964 engine and chassis numbers
Discussion
Given the age these cars are now I wouldn`t worry too much about the age of a car, look at each car on it`s individual merits. The barrel to head joint isn`t where oil leaks from, they leak from the barrel to crank-case joint and the crank-case through bolt seals. The theory is/was the the modified head gasket reduced any rotation of the barrels. Given that the leaks are caused because the silicone seals go hard and lose their elasticity I`m not sure what good a different head to barrel arrangement does.
Certainly buying a later car doesn`t gurantee an oil tight engine so look at all the cars on the market.
Henry
Certainly buying a later car doesn`t gurantee an oil tight engine so look at all the cars on the market.
Henry
964 engines built in 1989 (K), 1990 (L), and 1991 (M) model years had the early design of cylinder to head joint which is susceptible to a leaks due to distortion of the cylinder head sealing face. The number of engines with the early design are all those built up to 62M06836 (M64.01 manual transmission) & 62M52757 (M64.02 tiptronic).
All 964RS engines and on engines built after the above (mid 1991), Porsche used the flat top barrel with a sealing ring groove and flat face head to affect a more reliable seal.
Early engines can be converted to the later design by fitting later barrels and machining the cylinder heads flat.
I don't sell cars.
All 964RS engines and on engines built after the above (mid 1991), Porsche used the flat top barrel with a sealing ring groove and flat face head to affect a more reliable seal.
Early engines can be converted to the later design by fitting later barrels and machining the cylinder heads flat.
I don't sell cars.
My understanding, and it is only my humble understanding given that we do no service work on site is thus: The crux of the original question looked suspiciously like Martyn was thinking along the lines of, "I`ll make sure I buy a later 964 because then it won`t leak oil."
I reckon we must have sold close to a thousand 964`s by now and have bought the video, the T-shirt and the signed limited edition print to most of the common ailments that afflict these cars. I`ve never had a problem with engine oil leaks from the Barrel to head interface. You get a build up of gunge over a long period of time which is probably petrol seeping a combination of carbon and oil through, but in miniscule quantities and it eventually forms a gunky crust, but we are talking years rather than months. The 3.2 Carrera didn`t, as far as I`m aware, have any gasket twixt head and barrel, the 3.8 engines did because of the thinner barrel (I presume). Anyway I digress.
There have been 3 (I think but I`ll bow to someone`s superior knowledge on this), revisions in the material used for the "rubber" gaskets used for barrel base gaskets, through bolt seals and others. It is this improved material that contributes to some engines taking longer to leak than others. Temperature probably plays the biggest part though as the degridation of the seals is a chemical reaction and as we all know the speed of a chemical reaction increases with temperature.
We have had engines which leak combustion gasses through the head-barrel joint, But in every case this has been the result of a failed head stud. The subsequent damage from this can be significant as the hot gasses eventualy burn a track "eating away" the barrel, the head, or both. This is caused by the head stud breaking and wouldn`t be helped by a modified barrel top.
The 964 is 15 years old now (give or take), and there is a huge cavern of difference between individual cars to the extent that I believe selection based on specific model or year is not the answer, I believe selection based on a car`s individual merits is the answer.
Even if an engine isn`t leaking oil don`t assume all is well. A good part of an engine "freshen up" involves changing items such as piston rings, timing chains, tensioners, valve guides and the other items that wear over time and usage, it all points to chosing a car looking at the bigger picture. I have a favourite phrase. If you`re going to buy a forest, don`t just check out 40 trees, decide all is well, hand over the money then get home only to find the forest is on fire.
I`m just a simple country boy, but a country boy who gets his wedge out and lays it on the line 300 times a year, so it pays to have an inkling as to what makes the clock tick.
As usual keep smiling - Henry
I reckon we must have sold close to a thousand 964`s by now and have bought the video, the T-shirt and the signed limited edition print to most of the common ailments that afflict these cars. I`ve never had a problem with engine oil leaks from the Barrel to head interface. You get a build up of gunge over a long period of time which is probably petrol seeping a combination of carbon and oil through, but in miniscule quantities and it eventually forms a gunky crust, but we are talking years rather than months. The 3.2 Carrera didn`t, as far as I`m aware, have any gasket twixt head and barrel, the 3.8 engines did because of the thinner barrel (I presume). Anyway I digress.
There have been 3 (I think but I`ll bow to someone`s superior knowledge on this), revisions in the material used for the "rubber" gaskets used for barrel base gaskets, through bolt seals and others. It is this improved material that contributes to some engines taking longer to leak than others. Temperature probably plays the biggest part though as the degridation of the seals is a chemical reaction and as we all know the speed of a chemical reaction increases with temperature.
We have had engines which leak combustion gasses through the head-barrel joint, But in every case this has been the result of a failed head stud. The subsequent damage from this can be significant as the hot gasses eventualy burn a track "eating away" the barrel, the head, or both. This is caused by the head stud breaking and wouldn`t be helped by a modified barrel top.
The 964 is 15 years old now (give or take), and there is a huge cavern of difference between individual cars to the extent that I believe selection based on specific model or year is not the answer, I believe selection based on a car`s individual merits is the answer.
Even if an engine isn`t leaking oil don`t assume all is well. A good part of an engine "freshen up" involves changing items such as piston rings, timing chains, tensioners, valve guides and the other items that wear over time and usage, it all points to chosing a car looking at the bigger picture. I have a favourite phrase. If you`re going to buy a forest, don`t just check out 40 trees, decide all is well, hand over the money then get home only to find the forest is on fire.
I`m just a simple country boy, but a country boy who gets his wedge out and lays it on the line 300 times a year, so it pays to have an inkling as to what makes the clock tick.
As usual keep smiling - Henry
You're bang on Henry, I have seen dry & wet joints with both designs at similar mileages so you really do have to buy on condition rather than age.
The only other consideration is that the later engines have the black plastic intake system which has the potential to produce more power when the engine is tuned, so a true pistonhead would always plump for the later engine "just in case" an upgrade was on the cards.
The only other consideration is that the later engines have the black plastic intake system which has the potential to produce more power when the engine is tuned, so a true pistonhead would always plump for the later engine "just in case" an upgrade was on the cards.
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