SAI / leaking valve guides
05-02-2013, 03:36 PM
#1
Advanced
Thread Starter
SAI / leaking valve guides
Is there a connection between leaking valve guides and clogged SAI. Is either one caused by the other? One source I read stated. "If the secondary air ports in the heads become clogged due to coking or prematurely wearing valve guides, expect failing emissions and/or in worst-case scenario, a possible rebuild of the top end." Does the worn valve guides cause clogging of the SAI ports or does the clogged ports cause the worn guides? Or are they unrelated to each other?
05-02-2013, 06:02 PM
#3
SAI passages become clogged over time. 993 valve guides also wear over time.
But one could throw a CEL light because of clogged SAI ports and still be tens of thousands of miles until one needed a top-end rebuild due to poor valve guides.
If you need to pass smog, a mechanic can clear the SAI ports for about $500-$1000, or you can do it yourself if your handy. If you are consuming more than 1 qt. oil every 600 miles, then it's time to rebuild your mill.
Also, search is your friend. Lotsa discussions on this subject.
Welcome to Rennlist
05-02-2013, 06:10 PM
#4
Drifting
It is a "band-aid" but needs to be done at some point even if you rebuild with new valve guides (of course easier with engine out during rebuild). On the plus side, it keeps the dreaded CEL from making you fail emissions inspections, which allows you to schedule a rebuild when YOU want, not when the emissions inspector says. When you want = clutch is worn + leaks get "too bad" + burning too much oil.
Most rebuild based on oil usage (burning oil) due to oil seep through the valve guides being burned in the cylinders. This then clogs the SAI ports. There's not an exact number, but IIRC >1quart/1k miles is where people start to consider it, some even run down to 1q/500mi, and if you are smoking out the tail pipe continuously , its probably past time...
do some searches here on the RL993 board for things like:
SAI, CEL, SAI clean out, SAI clogged, valve guides, engine rebuild valve guides, oil usage, burning oil
Tons of reading on this subject.
Most rebuild based on oil usage (burning oil) due to oil seep through the valve guides being burned in the cylinders. This then clogs the SAI ports. There's not an exact number, but IIRC >1quart/1k miles is where people start to consider it, some even run down to 1q/500mi, and if you are smoking out the tail pipe continuously , its probably past time...
do some searches here on the RL993 board for things like:
SAI, CEL, SAI clean out, SAI clogged, valve guides, engine rebuild valve guides, oil usage, burning oil
Tons of reading on this subject.
05-02-2013, 07:17 PM
#5
I don't understand what it is that you disagree with?
I said valve guide clearance not ware. This was a problem we even faced when the 993's where new.
A quart of oil every 600 miles lol, only in LA.
I said valve guide clearance not ware. This was a problem we even faced when the 993's where new.
A quart of oil every 600 miles lol, only in LA.
05-02-2013, 07:44 PM
#6
Except for spelling. They have you beat on that.
"Where" new? "Ware"? Only in Cave Creek, Arizona. Time to get out of the cave and git yer learnin' on
05-02-2013, 07:48 PM
#7
haha, what a joke
Edit; After looking it up, Porsche max consumption is 1.5L / 1000 km
which is just a lizard toe over 600 miles. Seems extremely libral to me.
Or is that liberal?
Edit; After looking it up, Porsche max consumption is 1.5L / 1000 km
which is just a lizard toe over 600 miles. Seems extremely libral to me.
Or is that liberal?
Last edited by CalvinC4S; 05-02-2013 at 10:17 PM.
Trending Topics
05-03-2013, 09:45 AM
#8
SAI port is upstream of valve guide, unlikely that the miniscule amount of oil that leaks by a worn valve guide can flow upstream against exhaust pressure into the SAI ports. Port blockage is probably from the huge amounts of gasoline that is burned and a dysfunctional check valve as opposed to oil burn from worn valve guides.
05-03-2013, 12:23 PM
#9
on this one.
I said valve guide clearance not ware
"Where" new? "Ware"? Only in Cave Creek, Arizona.
Book learnin is not jus fer liberals anymore. Conservatives can spell too.
Did I use two many zero's in that "to"?
Last edited by nine9six; 05-03-2013 at 12:41 PM.
05-03-2013, 01:26 PM
#10
Race Director
SAI port is upstream of valve guide, unlikely that the miniscule amount of oil that leaks by a worn valve guide can flow upstream against exhaust pressure into the SAI ports. Port blockage is probably from the huge amounts of gasoline that is burned and a dysfunctional check valve as opposed to oil burn from worn valve guides.
I don't rebuild engines for a living but I would certainly believe the SAI port is downstream the guides. It's excess oil getting down the valve stems into the combustion chamber then blown out into the exhaust port (where the SAI port is). At least that's my understanding.
05-03-2013, 01:31 PM
#11
Rennlist Member
. Funny.
05-03-2013, 02:48 PM
#12
It is??
I don't rebuild engines for a living but I would certainly believe the SAI port is downstream the guides. It's excess oil getting down the valve stems into the combustion chamber then blown out into the exhaust port (where the SAI port is). At least that's my understanding.
I don't rebuild engines for a living but I would certainly believe the SAI port is downstream the guides. It's excess oil getting down the valve stems into the combustion chamber then blown out into the exhaust port (where the SAI port is). At least that's my understanding.
It is.
SAI outlet hole is located in the exhaust port of the cylinder head just upstream of where the exhaust stem protrudes into the port. Not only is the SAI hole upstream in relation to exhaust flow but also physically higher in the port. So at rest, any oil that runs down the exhaust valve stem can not run into the SAI hole either.
