355 Exhaust Bypass Valve Rattle

For everyone who following me down Hurricane Ridge and heard a rattling sound from the rear of my car kind of like the exhaust twang of a VW accelerating, this is what I discovered today.

Installed the microphones of the Chassis Ears and isolated the rattling to the central exhaust, near the bypass valve. Took the air filters and muffler heat shield off. Started the car and sure enough the butterfly valve was opening and closing rapidly at 2,000 to 2,500 RPM. Discovered way to much play in the shaft about .040 side to side. Upon closer inspection, noticed there use to be an end cap on the valve which was missing, allowing the shaft to move up and down. Appears the detents securing the end cap loosened up and allowed the cap to fall off (somewhere in the tunnels at Hurricane Ridge).

Now, rather than just buying another Valve at $1,400.00 (this is the second valve in two years, bone heads at Ferrari obviously didn’t consider all the variables) I set out to PERMANENTLY fix the problem which has pissed me off since the first time. That bill was $2,400.00 total.

Below is what I did.

1.) Bypass valve with end cap missing.
2.) Detents obviously didn’t hold.
3.) Valve out of car.
4.) Both valves, left current model (casting), Right older model (machined).
5.) Valves side view, older one on right had welded end cap.
6.) Machining new end cap mat: 303 SS.
7.) End cap finished.
8.) End cap welded in new cast Bypass Valve.
9.) New valve with welded end cap in car.


Don’t know if the fix will work yet, not sure if I allowed enough tolerance for heat expansion, if it doesn’t work, will add a couple thousandths more next time.

Hope this helps someone else with the same problem.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Such a simple thing and 'they' couldn't get it right. Careful you may find yourself in the bypass valve refit business. Could be a good deal at half the dealer cost.

 

Spasso

FoS charged me $2,400.00 of which $1,400.00 was the valve. $1,000.00 for labor? you would have to be a half dead retard to spend any more than two hours R and R ing the valve, including the test drive! You do the math.

 

Did I mention "No love lost"?

 

From you?

BAAAAAAAAWWWWWWWWHHHHHHAAAAHAHAHAHAHA!

 

I'll venture out on a limb here to say:

$500 Parts
$500 Labor

$1400 Profit??????? Hmm.....just a guess, doesn't mean Im right

I know who Im calling if I begin to hear any "exhaust Twang"!!!!

Keep us posted on the outcome please....

 

CMac

Mat: 1.0” 303 SS; Scrap, it was Free.
Labor: 5 hours including R&R, machining, welding and test drive.

It took longer than normal because I didn't have a build print so I would make a part, test it then make small adjustments. I ended up making about 8 parts before I was happy with the Pression Blue results.

I left .006 thousandths clearance for heat expansion between the shaft and bore, which should be adequate given both materials will expand at close to the same rate, and the valve only opens 90 degrees in total.

The end cap in now welded so it will not fall off like before. Currently the only concern I have is if there is enough clearance between the shaft and bore for heat expansion. If not, the valve will stick open and upon returning home I will remove it and cut another end plug with more clearance. PROBLEM SOLVED.

I wonder if Ferrari SPA is looking for a good Engineer. Na, might screw up there planned obsolesce parts program.

 

I would just let the valve stick open

 

I like your "worksheet" better.....my pricing was refering to what you were charged in your previous ventures!!!!! Do please keep us poste don the results!

 

Their Profit?

Cost of Valve $400.00?
Time spent 2 hours @ $100.00 / hr; $200.00?

Total Cost $600.00?

Total Profit $1800.00 give or take a couple bills.

DJ,
Does sound better!!!!!!!!!!!!

 

Great work! Nice fix...doesn't hurt to have your engineering and machine skills...or and all the necessary tools!

BTW, you should most definitely post this in the "technical" section...

Dave

 

Dave,

Thought about that, didn't want the endless harassing "Ferrari wouldn't make a substandard part, blah,blah,blah!!!" BS.

Just wanted the guys who thought my car was rattling apart to know what all the noise was about, and to know hopefully there is a permanent fix if others end up with same problem.

 

JH,

Thanks for posting..............

This is what is great about the 'net

 

Rest assured John, As a 308 owner I can attest to the substandard part phenomenon.

I think your fix would be well received by most, especially those that believe in improving on a design for dependability and longevity.

 

Great fix, John.

By the way, I was wondering, engineer to engineer, do you think you kept loosing the cap because of vibration or because the valve shaft axial expansions tend to work the cap out of its detents? Do you know how much clearance there is between the end of the valve shaft and the inside of your cap? I always find it interesting to go back and figure out what went wrong in their design process - what it is they didn't account for.

That's a really elegant fix, John. It's always good to see something done right!

 

D-348,

Not sure what went wrong, I only had two broken pieces to sample, both of different designs.

The first valve stuck open and set off the check engine light, upon inspection, there was significant buildup of carbon and rust around the butterfly valve. When the valve was opened, the shaft side to side end play was approximately .125” and allowed the valve to chalk open when shifted in this fashion. Probably why it was stuck open.

I can only assume the reason Ferrari replaced the old design was too many warranty replacements. Also in quantity, cast parts are less expensive than machined, especially in 303 SS.

The end cap on the diaphragm end of the valve looked like a stamped part, so the other end probably was similar, again less expensive to manufacture. It is also less expensive to swedge or peen the cap in the bore rather than tack weld the two pieces together.

In conclusion, I didn’t observe any galling on the shaft, so that would leave heat expansion, vibration, or just poor quality workmanship as the culprit for failure. I’m sure if Ferrari had added a small tack weld to the end cap it probably wouldn’t have gone missing.

 

Hmm. That's interesting. I guess that means that they didn't test the part to the right environment on a shaker table, etc. Otherwise they would have observed the cap coming off and taking out a nearby tech. That, you would think, would have convinced them to design a decent swedge fit or to tack weld the cap. So it seems like what we get to in this case is that they failed to understand the operating environment during the design.

Good job again on that fix!

 

Planned Obsolence = more money

No incentive to spend the extra couple bucks.

 

Being freshly reamed from a 30K, I can vouch for that equation!

I STILL have trouble sitting comfortably!

 

As luck would have it, the exhaust just began rattling at startup. My car has a Tubi. You can definitely tell when the bypass valve opens. At times this evening, it would appear that the valve was not opening. The exhaust was more subdued when full throttle was applied. Will wiring open the bypass valve do away with the rattle. Does my problem sound like the notorius 355 bypass valve. These cars can drive one nuts!
Thanks,
Speeder