Mondial has forward bank cams in backwards!

Hi Everyone,
This is an interesting story. I'm working on the "new to us" Mondial and I had to remove cam covers to fix oils leaks. Well, what better time to do the timing belts and tensioners, right? So this morning I was out there getting everything all lined up to check the timing marks before changing belts. I put the crank on TDC and the cams on the rear bank were lined up with their timing marks. But the front bank wasn't. In fact, the timing marks were nowhere to be seen on the front cams. It took me a few turns of the flywheel, and head scratching to realize that the front bank cams are EXACTLY 180 degrees out of phase with how they should be. Meaning....if I rotate the crank 360 degrees from 1-4 TDC, the front bank cams are perfectly aligned with their timing marks. Hmmm.

But the car ran perfectly well before I took it apart.

I called Verell and asked him what he thought. His first response was "Say WHAT?" and asked me if I was sure that I hadn't been hallucinating. Then he thought about it and realized that if the firing order was changed by 180 on the front bank as well, the car would still run fine with those cams out by 180.

I checked everything on the distributors to see if any wires had been put in the wrong positions, anything that would account for the fact that the cams were 180 deg. off and the car runs fine. Then I realized that OF COURSE the distributor rotor is connected directly to the intake cam, and if the cam is in "backwards" so is the rotor, so the ignition on that bank is also 180 degrees out of phase.

Net result?

The car was running perfectly fine, except with the wrong firing order. It should be 1-5-3-7-4-8-2-6 but it was running as 1-8-3-6-4-5-2-7! (God only knows what strange forces act upon the crankshaft like that!)

An interesting exercise in learning about the firing order of a V-8 Ferrari.

I have no idea how on EARTH someone managed to do this, but I'll be putting it back the way it's supposed to go!

Birdman

 

Nice find on that.

I admire your diagnostic work.

Please update us with a report on if you feel any change when its back together. That will be interesting too.

 

I expect the only potentially noticable difference will be reduced engine vibration due to the proper firing order giving a more balanced load distribution on the crank.

It may be hard for Birdman to notice tho as he just got the car & doesn't even have a dozen miles on it, & it's not been on the road for over a month. Not enough time to get familiar with the feel of the engine.

Got to admit tho, when he first called me it blew my mind until I realized that the front bank would run fine if the timing was also 180 degrees out as well. I believe that this is the first time this little phenomenon has ever been reported on Fchat or the Flist.

Took some real head scratching before Birdman realized that the timing would automagicly be off because it's taken directly from the intake cam!

 

I never even had it registered before taking it apart. It came on a truck at Xmas. I took it on an illegal joy ride (or two, I'm not saying!) around the block a few times, and then it snowed and they salted the roads, fun over. I can say this, it started right up even when the temps were around 0 F, idled well, and ran perfectly. The only reason I took the cam covers off was to fix a gasket that was leaking. If it hadn't been leaking, I would have just changed the belts and tensioners with the cam covers on. (There goes the hacker alert!)

I doubt I'll notice anything different, unless of course the car doesn't run after I "fix" it!!

Birdman

 

Birdman, you have to ask yourself "Why?". To me it appears more difficult to install the cams 180 degrees off, establish and wire for a different firing order etc. Why would a mechanic do this? There has to be an underlying reason. Very interested in how the Mondial runs after all is set right!

 

They didn't have to change the wiring to get the ignition right. When the intake cam is installed out of phase, the dist rotor on the end of it is out of phase too--built in ignition rewiring!

What I expect happened is someone set the timing on the front bank cams by setting the flywheel to TDC without looking to see if piston #1 was actually at TDC. Instead, they were 360 degrees off!

Birdman

 

I wonder if the engine will "sound" different afterwards? Will the proper firing order have different pulse-interferences in the headers & therefore a different "note"?

 

Maybe,
But you'd have to have a side by side comparison & a really good ear to tell the difference.

Hard to predict tho, the individual header pipes are separate for most of their length, and very closely matched in length, there might not be enough difference in the exhaust routing to be detectable.

Since it's being setup correctly, we'll probably never know.

 

I had a look in the textbooks Birdman and strangely enough 1-8-3-6-4-5-2-7 and 1-6-3-5-4-7-2-8 are recognised firing orders for a flat crank V8. So maybe the Ferrari order is the strange one!!

Either way I think so long as it fires on alternate banks then with a short stubby crank, it won't make a lot of difference.

Richard

 

Ferrari numbers the cylinders differently than I ever seen....although I have lead a sheltered life I guess. Usually the pistons are counted front to back, so 1,3,5,7 are in one bank and 2,4,6,8 in the other. But your 1-8-3-6-4-5-2-7 doen't make sense unless it's a horse shoe numbering and I don't see how they would need to be numbered to make 1-6-3-5-4-7-2-8 work.

 

They are horseshoe with 1234 being F to R on right and 5678 R to F on left.

 

Yes, I was commenting (clearly in a confusiong way) that 1-6-3-5-4-7-2-8 doesn't make any sense, I don't think I would trust any sorce that published it.

 

Oh my God my head is spinning!

Glad to hear this has happened before! Gotta wonder what the guy who worked on this before me was thinking though!

Birdman

 

Ken,
Yeah, but your Lotus is a 4 cylinder engine with only one bank of cylinders! My engine had the rear bank set up properly, and the front bank cams 180 degrees out of phase...and it not only didn't blow up, but ran fine!

Birdman

 

A Ferrari 90 degree V8 is two four bangers joined at the hip.

With the cavalino shoe numbering, and the flat (TBBT) crank, 1-6-3-5-4-7-2-8 wouldn't work. 45 degrees after cyl 1 is TDC, cyl 6 is BDC not TDC.

Consider: With the flat crank, cyls 1 and 4 are at TDC when 2 and 3 are at BDC. 45 degrees later, 5 and 8 are TDC and 6 and 7 are BDC.

1-5-3-7-4-8-2-6 is one sequence of cylinders hitting TDC in sequence.

But since 5 and 8 are TDC at the same time, they could be either TDC, intake/compression or exhaust/intake.

Oddly enough, the "correct" sequence might actually produce more vibration. Power on 1 followed by 5 means torque is being applied to opposite ends of the crankshaft 45 degrees apart. The same with 4-8.

With the "wrong" sequence that was in place, each cylinder's power stroke is followed 45 degrees later by the power stroke on the corresponding opposite bank cyl -- 1 followed by 8 on the same crank arm, then 3/6, then 4/5, then 2/7.

With the "correct" sequence, the power strokes are distributed on different crank arms, potentially adding torque stresses to the crankshaft, which might add vibration as the crankshaft flexes microscopically.

I think the biggest impact you might notice between the two orders is that the "wrong" sequence sucks air from the same "end" of the intake plenum in sequence, potentially leading to pressure (or vacuum) pulses across the plenum. The "correct" sequence would suck air in an more distributed fashion, so there might be less vac pulses at any given point in the plenum.

Cyl 8 would have been sucking from the plenum at a point already depleted by feeding cyl 1. Your front/back mix may be a hair more consistent with the correct sequence.

But it's a minimal effect either way. You probably won't notice much difference at all. It just won't confuse mechanics as much.

 

DGS,
It's funny you mention that, because when I plotted it out on paper, the "wrong" firing order seemed more logical to me in terms of stress on the crank, but what do I know? I think I'll put it back the way Enzo intended!

Birdman

 

Oops. Substitute "90 degrees" for "45 degrees" in my message, above. (Crank angle versus cam angle.) It's a "90 degree" V8.

It's been one of those weeks. All month.

Presumably, the crankshaft is fairly stiff -- not too much flex. While the "wrong" sequence might be microscopically smoother at idle, I think the "right" sequence would theoretically put smoother power to the drivetrain -- given that the drivetrain hooks up at one end.

 

In '90 I had purchased a '82 Mondial thru a broker, never again, and I was assured it was fine example. Upon delivery I found many things wrong with it that the broker did not see or acknowledge to me. Although the car ran fine to a neophyte its only obvious issue was the oiled clutch that would slip as soon as power was put to it. Okay, no big deal, I'll just replace the oiled clutch which turned out to be caused by a bad rear main seal behind the flywheel.

Second symptom was it would die on the road only to reignite intermittently, took it to the local Alfa shop and of course he raped me for an ignition switch and a cold start switch and informed me it was down on power(he was hiding the other issue from me).

I replaced the clutch and main seal and reengineered the clutch throw out shaft by drilling a grease gallery so the outboard needle bearing in the bellhousing could be lubricated by zerk fitting as it is exposed to the weather and factory provided no way to lube it. The throw out shaft was rewelded where it bore on the bearing and turned down to the correct diameter. Welding and remachineing was difficult as the shaft material was very impure and very soft.

Once this was done it was obvious the car was down on power but why?. Still a novice with this car and with the Ferrari redundant ignition system it ran okay, In trying to set the timing I was tugging at the distributors to get the rubber boots off, the coil wire came free from distributor and was free in my hand. After pulling the distributor cap off, it was apparent that the source of trouble was the center coil wire was missing its staking screw and the center carbon brush and spring was missing, so one whole bank of cylinders was not firing but because of redundancy it would run. $10.00 later with a used carbon brush and a new staking screw, it fired up made more noise and appeared to be running on all cylinders but was very smoky.

I had only put 500 miles on car total prior to this but who knows how much more it had without being ignited. I let it idle, in the beginning it belched huge clouds of oily smoke slowly dissapating as time went on, with all the unburned gas and oil I'm surprised I didn't explode the exhaust system, after 25 mins of idling it then ran clear and clean. At that point it was dream on the road.

That age old question of "why would a mechanic do that" ?. I'm sure a shade tree mechanic got a hold of it and did something terrible and frustrated the owner who gave up and sent the car on its journey for a new owner.
Since the factory did not have a step by step method for clutch change out in the repair manual or parts catalog, I wrote a 3 page step by step methodology for changing out the Mondial clutch if any one wants it.
Ross

 

I dont think its a question of what he was thinking, as much as what he was smokin or drinkin, lol. Obviously he rotated the motor one full turn and put the other cams in on thier marks. Man, if it had a dual plane crank that motor would have coughed out those valves right away. Amazing how idiot proof something complex can be. I never thought about it until this came up, except knowing that as long as the crank was rotated 45 degrees from TDC on any cylinder that you were in a safe zone where no pistons could hit valves.
Now, without trying to make me pop a blood vessel, could someone explain why the ignition would follow it around and still work? I would think that if the cams are on thier mark with the crank at its mark, the number 5 hole is going to fire. Or are you saying it now was 180 off as well and number 8 was firing? maybe I just seen it myself. In the voice of Roseanne Roseanna Dana, ...nevermind~

 

Right. The ignition computer only fires the bank coil once per 180 crank degrees, and lets the distro sort it out. With the distributor rotor attached to the cam, the distro follows the cam. Put the cam 180 out, and the distro follows.

Even in the 328 with a single Marelli Multiplex, the crank sensors only give enough resolution to say "front bank ... rear bank" alternate coils, and the two cam mounted distros say which cyl.

Now on the 308s that had the single distro, there'd be trouble in sparkville if the bank cams were opposite each other (unless Conan the Wrench also resorted the plug wires).

Anyone seen a good distro replacement sensor that will fit on a 3x8 (per bank) distro ... without having to resort to Verell's machine shop?

(The 3x8 seems a perfect candidate for individual plug-mounted stick coils, but the crank sensors can't tell a 'puter what cyl to fire on its own.)

 

Post it in a new thread. Good stuff.

 

I agree, start a thread on this. Do you have pictures to go with it?

 

Well, I put the cams back the right way, changed the timing belts/tensioners, and Verell helped me get the cam cover back on without leaking. (This is an elaborate dark art involving all kinds of various witchcraft methodologies, adhesives, etc.)

Today I finally took the plunge, put the key in, and started her up. She fired right up and ran perfectly well...exactly the same as when the firing order was wrong. All is well. A few more things to address and spring is almost here. Time to drive!

Birdman