TDC mark and timing issues

[Cushing]

Hi all, I'm still having problems with trying to figure out what's going on with the timing on my 88my Turbo.  Red dot cams.

When I turn the crank to TDC ( TDC mark on flywheel), it's lined up on the front pulley but the cams are slightly off (see pic) as you can see it's not a tooth out, I tried moving the belt and it's worse. But if I turn to get the cams lined up it's off on the flywheel TDC mark, but, someone has hard stamped a DOT on the flywheel and it's lined up perfect with the flywheel indicator pointer ??? it's about 4° ATDC

I've had the head skimmed 0.14mm but used extra thick head gasket to compensate, but as the cam belt decides where the cams are set (lower side from crank to EX cam) the problem must be here. Imagine if pulled the head up with belt attached then the cams turn anticlockwise and would line up .  What do you think ?  do I need to get a new head ?

Sorry, can't upload pics for some reason.

[Cushing]

Hi Buddsy, it's ½ a tooth out, trying to upload a pic. 

 

[Cushing]

if you look at an earlier post (Timing issues) there are pics there.

 

[Cushing]

I've tried moving one cam sprocket at a time but then it's way off, even looked at the crankshaft pulley to see if it's  on the wrong way, but that can only go one way. If I line up the cams then there's no way the belt will fit from the EX cam down to the crank pulley when on TDC..... I've got a feeling the head may have been skimmed one before I had it done again. Looks like I'll have to bight the bullet and order a new head :-(

[910Esprit]

Stephen - your pics aren't working - or maybe they are not getting through my work firewall.   However, sounds a little expensive & premature to consider a new head just yet! .   You could run a compression check to help assess how much material has been removed.    You could also consider vernier sprockets to get your current setup spot on.   May also be worth using a dial gauge off a piston crown to validate your TDC (although that would be V fiddly) .  Have you also checked the flywheel timing - perhaps you  have some play in your front pulley keyway?         

[Cushing]

Hi Steve, yes, I've got a mate coming around with a piston crown gauge to check flywheel TDC marks, i'll check this before I order a new head.  Had a compression test done and all was good. Front pulley is tight, no play. Maybe look into vernier sprockets, that should fix it :-)  

[CHANGES]

Hi Stephen

Confirming the center dwell TDC is something that should always be done, Not all TDC marks seem to be consistent.   When you have established this, set up again ensuring the belt between the exhaust pulley and crank is tort. Failure to do this will give you false values.  It is not unusual to find the cam pulleys slightly out , even half a tooth.  In most cases like this I will time closest position but always towards the 104. especially on the 100-110 setups.  The truth be know very few engines cam time dead on with standard pulley system , mainly due to head gasket change and head skim.. This is not that big an issue.  If you want your engine to be the best it can be then vernier adjustable pulleys is the way to go.  Fitting a new head is pointless as you will still have discrepancies.  There is a thread all about vernier set up and cam timing that may enlighten you a bit more on how to accurately check your timing, which would be wise before you make any decisions.    

[Vulcan Grey]

my head has been skimmed, and I have the thicker head gasket.

My timing looks like this

[Cushing]

Thanks guys, mine do not line up like yours Travis, no way. Spoken with Steve at SJSportscars and he says it can be like this sometimes so I've ordered a set of vernier sprockets, this should tune out the problem.  I still can't up-load pictures, don't know why. Thanks again for the input.

[Cushing]

Just to let you know the outcome, I've installed vernier sprockets and now timing marks all line up. I did however find out by use of a TDI gauge my flywheel TDC mark is off by 5°, this put my timing at 14 - 15° BTDC. Dwell angle was between the DOT hard stamped and the TDC mark. I'll let you know how she runs when I get her started. 

[Cushing]

Engine running like a dream :-) but still leaking oil from lower cam house :-(  looks like it's a new head needed.

[Chillidoggy]

Are you serious?

[Cushing]

The head to cam housing threads had been stripped and drilled out to take M10, same for the cam housing, and when I stripped the engine down found that 3 of them were drilled slightly off centre and had in fact been stripped causing the leak at the cam housing joint. I've cleaned up the M10 threads as best I can and used M8 Timeserts, As the old M10 threads were not in the best of shape I epoxied the M8 insert, managed to get 20kNm torque but still not holding. One option I have is to get the bad M10 threads in the head plugged and re-tapped to M8, and in Norway the cost of a machine shop is about £120 per hour, or buy a new head which would be better in the long run. I have a spear set of cam housing with M8 bolt holes so I can use these. 

[fjmuurling]

Maybe this is an idea : https://www.aluminumrepair.com/

[Cushing]

Thanks Fjmuurling, just ordered a kit on line, I'll pull the engine again and give it a try, It's a lot cheaper than a new head. :-) thanks again, great forum.

[910Esprit]

I used these to successfully recreate a missing gear cable mounting lug on the transaxle.   The downside is that you need industrial amounts of heat - such as oxy acetylene to get enough temperature into a large casting such as a bell housing or a cylinder head.         

[Cushing]

I can get hold of Oxy acetylene gear so no problem there, but I guess I'm going to be careful of how much heat I use, don't want to damage the head. I'm planing to use M8 studs instead of the bolts, I guess this should be ok ?   Thanks again for all the advice.