Alfa Romeo Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Hi all, first post but long time reader.
Thanks in advance to anyone who can assist with the following;

I'm in the reassembly phase on a bottom end re-build of a 1970cc CF3 twin spark engine, which has been battling me from the start.
Latest problem is that there is evidence of interference between the side of main bearing #1 journal and the rear gerotor cover of the lube oil pump.
Clearly the two have been in previous contact with signs of spalling on the oil pump cover corresponding with the side face of the #1 main journal.
Crank is fine (just crack tested, re-ground 10/10 and polished), end float is in spec. Nothing untoward on the crank noted during inspection by myself and also the machine shop.

It's clear that the #1 journal clearly stands proud of the block by a couple of mm, (don't have exact measurements yet, but will survey in the next few days).
At some point they have clashed in the past as the inspection of the oil pump revealed yesterday.

So, either one (or a combination) of the following must apply for this to occur:
a) The #1 crank journal has been manufactured incorrectly and is too wide.
b) The block is machined incorrectly in terms of the thrust bearing register location e.g. to far towards the free end of the block.
c) The oil pump is incorrectly manufactured.
d) The oil pump is ok, but is for another variant with different stand-off spacing and therefore reduced clearance on the CF3.
e) Someone has replaced the oil pump previously omitting the gasket, then removed and refitted a gasket because there was definitely one there on strip down.

Just wondering if anyone has seen/heard of anything like this before?
Assuming the interference still exists (ref e) above and the fact that I haven't accurately measured yet), the current plan will be to machine ~.020" off the back of the gerotor cover to provide at least .020" clearance.

Thoughts & comments appreciated
Vne
 

·
Registered
Joined
·
7,120 Posts
not sure this is the same, but my 145 had a similar issue. I thought the clutch bearing was on the way out as it was noisy on depressing the pedal, clutch duly changed but the noise was still present.It turned out the noise was the crank catching the back of the oil pump as the clutch spring was pushing the crank towards the oil pump. Solution was new thrust washers.

Hope this helps

and welcome BTW
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
not sure this is the same, but my 145 had a similar issue. I thought the clutch bearing was on the way out as it was noisy on depressing the pedal, clutch duly changed but the noise was still present.It turned out the noise was the crank catching the back of the oil pump as the clutch spring was pushing the crank towards the oil pump. Solution was new thrust washers.

Hope this helps

and welcome BTW
Thanks for kind response Purple - that would make sense given the state of the rest of the engine. I didn't measure end float on strip down sadly, but did keep the worn thrusts which I'll measure. Will revert once I know what the cause was. Cheers Vne
 

·
Registered
Joined
·
7,120 Posts
if you register on Alfa145.com you can gain access the to the Alfa engine repair manuals in pdf format which will have the specs of the thrust washers in the engine

HTH
 

·
Registered
Joined
·
5 Posts
Discussion Starter #5
if you register on Alfa145.com you can gain access the to the Alfa engine repair manuals in pdf format which will have the specs of the thrust washers in the engine

HTH
Purple,
Couldn't access that link for some reason. But thought I'd follow up with some results of the survey I did over the weekend. Assuming I have the correct oil pump, it appears that the design of the engine is right on the feathery edge in terms of design clearances. The measurements revealed that there is only .006" minimum clearance between the oil pump cover and the side face of #1 crankshaft journal. I'll try and attach some photos...

First showing galling on oil pump gerotor cover where crank journal has been hitting.
The second, is on the pump side where it's lucky that the thing didn't seize up.
 

Attachments

·
Registered
Joined
·
5 Posts
Discussion Starter #6
Purple,
Couldn't access that link for some reason. But thought I'd follow up with some results of the survey I did over the weekend. Assuming I have the correct oil pump, it appears that the design of the engine is right on the feathery edge in terms of design clearances. The measurements revealed that there is only .006" minimum clearance between the oil pump cover and the side face of #1 crankshaft journal. I'll try and attach some photos...

First showing galling on oil pump gerotor cover where crank journal has been hitting.
The second, is on the pump side where it's lucky that the thing didn't seize up.
Further pictures...
Firstly, crankshaft journal #1 side face...
The second picture shows my solution - a .024" relief machined on the back cover to give some breathing space.

Clearly the thrusts were badly worn, as there is corresponding core marks on the outside of the oil pump where the cam belt pulley has been contacting the oil pump housing. Interesting...

Cheers
Vne
 

Attachments

·
Registered
Joined
·
6,333 Posts
Thrust half rings have a thickness of 2.342 to 2.358 mm, oversizing is 0.127.

Crankshaft axial clearance is 0.059 to 0.221.

All measurements in mm.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #8
Thrust half rings have a thickness of 2.342 to 2.358 mm, oversizing is 0.127.

Crankshaft axial clearance is 0.059 to 0.221.

All measurements in mm.
All the clearances measured above were with new thrust washers - end float measured as .012 mm, so spot on. Cheers
 
1 - 8 of 8 Posts
Top