Compression Test Results a Concern? |
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Compression Test Results a Concern? |
Alfafan |
Mar 26 2019, 03:00 PM
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#1
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Newbie Group: Members Posts: 5 Joined: 26-March 19 From: Los Angeles Member No.: 22,993 Region Association: Southern California |
Hi All,
I'm looking into the purchase of a '73 2.0L and have the car at a local specialist shop for a PPI. The car has a recent engine rebuild with about 500 miles since. It runs well with the only exceptions that it surges and falls a bit at idle (I wasn't too concerned about that), but the compression test readings that were just relayed back to me are a concern. The compression readings are 110, 110, 110 and 120psi. Would these numbers be in the normal range for a fresh engine? They seem low to me. I'm waiting for a call from the mechanic with the particulars including confirming how the test was done (hot engine, thottle wide open, plugs out...etc?). Assuming the test was done correctly, would these values point to a problem? Is it possible that the engine is not fully broken in and the readings would be expected to rise? Thanks for your help! |
914_7T3 |
Mar 26 2019, 03:47 PM
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#2
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Please forgive me, I'm new to all of this! Group: Members Posts: 1,862 Joined: 3-April 17 From: Los Angeles, CA Member No.: 20,991 Region Association: Southern California |
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When I did a PPI on my '73 2.0 with the original FI, the compression numbers were 135, 140, 140, 145. Just wanted to put that out there as a reference. However, with that being said, the valve guides were shot and the motor needed a full rebuild. Odometer was reading 105,000, but it appeared that it at least had a top end refresh at some point previous. Out of curiosity , what part of LA are you in and what shop do you have it at? The 914 community is quite strong in these forums especially here in SoCal. Good luck with your search. (IMG:style_emoticons/default/beerchug.gif) |
BK911 |
Mar 26 2019, 04:00 PM
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#3
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Senior Member Group: Members Posts: 672 Joined: 19-February 04 From: Rocky Top, TN Member No.: 1,674 Region Association: None |
Leakdown
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thelogo |
Mar 26 2019, 04:10 PM
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#4
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Senior Member Group: Retired Members Posts: 1,510 Joined: 6-April 10 Member No.: 11,572 Region Association: None |
Hi All, I'm looking into the purchase of a '73 2.0L and have the car at a local specialist shop for a PPI. The car has a recent engine rebuild with about 500 miles since. It runs well with the only exceptions that it surges and falls a bit at idle (I wasn't too concerned about that), but the compression test readings that were just relayed back to me are a concern. The compression readings are 110, 110, 110 and 120psi. Would these numbers be in the normal range for a fresh engine? They seem low to me. I'm waiting for a call from the mechanic with the particulars including confirming how the test was done (hot engine, thottle wide open, plugs out...etc?). Assuming the test was done correctly, would these values point to a problem? Is it possible that the engine is not fully broken in and the readings would be expected to rise? Thanks for your help! No offense but. Wouldn't the specality shop who performed the comprssion test advise as to what those numbers reflect . blow by etc. And usually a leakdown is also done ? If its got djet then you most likely have impossible to detect surging . and that leads to accelerated engine wear . I would think a 73 2.0 in socal is asking for a big price But the motor is really the least or last thing i would worry about . Solid bones or lack of rust is what its all about . |
worn |
Mar 26 2019, 05:18 PM
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#5
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can't remember Group: Members Posts: 3,290 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
Hi All, I'm looking into the purchase of a '73 2.0L and have the car at a local specialist shop for a PPI. The car has a recent engine rebuild with about 500 miles since. It runs well with the only exceptions that it surges and falls a bit at idle (I wasn't too concerned about that), but the compression test readings that were just relayed back to me are a concern. The compression readings are 110, 110, 110 and 120psi. Would these numbers be in the normal range for a fresh engine? They seem low to me. I'm waiting for a call from the mechanic with the particulars including confirming how the test was done (hot engine, thottle wide open, plugs out...etc?). Assuming the test was done correctly, would these values point to a problem? Is it possible that the engine is not fully broken in and the readings would be expected to rise? Thanks for your help! At least they are consistent. They do seem a bit low though, but not horrible low. How does it drive? |
jdamiano |
Mar 26 2019, 06:37 PM
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#6
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Member Group: Members Posts: 335 Joined: 18-March 18 From: Jacksonville Member No.: 21,981 Region Association: South East States |
They are very consistent across all cylinders. Normally you will see a swing between cylinders when there is a problem. If it’s not burning oil or has unusually high crankcase pressure it should be fine. I would try another gauge before making and conclusions.
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SirAndy |
Mar 26 2019, 06:39 PM
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#7
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Resident German Group: Admin Posts: 41,815 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
How were those 500 miles accumulated? Maybe the rings haven't fully seated yet?
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VaccaRabite |
Mar 26 2019, 07:19 PM
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#8
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En Garde! Group: Admin Posts: 13,554 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
A fresh T4 should have about 150-160
120 is serviceable, but not fresh. If it has been babied, its possible the rings were never seated. Its also possible it needs a valve adjustment, and the compression test was improperly done (cold engine, throttle closed, etc.) Zach |
bdstone914 |
Mar 26 2019, 09:21 PM
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#9
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bdstone914 Group: Members Posts: 4,673 Joined: 8-November 03 From: Riverside CA Member No.: 1,319 |
The numbers depend on how the engine was built and if they calculated what they wanted it to be or slapped together a bunch of parts without a plan.
I had one engine that had 180 average. It was 10 to 1 CP. Another was 100 flat. It had 6.5 to one CP. Can they provide a build sheet t with the details ? As Andy said the rings may not be fully seated. How is the car overall? |
Alfafan |
Mar 27 2019, 07:41 AM
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#10
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Newbie Group: Members Posts: 5 Joined: 26-March 19 From: Los Angeles Member No.: 22,993 Region Association: Southern California |
The shop did a second compression test yesterday and the numbers came up somewhat. The tech apparently didn't have the throttle wide open when first done. The new numbers are 115, 120,125, 125.
I had a long conversation about the engine with the mechanic that worked on it. I learned that the engine was sent out for rebuild to FAT Performance here in SoCal. The install and rest of the refurbishment was done at the shop. The engine apparently has a hotter cam and various other upgrades that I'll learn more about. The engine may not be fully broken in yet and according to the mechanic, could probably use a valve adjustment. If I understand correctly, the build and cam may have something to do with it as well. It really goes though, running very strong with no smoke. I'm feeling better about the engine. The rest of the car is in great condition. The car is dry with no signs of rust. Excellent body, paint, and interior. It could use front tie rods and an alignment. That's about it. Looks like a keeper. I've owned a bunch of Alfa Romeo's through the years but this is my very first Porsche. There's a smoothness to the Alfa on the road and in the way the engine loves to rev. The 914 compared to that is all business, low, balanced and connected. What a blast to drive! I'm really going to enjoy this and the community here on the forum. Thanks again for all your help! |
DickSteinkamp |
Mar 27 2019, 08:23 AM
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#11
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Senior Member Group: Members Posts: 500 Joined: 27-February 17 From: Bellingham, WA Member No.: 20,876 Region Association: None |
I wonder if FAT built it as a turbo/blower motor?
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Tdskip |
Mar 27 2019, 08:39 AM
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#12
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Advanced Member Group: Members Posts: 3,697 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None |
Welcome!
Not too many of us have Alfas here but there are some (I have a handful of 105s). 914 is a totally different drive, very complementary driving experience. 914s are a bit less fidly than the 105 or early cars. Lots of SoCal 914 people here and we do events and tech days and drives all the time. That compression is low - I’d want to know why before buying it unless priced in. |
tmessenger |
Mar 27 2019, 08:49 AM
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#13
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Member Group: Members Posts: 70 Joined: 6-December 18 From: Iowa Member No.: 22,707 Region Association: Upper MidWest |
If it was a standard Fat 2056 street build it would have 8.3~8.5:1 CR.
The shop did a second compression test yesterday and the numbers came up somewhat. The tech apparently didn't have the throttle wide open when first done. The new numbers are 115, 120,125, 125. I had a long conversation about the engine with the mechanic that worked on it. I learned that the engine was sent out for rebuild to FAT Performance here in SoCal. The install and rest of the refurbishment was done at the shop. The engine apparently has a hotter cam and various other upgrades that I'll learn more about. The engine may not be fully broken in yet and according to the mechanic, could probably use a valve adjustment. If I understand correctly, the build and cam may have something to do with it as well. It really goes though, running very strong with no smoke. I'm feeling better about the engine. The rest of the car is in great condition. The car is dry with no signs of rust. Excellent body, paint, and interior. It could use front tie rods and an alignment. That's about it. Looks like a keeper. I've owned a bunch of Alfa Romeo's through the years but this is my very first Porsche. There's a smoothness to the Alfa on the road and in the way the engine loves to rev. The 914 compared to that is all business, low, balanced and connected. What a blast to drive! I'm really going to enjoy this and the community here on the forum. Thanks again for all your help! |
Tdskip |
Mar 27 2019, 08:53 AM
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#14
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Advanced Member Group: Members Posts: 3,697 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None |
Oops-should’ve added that the people at FAT are good to work with and I would not be shy about picking up the phone and calling them, they stand behind their work.
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Dave_Darling |
Mar 27 2019, 03:35 PM
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#15
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914 Idiot Group: Members Posts: 15,048 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
The motor on the car I bought was dead-nuts on 100 PSI compression across all 4.
Found out a few years later that it was a rather tired motor; it started dropping valve seats and had mostly eaten the thrust part of the main bearings. That said, there are a lot of things that affect compression pressure. Everything from battery condition to throttle open/closed to engine temp to altitude and on and on. I'd say be cautious but not to immediately decide the engine is junk. --DD |
worn |
Mar 27 2019, 06:15 PM
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#16
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can't remember Group: Members Posts: 3,290 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
The numbers depend on how the engine was built and if they calculated what they wanted it to be or slapped together a bunch of parts without a plan. I had one engine that had 180 average. It was 10 to 1 CP. Another was 100 flat. It had 6.5 to one CP. Can they provide a build sheet t with the details ? As Andy said the rings may not be fully seated. How is the car overall? A bit of a side-track but wondering whether the 10:1 motor ran hot? |
Valy |
Mar 27 2019, 06:26 PM
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#17
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Senior Member Group: Members Posts: 1,677 Joined: 6-April 10 From: Sunnyvale, CA Member No.: 11,573 Region Association: Northern California |
There is a lot in common between the 914 and the Alfa Sud, but that was never imported to US
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Tdskip |
Mar 28 2019, 06:15 AM
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#18
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Advanced Member Group: Members Posts: 3,697 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None |
Btw - if you post pictures of the car (loads of them) you can get a virtual PPI here for free. People here have saved my bacon many times over with that.
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Alfafan |
Mar 28 2019, 10:00 AM
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#19
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Newbie Group: Members Posts: 5 Joined: 26-March 19 From: Los Angeles Member No.: 22,993 Region Association: Southern California |
Great idea on checking with FAT Performance about the motor. I called and spoke to a rep. He said these numbers were fine for the likely build type of a lower compression street engine . Bottom line was he said the tested compression and variance was within spec. He recommended putting some miles on the engine.
Thanks! |
Tdskip |
Mar 28 2019, 10:46 AM
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#20
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Advanced Member Group: Members Posts: 3,697 Joined: 1-December 17 From: soCal Member No.: 21,666 Region Association: None |
Great idea on checking with FAT Performance about the motor. I called and spoke to a rep. He said these numbers were fine for the likely build type of a lower compression street engine . Bottom line was he said the tested compression and variance was within spec. He recommended putting some miles on the engine. Thanks! Glad that helped, just to set expectations that is the single only useful thing I’ve ever uttered here. Don’t be shy about posting pictures of the car if you want additional thoughts on it, don’t be shy about questions as you’ve discovered already it’s a good group here that has an amazing amount of knowledge about these cars. Hope it works out and we get to see you in the car in the near future. |
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