Time for a 355 Bypass Valve DYI Update

I thought somebody had taken an old one apart and machined a brass bushing to fix it at some point - seems like that would be the way to go.

 

I have a refurbished OEM unit in my car now. Has been fine so far but only around 3k miles on it so far.

Apparently it should never rattle again with the way it was rebuilt but only time will tell.

 

+1 would like to know where you had it rebuilt?
first time I hear of a bypass being rebuild.

 

Mines making a racket and would love a cost effective solution too.

 

Ebay ones will not open, they need much more vacuum and some machining to fit

 

It was posted in the forums, maybe you have the patience to endure the torture that is fchat search to find it? If nobody chimes in I might take a stab at it tomorrow.

 

i think this is the one.. to modify the cheap ebay valve..
http://www.ferrarichat.com/forum/348-355-sponsored-bradan/439181-%24139-new-aftermarket-bypass-valve.html

but I am more curious about rebuilding the oem valve..
where, who does it, how much $$..?

 

Thats the one I thought I had working but did not open all the way
Very intermittent at best. Car does not pull enough vacuum volume to open it correctly
This valve seems more of a hook it up to a vacuum switch to turn it on or off, not for dampening use like the 355 needs

 

i dont know if this is what you are looking for. seems to be a simple diy. good luck

http://www.ferrarichat.com/forum/348-355-sponsored-bradan/179962-possible-fix-noisy-rattling-355-exhaust-valve.html

 

Responding to TrojanFan I rebuilt to bypass valve on my 1998 F355. Let me start with my thoughts on the root cause of the rattle, where there are two major factors, the amount of play in the valve spindle, and the ability of the vacuum/spring actuator to hold the valve firmly in the fully open or closed position. If the actuator is working properly and correctly adjusted, the load in the fully open and closed positions will to some extent compensate for excessive spindle play.

On my valve the spindle was supported by self aligning ceramic bearings/bushings that mate with a hemispherical surface on the valve body and are held in place with coil springs under the end caps. There is no control of end play except for the butterfly disc contacting the body, where some wear was apparent. The bearing at the actuator end had cracked in three places resulting in excessive shaft play. At the free end there was some shaft wear with a total clearance of about 8 thou. Since I could not find replacement ceramic bearings I made stainless substitutes. I’m not very happy with this from a long term wear perspective and bronze may be a better option. As noted on another bypass valve thread, bearing clearance is hard to gauge due to relative thermal expansion of the various components. I went with 6 thou total clearance as I did not want to risk any binding.

The only other issue with the repair process is that the screws on the actuator bracket and the butterfly disk are tack welded in place. I’m not really sure that I have a long term solution as I only have about 1500 miles on the repair.

 

unaware of any rebuild of the valve with success. Its basically a cappy valve and away you go. simple as that once you realize the rebuild doesnt exist... Plus new they are pretty good price.

 

You don't have much to lose...

 

Speaking of aftermarket valves that may not open....is there any concern for damage to the engine from a bypass valve that was stuck in the closed position? Obviously the exhaust flow will not be as efficient so horsepower may be down a touch, but could a closed valve cause any other problems?

 

Yes. Get a Capristo. It fails in the open position,so it doesn't fry things!!

 

I believe mine is frozen and not working. I am going to take it off and see what it looks like. I know a 70 + guy who is a carburetor specialist and has re shafted all types of carbs and has some great skills. Depending on what I can do or what needs to be done, if anything can be done I might let him look at it. I might also look at trying one from eBay that open at a low vacuum pull. I think it was 2 to 5 1/2 psi vacuum pull, which I haven't looked up in the wsm, but believe in another thread that was about where it opened. $139 is worth the effort.

 

Please correct me if I'm wrong but the issue comes from the muffler, not the bypass? I was reading on Capristo's site but kind of skimmed through it.

From what I understood, the way the factory mufflers are designed, the gasses from both the bypass and the regular passage mix. Thus, if the bypass valve gets stuck (whether the bypass is stock or Capristo), you'll have a back pressure issue.

However, the Capristo exhaust fixes this by having the exhaust gasses completely separate. Am I off?

 

Capristo's twin sound exhaust removes the single bypass and implements a setup like the 360 with twin by pass and a different bypass path to remove what they believe is a vacuum which causes the exhaust gases to revert towards the cats and headers adding more heat and eventually burning through the headers. This exhaust also removes the F1 scream. Its different from the Capristo 1,2 and 3.

 

If the carburetor guy decides to re-shaft, make sure he is aware of the operating temperatures of the by-pass valve.

 

I took mine off yesterday and it wasn't even connected properly. The vacuum actuator rod was not attached . I tested the vacuum actuator and it worked perfectly FYI starting movement with approximately 3-5 lbs vacuum . I was using a brake bleeder so not very accurate . I am going to hook up a vacuum Guage in line so that I can get a more precise reading. I have measured the existing stock bypass valve also. The shaft is stiff but not frozen, so I don't know if it can be saved . Maybe I can use my vacuum actuator with one of the aftermarket by pass valves if they Don,t open at the same vacuum . Just thinking out loud . Will report back in on progress . Mark

 

Took it to my carb guy this morning and after a careful study of it, he saw that the shaft was bent and caused the binding. He says it is working and I am stoked, but until I get it and test it to see how much vacuum will open it am how smoothly it operates I am holding my breath. I am still ordering the by pass valve from eBay as a potential back up or to see if it will work to possibly help out others with the same issue.