I realize Jose is trying to do this for as little money as possible, but the measurements can be done in a hour, and are easy to do if the head is off anyway. A new head gasket would be required no matter what, so there is little cost difference in getting one that isn't factory and also seals better. If there is the potential of coolant entering the oil through the head gasket interface a better sealing gasket would help. It might save needing to get the head skimmed. The difference in price between the two gaskets is around $50.

When I first got my E Type it had a leaking headgaset, I replaced it with the standard metal gasket and it still leaked and I had to do the job again. I know that's something Jose would want to avoid.

Going from memory, Ray's engine had the head skimmed several times and his actual CR was over 10:1, so that's why he was having problems and developed the spreadsheet. It's a useful tool.

 

Yes ~ I have all those tools available to me via our oilco online but they are proprietary & I'm not allowed to share them in terms of our IP policy. I also have a MON engine available to me to check Motor Octane Number (MON). The AKI (Anti Knock Index) that NA marks it's pumps with is just an average between RON & MON.

I think the point I was trying to make is that if your CR is 8.8 & you increase it to 9.3, as an example, it is going to make little difference to the onset of knock whereas correct timing will.

 

Jose I think with the engine out you need to go the whole 9 yards. It would be stupid really not to and then either have to take the engine out out again later or even work over the top of the wings to remove the head. We all appreciate that one persons mechanical skills might be greater or poorer than the next but we have all been there and made the mistakes. With my engine I had the skills to remove it, strip out, clean it and reassemble it but the bits in the middle, the rebore, fitting new pistons, grinding the valve seats, fitting new valves, fitting new shells, grinding the crank, fitting the rear main oil seal, setting the valve gaps, these were all done by my engine shop. I supplied the parts, £1000 or so and they machine it all for £1000. I probably saved £1000 in labour taking the engine out and putting it back along with the assembly of certain parts. Personally I would repeat the process if I was in your shoes now. Having taken the engine out and stripped it down, hand it over to an engine builder and let them do the hard graft. They can decide if the crank needs a regrind. They can skim the head and fit a new head gasket.They will also fit the rear main oil seal for you. You will also get a guarantee with the work they have done so if the rear main oil seal leaks it is up to them to rectify it.

 

This is very important.

quote ~ "You will also get a guarantee with the work they have done so if the rear main oil seal leaks it is up to them to rectify it."

 

I agree, I would try to squeeze the funds and have the engine rebuilt to some degree, ideally new pistons, change the valve seats to Nickle bronze to handle the lead free gas, new seals, bearings, timing chain, etc. so that you can have an engine you can rely on and not worry about how many miles you drive it. Jose, you are a great Jag lover and if my car had come with a 3.8 engine I would have given it to you for free so you could get the car on the road where she belongs. It might hurt temporarily in your cashflow but it will be worth it.

I do not know about Jag engines but on one of my Datsun Z cars, we "O" ringed the engine block cylinders which creates a groove around each hole that increases reliability by reducing potential for head gasket failure and destroying things. I got over 300,000 miles out of that engine before I rebuilt that engine but that was done purely for performance as it could likely keep running for whom knows how long before it started to burn oil and need a rebuild.

I am already planning for rebuilding my 5.3 LS V8 engine as I am already nearing 200K miles on an engine that I do not believe was a full rebuild but just a lightly freshened up engine with new rings, cam, etc. My engine is strong but for me it is a daily driver and I have already got my money's worth the engine/trans as it was so cheap but that also means it was most likely not a complete rebuild so rather than wait for something to grenade, I will likely rebuild the same engine for reliability, some more power, and to avoid any issues with getting a different LS V8. The point is once you have a true rebuilt engine, knowing whom and how it was done you will have the confidence to drive and enjoy it so it is not in storage or even a delicate weekend car anymore. I hope you can drive her again with confidence as you deserve it.

 

I obviously encourage a proper ground up rebuild. One thing that we have found however is that the standard Jaguar valve seat is more than robust enough to operate on lead free fuel. Valve seat recession is not an issue on XK engines. Other BMC etc. UK engines where the valve seats on the head material all require suitable valve seat inserts to be fitted.

 

I'd second or third on a thorough re-build. In particular, don't try to save on items or activities that are not all that expensive.

I agree with Glyn on valve seats. Very few any engines that have seat inserts need them swapped for unleaded and certainly Jaguars are fine. I'd leave the seats in place unless there's something else going on.

I often read that the power of XK engines is insensitive to compression ratio. As a long standing student of thermodynamics and a very amateur engine lover, that makes no sense to me and goes way against a study of the late 1970s that showed the XK gains significant power and efficiency with increasing c.r. Especially if you are sticking with carburetors and conventional centrifugal and vacuum advance (rather than an ecu) and not spending a fortune on asymmetric pistons or twin spark plugs, you definitely don't want to go too far. Until we're running our cars on ethanol, I'd guess 9:1 as an upper value with a small margin. Even then (in fact always), I'd use a premium gasoline with cleanliness additives (BP Ultimate, Shell V-Power, Chevron and Exxon equivalents). And don't rely on hearing pinging. That's low speed knock and not so damaging. Unless you have a very highly trained ear positioned close to the engine, you'll never detect high speed knock before the catastrophic failure. There was an old fuel scientist called Geoff Harrow who had a wonderful collection of pistons from his various experiments. They looked as if they been subject to machine gun fire.

 

As an aside I've toured the Waukesha factory where they make those engines. Quite an interesting piece of equipment that hasn't changed in nearly a century. It's a small corner of their factory that makes the much larger industrial engines.

 

Makes no sense either, as if you look at later accurate HP ratings the European market 8.7 CR 4.2 engines were rated at 205hp, while the North American market with 7.8 CR was rated at 171hp. Yes the North American market had catalysts, but the Daimler limo on carbs with no cats and officially 7.5 CR was rated at 164hp.

 

Very crudely, and this is for an abstract average unspecified engine rather the XK, 2 octane numbers is equivalent to 3 deg on spark timing and half a compression ratio. Somehow 3 deg doesn't sound much compared with half a compression ratio. I'm sure a lot of modern engines avoid knock by retarding the ignition under full load conditions rather than setting a c.r. that always avoids knock at mbt.

 

Yes Peter. I'm not suggesting that the power of XK engines is not sensitive to CR. I'm purely talking knock. Jaguar in fact built a test 2.4 engine with 10.1 to 1 CR. The only way to detect high speed knock reliably is with decent knock sensors. The Jaguar 3.8 engine with approx CR of 9 to 1 can be sensitive to high speed knock at just below 4000RPM from what I've ascertained. I've been trained to detect high speed knock & I certainly don't trust myself.

Agree use highest Octane additised fuel available.

 

guys, Crankshaft is out, have it in my van to take it to machine shop.

but I need to find out what is/was the Standard journal size. Nothing in the manual about that.
Thanks.

 

Yes ~ I've also been in the Waukesha plant. Their gas engines are iconic in stationary power generation. Asia is a huge market for them & they are on just about every major pipeline in NA. We also make a tailored oil for them plus some specials for countries like Pakistan to suit their gas feed.

 

Good. The first thing they must do is measure the journals, estimate minimum cut to get them to measure true with all damage removed & no ovality. & then find out what oversize bearings are available & cut the crank in accordance with that.

If you look at the Barratts site both mains & big ends seem to be available in a range from +10 thou to +40 thou (10 thou steps)

You need to have that conrod checked that the bearing spun in.

Jose ~ Read & print out WSM pages B6 onward for standard crankpin sizes & tolerances for your machine shop. Covers conrod as well. Also end float & thrust washers.

 

Glyn, I wasn't aiming at you at all in my rant on c.r. I know that you know better. Rather I was thinking of statements in some books and internet forums.

With an ecu, it's possible to work around a range where knock is a risk by retarding a few degrees and possibly richening the mixture. This could be via a knock sensor or in the tuning process. However, the latter is putting some trust in the operator of the chassis d.

 

No problem at all Peter. We are both big boys & speak openly. Both have our strengths & weaknesses. If you ever think I'm wrong tell me. No sensitivity.

Very clever ECU's & highly accurate knock sensing make the Benz variable compression Diesotto engine possible.

 

Jose ~~ in case you miss my EDIT above.

Read & print out WSM pages B6 onward for standard crankpin sizes & tolerances for your machine shop. Covers conrod as well. Also end float & thrust washers.

I will provide Cylinder Head/Camshaft material when needed.

Here you go.

 

Just in case you don't have it, main bearing journals are 2.750-2.7505", crankpin diameter 2.086", +0.0006", -0.000"

 

Jose ~ I've posted with tolerances above.

 

Thank you Glyn, I could not find that info previously, but it is all there.