Monday, 30 August 2010

6. ENGINE REASSEMBLEY


The crankshaft and flywheel have been checked for size, damage and reground as neccessary. They are then balanced ready for reassembly.

The case is carefully measured when assembled with the nuts torqued correctly. For the 50mm A/B crank and case the case bore is 60.235mm to 60.245 mm for bearings 1,2 and 3 and 50.0mm to 50.025mm for bearing 4 in the third piece.

Use a bore guage to measure the diameters of the case bore.
Both sides of the case are thoroughly cleaned and all oil passages blown through with wd40.

The left half of the case is attached to the engine stand.
All mating surfaces are cleaned thoroughly using a bearing scraper.


Cleaning the mating surfaces with a bearing scraper.

Clean off any debris with solvent. Make sure there are no deep scores on the mating surfaces.

Clean out the oil passages by squirting wd40 into the oil holes where the oil cooler sits on the top of the engine to ensure they are completely clear before reassembly. Repeat for all the oil holes of the engine and also clean out the cam bore holes and cam oil holes. Repeat for the main bearing oil holes and for the oil pressure relief valve area. Use a whole can of wd40 to ensure there is no debris in any of the oil sytem.
Wipe of excess oil particularly from the bearing areas.

Once the left half of the case is clean move over to the right side which does not have any oil lines but clean the cam follower holes and clean and dry of the grooves in the main bearing seats which are oil flow channels. Wipe of excess oil and check no pieces of paper left behind!

The cam is the first part to be fitted. If the timing gear has been removed then it is important to check that the oil pump drive groove on the camshaft end points towards the mark on the gear. If there is any wear to the groove then the cam should be replaced to avoid problems in the future. The groove is where the oil pump drive fits and wear can lead to the loss of drive to the oil pump and certain disaster.

There are 3 possible ways the timing gear can be put on and only one is correct. If this is not lined up correctly your engine WILL NOT run. Use new lock washers for the 3 cam bolts that attach the timing gear. Torque to 18ft lbs. The bolts should be 14mm across flats.



Oil pump groove points towards mark on timing gear.




The cam gear size is stamped on its inner face as per photo and is either 0,-1,or+1. It should match the number stamped on the crankshaft gears. This is a zero in this case.




Inner face of cam timing gear. The zero can just be seen at the bottom of photo.


The cam followers need to be put in place and can be retained by wire cam follower or with assembly lube. Place molylub on the faces as per photo. Blow the cam followers through with WD 40 to make sure their oil holes are clear and clean.

Lubricate the cam bearing journals with some assembly lube or stp/oil mix.
4 cam followers held in place with white assembly grease with molylub on their faces.
Spring clips for holding cam followers Porsche part P241


Cam and timing gear in place.

The next task is to get the crankshaft ready for fitting. The use of a crankholder makes life a lot easier. Alternatively the crank can be bolted to the flywheel and this used as a base for construction.



The Crank has been reground to 2nd under ready for fitting using a 0.5 over set of main bearings. If the number 3 bearing is being replaced (never reuse old bearings!!) then the crank gears will need to be removed using a 15 ton press. The old bearing is removed and the new one fitted (see later as fitting this correctly is essential) The gears and spacer and lock ring can then be replaced. they can be heated to aid getting them back on.
Make sure the main camshaft drive gear (the larger one) is fitted with its bevelled edge towards the crankshaft and the timing marks visible on its outer face. (2 small dots). They will later need to be aligned with the mark on the cam timing gear.

Part number 502.03.105 are early type A rods and have a rod bearing tab on the left hand side. These rod bearings are hard to find. On these rods the tab was moved to the right hand side between 1960-61.
616.103.101.00 are late rods from 1961-1963 . The tab is on the right hand side. Finally rods 616.103.101.01 are the c/sc/912 rods and are the best and again the tab is on the right hand side.
 



Rod Beam with bearing in place, tab to the right.

Clean the rod bearing faces with wd40 and dry with kitchen towel. Insert the rod bearing shells by carefully pushing on the ends not the middle of the bearing shells. The early bearing shells have a tab on the left hand side and the later bearings a tab on the right. They are not interchangeable.
Clean the bearing faces as above.





The next task is to fit the rods to the crank. Carefully clean the crank and blow out all the oil holes using wd40. Mop dry using a paper kitchen towel or lint free cloth. The rods should be weighed to ensure they are close in weight -to within a gram of each other. The rods beam and their caps are numbered or have punch marks, so make sure the numbers are on the same side when assembled.



Fit the first rod to the crankcase lubricating the crank using a mix of mix of stp and oil 50/50 over some molylub. Do not get into the oil holes of the crank. First fit the rod cap over the crankshaft rod journal. It is best to fit the rod beam such that when it is held vertically the tab of the beam is on the right hand side as viewed from the rear of the engine (cam gear end). This minimises the chance of a spun rod.

Snug the nuts down using a little loctite on the nut and thread. Keep alternating nuts as you tighten down to ensure the snugging down is done evenly. Then torque the nuts to 15, 20, 25, 30 and finally 32.5 ft lbs using a torque wrench. check toque at 32.5 ft lbs three times to ensure it is correct

Repeat for the other 3 rods. When finished hold the rods in the air and let them fall under gravity. they should all fall at approximately the same pace or rate. Check none are binding and move freely when spun around the crank

CRANKSHAFT


Crankshaft with number 3 bearing in place.

Before fitting the crankshaft gears the number 3 bearing needs to be put onto the crankshaft.
The number 3 bearing has 2 oil inlet holes and a dowel pin recess for it to sit on the dowel pin in the case. The 2 oil inlet holes may look to be equidistant from the dowel pin recess but they are not!!
It has to be fitted such that when the crankshaft and bearing are fitted to the left hand side of the case, the bearing oil hole that is furthest from the dowel pin hole and that is visible out of the case,  faces towards the cam.
It is a very good idea to fit the number three bearing in its correct position in the case so it sits on its dowel with the oil holes visible and check the correct position before fitting to the crankshaft. 

It is essential this is fitted correctly before the crankshaft gears are replaced on the crank.



The cam drive gear goes on first followed by a spacer, then distributor drive gear and then the lock ring.
The parts need to be heated to 250 degrees to allow them to fit. The cam drive gear is bevelled and must be fitted with the bevelled side downwards facing the crank (there are 2 timing marks on the non bevelled face which you will be lining up with the cam gear). 
You will need heavy duty snap ring pliers to open the spacer to allow it to fit snugly. Tap each part down gently with a screwdriver to make sure they fit nicely. Fit the distributor drive and finally the snap ring, check the snap ring is properly in its seating. Spray with WD 40 to cool the parts and check the bearing turns freely.



Carefully clean both sides of the engine case ready for the crankshaft fitting. Blow out all the oil holes, bearing dowel holes and oil cooler holes using WD 40 and carefully clean with kitchen roll. Use a whole can of WD 40 to ensure everything is clean.
Clean the Sump areas.


Now fit the 4 dowel pins. (two for number 2 bearing one in each case half)



Dowel pins fitted to the bearing areas of the case


Fit the flywheel main bearing to the case. It only goes in one way and it is sensible to mark the outer  face of the  bearing with a pencil to indicate where the dowel hole is. This makes it easier to line up later when fitting the crank.

The middle main bearing is a split bearing. Line up the oil hole in the bearing with the oil hole in the left case half and gently fit the bearing by pushing on its ends, not its centre. The other half of this bearing also has an oil hole but there is no corresponding oil hole in the right hand side of the case meaning it can be fitted one of two ways. I tend to fit it with the oil hole facing the case bottom or cam side.

We are now ready to fit the Crank.
Remove the camshaft for the time being.

Put the main bearing back onto the crank with the pencil mark indicating the dowel position visible. lubricate the bearing areas in the case with stp/oil mix and also the middle bearing shell.

Hold the crank by the number 2 and number 4 rods and drop the crank onto the case half. Rotate the number 3 bearing until it sits on the dowel pin. Do the same for the main bearing using your pencil mark to help seat it on its dowel pin. Make sure the crank is properly seated and rotates freely because if it is not, when you tighten the case halves together you will end up with a sized bearing!!


Crankshaft in place


We  are now ready to re fit the camshaft. Lubricate the cam bearing surfaces with assembly grease.

The positioning of the Camshaft timing gear is very important, Look carefully until you find the mark on the cam gear and line it up with the two dots on the crankshaft gear. (see photo below)

You will need to rotate the crank and cam until lined up.


The single dot on the camshaft gear must be between the two marks on the crankshaft gear



We are now ready to fit the right side of the case. 
First fit the cam plug (it looks like a bottle top!) with the case sealant. I use a Wurth product called flange sealant. (see picture below)




Cam plug fitted with sealant to the left of crank.

Next apply a coat of gasket sealant to the mating surfaces. it can be spread to a thin even layer with a spatula or knife. 
Balance the rods so they stand upwards and carefully mate the right side of the case to the left. Note you do not need sealant on the face where the timing case cover is attached.



Flange sealant on mating surface


Both sides mated and ready for bolting together.


Take the long through bolt and place a bevelled case washer onto the bolt with the bevel facing towards the engine case. Open your gasket set and get out the rubber "O" rings and lubricate with oil/stp mix. Carefully push the "O" ring over the threads of the bolt and down the shaft so it fits in the bevel of the case washer.
Bevelled case washer

Pass the through bolt through the case and place another "O" ring on its threaded end. 
Some early engines only have one through bolt and later ones have two.
Now place lubricated "O" rings on all the other case studs.


Placing "O" rings on case studs

Place a bevelled washer over each of the studs with the bevel towards the case so it will compress the "O" ring when tightened. Get your acorn nuts and hand tighten them on each of the studs and on the long bolt.
It does not do any harm to use a small amount of blue loctite on each acorn nut.
The best acorn nut should be used at the rear of the engine where it will be seen when the engine is fully assembled. You will need a 17mm spanner for the head of the through bolt and a 15mm socket for the acorn nuts. Tighten the through bolt first. Then tighten the other acorns to hand tightness alternating from side to side.

6   2   4
5   1   3 
This is the pattern I use for tightening

we now need to put on the cam plug nuts and spring washers. The washers are slightly larger to fit the 14mm nuts which are hard to find now. Use a little loctite and snug down to hand tightness. 

Get your torque wrench and tighten the acorn nuts to 14-15 lbs. Again alternate from one side to the other and from front to back while tightening in the order above.

CHECK THE CRANKSHAFT TURNS FREELY.

Set your torque wrench to 20 ft lbs and repeat the tightening of the acorn nuts.

CHECK THE CRANKSHAFT TURNS FREELY.

Repeat the process at 25 ft lbs torque.

CHECK THE CRANKSHAFT TURNS FREELY.

Repeat at 29 lbs torque. Check the torque 3 times for each nut.

CHECK THE CRANKSHAFT TURNS FREELY.

Now clean up any flange sealant that has been squeezed out of the case halves using kitchen roll. 

NB Some very early 356A engines used copper washers instead of bevelled ones. These case are only torqued to 22 ft lbs.

Now tighten the cam plug nuts. you wont be able to get a torque wrench on them but tighten firmly but do not over tighten  (15-18 ft lbs.)

We are now going to fit the eight case perimeter bolts. These are 14mm nuts and bolts and are very hard to find. they also have a special sized washer with larger outside diameter so look after them carefully.
There are seven of the same length and one longer one that goes on the bottom of the engine at the rear.
These are put in from the left hand case side with nuts on the right hand side.
Use the best 2 at the third piece end of the engine as these are visible.

Nuts should be used with logo facing outwards

Snug the nuts down and then torque to 17 ft lbs using a side to side and end to end torquing pattern.

Congratulations you have finished your assembly of the Lower End.





1 comment:

  1. keepup the good work I'm just about to start a rebuild. thanks craig

    ReplyDelete