Compression Test Results

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Kal
Posts: 21
Joined: Sat Nov 12, 2022 1:19 pm
Dino: Fiat Dino 2.4 Coupe

Compression Test Results

Post by Kal »

Hi All,

Looking for some guidance from people with experience. I've been negotiating on 2400 Dino Coupe located in the UK (I'm in Aust), and requested a compression test be done on it. The results have come back, and it's lower than I was anticipating - 110-115psi across the board. All the cylinders are within 5% of each other, which is good, but I would have anticipated a higher psi result.

The previous owner to the current one had the top part of the engine checked and rebuilt. Valve clearance and timing was adjusted + new chain tensioners fitted, but they said nothing else was done, as the compression was close to factory when they tested it.

The car has done no more than 900 miles since then (over a 7 year period).

Any idea's?

thanks.
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ThomasK
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Dino: Fiat Dino 2.4 Coupe

Re: Compression Test Results

Post by ThomasK »

Compressions close to each other is good as you mention, it is an indication that nothing serious is damaged in one place. The total value is from secondary importance, but from my experience with my Dino engines I have 9,5 to 10,5 bar. Your lower values could show wear, but maybe they have used a thicker head gasket…I would do as next step a „pressure lost test“, where you can locate wear in compression rings or in the head. How much kilometer (mileage) has the engine done?
Kal
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Joined: Sat Nov 12, 2022 1:19 pm
Dino: Fiat Dino 2.4 Coupe

Re: Compression Test Results

Post by Kal »

The engine has done around 46,000 km.
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ThomasK
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Re: Compression Test Results

Post by ThomasK »

That’s not a lot. If the engine does not smoke, delivers power, runs smooth and doesn’t consume much oil It sounds not too bad but but of course it’s difficult too give an opinion from the distance. A TestDrive an an experts opinion on-site is definetly recommended.
Fanalone
Posts: 122
Joined: Wed Jul 01, 2015 7:15 pm
Dino: Fiat Dino 2.4 Coupe

Re: Compression Test Results

Post by Fanalone »

Hi

I suspect you may have worn camshafts!
Worn camshaft gives lower lift of the valves, with the result of bad sylinder filling.
This gives lower effective compression, so if you make a cylinder leakage test with good result, I think you should inspect & measure your cam lobes.
This is not an uncommon problem on the Dino engine, on my own engine the cams where missing 3mm lift!
So I have got them re-grinded & drilled oil holes on the ramp of the cam lobes, to prevent this re-happening.
When the cars where in regular daily use, this cam were was no/ less an issue, but no as an entusiast vehicle the engine is standing still for long periodes, and the cams has "dried-up" when cold starts are performed, resulting in worn camshafts in the long run.

Here you can see a picture of how this drilling is from Dinopart`s, who can perform this regrinding - oil drilling - hardening.
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ThomasK
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Dino: Fiat Dino 2.4 Coupe

Re: Compression Test Results

Post by ThomasK »

I fully agree that the wear of the camshafts is a problem and drilling these holes is recommended. I did and do this on every Dino engine I did/do. As compression is build up when the valves are closed it should not influence the compression.
Kal
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Joined: Sat Nov 12, 2022 1:19 pm
Dino: Fiat Dino 2.4 Coupe

Re: Compression Test Results

Post by Kal »

Great. Thank you. If the cylinder leakage test comes back ok, is a camshaft/drilling an expensive exercise?
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ThomasK
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Re: Compression Test Results

Post by ThomasK »

Check Dinoparts Website, around 500 Euro.
Dario
Posts: 117
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Re: Compression Test Results

Post by Dario »

I would not worry too much about the actual values if they are the same and the milage is low. The values depend on the dead volume of the rubber hose and fitting wrt that of the cylinder volume and compression. You can correct for this if you know both. Evenly low compression on all cylinders could come from worn piston rings due to high milage. A leak-down test is much more informative.

Good luck,
Dario
4cambob
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Dino: Fiat Dino 2.0 Coupe

Re: Compression Test Results

Post by 4cambob »

I may well be wrong but if the compression test is not done with fully open throttle that would give a lower reading as well as if the valve/shim gaps are wrong and also if the cam timing is out.
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