73 1608 Engine with limited power

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Funcar
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73 1608 Engine with limited power

Post by Funcar » Wed Jun 05, 2019 7:06 am

I finally got my 73 Spider running last summer and the compression test showed I had low compression on all 4 cylinders.. 85- 115-115 78. I drove it for about 300 miles before putting it away in storage. The car still ran fairly well and I really didn't have the money to spend...(putting in new kitchen). After taking it out of storage this spring I have very limited power. It feels like I am running on 2 cylinders.

Can someone explain how I diagnose what my problems are? Right now I am looking for a replacement engine .

Thanks
Glen Tschirhart
Kitchener Ontario Canada
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friedman
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Re: 73 1608 Engine with limited power

Post by friedman » Wed Jun 05, 2019 8:22 am

With the compression figures you quoted, you probably are effectively running on two cylinders, Take another compression check. Normal readings would be about 150. When you took the compression test, was the motor warm, choke off and throttle held wide open?
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Re: 73 1608 Engine with limited power

Post by miker » Wed Jun 05, 2019 12:39 pm

A replacement engine might not be required. You could get those same low compression readings from burned valves, which would involve pulling the head and having a machine shop recondition it. It's somewhat time consuming, but probably easier than an engine swap and probably less expensive unless someone gives you a known good engine.

BTDT.

https://www.mirafiori.com/forum/viewtop ... er#p260277
MikeR (mirafiori.com since 1995)


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'86 Bertone X1/9
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Re: 73 1608 Engine with limited power

Post by davedecker4 » Wed Jun 05, 2019 1:04 pm

Verify that everything turns freely with no untoward noises. Check the timing marks line up. Static timing on the crank and cam pulleys to verify not jumped a tooth or anything. Ignition timing that it isn't way off, causing low reading. Test compression, full throttle, coil wire disconnected, all plugs removed and crank several revolutions, make sure is the same 10 or so on each cylinder. After not all that, check with teaspoon or so oil down each cylinder in turn while rechecking reading. If the numbers come up a lot, you know that at least your piston rings are worn and could use replacing. If no change, the problem is likely in the head as Mike suspects. Rebuilding an engine is not necessarily much more expensive than replacing, and only somewhat harder. Many can do it themselves with a little time, attention to detail, and laying things out carefully. Make sure you have enough undisturbed space to do that. Nice big table helps. Cleanliness when refitting too. Torque everything properly, lube it up and get her back on the road.
Even just new rings, bearings and minor head job (along with gaskets and seals of course) can work wonders.
Even a bad head gasket can give low readings.
Are you sure its 1608cc btw? '73 could be either a 1608cc or 1592cc and still be called a 1600
Dave Decker
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Re: 73 1608 Engine with limited power

Post by rridge » Wed Jun 05, 2019 1:31 pm

The usual reason for a sudden loss of power and low compression in a Fiat Twin Cam is that the timing belt that has skipped a few teeth, often because it is well past its useful life and has been stored for long periods. If you don't know how to check timing belt issues it might be best to find a mechanic who does. It could make the difference between a timing belt replacement and an engine replacement.
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Re: 73 1608 Engine with limited power

Post by bartigue » Wed Jun 05, 2019 2:11 pm

First off, check the timing of the crank and cams. It may have been wrong even last year when it ran. Verify it is correct and, if so, contemplate the future:

- At the very least the head has to come off and the head gasket replaced. Pull the head and inspect the valves, piston tops, bores, etc.
- If there are obvious issues with the head you may have found the issue, fix it, install a new gasket, belt, water pump, etc.
- If there isn't anything obvious then the block needs to come out.
-----------------------------------------------------------
Brad Artigue
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Funcar
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Re: 73 1608 Engine with limited power

Post by Funcar » Thu Jun 06, 2019 6:27 am

Thanks to all who provided feedback on my post. Firstly I will check to make sure I have the cams set on all the timing marks. Also check the ignition timing. Then I will complete another compression test as prescribed with both engine cold and warm. Then the oil in the cylinder and provide results. Will need to contact a friend with tester and timing light to give me a hand then get back to the forum with results.

Dave my engine plate # is 125 BC 040 ..0648682. Vin # 55864. When I looked at the identification chart it comes up as 1608.
Glen Tschirhart
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Re: 73 1608 Engine with limited power

Post by fp55scca » Thu Jun 06, 2019 11:09 am

Funcar wrote:
Thu Jun 06, 2019 6:27 am
---I will check to make sure I have the cams set on all the timing marks. Also check the ignition timing.
---I will complete another compression test as prescribed with both engine cold and warm. Then the oil in the cylinder and provide results.

---engine plate # is 125 BC 040 ..0648682. Vin # 55864. When I looked at the identification chart it comes up as 1608.
--------------------------------------------------------
--Glen, your engine is indeed a 1608. The 1592 offered in '73 would be a 132 series motor.

--Also, your troubleshooting plan is spot-on. While you are at it, you may also want to do a general ignition inspection (points, condensor, rotor, cap and ignition wires and plugs), and a visual check of any inline fuel filter. You may also have to check for dirt in the carb float bowl, or a fowled jet.
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
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1974 CSA Abarth Replica
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Funcar
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Re: 73 1608 Engine with limited power

Post by Funcar » Fri Jun 14, 2019 6:58 am

Finally co-ordinated with my friend to complete the the compression and timing tests. I have the timing belt cover off from last year. Both cam wheels were dead on there marks as was the auxiliary shaft wheel. So we proceeded with the compression test. #1 125 # 2 95 #3 120 #4 125. I really don't know why I was given the previous numbers from the mechanic and perhaps misheard him. During the test we noted that the spark plug in #4 was not seated properly. We used a different plug and ensured it was seated and the car ran pretty well as a matter of fact almost like the previous year.

We didn't know how to complete a timing test with the cover off...is there a way? We did it by ear and set the distributor to best run position. I took it for a run and all seems as good as before.

I should note that I had used one of my wifes nail file sticks to clean the points and tightened the alternator belt which was the source of a screeching noise as I revved the engine.

I feel somewhat embarrassed about not noting the $4 spark plug not properly installed which I think was the culprit of my engine running with limited power.

I plan on running the car for our limited Canadian season but am open to suggestions and advice going forward. How to I proceed over the winter with bringing my compression number up to 150 per cylinder?
Glen Tschirhart
Kitchener Ontario Canada
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Re: 73 1608 Engine with limited power

Post by bartigue » Fri Jun 14, 2019 8:17 am

The engine is simply wearing out and needs to be renewed. At the very least it means taking the engine apart and checking the bores, replacing the worn parts (rings, bearings, seals, gaskets). You're only really low on one cylinder (95) but you can't just fix the one unless the problem is with the head gasket or a valve in that one chamber, which it might be.

A leakdown test will tell you if the cylinder is losing compression upwards (a head problem or gasket problem) or downwards (a ring problem). Start there.
-----------------------------------------------------------
Brad Artigue
1969, 1969, 1970, 1979, 1980, 1981, 1982, and 1982 124 Spiders
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77 X1/9
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