F355 Project Restoration: 1995 F355 Berlinetta - Page 30 - Ferrari Life
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post #581 of 760 Old 06-15-2015, 06:10 PM Thread Starter
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Dave, sorry but I must disagree in one respect. From my memory the normal clearance is up to .004 (again, IIRC)

Even the .001 clearance I measured can be felt with the valve right off the seat. To not feel movement the fit would need to be .0001-.0002. And that is not practical or needed.

The .015 you mention is wild and scary - I can't wait to check my bank 1.

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post #582 of 760 Old 06-15-2015, 06:47 PM
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Dave,
Not many of us has had the opportunity to see inside a Ferrari engine. And even fewer want to see the inside of one they own. ;>) Thanks for the continuing education.
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post #583 of 760 Old 06-15-2015, 06:52 PM Thread Starter
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Hi Richard,

I'm on a journey to observe, study and learn. I'm sharing all I can.

While sometimes my views are different, I still greatly respect and appreciate the help from guys like David who graciously share many years of experience.
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post #584 of 760 Old 06-15-2015, 07:53 PM
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Keep Up the great work my friend. Looking very very good so far. I know from doing my own engine out and documenting it, mostly for my own purposes, that all this documentation takes a great deal more time so i want to make sure everyone on here understands and appreciates what you r doing for us.
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post #585 of 760 Old 06-16-2015, 02:53 AM
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We do.

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post #586 of 760 Old 06-16-2015, 03:46 AM
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Dave, sorry but I must disagree in one respect. From my memory the normal clearance is up to .004 (again, IIRC)
That may very well be true. Ferrari refers to that particular spec. as "the serviceable limit.." I guess if you were building a lawn mower, that would probably be OK. As I know that not to be your goal, I would defer to what's been tried and proven on a "near" race motors; ideally .0012" plus/minus. The looser the guide, the faster the valve seat/valve sealing area wears which ultimately results in higher leak down figures. I have all my valve guides made undersized on the i.d. to the point where the valve will just barely pass, then precision ream/finish to size.

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Even the .001 clearance I measured can be felt with the valve right off the seat. To not feel movement the fit would need to be .0001-.0002. And that is not practical or needed.
To perceive motion versus rattling is the message I was trying to convey. Keep in mind that I've been at this particular rodeo several hundred times. The WSM is a guide, nothing more...and has many "oversights" carried through the decades. Think about it for a moment. Does 0.004" make any sense on such a short guide with a 6mm valve stem in an engine the revs to 8500 rpm?

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post #587 of 760 Old 06-16-2015, 03:48 AM
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Fresh guides with very sloppy machine work...
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post #588 of 760 Old 06-16-2015, 03:50 AM
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Valve guide problem imagined? Only 15K miles on this one...I used my precision yard stick to measure valve guide clearances in this one. LOL!
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post #589 of 760 Old 06-16-2015, 04:11 AM Thread Starter
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Dave, I was not suggesting .004" of clearance would be acceptable to me - it's not.

What I'm stating, as you mentioned, that even .001" of clearance will still allow movement.

Not sure I would want a fit any tighter than .0005". I've been guilty in machine design to over tolerance stuff and too tight can be bad just as too loose.

And of course you have been at this rodeo far more times than I. I'm not saying guide problems are not real, I'm saying I feel they are often mis diagnosed and guides are replaced when not needed.

.001" of clearance absolutely indicates no guide wear (or extremely minimal)

Keep in mind, while you are a detailed guy, and a guy with integrity, that does not represent the pool of shops. I'm sure you would agree that some shops might like the revenue from guide replacement, needed or not.

My 95 is an example of a car not well cared for that may have more miles than the OD states. If my bank 1 clearance is .001", it will be clear that my poor leakdown is a result of carbon buildup.

Too rich of fuel mixture? I'm kinda guessing that.

Last edited by dave rocks; 06-16-2015 at 06:04 AM. Reason: spelling (again)
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post #590 of 760 Old 06-16-2015, 05:59 AM Thread Starter
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For anyone interested, here is a short video illustrating the side-to-side play of a valve with .001" guide clearance when just cracked open (enough for me to grab with my fingers)

https://www.youtube.com/watch?v=2f77G_iRUjM
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post #591 of 760 Old 06-16-2015, 06:00 AM Thread Starter
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Valve guide problem imagined? Only 15K miles on this one...I used my precision yard stick to measure valve guide clearances in this one. LOL!
Is this a 355 in that picture, David?
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post #592 of 760 Old 06-16-2015, 12:55 PM
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456M "crop duster" edition

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post #593 of 760 Old 06-16-2015, 01:36 PM Thread Starter
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Quote:
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456M "crop duster" edition
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post #594 of 760 Old 06-16-2015, 03:52 PM Thread Starter
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Ok so the suspense was killing me. My bank one had the lowest compression and highest leak rate and I could feel air coming out the exhaust valves. Cylinder 4 had a 65% leak rate at 40 PSI input.

I've measured both exhaust guides tonight and both measure .236" with .236+ gage pins. .237" will only enter the guides .125" or so. Both valves measured .2348" indicating .0012" clearance.

That said, it seems clear to me my car's issues are not valve guides and valve guide premature wear. I've suspected this all along as I've suspected in other cars that folks passed on prior when one or two cylinders has lower compression and valve leak, especially when the car had been sitting. Other techs had indicated corrosion or carbon build up on seats.

See this brief video. I made this one handed so pardon the sloppy nature.

http://youtu.be/oY0jqb8Ld-4
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post #595 of 760 Old 06-16-2015, 05:28 PM
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Ok so the suspense was killing me. My bank one had the lowest compression and highest leak rate and I could feel air coming out the exhaust valves. Cylinder 4 had a 65% leak rate at 40 PSI input.

I've measured both exhaust guides tonight and both measure .236" with .236+ gage pins. .237" will only enter the guides .125" or so. Both valves measured .2348" indicating .0012" clearance.

That said, it seems clear to me my car's issues are not valve guides and valve guide premature wear. I've suspected this all along as I've suspected in other cars that folks passed on prior when one or two cylinders has lower compression and valve leak, especially when the car had been sitting. Other techs had indicated corrosion or carbon build up on seats.

See this brief video. I made this one handed so pardon the sloppy nature.

http://youtu.be/oY0jqb8Ld-4


There is way more of that then you think going on !!!!

We finished a thingy last week at Leno's garage where a new motor was torn down after a cross country test.
Amazing how much buildup on the valves. seen it first hand and spoke to all the engineers and drivers.

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post #596 of 760 Old 06-16-2015, 05:35 PM Thread Starter
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post #597 of 760 Old 06-17-2015, 07:27 AM Thread Starter
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I put one exhaust valve in our ultrasonic cleaner in attempt to remove the carbon. I did remove some but not nearly enough.

These photos were taken under a microscope and you can see how pitted and corroded the valve seat contact surface is.
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post #598 of 760 Old 06-17-2015, 08:14 AM
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The fresh carbon will seal that up in 2 weeks

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post #599 of 760 Old 06-17-2015, 08:49 AM Thread Starter
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The fresh carbon will seal that up in 2 weeks

LOL.

I'll post another photo later. It's hard to see but after the seat angle going down the valve where it protrudes into the combustion chamber, an edge of build up / rust has formed. That clearly is part of the poor seating of the valve, hence the leak.
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post #600 of 760 Old 06-17-2015, 01:07 PM
 
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Love the videos Dave...let us pitch in and buy you a tripod lol...great stuff! I have a quick question though. On my car is there any way to reduce the amount of carbon build up without tearing it down? There are products that claim to help but not sure they are right for a 355 engine.
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