1980 Fiat 124 Spider aka Mozzy - restoration part 1

[18Fiatsandcounting]

Good, and there are notches in the main bearing caps as you can see. No notch = towards the front of engine, then 1 notch, then 2, etc up to 4 notches for the rear cap.

The arrow on the pistons "usually" points towards the front of the engine. This looks correct from your picture, as the cutouts for the intake valves are larger than the ones for the exhaust valves.

And since you're in San Jose, my offer to drive down from Livermore still is available!

-Bryan

[fiat124pauk]

Hey folks,

i'm back from a hiatus! We moved house and with my little kid, there is just not enough time and energy in the day to do everything that i want. But enough with all the excuses.

Since the last update, I've started assembling the block, managed to take the head apart, do a home valve seat cutting job following Nut124's advice!

Now i'm starting to put together the head and cannot for the life of me figure out where these o-rings go. They were in the same bag as the valve seals. See the last image in this post.

Any ideas?!!!!

[18Fiatsandcounting]

Now i'm starting to put together the head and cannot for the life of me figure out where these o-rings go. They were in the same bag as the valve seals. See the last image in this post.

Any ideas?!!!!]

Some gasket sets have a few more items than your particular engine might need, but the o-rings look like the ones that go between the crankshaft pulley and the crankshaft gear on certain engines (yes, these two parts come apart). There should only be one, though. I sorta recognize the flat rubber gasket but I can't quite remember where it goes. The two red fiber washers go under the knurled "knobs" that hold down the cam box covers to the cam boxes. There should be 4 of them.

-Bryan

[fiat124pauk]

Bryan, i figured out the large flat one. It goes to the coolant neck that connects to the head. I'll check the round ones for pulleys.

The fibers one----why am i missing two more?

[18Fiatsandcounting]

Yes, that makes sense on the coolant neck for the large flat rubber "washer". That's what it looked like to me, but it seemed a bit too wide. Perhaps my bad eyes, or even more likely, my bad memory...

I don't know why you don't have 4 of the reddish fiber washers. Are 2 of them stuck together? I have a bunch extra, so I could mail you some. Unless of course these 2 red washers are for something else entirely, but they sure do look like the ones for the cam cover "screws".

-Bryan

[fiat124pauk]

Started to put the head back, put all new valves in, secured the valve springs.

When i was putting together the valve extensions with the camshafts i noticed something interesting.
It seems like the camshafts are making contact with the valve tappet partially through a revolution and for most of it there seems be a pretty good gap. Does that make sense?

I've always thought that the lobe rides on the tappet the whole revolution cycle. See images below and could you please let me know if im doing something wrong?

Okay, actually spent 10 minutes googling and found that in deed this is normal - https://www.fiatforum.com/threads/measu ... nt.241987/

I will measure the clearance and report back.

[18Fiatsandcounting]

I think you've figured it out, and yes, the cams do not "ride" on the buckets like you might see with an engine using hydraulic lifters. The clearance is 0.45mm on the intake side (0.017") and 0.50mm on the exhaust side (0.019"). Some performance cams use less, but for stock, I aim for these numbers. Clearances are adjusted by changing the tappet shims, and measurements have to be done with the camshaft/cambox bolted to the head using the appropriate cam box gasket.

-Bryan

[Nut124]

I would consider the 17/19 thou as the high end and accept anything over 0.012. My new cam runs 0.008"/0.010".

Unless the cam profile is precisely known, running a lot of clearance risks getting off the deceleration ramp and having excessive valve seating velocity -> noise and wear. Fiat, I think, was seeking long valve train service life by recommending the high clearance to accommodate for seat and stem wear.

With a stock cam, having a little bit of extra duration from the tighter clearance hurts nothing and it runs quieter as well.

[18Fiatsandcounting]

With a stock cam, having a little bit of extra duration from the tighter clearance hurts nothing and it runs quieter as well.

Good to know, thanks. So for a stock engine (stock cams), what would you recommend as an optimal clearance? 0.012" intake / 0.014" exhaust? I drive my cars so little each year that valve train longevity is no longer a factor, and 100% of the driving is just routine street driving. No racing.

-Bryan

[Nut124]

Bryan, it's hard to say what is ideal lash w/o having an accurate cam profile, particularly, measurements of the ramps.

I have profiled several different after-market cams in the past few years and I always measure the ramps carefully and calculate seating velocity. The industry recommendation seems to be that seating velocity for these applications shall not exceed 0.001" per cam angle. In the cams I have measured, the ramps seem to be in the 0.75-0.85 thou per deg range, so below the limit.

Also, the recommended lash setting seems to be safely on the ramp, i.e. even if clearance grew a few thou while running, the seating velocity would still be below the limit. I'm told, against my intuition, that valve clearance grows rather than shrinks when hot. This is said to be because the valve head heats up the most and grows radially and climbs up the seat bevel. This could be why the cam makers leave a safety marging of a few thou to stay on the ramp.

In a hot, performance cam, a clearance too tight delays the IVC event and will hurt low end torque w/o any of the benefits of the little extra duration. In a stock cam, the IVC event is so early that even 5 deg later makes no difference.

So, what I'm saying is that with a factory cam, I would err on the tighter side when setting the lash.

Perhaps I will profile a factory cam I have sitting in the garage to see how generous the ramps are.

Below is the Piper 300 cam measurements incl. the seating velocity at various clearances.


Below are profile plots of cams at recommended lash settings. I set the Piper at 0.010" vs. recommended 0.008" because the plot seems to show almost 0.010" safety marging before the lift slope increases.

[fiat124pauk]

Values:
E1=0.016"
E2=0.016"
E3=0.018"
E4=0.015"

I1=0.024"
I2=0.024"
I3=0.024"
I4=0.024"
For the Intake side i ran out of feeler gauge, so it might be even higher. Does that make sense? Why is my exhaust pretty close to the right value and my intake so far out?

[Nut124]

Ex looks good to me.

New valves are never exactly the same as the old and you cut the seats. Clearance always needs to be adjusted with shims. Is the cam the same as before? Did you buy the oversize valves? Or stock size? Oversize valves need the seat cut to the max or they run low in the head, need a lot of shim. 5mm I think is the biggest shim available.

[18Fiatsandcounting]

You can also play around with different cambox gaskets although this changes all 4 valve clearances at once. Different manufacturers have slight variations in thickness. I used to see specialty gaskets for sale at some of the vendors, but I don't see them listed as much these days. You might give them a call and see if they sell a thinner cambox gasket, or know where to get one.

And by the way, the cambox and gasket need to be torqued to spec to get an accurate measurement on the valve clearances.

-Bryan

[Nut124]

Values:
E1=0.016"
E2=0.016"
E3=0.018"
E4=0.015"

I1=0.024"
I2=0.024"
I3=0.024"
I4=0.024"
For the Intake side i ran out of feeler gauge, so it might be even higher. Does that make sense? Why is my exhaust pretty close to the right value and my intake so far out?

If the thickest available shims do not get you to acceptable clearance, then you have a few options:
1. Have the valves back cut to reduce margin and sink them a bit deeper into the head. Could gain maybe 0.020, no more than 0.030 depending on how thick the valve margin is now.
2. Cut the seat 45 a bit deeper if not at valve OD yet.
3. Use lash caps. This is what I had to do with my big new cam with a reduced base circle. I got 1mm/0.040" caps from Europe. This also allows the use of thinner, lighter shims.
4. Have the cam box machined. There is no easy way to hold the piece. Really would need adjustable cam pulley to chekk, fix timing.
5. Use a thinner gasket if you can find one. Same cam timing concern as above.

[fiat124pauk]

Hey guys,

these are standard valves, i measured the new valves and they seem to be about 0.010" shorter.
Side note, i thought i ran out of feeler gauges, but then a bright idea that you probably have already thought of - you can mix and match them to create a new thickness...yay!
Here are the update clearances
I1=0.024"
I2=0.030"
I3=0.029"
I4=0.028"

The valve shims are
Shim I1 = 4.25mm = 0.167" with goal of 0.008" new shim needs to be 4.65mm
Shim I2 = 4.20mm = 0.165" with goal of 0.008" new shim needs to be 4.75 mm
Shim I3 = 4.25mm = 0.167" with goal of 0.008" new shim needs to be 4.75 mm
Shim I4 = 4.30mm = 0.169" with goal of 0.008" new shim needs to be 4.80 mm
here is a Google sheet link - https://docs.google.com/spreadsheets/d/ ... sp=sharing

I think that all makes sense......right? its been a long day.