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Are you sure about that? 6 liter journals literally specced as much as a .0011" difference. That's even too much for me and my standards are stoopingly low! But maybe that PDF was overstating the possible variances which is very possible. https://www.google.com/url?sa=t&sour...sVOCuqQUdWh6xx
Gentlemen, obviously very few of you have built many engines. Clearance varies even in the most expensive engines in the world.
It’s a constantly changing target. The stone used to grind the crank wears as it grinds even though it’s flooded with coolant. The slight variation of the original journal is brought into close tolerance changes the wear on the stone. That is why constant Checking is done by experienced machinists.* *Realize much of the machinery at Jaguar is very old some dating pre WW2. Modern equipment used post Ford motors ownership has that checking automated and batch building is no longer used.
Then because Jaguar batch builds*. engines they assign grades to the crank and the bearings rather than discarding cranks and bearings that are slightly off either too thick or too thin. * batch building is a process of assembling slightly varied sizes to reduce waste and still produce high quality engines.
The tolerance they are talking about is fractions of the thickness of a human hair. If the Gap is too large extra oil flows in and that particular bearing will run fractionally cooler with greater oil volume. Too tight and less oil flows and it’s a tiny bit hotter.
The sum of the largest clearance is still less than approximately 50% of the volume of the oil pump. the oil cooler works on bypassed oil. Excess oil volume bypasses the engine and goes through the cooler ( except on engines destined for Germany) ( because of the Autobahn )
Standard race engine building is to build engines towards the high side of clearance. Oil pressure needs are relatively easy to meet but high RPM over The extended duration of a race tends to really heat the oil. Better to have a high volume of oil cooling things.
What that means is as long as the bearing clearance doesn’t exceed the maximum the engines will operate as designed and there will be plenty of excess oil to flow through the oil cooler.
You cannot build a good engine without actually knowing what the clearances are. High quality micrometers and snap gauges are required for a good engine build. Plastic guage serves as a crude cheap way to measure instead of expensive tools and the skill and judgement required to use them.
Realize bearings should never touch the crankshaft. They ride on oil. Keeping the bearing and crankshaft ( and every moving part ) from touching is the function of clearance. Where oil is feed to keep parts from contact. This the hardest thing on an engine isn’t use, it’s starting where the oil pressure is drained off and only residual oil remains.
Completely right I haven't done many engines. Like 2 lol. And I understand oil clearances and how many things decide them. It's probably the least black and white subject to talk about. On a few blueprint sheets I saw all the journals .003"-.0035" and thought every engine had that tolerance. I didn't know you could have more variances than that and be okay. I'm excited to throw in some bearings in my motor and hope that's all it needs. Will make a thread with results of the whole ordeal.
Completely right I haven't done many engines. Like 2 lol. And I understand oil clearances and how many things decide them. It's probably the least black and white subject to talk about. On a few blueprint sheets I saw all the journals .003"-.0035" and thought every engine had that tolerance. I didn't know you could have more variances than that and be okay. I'm excited to throw in some bearings in my motor and hope that's all it needs. Will make a thread with results of the whole ordeal.
Please at least plastic guage your clearances so you know what you’re working with. A lot of engines really need the crank checked to ensure it’s still round and not egg shaped ( I’m not kidding) but the Jaguar crank is one I've never found bad except where it was visibly bad. ( the mechanic failed to tighten the oil filter and The owner drove it home 30 miles pumping all the oil out)
He's measuring the journal clearance between the bearing shells and showing how the clearances very even between bearings that are "identical". In other words, the graded bearings for the 6.0 are basically irrelevant, as the manufacturing tolerances are greater than the grade spacing.
As an aside, until you tear down your engine and do measurements, you don't know what bearings you need.
I appreciate this forum. I am in no way claim to be expert in anything. I have built many many engines. It isn't rocket science. It is patience, and measuring. And measuring, and then more patience.
Purchasing high quality micrometers and snap gauges isn't that difficult nor does it have to be expensive. Many of these can be purchased on auction sites of estate sales, etc.
With all of that said, building a engine correctly, as stated requires the engine be disassembled, measure everything, do proper machining as required, and THEN install proper bearings. I have a 94 6.0 that I am using as a experiment to build a Jaguar V12 to supercharge with a Whipple 3.3L S/C.
The heads have been the biggest challenge as far as time.
Enjoy this while you can. Appears as though the Jaguar V12 as with all other V12s are becoming extinct. This is a expensive, although rewarding hobby.
With regard a supercharger. Sitting on my shelf is a 250 cu in Roots type blower, new. Made by BRM I intend to put on my PreHE V12. With 7.8-1 compression I can run a lot of boost without risking preignition. I’ll pull the pistons and increase the ring gap from .014- .020 to .025 on the compression ring.
.010-.015. to .025 on second compression ring
.015 - .045 to .025. On the oil control ring.
While slightly tighter than standard increase for supercharging , I plan on using E85 since it’s over 100 octane and with all that alcohol the engine will run plenty cool.
MG there was NO E85 way back when you were racing!
I started using Methenol alky back in 1962 stroked Chevy V8, and come 1964 a new upgraded car using 70% alky, and 30% NITROMETHANE, in a blown Chevy that dynod 900HP!
October 1964 finally made 200MPH , in a 1/4 mile!
winter set in and divorce ended my serious racing for a few years!
bought a nice 63ft yacht, moved to Florida, change of senery! me on roof arms in air,, entering Bahama waters! yup different life style!
Pulled 2 front main caps off and 4 front rod caps. No signs of excessive wear, just some minor gouging. Going to pull one more main and 2 more rods tomorrow. Reason I am starting at the front is because thats where the knock was from.
MG there was NO E85 way back when you were racing!
I started using Methenol alky back in 1962 stroked Chevy V8, and come 1964 a new upgraded car using 70% alky, and 30% NITROMETHANE, in a blown Chevy that dynod 900HP!
October 1964 finally made 200MPH , in a 1/4 mile!
winter set in and divorce ended my serious racing for a few years!
bought a nice 63ft yacht, moved to Florida, change of senery! me on roof arms in air,, entering Bahama waters! yup different life style!
Never said I used ethanol. Back in 1962. I messed around with methanol alcohol in offy’s and we were using some 5%? nitro to qualify with the small block Chevy’s When we ran the Minnesota state fair. No I wasn’t driving just part of the crew. I also drove Chet Wilson’s Offy killer back in 1974. Using Methanol but there I was just guest driver, a favor for his new Son-in-law.
