knocking sound caused by loose valve guides
Anyone has seen this problem? When engine is hot, my 164QV's engine starts to knock. Not main or rod bearings as the frequency seems to indicate the knock's frequency is around cam speed. I suspect the exhaust valve guide has loosened enough when hot. The only worrying thing is, should my suspicion is true, is that the head is pretty much done. The hole for the guide is probably oval now.
Z,Ive had valve seats come loose and occasionally give me a loud "clack" noise as the valve pushes it back in..Drove for over 500km like that not knowing what it was..
Guides?Dont know huh..If the giude migrates out it tickets for sure..
Guides?Dont know huh..If the giude migrates out it tickets for sure..
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
I'm not speaking from experience so I might be wrong here.
I see it very unlikely that the guides would come loose. There's no real force making them loose and they don't move so they can't wear in their place.
I have seen valve followers wear their holes badly though. At least for 4-bangers there are oversized followers available. The price is about same as swapping to a better head. When they start clacking you can feel by hand that the followers are loose.
I'm about to do some diamond coated valve followers for 8 and 24V. This should fix the problems of worn followers and cams at least. Should fix this problem too if it is what I guess.
I see it very unlikely that the guides would come loose. There's no real force making them loose and they don't move so they can't wear in their place.
I have seen valve followers wear their holes badly though. At least for 4-bangers there are oversized followers available. The price is about same as swapping to a better head. When they start clacking you can feel by hand that the followers are loose.
I'm about to do some diamond coated valve followers for 8 and 24V. This should fix the problems of worn followers and cams at least. Should fix this problem too if it is what I guess.
I have had similar experience with various engines(not alfa v6) and have found camshaft end float to cause knocking noises mainly at idle to low engine speeds. Check the specifications with the workshop manual. I have found that camshaft end float noise happens when clearance is above 0.006".
I have also experienced a faulty new timing belt not running parallel on a ferrari 308 to cause knocking noises.
As for valve seats and guides they should be iscolated by compression checks.
Cam followers in head can also be a problem.
I have also experienced a faulty new timing belt not running parallel on a ferrari 308 to cause knocking noises.
As for valve seats and guides they should be iscolated by compression checks.
Cam followers in head can also be a problem.
From the old GTV6.org site, showing that everything old is new again:
By Tim on Sunday, May 18, 2003 - 11:08 pm:
This is a very interesting thread regarding the mysterious warm engine knock that seems to be common for the Alfa V-6.
I don't believe this knock is always lower-end related as some suggest. The lower end of the Alfa V-6 is built especially rock solid as independent test have proven; for example as the Callaway turbo dyno bench test showed.
Wrist pin knock typically will occur when an engine is cold and then it will decrease with the rise to operating temp. My BMW 2002 has this type of knock.
I believe this myterious V-6 knock is coming from the upper end, perhaps worn cam bearings, push rods, rockers or something up there? Obviously temp related.
BTW: A decent test for worn main bearings is to run the engine to full temp and put the gas on hard, if the oil pressure drops while doing this then more than likely the main bearings are badly worn. For accuracy sake it is probably a good idea hook up diagnostic digital oil pressure meter while doing this type of test.
A good test for rod bearings is to run the engine to full temp and then increase the gas, then let off the gas suddenly. During this transition, when letting off the gas, worn rod bearnings will knock slightly. Also at cold start the rods will knock until oil pressure comes up, sure fire sign that the rod bearings are worn. HTH.
Tim
'87 Milano 2.5L
By ralph on Monday, May 19, 2003 - 09:09 am:
Tim, your right about the knock. the noise comes from worn cam buckets and cam lobes and excessive valve lash. It sounds like a deep hollow knock.
By Tim on Monday, May 19, 2003 - 10:33 pm:
Ralph,
I guess I know now what the next project is for my Milano; new cams and complete head rebuilds.
This knock dosn't bother me too much as it is not too loud and it seems to be more quiet sometimes than at others. It sure would be nice without it though!
Tim
By ralph on Tuesday, May 20, 2003 - 09:44 am:
The crankshafts on the alfas are nitrated for hardness l have yet to see a bad one. Camshafts and valve train well thats another story.
By Tim on Sunday, May 18, 2003 - 11:08 pm:
This is a very interesting thread regarding the mysterious warm engine knock that seems to be common for the Alfa V-6.
I don't believe this knock is always lower-end related as some suggest. The lower end of the Alfa V-6 is built especially rock solid as independent test have proven; for example as the Callaway turbo dyno bench test showed.
Wrist pin knock typically will occur when an engine is cold and then it will decrease with the rise to operating temp. My BMW 2002 has this type of knock.
I believe this myterious V-6 knock is coming from the upper end, perhaps worn cam bearings, push rods, rockers or something up there? Obviously temp related.
BTW: A decent test for worn main bearings is to run the engine to full temp and put the gas on hard, if the oil pressure drops while doing this then more than likely the main bearings are badly worn. For accuracy sake it is probably a good idea hook up diagnostic digital oil pressure meter while doing this type of test.
A good test for rod bearings is to run the engine to full temp and then increase the gas, then let off the gas suddenly. During this transition, when letting off the gas, worn rod bearnings will knock slightly. Also at cold start the rods will knock until oil pressure comes up, sure fire sign that the rod bearings are worn. HTH.
Tim
'87 Milano 2.5L
By ralph on Monday, May 19, 2003 - 09:09 am:
Tim, your right about the knock. the noise comes from worn cam buckets and cam lobes and excessive valve lash. It sounds like a deep hollow knock.
By Tim on Monday, May 19, 2003 - 10:33 pm:
Ralph,
I guess I know now what the next project is for my Milano; new cams and complete head rebuilds.
This knock dosn't bother me too much as it is not too loud and it seems to be more quiet sometimes than at others. It sure would be nice without it though!
Tim
By ralph on Tuesday, May 20, 2003 - 09:44 am:
The crankshafts on the alfas are nitrated for hardness l have yet to see a bad one. Camshafts and valve train well thats another story.
'84 GTV6 3.0L
'81 X1/9
'81 X1/9
on my 12v I had the knock and it ran low oil PSI any time hot(if you can trust the alfa gage) no light
over 230K miles
When I puled it, the main bearings were very bad and the rod were a bit bad.
I put the same rods and crank in a S block (wanted the piston oil jets)
with new bearings. now no more knock. the top end was in very good shape.
my oil PSI seemed a whole lot better. Then the alfa gage packed it in. And I have not riped open the dash to fix it. but I also found out that the S runs the oil pump faster. that is why the gear in the head will not mesh with the old gear with the slot. As I tossed the dizzy in the trash at the same time I never knew that it spun faster.
over 230K miles
When I puled it, the main bearings were very bad and the rod were a bit bad.
I put the same rods and crank in a S block (wanted the piston oil jets)
with new bearings. now no more knock. the top end was in very good shape.
my oil PSI seemed a whole lot better. Then the alfa gage packed it in. And I have not riped open the dash to fix it. but I also found out that the S runs the oil pump faster. that is why the gear in the head will not mesh with the old gear with the slot. As I tossed the dizzy in the trash at the same time I never knew that it spun faster.
1987 black Milano Verde
1972 White spider 2000 Veloce
1972 White spider 2000 Veloce
Slyalfa,
You are correct about the different gears for the oil pump drive. The 164 engines have a faster running oil pump. Maybe this is mainly for idle? I mean when the engine speeds up and the oil pressure is at a certain point, the pressure relieve valve opens, so that is why I don't know what benefit there is to make the pump run faster. Only think I can think of is at idle, assuming that the valve opens at the same pressure.
Anyways, I guess the question would be, is it ok for the 75 oil pump gear to stay in there if the heads were installed in a 164?
OK my engine has all new mains and rods. My mechanic said that the crank journals were good. Oil pressure is much better than what you see in ye olde 3.0 anyway.
But thanks for the good feedback guys. I'll check into the heads first.
You are correct about the different gears for the oil pump drive. The 164 engines have a faster running oil pump. Maybe this is mainly for idle? I mean when the engine speeds up and the oil pressure is at a certain point, the pressure relieve valve opens, so that is why I don't know what benefit there is to make the pump run faster. Only think I can think of is at idle, assuming that the valve opens at the same pressure.
Anyways, I guess the question would be, is it ok for the 75 oil pump gear to stay in there if the heads were installed in a 164?
OK my engine has all new mains and rods. My mechanic said that the crank journals were good. Oil pressure is much better than what you see in ye olde 3.0 anyway.
But thanks for the good feedback guys. I'll check into the heads first.
I think alfa put in the faster pump when they added the piston oil jets.
I had a older 164 with the old type gears in the head it even had the slot cut in to it.
my guess is the faster pump makes up for the new demand for the 6 oil jets.
and any block after x s/n or after x year also had the oil jets. I would think it would not be good to use the slow pump if you have the oil jets.
I have seen the info on the alfabb somewhere at which year and which s/n they switched over to the oil jets.
I had a older 164 with the old type gears in the head it even had the slot cut in to it.
my guess is the faster pump makes up for the new demand for the 6 oil jets.
and any block after x s/n or after x year also had the oil jets. I would think it would not be good to use the slow pump if you have the oil jets.
I have seen the info on the alfabb somewhere at which year and which s/n they switched over to the oil jets.
1987 black Milano Verde
1972 White spider 2000 Veloce
1972 White spider 2000 Veloce
In our engines with distributors, oil pumps always run at 1/2 engine speed, there's no fast or slow about it. Pump internal parts for 75/164 are the same = same delivery. Distributorless engines can have different gears (head+shaft) for other pump speeds.
I just checked the pump shaft gears from various 12 and 24v engines I have (with and without slot); they all have 15 teeth.
Jim K.
I just checked the pump shaft gears from various 12 and 24v engines I have (with and without slot); they all have 15 teeth.
Jim K.
So does my granma!!15 teeth!JimGreek wrote:In our engines with distributors, oil pumps always run at 1/2 engine speed, there's no fast or slow about it. Pump internal parts for 75/164 are the same = same delivery. Distributorless engines can have different gears (head+shaft) for other pump speeds.
I just checked the pump shaft gears from various 12 and 24v engines I have (with and without slot); they all have 15 teeth.
Jim K.
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
This would only be on the motors with the cam mounted distributors.(EDIT: or no distributor 
)
did you count the teeth on the other gear too?
I have not checked this myself but one of the other guys that was puting in a S in cut the slot in and he said it did not spin at ½ speed. he ended up cuting the firewall so he could use the cam mounted one.
I do know the mesh is way different with the gear with the slot vs the one whith out the slot. the cut angle is different.
And it seemed the the one with out the slot seemed to line up time wise when they started to add the oil jets. I guess I need to mark mine with a felt tip and check for myself.
)did you count the teeth on the other gear too?
I have not checked this myself but one of the other guys that was puting in a S in cut the slot in and he said it did not spin at ½ speed. he ended up cuting the firewall so he could use the cam mounted one.
I do know the mesh is way different with the gear with the slot vs the one whith out the slot. the cut angle is different.
And it seemed the the one with out the slot seemed to line up time wise when they started to add the oil jets. I guess I need to mark mine with a felt tip and check for myself.
1987 black Milano Verde
1972 White spider 2000 Veloce
1972 White spider 2000 Veloce
I have a stock 2.5 GTV6 that blows smoke upon initial take off after idling. When cruising, there's no smoke on either acceleration or decelaration. Car seems to pull strongly throughout the rev range. Most of the plugs are nice and clean except plug in cyl 2 which was a bit sooty. Would this signify a worn exhaust valve guide in cylinder 2. Could it just be a dud valve stem seal?? According to last owner's previous receipts, engine was supposedly reconditioned with new exhaust valve guides about 50000kms ago. Any ideas on what could be the cause and what's involved to fix it, do I need to pull the engine out or just the heads off? If it's valve stem seals, do the heads need to come off???
Any info is much appreciated. Cheers
Any info is much appreciated. Cheers