It is entirely possible there are bent valves, but may also be caused by insufficient tappet clearance or valves that are not fully closing. I don't remember how to easily tell the Series II camshafts from the Series III other than measuring them with a micrometer. Perhaps someone else can answer that question better.

It's always best to use the number one cylinder, which is closest to the bulkhead so you are also synchronised with the ignition timing. Either way, you can tell if the engine is at the top of the compression stroke by the position of the camshaft lobes.

NBCat

 

I meant how do you tell the diff between the exhaust & inlet Cams? And if they're swapped would the valves foul pistons etc, I don't want to try swapping them if all I'll acheive is bent valves.

 

If the engine seems like it wants to start, but doesn't,then the timing is 180* out; found this out the hard way when i did my first head overhaul. To check top dead centre, put a screwdriver down plug hole closest to firewall, (as Jaguar number these motors from the back). Turn motor over using spanner on the water pump pulley (I think), being careful not to trap screwdriver, lean on fan belt to get traction. See that TDC lines up with marks on crankshaft pulley, (white paint is good). Remove top from distributor, check that rotor button points to #1 plug or #6 plug. If so, swap plug leads around; ie swap1 with 6, 5 with2, 3 with 4. Should start.
I think your fuel leak problems will be fixed with new float needles.

good luck
Pete

 

The main issue is compression is down to ~40PSI in every cyl where-as compression was 160PSI in 4 cyl before rebuild, I believe the pressure must be leaving through the tappets possibly because I've possibly maybe swapped the inlet & exhaust cams, I don't want to try swapping them back if I'll simply find this is not the case & therefore succeed in only bending so far unbent tappets. ( I'll check the timing again first, it seems to be right but maybe the Haynes manual etc has got me confused.)

 

It's not out 180' , the rotor points to no1, the timing mark on the crank lines up, the cams are in position, piston 1 (at rear) is at TDC.
Inlet tappet 3 is fully up .013" gap, Inlet tappet 4 fully down, Exh tap' 2 full up .006" ( spent ages getting them spot on now!!!) Exh tap' 5 full down. Next tappet to go down Inlet no. 1 & Exh no. 3

I'm guessing tappet 1 should go down after TDC as its cycle is to suck/let fuel in as the cyl starts to descend so I guess the cams are in their correct position! Am I right?

 

When you have the number one (closest to the bulkhead) cylinder at TDC, what is the position of the camshaft lobes on that particular cylinder?

 

Both lobes are pointing in towards the spark plug (horizontal), as the engine rotates clockwise (viewed from front) the inlet is next to be pushed down.

 

The valve timing is therefore incorrect. Both cam lobes should be facing towards the outside of the head in a position similar to 'rabbit ears' since the next valve to open after TDC as the engine is rotated is the exhaust valve.

 

Thank you, thank you, thank you- ie the cams are swapped inlet to exh, they're pointing in & should be pointing out, Am I likely to have bent valves then or am I lucky enough that .....? Off to swap'em & I'll turn by hand first just to be sure

 

I believe once the camshafts are correctly timed and the clearances adjusted accordingly, you will have proper compression once again.

To be sure, rotate the engine by hand with a spanner on the crankshaft pulley bolt to see if there is any 'fouling' of the valves by the pistons. You will know if there is any fouling or resistance to rotating the crankshaft with all the spark plugs removed. If there is, the cylinder head will need to be removed and damaged valves replaced.

 

It's a very long time ago, but I am almost sure there are markings on the camshafts to indicate inlet or exhaust, but for the life of me I can't remember. I had camshafts on and off many times and never had a problem replacing them, but never labelled them up when storing them.

However, NBCat's post does ring a bell somewhere, as I remember seeing a photo in an article about rebuilding the XK engine, showing how the cam lobes should appear with the cams set using the tool, (the one that fits in the notch at the front of each camshaft)



Have a read of this especially the section headed:

If any of the valves need adjustment:

Jaguar XK Engine Valve Adjustment

Unfortunately no photos which with the XK engine are worth a thousand words.

 

Your average workshop doesn't have the odd clucky chicken, rooster, turkey, possum or cat rooting around on the carefully set out workbench The cams aren't marked differently but my carelessness has obviously caused more work. Swapped the cams & tappet gaps now out to b**** no binding noticeable so tried to start it- no good, checked compression starting cyl1 100, 40, 110, 70, 110, 100PSI so I guess the heads coming back off to inspect the damage

 

Cams WERE NOT WRONG/swapped according to the Haynes restoration manual photos & other sources on the net,... gave up in frustration ages ago- recently nearly got a donor car/engine- fell through Now I'm back to the old project with renewed determination.

The cams WERE NOT SWAPPED, the "rabbit ears" described appear at THE FRONT of the engine- a pox on the engineer that decided to number the cylinders BACKWARDS & cause endless confusion for poor mugs like me years later.
I gave up 18 or so mths ago because of this confusion with cylinder numbering & TDC & I am not alone. It was the final nail in the coffin for me.

Here is a copy paste from elsewhere by MICVIC "Hmmmm looking at page A22 re fitting the cylinder head and setting the valve timing I see they specify first thing you do is set no. at tdc and set the distributor with the rotor arm opposite number 6 segment.
This confirms that the jag engine is set with number 6 piston at tdc on compression stroke and my cam timing is correct (lets hope). Answered my own question, helps to read the book must remember that next time. Mick"

That just confirms I was given a complete b*msteer 18 mths ago.

Now I've got that off my chest.
There does not seem to be any bent valves (strange) now I have the head off I will set it up again - still wondering why an engine that had good compression in 4 cyls ended with none- 18mths & another expensive gasket set later (& much shimming & gapping) I fear I will soon be in the same position again

 

Another source of very good info on the cams & valve clearances etc Camshafts

 

Odd, I do fairly well with SAE sized wrenches and fasteners. Although metric is far easier to comprehend, I don't do as well.

SAE: 5/16, 3/8, 7/16, 1/2", 9/16, 11/16, 3/4. These are the most common sizes needed to work on the Jaguar that i've used.

10mm and 13mm showed up a time or two.

And, once or twice, a Whitworth!. I've two. One fit!!!!

And, i respectfully disagree as to the FI cam profile being ioncompatible with a carb intake., because the carb'd engnes had a different cam profile.

It only matters that the lash matches the need of the profile. I understand that they are different.

As long as the cylinders get a combustible mixture, they care not how it was produced.

Caveat. As i understand, sorta, one must be very careful in moving the head around on a bench as the valves stand proud and are susceptible of getting bent in a just so slightly open position hence, a leak and healthy compression is an impossibility.

A dial guage might be rigged to meaure valve travel. Compare the bad cylinders to the healthy ones. A bent stem will mean a short stroke.

When my DOHC went to ) in all holes, it departed and an LT1 now resides in the bay. But, I've learned a lot about these engines here. Had i known then, I mnighta tried a fix. Off with it's head!!!! Stripoed gear vernbiers a liely cause and a bunch of bent valves resulted. Over heat induced!!

Carl

 

Correction: Zero in all holes.