Vauxhall Viva OHV Engine Assembly Guide
One of the engines collected last week had already been built by me, but it had been in storage for a couple of years, so I broke it down to check it all over and rebuilt it back up. At the same time I thought I would do a poor mans Haynes guide. So without further ado here we go on a hell of a long post !!!
Take a clean block, this one has had a re-bore + Hone and new cam bearings (in an ideal world if needed new core plugs as well). Wipe everything dry and clean, make sure you have plenty of room and access to all side of the block.
The crankshaft is first. (for no specific reason) start with the main bearings, rear main bearing first, making sure the tab is located the correct way around in the block (see the right edge of the bearing has a locating tab).
Add the middle main bearings (note this has the thrust faces on the bearing, an automatic engine would have two of these. This is a manual engine so only one is used).
The last main bearing is added and the Rear crank oil seal sat in place.
I use a paste that graphite based, which lubricates the main bearings. The principle is that this is a friction free barrier in the engine for a short while once the engine is first started, and will protect the bearings whilst oil is being distributed around the engine at first start up. It never drys up and is so sticky it will not run away whilst the engine sits in storage.
The crankshaft is then lowered into place with the rear crank oil-seal sat in its channel at the rear of the engine.
The front and middle main caps are then lubricated with the same graphite paste and placed into position on the block.
The rear main cap needs a sealant along its edges to form a seal, I only place a very small amount on the outside edges of the main cap. Be careful not to drop sealant into the engine block.
Then fit the main cap in place and tighten down, sufficiently to close and seal the cap in place. You are now ready to torque the main bearings down. In the case of this engine 55 pounds (it differs for engines so one must check the book first).
The crank is now fitted and the rest of the engine can be built around it..
Next comes the camshaft.
Clean up the followers (there is a whole story on new or old, lets bypass that for now and just get on with putting it together). I put a drop of STP in the top of each follower, so that when it is pushed into place it assists by lubricating the follower holes in the block. Once each one is in place, pushing them in and out a few times will confirm the fit is good.
Each follower is then lowered into place into the block (small hands required and patients for the ones under the oil pump support).
Don’t forget to wipe then clean and make sure no dirt is in the cam bearings, before you attempt to fit the camshaft. Clean the camshaft including the gear teeth for the oil pump. carefully slide the camshaft into the block, remember the bearings are easily damaged so its best to support the cam with both hands and slowly move it into place.
Once its in place, bolt on the cam plate, make sure you get it the right way around if its an automatic chain tensioner. The older style external chain adjuster type don’t have a handed side.
Now its time to “Time” the engine, its worth spending some time on this, as its very easy to be one tooth out and not realise it. I normally mark the tooth gear wheels and use a rule to make sure the two dots are in line with each other and pass through the centre line of the pulley and adjuster stud.
The difficult part is knowing if you have timed it 180 degrees out or not! First rotate the camshaft so that when the tooth gear wheel fitted the LOBES on the cam for cylinder 1 are not pushing the followers up. Then rotate the crank shaft till its at TDC, you should now find the two wheels fit the crank and camshaft and line up.
Once thats all in place you can fit the Chain tensioner (and at this point got bonkers as you realise the camshaft plate is the wrong way around and prevents you fitting the tensioner correctly!
Its out again with the Torque wrench and 35 pounds on the camshaft pulley bolt.
Next put a gasket and some sealant on the timing case cover and fit it. make sure the case is level with the block before you nip it up fully.
Next are the pistons.
Its worth getting a good piston ring compressor and having some confidence in fitting pistons, as its very easy to break a ring by being weak about pushing pistons in place.
Starting at front of the engine (number one) I slide the first piston in place making sure I have the FRONT mark on the piston to the front of the engine! make sure you have first rotated the crank to the bottom of the stroke, as its not good to bash a con-rod into a crank at this stage.
Using some of the graphite paste on the big end bearing rotate the crank towards TDC and engage the con-rod.
Use some more paste on the con rod end cap bearing. place the end cap in place and loosely tighten the two end cap bolts. Make sure when you place the cap on the con-rod it is the right way around, the bearings have locater tabs and these should be placed together when fitting the caps.
Continue the same method for all pistons. Then its now time to Torque the Big end caps (25 pounds)
Oil Pump, and this is where most people make the mistake. First rotate the engine to TDC on the number 1 cylinder.
Check that it is Number one at TDC and not Number 4, look at the camshaft and make sure the lobes are not pushing up the followers. If they are then its on TDC number 4, so the engine needs a 360 degree rotation.
Use a new gasket on the oil pump and slide it into place, then looking down the dizzy shaft hole make a note of the oil pump slot.
This is an offset pump and the thin side of the oil pump slot should be towards the rear of the engine (in the picture the rear of the engine is downwards, the securing bolt hole for the dizzy denotes the rear) with the dizzy slot at 90 degrees to the block. We can see that this is not the case in the first fit.
I use a big old screwdriver that is slotted into the top of the pump, I then slowly withdraw the pump from the camshaft teeth, turn the screwdriver and re engage the pump. A few tries should get you to position the pump correctly. (remember NOT TO TURN THE ENGINE). There is 15 degrees of tolerance so don,t worry if its not 90 degrees perfect to the block.
You should now see the slot is correctly positioned in the block and one can bolt it into place (20 pounds on the torque wrench)
The oil filler pipe is supported off the centre main cap using a small bolt, its now time to tighten this up.
Now we are ready to fit the sump. First fit the cork gasket seal to the rear main and use some sealant to stick it in place.
Line some sealant up around the whole block where the gasket sits, then lay the gasket on top of this sealant. Then apply another line of sealant to the top of the gasket, before finally placing the sump on top.
There are 19 screws / bolts to tighten down the sump, the key is to evenly screw them down!
We now have a finished short engine, ready for the head and external bits to be fitted.
Thats it folks…. When I am ready to build the head up I will do a similar post.