i bought a couple of these, probably from moss. have yet to mount them. i'm expecting fitment problems. do they actually fit inside a 3.4l mk2 engine compartment?

 

Yes-just.

 

jayd2: Backfiring through the intake is often a sign of a timing issue. Did you overhaul the distributor? Weak springs in the advance mechanism can cause the timing to advance too quickly...

 

thanks. now looking forward to fitting them!

 

Several issues with fuel: appears to be lean during acceleration. Could be float level in one carb, manifold air leak, throttle shaft air leak, weak piston return spring, light oil in dash pot.
You may want to try a richer needle and new springs, squirt some heavy motor oil around throttle shafts while idling.
More detailed explanation of when roughness occurs: 1500 2000 2500 3000 RPM, light or heavy acceleration, does increasing RPM cure the roughness?
The Distributor must be timed to Pertronix instructions, not Jaguar numbers.
With more details, others can way in with high probability cures.
Rgds
David

 

I found out why the engine is running rough, its got a dead cylinder. Five of the cylinders have around 150 and one is 0. The engine ran smooth on the test stand, after installing it in the car it started running rough. A compression test showed 0 on cylinder 2. I did a basic liquid test on the valves and they did not leak, it looks like a ring issue. All of the cylinders had a proper cross hatch before assembly. I don't know why the rings didn't seat properly on the dead cylinder. There was some light surface rust on a few cylinders but the bad cylinder was rust free.
There are no .030 rings available anywhere, Moss shows rings on back order but it could be months before they're in stock, if ever.
It looks like the small block chevy is going back in. I don't have much invested in it, just a lot of hours. I'll most likely part it out, it was fun while it lasted.

 

Do a Leak Down Test.

 

Hastings makes rings, you might be able to order from any Hastings dealer.

 

If you have "0" I would be looking at a valve stuck open not a ring issue. 150 on the others is OK. I have 165 on mine across the board on a 3.4 rebuilt engine with 9:1 compression pistons so running 8:1 would bring it down a fraction.
Do you have a borescope inspection camera that can have a look down the plug hole and rotate to look up at the valves. I saw a post on face book Mk2 jaguar page the other day and a guy used his borescope and could see the valve was cracked around the edges.
Check the valves are closing on that cylinder by turning the engine over with the cam covers off and looking at the top of the valve.
Check your valve clearance's on that cylinder.
All basic stuff that I am sure you have already thought of and done.

 

i.e. Do a Leak Down Test. It will give you all.

 

Google for method. Stops me wasting time.

 

Here's what I know about the bad cylinder.
I inspected the cylinder with a basic USB camera and there's no damage to the piston and no scoring on the cylinder walls, cant look up at the valves.
The leak is so bad that the compression tester gauge needle doesn't even move during the compression stroke.
The plugs all looked ok, it was not running extra rich.
The tappet clearance is correct on both valves.
I removed the intake and exhaust manifolds and injected some isopropyl alcohol on top of the valves through the intake and exhaust ports. It set for several hours with no change in the level. If it where the valves then the levels should have dropped, especially with 0 compression.
There's no water in the oil, and no oil in the water.

I'll be doing a leak down before deciding if I'll part it out.

 

and i may be mistaken, but a stuck valve could be "adjusted" correctly by someone that isn't aware it's stuck. possibly a previous owner.

i've found that removing the valve cover(s) and watching the valves move up and down as the cams turn is the most effective way to ensure they are not stuck. it may reveal other things too.

 

If there is a stuck valve, being an interference engine, it's probably now bent, hence zero compression.
Removing the cam covers as you say should indicate the problem.

 

Yes ~ You can't be too far out with shimming and you are in trouble.

 

Zero compression is pretty well for certain a valve that isn't closing.

 

Its an exhaust valve. It measures 1 - 5/8" diameter, is that a stock size valve for B type heads?. I don't know enough about these engines to know what combination of cams and valves are possible.

I'm going to replace the intake also. It measures 1 - 3/4", I've seen valves with 30 degree seat and 45 degree seat. What should the intake seat angle be for a B head?

 

Standard size for all XK engines from yours up to the final Series III XJ6 in 1987. I see it on Rockauto for under $15. https://www.rockauto.com/en/moreinfo...t=5328&jsn=559

 

I replaced all of the valves and it's up and running. It started immediately on the first try. It runs so smooth now it's a completely different engine.

Once again, thanks for all the excellent replies. It made the whole project much easier.

 

i posted a couple months ago that i was thinking about installing a couple of these: https://mossmotors.com/37-0875-foam-...ilter-1-3-4-su

yesterday, i did. and they do fit as mentioned! it wasn't easy as the fuel line was in the way. it's a hard line and there was not 1/8" if extra length in it with which to re-route. i removed it completely, very carefully straightened it such that i got that 1/8" of extra (l) length out of it and re-routed it such that it and the new filter's mounting plate were not one another's way.

anyway, the good news is that that double snouted monstrosity of an air cleaner and its buddy, that aluminum runner from it to the carbs that for all intents and purposes prevents their tuning are now O-U-T out! ... the question remains of what to do with the breather, though. i've left THAT for another day...

i find it surprising that although the carbs have two holes each with which to attach them to the aluminum runner that sits between the carbs and the air filter , only ONE of them on each carb actually has a bolt and nut to secure itself to that runner. the other hole in each carb is only a, removeable, locating pin. and so leaking is inevitable between the carbs and the runner unless extraordinary measures are taken to re-glue it in place each and every time it's removed.

it's clear why that is so. those two locating pins are, as mentioned, removable once the runner is gone, and serve to hold the bracket for the Auxillary Enrichment Device. and that bracket's presence prevents access to the head of any bolt of sufficient length to reach the threads machined into the runner. the new air filter plates have no such restriction and i now have FOUR bolts and nuts and a gasket to hold the plates securely and without leaks (!) to the intake of the carbs. "...oh!, what a web they'd weaved!"

anyway that whole nightmare of engineering is now out and i can get at all the tunable screws, nuts and other mechanisms the SUs have with which to tune them. and i can now easily get to all the sparkplug wires and sparkplugs! ...not trivial in my book as i often inspect plugs to determine proper combustion. ...i'll soon have that unsightly air cleaner bracket off those head bolts its mounted to too.