128 Smog Engine Build

Intro
For the uninitiated... California is a great place to live except when it comes to dealing with modifying old (but not yet classic) cars. We have a very stringent set of emissions regulations including a dyno (or rolling road) test every two years. Common sense would dictate that if the car passes emissions at the tailpipe you'd be good to go. However, there is also a "visual inspection" where the technician is supposed to make sure all of the emissions-related equipment that your car was originally equipped with is both present and functioning. Your car could pass the "sniff test" but if it doesn't pass visual, well, you don't pass and cannot renew your vehicle registration. That's the short version anyway. Yes, there are ways around it but I won't get into that.
My '78 Rally is not old enough to be smog exempt (where you are exempt from having to do the regular emissions checks) and the time had come for another test. Somehow it had ended up with a 1500cc engine, big-valve head, cam, header, electronic ignition, etc., and none of the usual emissions gear. Being the law-abiding citizen that I am, I decided it would only be prudent to build a "bone stock" 1290cc engine to smog it with. No sense in going wild with the rebuild since it would be standard spec, so I called up a good friend who had at one time had a '74 X1/9 engine sitting in his shop. Said engine had supposedly been rebuilt so I figured it would save me a lot of time and $ to buy it outright instead of rebuilding one of my spares. The true history of the engine was unknown save that it had been gone through at some point, so we struck a deal that I would take the engine and check it out and after it was running in my car we would come to an agreement on value. This is where things get interesting...

Teardown
It had been, oh, 9 years or so since my last full engine build so I decided this would be good practice for future high-performance builds and would carefully go through the whole engine. It was rather dirty from years of storage anyway so it needed disassembly for a proper paint job and to swap the X1/9-specific gear for 128 hardware. It turned out there were also a number of bits & pieces missing that would necessitate heavy scrounging in my stock of spares (fasteners, covers, pulleys, etc.).

I removed the cylinder head and cam tower as an assembly. First noteworthy item was that standard 1500cc pistons had apparently been used in the rebuild, given away by the large valve reliefs (so much for stock compression).
Large valve reliefs indicate 1500cc pistons

After removing the cylinder head I flipped the engine over on the bench and began to tear down and inspect the bottom end. First item of concern was the #4 (flywheel side) big-end bearing. There was a piece of aluminum jammed in the oil hole behind the bearing. Had I run the engine like this, no oil would have been squirting on the cylinder wall of the #4 cylinder.
Aluminum debris stuffed in oiling hole. Sorry for the blurry photo...

Continuing on... I removed the pistons and rods revealing the next bit of questionable engine build work - the #1 cylinder had a deep gouge in the wall. Looks like the machine shop broke a boring bit or got something jammed in there while boring the cylinder. I measured the location relative to the rings and fortunately it is above the ring land so I decided to run with it. Had this been a competition or high performance street engine I would have sent it to the scrap yard though.

The rest of the disassembly was uneventful. The auxiliary shaft bearings had some scratches that gave me pause but the fit of the shaft was ok (measured with a micrometer and telescoping gauges) and fitting new aux bearings isn't the simplest procedure so I decided to leave them be (it's just a smog motor I kept telling myself). I measured all the bearing journals and installed bearing diameters - everything was within spec for .010" undersize. The ring gaps were close to their max limits, but measuring the bores showed some slight variation in diameter so I was able to shuffle rings between cylinders to get the end-gaps within spec.

The block was thoroughly scrubbed and degreased, then painted with Ford Engine Grey engine paint (a very close match to the standard Fiat grey). I ordered up an engine gasket kit from C. Obert & Co. and started piecing the engine back together, thoroughly cleaning each part on the way.

Assembly
The pistons were in, main bearing caps bolted on, and the first three big-end bearing caps installed when I noticed something I hadn't seen earlier - cracks on the #4 big-end journal. No... I guess I need better illumination in the shop. A more thorough inspection revealed fine cracks all around the circumference of the journal, cracks radiating from the oil holes, and the side thrust faces looked like they had been ground with an angle grinder! My best guess is that the bearing had been spun (the likely cause for the rebuild in the first place) and the journal had been welded up for regrinding (evidenced by the lack of relief radius between the journal and thrust faces). Either the weld job had not been done properly or they had been too aggressive in their grinding, but either way cracks were formed. No way was I going to run that crank - even in stock form, all the torque from the first three cylinders must pass through that journal and even under light load, enough RPMs would probably crack the crank through eventually.
Cracks all around the bearing journal, and poorly-ground thrust faces.

No sense in trying to repair that crank. I dug back into my spares and pulled a couple of serviceable cranks from spare engines. One was ground .010" under like this crank so I would be able to use the existing bearings but some shop had gripped the flywheel end of the crank too hard in the vise jaws of their grinding machine (or some machine) that left dents on the rear main sealing surface. I've dealt with enough leaky rear mains to not want to tempt fate. The second crank was standard size and in excellent shape. I polished the journals a bit on our lathe at work and ordered up a standard set of bearings from Obert.
Engine assembly continued... All sorts of pieces were scavenged from my stock of spares:

water jacket cover plates
front main seal carrier
tensioner assembly
tensioner plunger
engine mount
auxiliary shaft pulley
water pump housing
bypass pipe
alternator pivot and tensioning bracket
water pump to heater core pipe
oil drain tube
oil pan
all sorts of nuts & bolts

The oil pump appeared new (and the spring height measured within spec) but was for an X1/9 so I swapped the pickup from a used 128 pump.

Assembled short block.

The cylinder head was torn down, cleaned (the carbon hadn't been removed very thoroughly), valve stem seals replaced with new, and valves lapped for good measure.
Cylinder head reassembled.

Cylinder head studs were wire-brushed (like every other fastener on this engine) and installed. A light coating of anti-seize was applied to the shanks to keep them from corroding to the cylinder head. This makes it a lot easier to remove the head in the future. Deck height was checked and valve cutouts & combustion chamber volumes measured. I threw the numbers into my handy compression ration calculator and determined the new CR to be a whopping 8.21:1. Just goes to show how much valve pockets contribute to (or detract from) CR!
Installed the cylinder head and camshaft tower. The long tube with four ports feeding into the cylinder head is the air injection rail as equipped to US-spec cars. This is one place where I deviated from the truly standard engine for my car. '78s had the rail gun-drilled through the head with the ports branching from it internally. These heads are not very common (the one originally on my car was from a '79 1500cc engine with larger combustion chamber) so I opted to convert the air injection system to an earlier style. Functionally they are the same and no smog tech would know (or care about) the difference. The valve on the end of the air injection rail prevents exhaust gasses from being forced back through the system into the air pump. The valve above the #3 spark plug is another emissions-related device. It cuts off vacuum to the vacuum retard on the distributor. Whether it does this with the engine warm or cold I cannot remember at the moment.
New oil pressure & water temp senders were fitted as there's no sense in ruining a new engine by trying to save a few dollars. A new water pump is a bit more expensive but worth the trouble as well. They are not fun to replace with the engine in the car!

The carburetor was dismantled, cleaned, and inspected. The base was warped as usual. I took it in to work and fly-cut the base on our vertical mill. It took more than I anticipated to get it flat but wasn't beyond repair.
View of resurfaced carb base.

Standard '75-78 US-spec carb, a Weber 32DATRA with all sorts of ports for emissions stuff and water-activated choke. Venturi sizes are 22mm/22mm.

Final assembly. Note the big air injection pump hanging off the cam tower and driven by a small timing belt, also the Ducellier distributor with vacuum delay module. Dealing with all this emissions related equipment really makes one appreciate the advent of fuel injection!

Installing clutch & flywheel:

Note my quick & dirty clutch alignment tool - a deep socket (10 or 11 mm, I can't recall which).

Conclusion
I'm happy to say that all the trouble was worth it - the car passed the rolling dyno test on its first try! It even runs pretty good for a standard engine with all the smog gear and 0 degrees timing advance!

This page created: March 24, 2006

Courtney Waters courtney@mirafiori.com

Back to Court's Main Page

Intro For the uninitiated... California is a great place to live except when it comes to dealing with modifying old (but not yet classic) cars. We have a very stringent set of emissions regulations including a dyno (or rolling road) test every two years. Common sense would dictate that if the car passes emissions at the tailpipe you'd be good to go. However, there is also a "visual inspection" where the technician is supposed to make sure all of the emissions-related equipment that your car was originally equipped with is both present and functioning. Your car could pass the "sniff test" but if it doesn't pass visual, well, you don't pass and cannot renew your vehicle registration. That's the short version anyway. Yes, there are ways around it but I won't get into that. My '78 Rally is not old enough to be smog exempt (where you are exempt from having to do the regular emissions checks) and the time had come for another test. Somehow it had ended up with a 1500cc engine, big-valve head, cam, header, electronic ignition, etc., and none of the usual emissions gear. Being the law-abiding citizen that I am, I decided it would only be prudent to build a "bone stock" 1290cc engine to smog it with. No sense in going wild with the rebuild since it would be standard spec, so I called up a good friend who had at one time had a '74 X1/9 engine sitting in his shop. Said engine had supposedly been rebuilt so I figured it would save me a lot of time and $ to buy it outright instead of rebuilding one of my spares. The true history of the engine was unknown save that it had been gone through at some point, so we struck a deal that I would take the engine and check it out and after it was running in my car we would come to an agreement on value. This is where things get interesting... Teardown It had been, oh, 9 years or so since my last full engine build so I decided this would be good practice for future high-performance builds and would carefully go through the whole engine. It was rather dirty from years of storage anyway so it needed disassembly for a proper paint job and to swap the X1/9-specific gear for 128 hardware. It turned out there were also a number of bits & pieces missing that would necessitate heavy scrounging in my stock of spares (fasteners, covers, pulleys, etc.).
I removed the cylinder head and cam tower as an assembly. First noteworthy item was that standard 1500cc pistons had apparently been used in the rebuild, given away by the large valve reliefs (so much for stock compression).	Large valve reliefs indicate 1500cc pistons
After removing the cylinder head I flipped the engine over on the bench and began to tear down and inspect the bottom end. First item of concern was the #4 (flywheel side) big-end bearing. There was a piece of aluminum jammed in the oil hole behind the bearing. Had I run the engine like this, no oil would have been squirting on the cylinder wall of the #4 cylinder.	Aluminum debris stuffed in oiling hole. Sorry for the blurry photo...
Continuing on... I removed the pistons and rods revealing the next bit of questionable engine build work - the #1 cylinder had a deep gouge in the wall. Looks like the machine shop broke a boring bit or got something jammed in there while boring the cylinder. I measured the location relative to the rings and fortunately it is above the ring land so I decided to run with it. Had this been a competition or high performance street engine I would have sent it to the scrap yard though.
The rest of the disassembly was uneventful. The auxiliary shaft bearings had some scratches that gave me pause but the fit of the shaft was ok (measured with a micrometer and telescoping gauges) and fitting new aux bearings isn't the simplest procedure so I decided to leave them be (it's just a smog motor I kept telling myself). I measured all the bearing journals and installed bearing diameters - everything was within spec for .010" undersize. The ring gaps were close to their max limits, but measuring the bores showed some slight variation in diameter so I was able to shuffle rings between cylinders to get the end-gaps within spec.
The block was thoroughly scrubbed and degreased, then painted with Ford Engine Grey engine paint (a very close match to the standard Fiat grey). I ordered up an engine gasket kit from C. Obert & Co. and started piecing the engine back together, thoroughly cleaning each part on the way.
Assembly The pistons were in, main bearing caps bolted on, and the first three big-end bearing caps installed when I noticed something I hadn't seen earlier - cracks on the #4 big-end journal. No... I guess I need better illumination in the shop. A more thorough inspection revealed fine cracks all around the circumference of the journal, cracks radiating from the oil holes, and the side thrust faces looked like they had been ground with an angle grinder! My best guess is that the bearing had been spun (the likely cause for the rebuild in the first place) and the journal had been welded up for regrinding (evidenced by the lack of relief radius between the journal and thrust faces). Either the weld job had not been done properly or they had been too aggressive in their grinding, but either way cracks were formed. No way was I going to run that crank - even in stock form, all the torque from the first three cylinders must pass through that journal and even under light load, enough RPMs would probably crack the crank through eventually.	Cracks all around the bearing journal, and poorly-ground thrust faces.
No sense in trying to repair that crank. I dug back into my spares and pulled a couple of serviceable cranks from spare engines. One was ground .010" under like this crank so I would be able to use the existing bearings but some shop had gripped the flywheel end of the crank too hard in the vise jaws of their grinding machine (or some machine) that left dents on the rear main sealing surface. I've dealt with enough leaky rear mains to not want to tempt fate. The second crank was standard size and in excellent shape. I polished the journals a bit on our lathe at work and ordered up a standard set of bearings from Obert. Engine assembly continued... All sorts of pieces were scavenged from my stock of spares: water jacket cover plates front main seal carrier tensioner assembly tensioner plunger engine mount auxiliary shaft pulley water pump housing bypass pipe alternator pivot and tensioning bracket water pump to heater core pipe oil drain tube oil pan all sorts of nuts & bolts The oil pump appeared new (and the spring height measured within spec) but was for an X1/9 so I swapped the pickup from a used 128 pump.	Assembled short block.
The cylinder head was torn down, cleaned (the carbon hadn't been removed very thoroughly), valve stem seals replaced with new, and valves lapped for good measure.	Cylinder head reassembled.
Cylinder head studs were wire-brushed (like every other fastener on this engine) and installed. A light coating of anti-seize was applied to the shanks to keep them from corroding to the cylinder head. This makes it a lot easier to remove the head in the future. Deck height was checked and valve cutouts & combustion chamber volumes measured. I threw the numbers into my handy compression ration calculator and determined the new CR to be a whopping 8.21:1. Just goes to show how much valve pockets contribute to (or detract from) CR! Installed the cylinder head and camshaft tower. The long tube with four ports feeding into the cylinder head is the air injection rail as equipped to US-spec cars. This is one place where I deviated from the truly standard engine for my car. '78s had the rail gun-drilled through the head with the ports branching from it internally. These heads are not very common (the one originally on my car was from a '79 1500cc engine with larger combustion chamber) so I opted to convert the air injection system to an earlier style. Functionally they are the same and no smog tech would know (or care about) the difference. The valve on the end of the air injection rail prevents exhaust gasses from being forced back through the system into the air pump. The valve above the #3 spark plug is another emissions-related device. It cuts off vacuum to the vacuum retard on the distributor. Whether it does this with the engine warm or cold I cannot remember at the moment. New oil pressure & water temp senders were fitted as there's no sense in ruining a new engine by trying to save a few dollars. A new water pump is a bit more expensive but worth the trouble as well. They are not fun to replace with the engine in the car!
The carburetor was dismantled, cleaned, and inspected. The base was warped as usual. I took it in to work and fly-cut the base on our vertical mill. It took more than I anticipated to get it flat but wasn't beyond repair.	View of resurfaced carb base.
Standard '75-78 US-spec carb, a Weber 32DATRA with all sorts of ports for emissions stuff and water-activated choke. Venturi sizes are 22mm/22mm.
Final assembly. Note the big air injection pump hanging off the cam tower and driven by a small timing belt, also the Ducellier distributor with vacuum delay module. Dealing with all this emissions related equipment really makes one appreciate the advent of fuel injection!
Installing clutch & flywheel: Note my quick & dirty clutch alignment tool - a deep socket (10 or 11 mm, I can't recall which).
Conclusion I'm happy to say that all the trouble was worth it - the car passed the rolling dyno test on its first try! It even runs pretty good for a standard engine with all the smog gear and 0 degrees timing advance!
This page created: March 24, 2006 Courtney Waters courtney@mirafiori.com Back to Court's Main Page