| Author |
Message |
Antony R Chapman (Antonio888)
New member
Username: Antonio888
Post Number: 3
Registered: 5-2002
| | Posted on Sunday, May 05, 2002 - 8:54 am: | |
Thanks Peter, I think I'll check out the guides as well. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 2691
Registered: 2-2001
| | Posted on Saturday, May 04, 2002 - 11:43 pm: | |
THANX, |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1835
Registered: 12-2000
| | Posted on Saturday, May 04, 2002 - 11:38 pm: | |
Not that many Magoo: around 46XXX mi. (probably a couple thousand more, as the speedo unit was malfunctioning when I bought the car).
Your guess is as good as mine as to what a typical mileage point is, for guide wear. But they were quite sloppy even for that mileage I had.
I installed OEM guides in my car. I figured if it took this long to wear the guides out and considering my driving frequency, I have many more years of enjoyment out of the car, before I tear into it again (if I'm so lucky...). |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 2689
Registered: 2-2001
| | Posted on Saturday, May 04, 2002 - 11:29 pm: | |
Peter, How many miles were on your car at the time of replacement. Do you think the valve guides may have had more wear than what the mileage showed? |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1833
Registered: 12-2000
| | Posted on Saturday, May 04, 2002 - 11:16 pm: | |
The problem is, most valves can survive this beating and just bend, but the sodium-filled have VERY THIN walls to contain the sodium, so they can't take any beating.
I was very lucky and they bent only.
I have seen one that was broken and there's hardly any material there (O.D. of valve stem is under 8mm. The dia. of the cavity within the stem was around 5mm). |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 2684
Registered: 2-2001
| | Posted on Saturday, May 04, 2002 - 10:29 pm: | |
I had not heard of the valves being defective. As you say Peter, If the guides are worn badly they will allow the valve to cock itself sideways in the guide, strike the piston and bend or eventually break. |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1831
Registered: 12-2000
| | Posted on Saturday, May 04, 2002 - 2:12 pm: | |
These exhaust valves are sodium-filled, this provides cooling for the valve.
I had three bent ones in my engine. This was a result of the worn guides (valve rocked around and got bent by clipping the edge of the piston cut-out). If they rock around enough, they can break...
I replaced them with the Superformance ones. Great price compared to the original valves (huge savings). Very well made (Alloy steel, stellite-welded tips and valve-head seat-edge). |
Antony R Chapman (Antonio888)
New member
Username: Antonio888
Post Number: 1
Registered: 5-2002
| | Posted on Saturday, May 04, 2002 - 10:49 am: | |
This is my first post after reading this great site since Oct. Has helped clarify a lot of my qtns since my purchase of a 1980 308 GTS in Sept '01. Thought I would get more active. I've heard that there is a potential time bomb in the form of defective exhaust valves fitted into the V8 & V12 engines between 1975-80. Apparently they can crack for a number of reasons leading to some nasty engine problems. Anyone heard of this and what's the solution - replace the valves with OEM or go for something aftermarket. I get a number of my 308 parts from Superformance in the UK. They have aftermarket exhaust valves, anyone tried these ? |