75K mile motor refresh
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75K mile motor refresh
I have my motor out of my 97 993S for a 'freshening' and thought I would share what the techs have found (and I have witnessed personally) so far.
1) Leaking case through bolt
2) Collapsed lifters (10 of 12)
3) Cracked plastic intake spacers (these are the 3-4" tall spacers between the intake heads and the VRAM manifold.
4) Spark plug wires are oil soaked and cracking
5) Two cylinders have visible moderate vertical scoring marks - all have signs of piston ring wear around the top of the cylinder (worn rings leads to wobbly pistons at the top of the piston travel - you get perimeter marks around the cylinder at the top when this happens)
6) SAI ports are about halfway open - still showing about a 1/8" diameter passageway.
Note that I live in a hot climate (Texas) and have DE'd the car for 50+ track days so my wear would be expected to be on the high side given the use the car gets.
I did have poor compression/leak down results on two cylinders (I think it was the same two that have the ring wear signs) a few months back and my car dynoed about 20 hp lower the 'normal' for 993's on a DynoJet several months ago.
So none of this really surprises me and since I've turned the car back into a daily driver with the comfy Euro M030 suspension set up and Sparco Milano seats I'm going to invest in a thorough rebuild to bring the motor back to stock conditions. I'm probably going to open up the bottom of the motor to inspect the main bearings because at this point the additonal cost will be trivial if it is labor only - and if the bearings are showing wear it would be a real shame to do all the other work just to then spin a bearing...
Ben
Check out the lifter in this picture - the o-ring on all but two of them were GONE - the just fell out in the techs hands as he was pulling out the rocker arms.
Here you can see all the oil caked up on the motor from the through bolt leak
More oil mess....
1) Leaking case through bolt
2) Collapsed lifters (10 of 12)
3) Cracked plastic intake spacers (these are the 3-4" tall spacers between the intake heads and the VRAM manifold.
4) Spark plug wires are oil soaked and cracking
5) Two cylinders have visible moderate vertical scoring marks - all have signs of piston ring wear around the top of the cylinder (worn rings leads to wobbly pistons at the top of the piston travel - you get perimeter marks around the cylinder at the top when this happens)
6) SAI ports are about halfway open - still showing about a 1/8" diameter passageway.
Note that I live in a hot climate (Texas) and have DE'd the car for 50+ track days so my wear would be expected to be on the high side given the use the car gets.
I did have poor compression/leak down results on two cylinders (I think it was the same two that have the ring wear signs) a few months back and my car dynoed about 20 hp lower the 'normal' for 993's on a DynoJet several months ago.
So none of this really surprises me and since I've turned the car back into a daily driver with the comfy Euro M030 suspension set up and Sparco Milano seats I'm going to invest in a thorough rebuild to bring the motor back to stock conditions. I'm probably going to open up the bottom of the motor to inspect the main bearings because at this point the additonal cost will be trivial if it is labor only - and if the bearings are showing wear it would be a real shame to do all the other work just to then spin a bearing...
Ben
Check out the lifter in this picture - the o-ring on all but two of them were GONE - the just fell out in the techs hands as he was pulling out the rocker arms.
Here you can see all the oil caked up on the motor from the through bolt leak
More oil mess....
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Jonathan,
I'll probably replace the RMS but it is good because it went in with the RS Clutch/LWF about a year ago.
Looking forward to a strong motor after all this is complete.
I'll probably replace the RMS but it is good because it went in with the RS Clutch/LWF about a year ago.
Looking forward to a strong motor after all this is complete.
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Originally Posted by Ben in Plano, TX
6) SAI ports are about halfway open - still showing about a 1/8" diameter passageway.
How was your oil consumption -- under 1 qt / 2K miles?
TIA
Dan
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Dan - oil consumption was ~ 1qt/1500 miles - not too bad.
Mo - 75k - tranny is good - clutch new about 5k miles ago when changed to RS/LWF setup
Greg - I'm going stock but will have a new cam chain (old one maybe stretched) installed and timing set with Porsche special tool. From people I trust I get differing opines about 964 backdating, manual timing, etc. I'm using the RUF shop in Dallas and they have checked with the RufMeisters in Pfaffenhausen and they DON'T recommend manual timing in non-race motors. Their experience is that new cam chains, new ramps if wear shows, factory cams, factory timing brings you back to factory HP rating. Perhaps Rennlist heresy but I would submit these guys know what they are talking about. BTW - they'll do anything I want (and am willing to pay for) but really don't suggest much other than factory setup for a street 993. They can approximate RS setup with 3.8 P/C, sport cat, and ECU reflash and I have considered that option but think I will remain stock and save the sport cat & ECU $$. I will be doing 3.6 P/C to correct the two 'bad' ones and set up the motor for another 100k solid miles.
Ben
Mo - 75k - tranny is good - clutch new about 5k miles ago when changed to RS/LWF setup
Greg - I'm going stock but will have a new cam chain (old one maybe stretched) installed and timing set with Porsche special tool. From people I trust I get differing opines about 964 backdating, manual timing, etc. I'm using the RUF shop in Dallas and they have checked with the RufMeisters in Pfaffenhausen and they DON'T recommend manual timing in non-race motors. Their experience is that new cam chains, new ramps if wear shows, factory cams, factory timing brings you back to factory HP rating. Perhaps Rennlist heresy but I would submit these guys know what they are talking about. BTW - they'll do anything I want (and am willing to pay for) but really don't suggest much other than factory setup for a street 993. They can approximate RS setup with 3.8 P/C, sport cat, and ECU reflash and I have considered that option but think I will remain stock and save the sport cat & ECU $$. I will be doing 3.6 P/C to correct the two 'bad' ones and set up the motor for another 100k solid miles.
Ben
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I wish I could claim a DIY - Sorry Rick - even though I'm a former NC boy and not afraid to take anything apart I just don't have time for it right now.
Work is being done by my good friends at RUF here in Dallas. I just go over and take pictures when I have a chance....as such - you might not want to hear about the cost!
Ben
Work is being done by my good friends at RUF here in Dallas. I just go over and take pictures when I have a chance....as such - you might not want to hear about the cost!
Ben
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Luis,
collapsed lifters = clackity, clackity - it was audible valve train noise.
Quiet motor = happy lifters. I really think the TX heat + heavy DE usage led to my lifter demise. Probably accelerating what will happen in time to most of these lifters.
collapsed lifters = clackity, clackity - it was audible valve train noise.
Quiet motor = happy lifters. I really think the TX heat + heavy DE usage led to my lifter demise. Probably accelerating what will happen in time to most of these lifters.
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Originally Posted by jonathank2000
Ben,
Wow, great photos and info!!...
Wow, great photos and info!!...