Compression Test Results a Concern? Options

[Alfafan]

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]

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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.

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[BK911]

Leakdown

[thelogo]

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]

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]

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.

[SirAndy]

How were those 500 miles accumulated? Maybe the rings haven't fully seated yet?
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[VaccaRabite]

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]

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]

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]

I wonder if FAT built it as a turbo/blower motor?

[Tdskip]

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]

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]

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.

[Dave_Darling]

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]

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]

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]

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.

[Alfafan]

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]

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.