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If by meaning the HE produces less emissions, then yes, you are correct.
However, the myth of it being more efficient isn’t really correct. Yes it gets better fuel mileage, but that’s because of its higher compression. 11.5-1 compared to 7.8-1. ( here in America)
Take that same pre HE head and put 11.5-1 compression pistons ( with the Huron head design) and you’ll find the same fuel mileage.
Most of the other fuel mileage improvements came along with development. GM Turbo 400 (2% slippage in 3/4 of 1977 replaced the earlier Borg Warner (4% slippage)
Improved ignition and finer spray from the injectors. 3:07-1 final drive to 2:88.
Jaguar was developing the ignition and EFI. Constantly. In driving the earlier head, it’s less soggy in lower RPM than the HE is.
Some of the very first pre HE engines that came to America had 9.0-1 instead the 7.8-1
You can tell them apart because instead of a decal they had the word Jaguar cast into the valve covers.
I’ve had one of those engines and it was pretty snarfy at low rpm. I still have those valve covers.
Yes. I believe you do, it’s easier with the pre Flathead because you don’t have to work with the head on the side.
Super glue on the edge of the shim holds the shim in place so it doesn’t fall out as you put it together. It breaks off easily and brushes off clean for final assembly.
I’m sorry we disagree on the HE engine. Do you understand why?
Yes. I believe you do, it’s easier with the pre Flathead because you don’t have to work with the head on the side.
Super glue on the edge of the shim holds the shim in place so it doesn’t fall out as you put it together. It breaks off easily and brushes off clean for final assembly.
I’m sorry we disagree on the HE engine. Do you understand why?
Last edited by Mguar; 07-17-2024 at 03:17 PM.
Reason: Duplicate
Since I am waiting for the new heads to arrive, I stripped the A bank head of Camshaft Box, all of the studs, coolant blanking plates and valves, valve springs etc.
I have bagged and labelled everything so that they all go back where they belong.
Tomorrow, I will do the B bank head. As soon as the new heads get here, I will take care of the valves and reassemble them both.
@Mguar Yes I am sure that can be done. I will do the valves as you recommend to check the valve clearances before final assembly.
I believe the valve clearance is the same for both Intake and Exhaust Valves.
There are others who are way more experienced than I am on re-building the V12. However it occurs to me that they key thing is just to make sure that each piston is matched to a corresponding liner. That seems much more important than worrying about whether the CR is exactly the same for all 12 cylinders. I THINK that I would be minded to put the best matched tolerance A-spec Piston and Liner of the ones you have, to replace that damaged B one.
I'm sure that others will have better opinions!
Paul
Paul’s not far wrong.
IMHO without measuring things, given the mileage, really any Jaguar piston will fit and work in any cylinder. That’s because with such a short stroke piston speed is really low so wear on cylinder walls is very trivial. The question of new or used piston rings is certainly valid. Either way the rings will need to wear into the cylinder.
I’ve had very good luck reusing undamaged rings. I wouldn’t hone or in anyway disturb the bore. ( I’ll explain why if you are interested). Oil the rings and Just stagger the end gaps. Then using a ring compressor slide it in.
Remember to use a little break in lube on the bearing. if you don’t have any a light coat of white grease will lube the bearing until it gets oil pumped into it. Just don’t put a bare bearing in without something to lube until the pump gets oil to everything.
On that order remember to pre fill the oil filter and over fill the engine by at least 1 quart.
Use a 20w50 oil and remove all 12 spark plugs until you get oil pressure showing on the gauge.
It takes a really long time to fill the oil cooler, all the lines and passageways so start with a fully charged battery and don’t run the starter for more than 1 minute without a 4-5 minute cool down ( unless you enjoy replacing that starter).
On a rebuilt V12 I always rig up a cut off plastic bottle plus adaptor to fit in place of the oil pressure sender.
Leave it for a day full of oil to prime the engine.
That oils the exit side of the oil filter, reaches all the bearings and camshaft gear.
For oil filters with a non return valve it will not prime the pump.
Put the oil pressure sender back in and it does not take too much cranking to get the pressure up.
@Mguar and others:
I received the NOS cylinder heads yesterday. They were still in the original Jaguar wooden shipping boxes with rope handles and were never used. Nice and shiny.
I am going to start lapping the valves in and I want to come back to your method of installing the valves and checking the valve clearance before final assembly.
You stated: "First clean the valves, lap them in. Then lightly assemble the cam boxes. Set the head on edge. Then slide in the valve you think is right, the cam follower and guesstimated shim. Set the base of the cam down on top( don’t try to assemble anything yet. Slide the feeler gauge in and check clearance & adjust shims until correct". Doing the above, do I just hold the valve on the seat by hand and check the valve clearance? Please clear this up for me.
"DOING THINGS THE UNORTHODOX WAY TO GET THE RIGHT RESULTS"?
The cost of a new timing chain tensioner C30485 is way beyond my budget ($500 -$700)at this time.
Knowing that the tensioner is brittle that if I try to put it in the relaxed position to get the cam gear on I WILL break it. I was wondering whether the following procedure can work.
1. Install the cylinder heads snug but not torqued down.
2. Install the Camshaft snug but not torqued down.
3. Do not install the sandwich plate at the bottom of the engine.
4. Retract the tensioner just enough ( hoping it would not break) to install the Cam Gear onto the Camshaft. I think I have to retract the tensioner about 3/16-1/2 inch.
5. Release the tensioner.
6. If successful, install the timing chain cover and the sandwich plate.
If this works, what do I use to seal the top of the timing cover to the cylinder head gasket?
7. Torque down everything.
Those who have removed the timing cover to do work there without removing the heads will probably know.
Is this all just a very, very bad idea?
Yes!
New thought, rather than set the head on edge use a piece of shipping tape on each valve to securely hold the valves up.
Then you can put the head down flat and not bother with the glueing process at all. Check by tugging up on the vale stem that you properly secured the vale in place. If there is even a slight amount of looseness check that the tape is really secure all around the edge edge of the valve
Then just set the shim on top of the valve and slide the cam follower right down on top.
Etc.
Should be even faster.
"DOING THINGS THE UNORTHODOX WAY TO GET THE RIGHT RESULTS"?
The cost of a new timing chain tensioner C30485 is way beyond my budget ($500 -$700)at this time.
Knowing that the tensioner is brittle that if I try to put it in the relaxed position to get the cam gear on I WILL break it. I was wondering whether the following procedure can work.
1. Install the cylinder heads snug but not torqued down.
2. Install the Camshaft snug but not torqued down.
3. Do not install the sandwich plate at the bottom of the engine.
4. Retract the tensioner just enough ( hoping it would not break) to install the Cam Gear onto the Camshaft. I think I have to retract the tensioner about 3/16-1/2 inch.
5. Release the tensioner.
6. If successful, install the timing chain cover and the sandwich plate.
If this works, what do I use to seal the top of the timing cover to the cylinder head gasket?
7. Torque down everything.
Those who have removed the timing cover to do work there without removing the heads will probably know.
Is this all just a very, very bad idea?
that nylon really tends to break when pulling it by hand
USE THE CAMP CHAOS METHOD.
MAKE THE TOOL!
Getting ready to assemble the NOS cylinder heads I purchased. I have lapped in all the valves and I am getting ready to put it all together.
A query regarding Mguar's method. "First clean the valves, lap them in. Then lightly assemble the cam boxes. Set the head on edge. Then slide in the valve you think is right, the cam follower and guesstimated shim"................
Since you are checking the valve clearance with the cam box and camshaftlightlyin place, wouldn't the valve clearance change when everything is torqued down properly?
Doing it by the book means you have to assemble everything to specs and if the valve clearance is incorrect you have to disassemble everything to address the issue.
Some guidance is needed here.
I understand your procedure very well. My concern was whether there will be any difference in the valve clearance after you torque every thing together.
Also, I saw some very tiny O-rings in the cylinder head set. They are the size of the diameter of the valve stems. There are 24 of them. They came in the ziplock bag with the valve seals.
Do they get installed together with the valve seals?
When I disassembled the old heads, I did not see any O-rings on the Valve stems. Does anyone knows where they go? o-rings
07-17-2024, 02:40 AM
