Valve Guides

For the OP, it would certainly be of interest to many here if you could find out if you had bronze or steel guides, maybe even get some of the old ones and post some pics of them as well.

ARe they going to be doing any other valve work/machining as well or just guide replacement?

 

I just finished reading an older thread in which Brian was discussing the relative merits of bronze/copper guides vis a vis heat transfer for the tiny valve stems.

It sounds to me like it is a real trade off on building it to the balls strength and wear wise vs. other functional concerns, i.e heat.

 

If you get them out, send me a PM if you'll spare one. I'll reverse engineer the metallurgy as I did in the past for a whole range of Ferrari valve guides. In summary the 355 bronze guide was the best they used to that date, but the very high speeds and temperatures coupled with the tiny valve stems (sharp) caused failure in some % of guides. The steel doesn't soften at high temps like bronze does so it lasts much longer. One reason I was only looking for a '99

 

I'm in this boat also. I bought mine from Nick Cartwright - who said to me the car had a couple low compression numbers.

So as part of the price and preperation he sent off the heads to have the valve guides replaced. I'll be finally picking her up next week. I've heard some talk of upgrading the valve guides to non brass items?

1995 with 25,000 miles

 

Mine were done at 19.6k

 

I certainly would not pull the heads and replace the guides w/o doing the seats and valves. The seat are ground to be aligned with the guides. Then the valves need to be ground to match the seats.

Here is a vid of grinding seats with some nice machinery.

[ame=http://www.youtube.com/watch?v=4Q26dwembSw]Cutting and Grinding Valve Seats - YouTube[/ame]

 

Nice video John but the seats are not ground here, they are cut. Grinding is done with abrasive wheels, not cutters.

Many ways to skin a cat. This could be done on a bridgeport mill without a guide rod, one could indicate the valve guide center to then cut the seat.

 

Also, the 355 head has the values at multiple angles, and a bridgeport can be set to handle those angles - it would be time consuming to 40 times though...
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And, it looks like they have a portable grinder that can be used by piloting off the ID of the guide - I wonder how well this works?
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Here's another vid from Horse Power TV

Budget Cylinder Head Refresh | HorsePower | PowerBlockTV.com - Video

Just posting for an example of what needs to be down. Guides installed, seats cut or ground to properly align and angle, valves ground, and finally lapped in the seats. These guys cheap out and install liners, but it's all basically the same after than.

Also note that the tolerances on the valve stem should be checked for taper which is why it's a good idea the replace the valves too. I was lucky that the tech who did my car, even thought he was working for the selling dealer, insisted that all the valves be replaced too.

 

These work good used on my motorcycles in years past. The head picture looks a lot like my old Yamaha 750 owo1 superbike head.

 

Careful. You're going against the religion of '95.
Prepare to be shot down...

 

Thanks for the vid! Any idea how much it would cost to have machine shop do the heads (just the heads, not including engine and heads removal/installation)? And is that something most local machine shops can do?

If valve guides fail due to being made from soft metal, wouldn't that actually keep the valve stems from wearing out?

 

Hey at least when it's done you will have a very tight 355 and you won't have to wonder 'when is it going to happen', because it is inevitable.

 

Greetings,

New to this forum and have my eye on a F355. The car currently has just over 21000 with the major engine out service done Dec. 2013. I have all the detailed service records from the independent shop that the work. Today the same shop did a compression test and all cylinders are between 210-215 PSI. Headers are some what of a issue but a bigger concern is the state of the valve guides. There seems to be reams of conflicting information on this subject. Some suggest a leak down test but since this done at TDC I fail to understand how this will indicate anything about the condition of the guides. Short of removing the cam covers, cams and valve seals to physically inspect the guides is there any method to determine valve guide condition. Excessive oil consumption would be a indicator but is there any other method? I've read conflicting articles stating that even the engine number may not actually be a good indicator of what type of guide was originally installed.

Thanks,
Bill

 

The warranty ran out on these cars over a decade ago, so there are no guarantees. I don't think there is a way to tell other than tearing down the engine, but why are you concerned? If it is because you are anal about your potential baby, that I understand But if having to replace the guides puts you over the edge, maybe it's best to pass on it.

 

I understand this is your first post but this has been discussed ad naseum. A search will turn up enough reading material on the subject to keep you busy until you are too old to drive.

A compression and leak down test will in fact tell you how well the valve guides are working now but they have been known to go from not being symptomatic to symptomatic in a short span of mileage. It is due to the very small valves and stems. The small sizes reduce their tolerance for misalignment with the seats and is also why a better than average machine shop is strongly advised. Oil usage is an extremely unreliable indicator of anything on a dry sump car. The scavenge pumps create such a vacuum in the system that it changes dramatically some of the classic oil loss symptoms.

I strongly suggest that if these questions were not able to be answered by your mechanic that you need another one.


As for the same shop that has serviced the car doing a PPI, that is an extreme conflict of interest and I refuse such requests.

 

I had a major done at 39k and I have 40200 on it now 8mos ago). "while he was in there" we retooled the heads and replaced the valve guides. Very happy and it will be a very nice car for the next owner when I list it.

 

Take the time, leak test the thing. 355 engines have very tight piston to wall clearances so don't sweat trying to leak it while it's hot as it's not really going to be different with this particular engine. Most leakage will be through the valves due to excessive wear. These things are set up with some .0005 valve stem to guide clearance as the stems are just that small, and that x40 is no small task. Wear in the .003+ range will make itself known in a leak test as the valve face will have beaten itself into no particular mounting area on the seat thus causing leakage by way of the valves. It's my understanding the exhaust valves are the primary culprit, but replace them all of course.

 

Thanks, the information concerning the tight the valve stem clearance due to the five valve head and the effect that wear has on the valve seating properly is the information I was looking for. Does this ever show itself as low compression or is that really the extreme case with obvious oil consumption issues such a exhaust smoke?

 

Compression tests often show up fine even with bad guides. If you're going to get into a 355 and the guides have never been done and you plan on driving the thing and owning it for a while, prepare yourself accordingly taking into consideration having the valve/guides replaced eventually, as I understand all of them eventually need them done regardless albeit the much later cars seem to have a somewhat longer life than the earlier engines. For this, factor in another $5-6k while the engine out major service is being done. Check the exhaust manifolds too, if they haven't been done then factor in another $3-4k.

 

The warranty ran out on these cars over a decade ago, so there are no guarantees. I don't think there is a way to tell other than tearing down the engine, but why are you concerned? If it is because you are anal about your potential baby, that I understand But if having to replace the guides puts you over the edge, maybe it's best to pass on it.

 

Thanks once again. Aware of the exhaust header problems but at least you can inspect those without a engine tear down. I think every one I've inquired about has either had repairs made to the OEM ones or they have been replaced with aftermarket. This appears to be a certainty with this model.

As a side note, one seller stated that the guides had been "inspected" using a bore scope. Looking at a cutaway of the engine it looks like the guides could be seen if the the intake and/or exhaust manifolds had been removed but not sure exactly what this would tell you. I haven't seen that procedure mentioned any where in the volumes written on the subject either, Wondering if anyone has heard of this?