piston slap
11-08-2001, 04:39 PM
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piston slap
I have a 1987 951 with 95k. Recently there has been "knocking" in the area of the intake ports on the head. It appears around 3000 RPM and continues on up. My neighbors experience (back yard mechanic) tells him that there is piston slap. What does it sound like to you?
Also, if it is piston slap, would it be okay to use "RESTORE" oil additive to help restore the quietness and maybe help on the sealing of the piston rings? I have never used this product before and don't know what impact it would have on a Porsche engine.
Also, if it is piston slap, would it be okay to use "RESTORE" oil additive to help restore the quietness and maybe help on the sealing of the piston rings? I have never used this product before and don't know what impact it would have on a Porsche engine.
11-08-2001, 05:22 PM
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If what you are hearing is actually piston slap, and I am not qualified to say, you can not chemically cure it. I am opposed to adding any of that type of stuff to any car.
11-08-2001, 06:59 PM
#3
Three Wheelin'
If the engine has not been sleeved then there is next to no chance that the problem is piston slap. The Piston to clyinder wall clearance on these engines is minimal. Certainly not enough to result in piston slap.
Wayne
Wayne
11-09-2001, 04:54 PM
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Thanks for the input.
I have to wonder about the tweaked valve. I just had my entire head rebuilt less than 10k ago. All new valves and guides. My mechanic has been working on Porsches for over 20 years and has a good reputation in the area. I did not have the lifters worked on.
Are their ways to check these each out at home with basic tools? Would a compression test tell me more about the cause of the "knock"?
I have to wonder about the tweaked valve. I just had my entire head rebuilt less than 10k ago. All new valves and guides. My mechanic has been working on Porsches for over 20 years and has a good reputation in the area. I did not have the lifters worked on.
Are their ways to check these each out at home with basic tools? Would a compression test tell me more about the cause of the "knock"?
11-09-2001, 06:34 PM
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Hey!
I doubt that it's that simple. I'd put my money on a failed rod bearing (especially if you hear it over 3000 rpm). The only way to fix that is to overhaul the engine. Yes, you have to do it ASAP before you put a hole in the side of your block.
If you just had the head machined it might have not been cleaned thouroughly (especially if they don't do Porsche heads) and some metal shavings might have migrated through the oil system and plugged up the oil hole on the crank for the rod bearings.
I know this isn't what you want to hear, and I hope that I'm wrong, but that's what it sounds like to me.
Lifter noise usually will only be localized to the head area, and you can further localize it by using a mechanics stethascope or a screwdriver held to the ear. If it's a lifter (actually a cam follower on these cars) then don't worry about it it can't do any harm. On a 951 it's relitively easy to replace the lifters during the next timing belt change.
Good luck!
Dal.
'86 951
'90 944S2 http://members.rennlist.org/dkheger
I doubt that it's that simple. I'd put my money on a failed rod bearing (especially if you hear it over 3000 rpm). The only way to fix that is to overhaul the engine. Yes, you have to do it ASAP before you put a hole in the side of your block.
If you just had the head machined it might have not been cleaned thouroughly (especially if they don't do Porsche heads) and some metal shavings might have migrated through the oil system and plugged up the oil hole on the crank for the rod bearings.
I know this isn't what you want to hear, and I hope that I'm wrong, but that's what it sounds like to me.
Lifter noise usually will only be localized to the head area, and you can further localize it by using a mechanics stethascope or a screwdriver held to the ear. If it's a lifter (actually a cam follower on these cars) then don't worry about it it can't do any harm. On a 951 it's relitively easy to replace the lifters during the next timing belt change.
Good luck!
Dal.
'86 951
'90 944S2 http://members.rennlist.org/dkheger
