Follow along as I build a 79 Spider

The forum for all of your technical questions on your classic FIAT autos
whitehause
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First Name: Tim

Re: Follow along as I build a 79 Spider

Post by whitehause » Wed Jan 09, 2019 7:39 pm

Welllll.....As I'm cleaning up the block now that I have it completely stripped, I noticed this on the #4 cylinder. It's between the 4 and 3 cylinders. I "think" it's just scratch, maybe from a small piece of something that got in there from the oil pump issue. It's perfectly straight up and down with the piston stroke. I worked it just a little at the top with some 600 grit and it seems like it was shrinking. I just got my flex hone so I guess we'll see if that takes it out.

Question is....are these motors noted for cracking between the cylinders vertically like this?
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fp55scca
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Re: Follow along as I build a 79 Spider

Post by fp55scca » Wed Jan 09, 2019 8:12 pm

--Tim, I've never seen a failed block or piston bore in a Fiat TC motor that wasn't caused first by a failed timing belt, rod (bearing), or rod bolt. The most I have personally over-bored a block is .040".
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 CSA Abarth Replica
1981 Fiat Spider Ratrod
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friedman
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Re: Follow along as I build a 79 Spider

Post by friedman » Thu Jan 10, 2019 8:20 am

That was my first thought but the damage is on the none lobed part so there should be no contact.
Carl in Virginia
75 spider
86 Bertone
77 X1/9
whitehause
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Re: Follow along as I build a 79 Spider

Post by whitehause » Thu Jan 10, 2019 9:31 am

friedman wrote:
Thu Jan 10, 2019 8:20 am
That was my first thought but the damage is on the none lobed part so there should be no contact.
Looking at the aux shaft again, I realized there isn't really a "lobe" on the end of the shaft, the whole end is off centered to create a lobe
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whitehause
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Re: Follow along as I build a 79 Spider

Post by whitehause » Thu Jan 10, 2019 5:47 pm

andy wrote:
Wed Jan 09, 2019 5:28 pm
Another possibility is that at one point the aux shaft got out of sync with a timing belt change.

The 2L engine is non-interference except for the fuel pump lobe if the aux shaft is not indexed correctly. It can contact the rod cap bolts on the #2 con rod (if I recall correctly). Typically that results in a nice window in the block to view the aux shaft.

Perhaps this one was out just "right" to barely make contact and simply wore down the lobe?

Just a theory,
And we have a winner in the "what the hell did this to my aux shaft" contest !!!!

The #2 rod that faces the aux shaft
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whitehause
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Re: Follow along as I build a 79 Spider

Post by whitehause » Thu Jan 10, 2019 5:58 pm

After pulling out the Flex Hone and hitting the #4 cylinder it seems that mark was just a scratch, not a crack. A few strokes with the hone and it's almost gone. I'll do 20 or 30 more and it should remove it.

In the second pic you can see there is a bit of a ridge at the top of the piston stroke about 3/8" down from thedeck. I'm not sure if I should remove this, or if this is just common with these motors as it seems to be uniform in all the bores. It's not a lot, but I can just catch it with a fingernail.
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fp55scca
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Re: Follow along as I build a 79 Spider

Post by fp55scca » Thu Jan 10, 2019 8:05 pm

whitehause wrote:
Thu Jan 10, 2019 5:47 pm

.........And we have a winner in the "what the hell did this to my aux shaft" contest !!!!

........The #2 rod that faces the aux shaft
--------------------------------------------------------------
--Tim, that's exactly right. In your case your were lucky, the timing of the aux shaft was only off by a little, and the damage was slight. As I think Andy pointed out, in more severe cases the sheared lobe can be sent through the side of the block.

--This, of course, is exactly why it is common to cut the offending lobe off, and tap and plug the aux shaft. This would be my first recommendation to do while you have the aux shaft in your hand. About 20 minutes with a cutoff tool, a tap, a plug and a vice.

--As an absolute minimum, you could grind the lobe off of your aux shaft. After looking at a few other shafts, I'm convinced that someone did exactly that to the aux shaft on the left in this pic, and that it did not come from the factory that way.
Aux Shaft -1.jpg
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Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 CSA Abarth Replica
1981 Fiat Spider Ratrod
whitehause
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Re: Follow along as I build a 79 Spider

Post by whitehause » Thu Jan 10, 2019 8:41 pm

What's strange is there is no definitive lobe on my shaft, the entire far end is the same diameter, just off set from the center line. I plan to keep the mechanical fuel pump since I have a new one already. I just need to make sure the timing is right with this one.
fp55scca
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Re: Follow along as I build a 79 Spider

Post by fp55scca » Thu Jan 10, 2019 8:55 pm

whitehause wrote:
Thu Jan 10, 2019 8:41 pm
What's strange is there is no definitive lobe on my shaft, the entire far end is the same diameter, just off set from the center line. I plan to keep the mechanical fuel pump since I have a new one already. I just need to make sure the timing is right with this one.
----------------------------------------------------------
--Tim, that's interesting. That was my first impression, because the aux shaft (on the left) in my pic is the same, and I figured it was factory. I would not try to run a mechanical pump with it. I don't think the offset is sufficient, otherwise why would Fiat bother to put a lobe on it? I can send you one with a lobe if you need it, but really I don't recommend a mechanical pump. What carb are you running?
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 CSA Abarth Replica
1981 Fiat Spider Ratrod
fp55scca
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Re: Follow along as I build a 79 Spider

Post by fp55scca » Thu Jan 10, 2019 9:08 pm

--Tim, see if you can access this pdf document? This was posted on the internet some years ago (illegally), which pissed-off GC royally of course. Unfortunately, there is no real index for the book. I have a very dog-eared, hard copy of the book, and can probably help if you are looking for something in particular.

https://cardiagn.com/modifying-and-tuni ... gines-pdf/
Jim Scurria
Norfolk, VA

1972 Fiat 124 Spider
1971 Spider - SCCA FP-24
1974 CSA Abarth Replica
1981 Fiat Spider Ratrod
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