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MG MGB Technical - Changing Camshaft (Engine in)

Hi All,
Can anyone give me some pointers as to what exactly is involved when changing the cam shaft with the engine in place?
So far as I can gather, I will need to remove radiator, sump pan, oil pump and distributor drive shaft, timing chain cover and cam shaft timing gears.
New cam followers and push rods??
Plenty of cam lube on start-up and run at ~2000rpm for about 15 mins to run in camshaft.
What I would like are any useful tips or info on potential problems that I may encounter, like priming oil pump!
I currently have the head off the engine to ideally send to Peter Burgess for a fast road porting etc. (anyone know what the kind of turn around is for this kind of work, assuming current head is OK) I have heard great things about his quality of work.
Any recommendations for cams for this set up?, Burgess fast road head, tubular manifold and free flow exhaust, 1 1/4 SU's (anyone modified the throttle spindles as in Peter Burgess book?), Stock engine capacity and electronic ignition.
Last thing, what is the quality of the cylinder head gaskets offered by Moss Europe? and should I go for the one with copper rings around water ways etc. or the completely copper gasket?
Thanks in advance.

Matt
Matthew Crabb

Hi Matthew,

I'm sure you already know this but to get the sump off you need to undo the engine mounts and lift the engine about 2". You can do this with the gearbox mounts still attached, just lift the engine up until the gearbox hits the top of the tunnel.

Run new cams in at at least 2500rpm for a minimum of 30 mins, no less. Preferably more. Pro race engine builders set up their valves with weak springs and run the engines for an hour at 3k to make sure there's no problems later on.

In my experience, all of the head gaskets commonly available through MG parts places are equally good (or should I say equally bad). The only advice I can offer is don't get the one that's painted silver, it makes a horrible mess on the block that's a pain to remove when changing gaskets.

Good luck!
--
Olly
Oliver Stephenson

Matt. Generally speaking, it is much easier to replace the camshaft with the engine out of the car. It is harder to properly align the dimples on the camshaft sprocket and crankshaft sprocket properly with the engine in the car. Ideally, after that is done, the camshaft is "dialed in" by using a degree wheel on the crankshaft and a dial indicator on the number one intake valve to ensure that the cam fully opens the valves at exactly the right place in the crankshaft rotation. If I were going to have the cylinder head built up, I would want to verify the cam timing was correct to ensure the system was working as specified.

Headgaskets. I have been using the resin type as made by Payen with great success.

As to turn around time from Peter Burgess. He has had one of my cylinder heads for something over five months now with no idea when it will be returned so I can finish assembling the engine. You might see if he has a cylinder head in stock, already modified, rather than having your head modified. Les
Les Bengtson

I meant to say 1 & 1/2" SU's silly me!

Matt
Matthew Crabb

Matt. Sort of figured that out. Few people wish to put on a cylinder head which has been modified for performance, the go to a smaller carb. I would still, however, recommend pulling the engine. My thinking is that, if you are going to the expense of fitting a new cam, lifters and a modified cylinder head, why would you do it to a lower end of unknown quality? I would want to know the condition of the oil pump, the rod bearings, the main bearings and the rings myself. If the engine has been rebuilt within the last 10K miles, this may not be a problem. If it has been rebuilt within the last 20K miles, it would require some serious benefit analysis. If it had more than 20K miles on it, I would definitely remove, tear down and inspect to see what I would be dealing with. More money and more time, but, if you are willing to install a new cam, new lifters, new timing chain, new timing chain tensioner, new upper and lower gasket kits, modified cylinder head, rebuilt carbs, etc., etc. I would, very seriously, recommend inspection of the lower end and, as a minimum, bearing and seal replacements. What you are doing is a lot of work to have to tear apart in a year or two because the cam bearings or rod bearings are worn. Even more of a problem to do all this work and throw a rod. Please consider these options. Les
Les Bengtson

Matt - I have to agree with Les, the job is much easier with the engine out and in the long run, you will probably save time by pulling the engine. Good luck - Dave
David DuBois

Hi Matthew: If your car is an everyday driver I recommend a Piper BP270 camshaft. If it is a weekender used mostly on motorways and/or for the occasional time trial then a Piper BP285. Get Burgess' book for more info and ask him about cams when you have your head done.
Terry

Matthew-
I have to agree with Les and David. With all of the work involved, you'd be better off to just go ahead and pull the engine out, then inspect the condition of the lower end. Use a Payen head gasket as it's the best of its type. I've got a Piper 270 camshaft with a Burgess Fast Road head and find the combimation to be tractable and reliable. Plenty of power across the entire range with easy starting and a decent idle. Always use new tappets with a new camshaft or you'll ruin the camshaft. Prior to starting the engine it is essential to prime the oil pump. Failure to do this will result in all of your handiwork being destroyed due to a lack of oil pressure and oil flow. Install a magnetic oil sump plug (Moss Motors Part # 328-282) and fill the sump with the most inexpensive 20W/50 oil you can find. Pour a tablespoon of oil down the pushrod wells to lubricate the tappets and another tablespoon of oil into each spark plug hole to lubricate the rings, then oil the rocker arms and valve stems. Pour oil down the vertical tube of the oil filter stand to fill the high pressure oil gallery and supply oil to the main bearings. Disconnect the large external oil line at the back corner of the block, pour oil into the oil pressure hose connection port on the block to supply oil to the oil pump and then rotate the engine backwards to draw the oil backwards into the oil pump. Once the pump is primed, install the oil filter, disconnect the power supply to the fuel pump and turn the engine until your oil pressure gauge gives a reading. Now you may reconnect the electrical power to the fuel pump and start the engine.
At this point it is critical that the camshaft and its tappets be properly bedded in to avoid ruining them. Hold the idle of the engine at 2,500 RPM for twenty minutes, occasionally varying engine speed gently between 2,000 and 2,700 RPM. After this process is completed, change the oil and the engine will be ready to be broken in on the road. Drive for 100 miles and change both the oil and the oil filter again, then again at 500 miles to bed in the new cam and lifters, then let it cool and then retorque the head using the proper sequence pattern. You will find some nuts almost tight, some can take almost a quarter turn. Run the car for 100 miles and retorque the head again. You'll find that this time the studs have not lost quite as much torque. Run an additional 400 miles (or 500 total on new engine) and retorque. During this period do not exceed 4,000 RPM or 45 MPH, operate the engine at full throttle, or allow the engine to labor in any gear. Until the next 500 miles (1,000 miles total) has been completed, limit engine speeds to around 4,500 RPM when shifting gears. Cruising on the highway should be limited to no more than 3,500 RPM. Keep varying the throttle opening and engine speed. The secret is to constantly vary the speed and load without creating excess heat through full throttle laboring and high engine speed operation. After 1,000 miles of following this procedure, change the oil and oil filter and refill the sump with a quality oil such as Castrol 20W/50. After another 1,000 miles the engine will be properly broken in and ready for service.
Steve S.

Thanks everyone, you have convinced me that pulling the engine is the way to go. The bottome end was rebuilt about 12K ago so it would be nice to have a look and see what kind of wear there is. Also I would much prefer to do most of the work on and engine stand or bench.
Thanks again

Matt
Matthew Crabb

Counterpoint: I see no real benefit to yanking the engine. You do have to prop it up a little, but how hard is it to see the dimples on the cam gear? (Call me lazy, but I don't fancy pulling out the motor unless you really need to.) As far as the bottom end, I'd first off just take off the sump and look around! ... fairly common among MG mechs to do just that ...
Ted

Matt. My only addition to Steve S's post is that I change the oil after the initial run in, along with a new filter. It may not be necessary, but, it is not expensive and makes me feel much better.

As to cams, the stock chrome bumper cam has worked well for me. I also like the Piper 270 which will provide slightly more power. My understanding is that the Piper is a regrind. Moss sells new, County brand, CB camshafts and I am using one in the last engine I built with good success. Also, take a good look at the rocker arm assembly and rebuild as necessary.

Ted. On an engine with 12K miles on it, I could see not pulling the engine to replace the camshaft. However, since there will be cylinder head work done, I would prefer to "degree in" the cam myself. On a stock engine, I would agree that aligning the dimples is sufficient--that is what the factory did and it worked fairly well. We have, however, been told by several posters that, when checking their cams, they found them to be off. In some cases a minor degree, but others have been fairly significantly off. Eleven degrees in one case if I remember correctly. Since Matt is building up his engine, I believe that pulling it would be the more effective method. At least that is what I would do and have done in the past. Les
Les Bengtson

I replaced a cam in a 1980 'B not long ago and the sump did NOT need to be removed. After removing the manifolds and slipping the pushrods (loosen the adjusters fully off) off of rockers 2 through 7 and removing the split-pins and whole rockers 1 & 8, take off the side covers and lifters, then the timing cover is removed. Obviously the radiator has to come out, as well as the distributor and it's drive gear (if you drop the drive gear when removing or installing it, you WILL have to remove the sump to get it back! Use a LONG 5/16 fine threaded bolt to extract the gear.) After the sprockets and cam thrust plate are removed the cam is slid forward and being very careful it will snake around the oil pump drive gears. It was simple and did not require any gymnastics to come out, just go slowly and be careful not to knock the cam bearings with the journals as you slide it out. The new cam slides in the same way, just make sure you lube the lobes with the special cam grease and the journals too. There's no sense in removing the sump if you don't have to. Lining up the timing marks is not difficult with the radiator removed nor would dialing in the cam if you have an adjustable sprocket (or offset keys.) This procedure is from memory, so if I missed something please forgive me and let me know. I hope it helps and saves doing unnecessary work.
John Greenwood

No need to pull the engine. Did this twice. Once installing a kent cam(not impressed) and once installing a Crane ( the one Moss sells. Got it through a local american speed shop for $40.00 cheaper than Moss's price) I like the Crane cam very much. I did lift the motor off the front mounts, drop the pan and pull the oil pump, as I remember. All the other removals aply: rockers,push-rods, lifters(intall new ones), cylinder head, tappet and timing cover, timing gears and chain, distributer radiator etc. Check the cam timing as many "performance" cams are regrinds of stock cams, with the grind rotated to get the new cam profile. You'll need a drop indicator(used on #1 piston to find actual TDC) and a degree timing wheel. E-mail me and I will tell you exactly how that is done, if you don't know. Offset keys are available and much cheeper that a variable timing gear. I did all this with the engine still in. I see no need to add an engine pull to the list.
DB Bush

This thread was discussed between 05/05/2003 and 07/05/2003

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