MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Inlet Valve Stuck open...???

Head back on, Judson on ..all connections made. Phew...Judson was a real bastard to get in position.
engine started first time but needed loads of tuning..so started such. Half way, after about 15 mins ,and at full temp.,it got really lumpy ..not firing on all 4 so checked combustion in each chamber ( using gunston ) and no combustion in 3 but loads of spark to the plug.. Took off the cover and inlet valve in 3 is stuck open...all the way down. I was surprised as I would have thought the piston would have hit it...obviuosly(?) not.
I reassembled the valves using the stem seals recommended in Barneys bible. ....the ones with the teflon lips set in rubber sleeve .They cleared the springs easily and went on well..but now I wonder whether they have starved the stem of all lube...and it has bound up while hot.

I know the removal of the head is the honest righteous way to investigate but hands are still raw so want to try some other techniques first and have read up two on net..
ie....
1st Try...take off rocker assembly , loads of wd 40 and use a soft faced thumper on stem end.,keep going until moving freely. if no joy then...
2nd Try..
Step 1...all plugs out and feed length of curtain cord, or similar , into cylinder 3 until full..also loads of wd 40, marvel mystery oil or similar into cylinder ,.
Step 2.... manually wind shaft and raise piston until resistance felt. Do not try to push valve up with piston.Idea is just to hold the valve up.
Step 3...Fabricate a small spring compresser and use the rocker stud hole with a stud etc to clamp and compress the springs and release collets and prings , remove all jewellry from the stem
Step 4.... work shaft stem with loads of lube and rotation etc.until totally free..use different seal during assembly ( I have some without teflon ex Moss)
All thoughts , different ideas etc needed urgently...
.... .
Neil Ferguson

Neil

I can mount it in 15 minutes with the following tricks

Fit the carb manifold including carb to the Judson on the bench and then lay the complete unit in the depression between shroud and wing. I fit all carb connections while the Judson is lying here. No split pins on the carb or choke trunnions, just R clips which can be inserted / removed with a long-nosed plier. Change the accelerator cable trunnion at the pedal to one that allows the cable to be tensioned and clamped in the footwell on the pedal itself - it's a lot easier to get at than the SU conversion end. Use a bike brake cable to get a much longer accelerator cable (inner and outer).

1. Install Judson head manifold and insert the three bolts and gasket
2. Get a second pair of hands standing at the front of the car ready to start the bolts in the Judson casing - 9/16 open ended spanner at the ready.
3. Standing at the LH front wheel, lower the Judson into place, sliding the jockey tensioner under the radiator shroud.
4. Lift the front of the Judson to align with the front bolt and helper starts bolt in the thread, fingers first then a couple of turns with spanner if necessary.
5. Lift rear of Judson to align rear bolt, helper starts bolt in thread in the same way as 4.
6. You can now finish the two bolts alone and do the centre one too.
7. Manoeuvre drive belt(s)- (I have only one) - over the front pulleys and tension with the jockey wheel.

On LHD with the SU conversion I can actually fit the Judson alone by resting the abutment plate for the carb on the steering column and lifting the front into place. But with RHD you are missing this help.

With a Holley equipped Judson, the second pair of hands is always needed to fit.

No answer to your sticking valve- is the stem out of true? Don't use WD40 on anything, it's a water repellent not a penetrating oil. Get some proper release spray instead, it works much better without leaving sticky residues. I suspect the head will have to come off again, but at least the Judson will go on more easily. Did the float chamber arrive?

Dominic
dominic clancy

Dominic...
Thanks for your procedure..I had it from before and used it as far as practical for RHD car
Complications.
No second pair of hands..but don't think they would have helped for me ... Just Todd Sloane.
I needed to loosen the tensioner ..to rotate it to get it under the radiator cap
nozzle..
.Given no steering shaft as support I found it easier to get the front bolt in ...can be done with one hand easily ( other hand holding whole unit up in position ) ..plus the front bolt is not adjacent to pushrods etc.. so does not need feeding through a maze.
Like your ideas re the cable connections ..need to refine for next time...especially the accelerator cable footwell tensioning.....this is the stuff of bruised fingers.
Got the float chamber ..many thanks....post was very quick ( much better than from Moss UK )
No idea re stem straightness yet ..but all stems moved easily without sticking or sleeve slackness movement when assembled..so don't expect that is a problem.
Neil
Neil Ferguson

Do you have steel or phosphor bronze guides?
http://www.voc.uk.com/net/docs/3.3b/3.3-274-19.pdf
Eugene Gillam

Eugene..I have never replaced the guides or valves and have had the car for 27 years now. When I took the head off I noted that the exhaust valves looked like bronze and the inlet like standard . All valves moved freely in the guides but there was some carbon build up on the exhaust stems just above the seat area. After lapping and clean up all valves moved freely. and easily. The stuck valve is an inlet valve.
I have read about the bronze guide issue before ..thanks for posting as it was more detailed.
I do believe that the stem seal is the likely cause ( using Sherlock Holmes analysis ) as it is the only factor that has changed .
Neil
Neil Ferguson

referring to my post...removed rocker assembly and used a load of marvel magic all over the stem ..then placed a plastic handle on top of sten and hit it with a hammer...but not hard. 1st attempt and it popped up and closed and the gap was 15thou..as set. so at least no bent stem or pushrod etc ..
Thinking about next step while my battery recharges overnight...
Neil Ferguson

Neil,
Since my rebuild a few years back I always put a little Marvel Mystery oil in the fuel tank. Being that I was concerned about the bronze guides that were installed at rebuild and valves sticking, I thought the oil would prevent that problem. Seemed to work for me.
Ray Ammeter

Ray...I have a vacuum lubricator dripping the stuff continuously into my Judson supercharger and obviously then to inlet so stems should not be without lube . Will be getting back onto the car tomorrow to see if all goes well.
Neil Ferguson

This thread was discussed between 12/06/2016 and 14/06/2016

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.