be extremely uncomfortable without at least something to keep the rain off, even if it's just a lean-to or a car port. Do you have a concreted driveway area ? It is possible to remove engine and gearbox out in the open using a hired-in engine crane, then split the engine and gearbox, and mount the engine on a wheel-able engine stand and get that under cover somewhere. When I rebuilt my XJ6 engine the car had to sit outside whilst the engine was in the garage undergoing its rebuild.

 

It's pretty much impossible to tell what the bores are like just based in miles alone.
If the 60K was good highway miles where the car was not allowed to sit and idle when cold and the oil was changed regularly, then I would not expect much wear.
If those miles were short in town runs where and the engine is full of sludge and carbon, then I would expect a ridge.

Atmospheric pressure at sea level is 14.696 per square inch, so 9 time that would be 132.264.
It's not so much that it should be high, but it should be with in five pounds of each other.

 

1962 Mk 2 w/ 3.8/9.1 & automatic

Yes; it will be inconvenient and uncomfortable. No question about that. <g>

Yes; I can pull the engine even working in a dirt driveway.

Yes; I suppose a tent could be arranged.

But, If I remove the front suspension assembly -

Can I then remove, and later re-install, the oil pan with the engine still in the chassis?

CJE
--------------

 

Well; the engine oil that came in the engine was used / clearly not new but quite clean. And the area under the cam covers looks "clean" but not "cleaned up" - if you know what I mean. No sludge or yak in there..

BTW: the time the VIN was registered for road use was 1983 I have just found out. So 36 years of apparent idleness.

I get no sense that the car was tampered with, scrambled, and then the project abandoned. It appears to have been used, maintained, and then left in a garage. The last owner has been dead for at least twenty years. His grandson sold the car.

I was just curious what your experience has been with Jaguar bore wear. GM products from the 1950's would have a 1/16"+ ridge at 75K miles. Studebaker engines would have absolutely zero ridge at 250K miles. My 4.2's always ran like nice watches so I never had them that far apart. On the XKE's the oil pan drops easily so I did replace bearings when the oil pressure was suffering.

CJE
--------

 

What are the possible issues if the compressions are not within 5 or, say, 10 psi of each other?

 

..

 

The causes would be pistons rings that are not sealing well. And/or valve faces that are not sealing well.

The consequences of compression pressures exceeding a 10% variation are that the cylinders then each produce substantially different amounts of horsepower - which makes for a rough running engine which feels like it's out of balance.

 

Thanks Charles. So if you do have a greater than 10% difference and the engine still runs smoothly, is it such a big deal?
Also how do we assess this "10%". For instance say we have 6 cylinders with the following compressions
140,150, 150, 150,150,160.

In theory the average is 150 and all cylinders are within 10% of that average even though one is within -10% and the other within +10%

Thanks

 

It would not be any big deal to me; no.

If the engine ran satisfactorily enough - I would keep the data in mind without acting to correct it as I have long ago given up perfectionism - in keeping with Voltaire's observation on the subject. <g>

I Would chart the trend-line in compression pressures for each cylinder. Re-check it at every tune-up or maybe oil change and write down the numbers each time.

The varying internal stresses on the engine would vaguely concern me ('interest me' would be a more accurate description <g>) but I would put off correctly anything until it was impossible to live with.

 

Thanks Charles.

 

10%? Run it!! No it’s not perfect, but guess what, if you rebuild it perfectly there will still be variation.
Rings can stick just sitting around. 20-30 years? I’d be thrilled with only 10% variation
Just don’t try to start it with the old oil in it!!!!
I wouldn’t even crank it over with old oil. That oil has plenty of built up acids from sitting in dissimilar metals and the moisture in the air for all that time. Not to mention it probably needed an oil change when it was laid up.
Runnng it will cause rings to loosen up from heat and vibration. Same with valve seats.

 

JAGUAR’s have a tendency to wear more than shorter stroke engines like Chevy 350
That’s because Jaguar has a 4.17 stroke. While the 350 a has a 3.5 stroke. The Jaguar V 12 is only a 2.75 inch stroke and in looking at over 50 engines I’ve never seen a ridge.
The much greater piston speed is what hurts the bore wear.

 

old thread, and old post, i know...

assuming it's possible to insert pistons with connecting rods from below and the head has been removed, IIRC, the procedure goes like this: insert from below until the top of the piston is far enough ABOVE the block to install all the rings, and then push the piston back down.

 

What would the point of that be? One reason the pistons don't go in from the bottom is that you normally have the crankshaft bolted in place then push the pistons in from the top then connect the conrods to the crank. If the crankshaft is installed you cannot get the pistons and conrods past it to engage in the bores. If the crank is not installed and the head is off it is still easier to push the pistons down and compress the rings. By pushing the pistons up far enough to fit the rings is the same as pushing them down surely. Don't understand your logic here.

 

i didn't suggest a point as to why it should be done...just answering a question posed by a contributor, albeit a while back(!), and how it is usually accomplished if one should deem it necessary.

and it may be necessary if the connecting rods are too large to fit through the cylinders from the top.

 

Charles
Have you tried a leak down check.?
That entails putting each cylinder to top dead centre and inserting air pressure typically 60 to 80 PSI to listen to leaks.
e.g. noise in the inlet or exhaust indicates valve problems and noise in the crankcase (listen in the oil filler cap) indicates rings.

I have done a couple of "dirty" rebuilds with new rings and big ends and a valve grind on MK7 and MK1 cars. I also replaced the primary (lower) cam change and tensioner.
They were quite successful. The Mk7 had done another 50Kmiles when I sold it and the MK1 was still running OK (with a new owner) 10 years later.

 

Great point. All too often engines are rebuilt more because the owner wants to or thinks doing that will solve all the problems.
I’m a racer. At first I used to carefully go through engines and do everything.
It wasn’t that unusual for me to spend a massive amount of money on parts and machine work.
There is a racing series that used to take $500 cars and race them for 24 hours..
That was fun. Surprisingly a lot of cars went trouble free the whole race. Or just a few minor issues.
OK some blew up spectacularly and some were basically walking wounded. But the amount of fun wasn’t limited. It was just as much fun to finish 87th as 1st.