|The MGA With An Attitude
R&R OF THE CAMSHAFT -- CM-104
This does not require removal of the engine from the car
or removal of the cylinder head.
At 09:57 PM 11/4/01 -0400, Enrique Claure wrote:
>.... If I plan to remove the cam with the engine inside I guess I must
>1. Remove Radiator
>2. Remove Head
>3. Remove Front engine Cover
>4. Remove Chain and Tensioner
>5. Pull the cam out.
>Anything else I am skipping?
Yes, you missed a couple of small steps, but you also included one that you don't have to do. You don't have to remove the head. SURPRISE! But you will have to R&R the intake and exhaust manifolds.
Remove radiator, fan blade and water pump pulley, crankshaft pulley, timing cover, timing chain tensioner and sprockets and chain (save the shims you find behind the crank sprocket, or leave them in place). Also remove the thrust plate (3 screws) that locates the front of the cam front to back. If you have an oil cooler mounted above the air pan ahead of the radiator you will have to unbolt the cooler and move it aside. You do not have to remove the grille.
Remove the valve cover, back off all of the rocker adjuster screws, move the rockers to the side out of the way. For the front and rear ones you need to remove the rockers from the ends of the rocker shaft. Remove the carburetors and intake and exhaust manifolds. Remove the tappet covers on the left side of the block. Pull the pushrods out the top, and lift the tappets out through the side. If you are installing a new cam, discard the tappets, as you will have to have new ones to go with the new cam. If you think the old cam and tappets may still be in serviceable condition and you want to save them, then you have to carefully arrange to keep all of the tappets in the correct order, as each tappet must be mated to the same cam lobe in order to be reused. If you mix up the tappets they are trash, and you would have to buy a new set to reuse the old camshaft.
You should also remove the distributor, and the dizzy mounting base, and withdraw the dizzy drive gear from the block. You might get the cam out without doing this, but you will surely lose the index position of the gear in the process, and would have to R&R the gear later anyway to realign the dizzy drive after the new cam is installed. Use a long 5/16" fine threaded bolt to capture and manipulate the dizzy drive gear. One of the longer thin rocker pedestal studs works well for this. Be careful not to drop the gear into the engine, as that would require R&R of the oil pan to retrieve the gear. You do not otherwise have to remove the oil pan or the oil pump to R&R the camshaft.
You can reinstall the cam sprocket temporarily to use as a handle. Withdraw the cam from the front of the engine. By the time a cam lobe gets into the vicinity of the oil pump drive gear the cam bearing journals will be out of the bearings, and the cam can be turned or moved laterally slightly to clear the oil pump drive gear. Once the cam is pulled forward a few inches you will need to remove the sprocket, as the bare cam just clears above the horizontal air pan on the body.
You will likely need to transfer the tachometer drive gear from the back end of the old camshaft to the new cam. Installation is easy enough, but getting the gear off the old cam without damaging the gear teeth is a trick. For a tool and technique to do that, see Tach Drive Gear Puller.
Reassembly is the reverse of disassembly. Use lots of grease or assembly lube on the new cam lobes. Always install new tappets with a new camshaft. Do try to get the timing sprockets aligned correctly the first time (read the shop manual carefully). Shims behind the crank sprocket are used to align the sprockets to be in the same plane. Install the timing sprockets without chain. Lay a straight edge across the face of the sprockets, holding it in firm contact with the cam sprocket. Use a feeler gauge to measure any gap you may find between the straight edge and face of the crank sprocket. Add or remove shims behind the crank sprocket as required to bring the crank sprocket into alignment with the cam sprocket.
If it is a special grind camshaft, then you need to follow the manufacturer's instructions to set the cam timing. This may require an offset cam key, skipping the chain over one tooth, or the use of an adjustable cam sprocket. Please review Cam Timing Tech. The last admonition is that if the new cam has higher lift than the old cam, then you should be very careful to check that the valves have adequate running clearance so they do not hit (or even come close to) the top of the engine block at full lift. This may ultimately require removal of the head to cut clearance eyebrows in the top of the engine block. Please review Valve Clearance Eyebrows.
You may also consider replacing the cam front retainer and thrust plate, as the MGA part has a soft white bearing material on the back side. When that part wears from the cam rubbing, it can allow increased end float for the cam when running. This is not generally a serious problem, but it can cause an irritating tapping noise that may sound suspiciously like a knock from a bad connecting rod bearing, and it can sometimes cause some fluctuation in the ignition spark timing. The bronze thrust plate from the MGB engine may also be substituted here to reduce future wear. Install a new seal in the timing cover and use all new gaskets for reassembly. Set valve clearance by the book, unless instructions with the new cam say otherwise.
Reinstalling the distributor drive gear in the correct orientation is a bit tricky, especially since the factory manual instructions may be confusing. They don't necessarily mention that when the timing sprockets are installed with the punch marks aligned the #1 cylinder is at Top Dead Center on the exhaust stroke (not on compression stroke). Before installing the distributor by the book you need to turn the crankshaft one full revolution to bring #1 cylinder to TDC on the compression stroke (both valves closed). Please review Distributor Drive Gear Alignment.