Unleaded cylinder head - page 2


Welcome back, the saga of my head was actually going quite well at the end of the first page, obviously the gods of the car modifier thought that I should have a little pain as well as pleasure.


Barry at T&L had offered to build up he head for me, leaving me to screw the studs in and fit the head to the engine.  Being a nosy sort, I wanted to inspect his work and seeing as it's many years since I last built  up a head, I thought that it might be fun to do it myself.


I decided that whilst I had the engine apart, I would checkout the noisy timing chain and take the opportunity to upgrade to a duplex timing chain and sprockets.  I priced them up and thought again, eBay came to my aid with a search in automotive for "MGB duplex".  I bid and got a stunning deal (too good as it turned out).


I called Brown & Gammons (B&G) ordered the studs, a new thermostat and aluminium housing, timing chain tensioner etc. to build her up.  I was lucky with the valve springs, as you can see the head now has double springs.


Ben Clayton - he of www.fastmarinamagazine.com and the secretary of the owners club, gave me a set of 7 new Kent Cams double valve springs for a B series engine.  Seven? I hear you say, yup, Ben had been given them himself, but the previous owner had lost one.  Ben is now building a Ford Zetec engined Mk1 Coupe so, they were surplus to his requirement.


Not being the type to look at gift horse in the mouth, I accepted his gift.  I got straight on the telephone and chatted to Kent Cams - and bought ONE pair of their fine double springs to make up the deficit.


I set to on a Sunday morning and with the aid of a nice new valve spring compressor, soon had the valves and springs all seated properly.


Having got this far, I re-read my Haynes manual and realised that I hadn't fitted or ordered any valve stem oil seals. 


Monday - a telephone call to B&G sorted that out and they arrived the following day.


Thursday after work - I spent a fruitless four hours trying to fit one of the seals.  They are so small that  I couldn't get them over the stem.  I tried everything, putting them in v hot water, fairy liquid, offers to the deities, I even asked the wife (who laughed).


Friday - call to Brown & Gammons to check that they had sent me the right thing.  They had unfortunately and couldn't help with their fitting as "the man who knows" wasn't there.



Saturday - I was stuck and really down about it, having run out of ideas in desperation I emailed Practical Classics helpline.


Monday - call to Barry at T & L  - "yup" he says, "we have the same problem so we fit our own better ones, easier to fit".  I would have paid him 20 plus delivery if he had asked, but he said 50 pence each and he'd get his delivery van to drop them in for nothing - yes please.  Just compare the difference in the size. 


Monday evening - 25 minutes in the garage stripping down the head (again) and fitting the new seals.  The picture above is of one on a stem - I hadn't rolled it into position at this point - success!


Saturday morning - fit the various studs for the manifolds, rockers and thermostat.  One felt a little strange as I wound it in, but hey-ho.

built_up_2.JPG (73178 bytes)

click on picture to enlarge

Saturday afternoon - better start stripping the car then (sorry the shot is a little out of focus).


I decided at the same time to do the timing chain.  I stripped of the radiator, and fan and removed the timing chain cover to find the chain (below).  Everything was covered in thick black slime - but I guess it's the first time the cover had been off in 70,000 miles so fair enough.


Off came the tensioner and sprockets.  The chain and sprockets were fine on close inspection, the tensioner had two huge grooves in the rubbing surface - 70,000 miles of wear - replacement cost 5.00 + 85 pence for a new gasket.  If your timing chain is noisy - try replacing the tensioner first it's a lot cheaper.


Strip off simplex timing gear and fit new tensioner, trial fit duplex cam sprocket - no probs.  Trial fit new crankshaft sprocket - argh!  It won't fit on the crankshaft.  Kick self/dog/car for trusting strangers, but on reflection with over 60 deals on eBay this is the first problem - there are mainly good people out there.


Saturday night - email eBay vendor.


Sunday - quick reply, "Sorry mate must have sent one for an MG Midget.  I'll pop one in the post".



I am still waiting.  This is the wrong one - now sold on eBay with a proper description.


Thursday - Call to B&G (again) flex my credit card and hey presto the following day an MGB crankshaft sprocket.


Saturday - the sprocket fits first time.  I torque it all back up, before moving onto the main course.  Whip off the old head - sounds easy - it was actually a pig.  The rockers came off OK and I kept them in one piece.  Two of the block studs wound out of the block rather than the nuts loosening.  Also, I had to borrow some malleable iron wedges from a friend, to split the head from the block.


("Here there's something missing")


As I stripped the engine down I took off the valve chest panels (on the side) and water pipes etc. and took the opportunity to clean them up and spray them with black Hammerite Smooth - it goes on nicely and dries in a matter of hours, before a second coat.  Spent what seemed like forever scraping the old gasket off the block, until I was happy with it.


Sunday - before fitting the new head I refitted the rear water pipe and trial fitted a new thermostat housing.



The thermostat housing pointed the wrong way!  My fault, I had ordered the wrong one, expecting that the Marina housing would be the same as the MGB housing from the same year.  It's not - go for the earlier MGB housing - up to 1967.


I had bought a new one in the first place because I expected that the old one would break as I removed it from the old head.  Now I had to find out.  Using two nuts locked together on the thermostat studs, I removed them and left the housing stuck to the head by 30 years of crud - nothing a rubber mallet can't shift though.



The gods this time smiled on me and it came free - I rubbed the old paint and muck off with fine emery paper and time for the Hammerite Smooth look.  The pic is of the wrong one, now sold on eBay with a proper description.


I dropped the new head onto the block and breathed a sigh of relief.  You can see the newly painted valve chest covers and thermostat housing - I'll see how long it lasts.



By comparison to what had gone before, the rest of the rebuild went quite well.  I took it steady and torqued everything down as per the manual.


I spoke too soon, .... as I bolt the combined inlet and exhaust manifold back on, number five stud just turns round and round.  I pull it out to find that I had over tightened it when fitting it in the head and stripped the thread in the head - oh b***er!  Anyone got a Helicoil kit handy?  I need a new stud and take the head off again.  I have come too far now.  I take a stud out of the old head and find my trusty tube of Locktite.  I squirt a drop into the threads in the hole and go and make a cup of tea.


I give it 20 minutes and gently screw the new/old stud in - it bites!


Whilst the car was in bits, I took the opportunity to fit a good used MGB Lucas 25D distributor, that I bought some time ago.  It has a vernier wheel on the outside which makes adjusting the timing a lot easier.  It also has a better advance curve, which won't do any harm to the performance.  I fitted the distributor with an Aldon Ignitor electronic ignition module - time to do away with contact breaker points I think.


I reconnect all the hoses, the accelerator and choke cables, exhaust system, plug leads and the battery; a drop of water in the radiator, check the oil.  Position the distributor somewhere near where I think it should go, err ... that's it.


So, finally, the moment of truth, will it start?  Choke out, a little gas, turn it over - no spark.  Ummm, maybe the petrol pump needs priming, try again?  Bursts into life but sounds funny.  I flash the strobe gun on the timing marks - it's running about 30 degrees retarded, so I swing the distributor until the strobe light shows I am somewhere close and set it up for 6 degrees retarded at tickover.  Sounds much better.  I shall play with this and get it spot on later.


I let it warm through and check for oil and water leaks - none!


OK time for a drive - feels good, better pickup and a lot smoother - out to the bypass - whoa there.  It's a different car, so much nicer to drive.


Can I recommend the unleaded head?  Yes - with the flow work done as well.


Will I ever make up the costs? One day perhaps - it cost me about 275 with all the bits and bobs, gaskets etc.


Was it fun doing it myself? Yes, the outcome was worth it and I like the challenge.


Would I do it again?  One day - but not for a while.


Update May 2008


I have dropped the engine out of the car whilst her bodywork is being done and took the inlet/exhaust manifold off.  Remember the loose manifold stud? well it came away in my hand!  So head off and a short time later one Recoil'd hole with a new stud in.  I did it myself in about 30 minutes, the key is drilling out the hole exactly perpendicular (at right angles) to the manifold face.  I tapped the hole with the tap supplied and wound in the coil, could be easier.  Not for everyone, but I'd recommend that you have a go if you are careful.