| Author | Message | ||
| Larry (Larry)
Junior Member Username: Larry Post Number: 101 Registered: 3-2001 |
"another GT4 F'Chatter"; and it was a 75, w/75k on engine. replaced all 8 as well and a few bent/worn intakes. | ||
| Dave (Dave)
Member Username: Dave Post Number: 572 Registered: 4-2001 |
Jonathan, up through 82... As JRV indicated the design changed with the 4 valve engine. | ||
| Mitchell Le (Yelcab1)
Member Username: Yelcab1 Post Number: 634 Registered: 11-2001 |
Scale of 1 to 10, with 10 the hardest. Say, oil change, difficulty of 1. Full engine rebuild, difficulty of 10. Valve adjust: difficulty scale of say 3. Valves replacement: difficulty of 8 on a Ferrari. and it would take about 4 weeks to do in your garage, if you are lucky with the machine shop. | ||
| Mike Procopio (Pupz308)
Member Username: Pupz308 Post Number: 487 Registered: 10-2002 |
So, say you're going to do a valve adjust. Is this the time to replace the exhaust valves? How much extra effort is involved to do this? | ||
| Jonathan (Birdman)
Junior Member Username: Birdman Post Number: 128 Registered: 6-2003 |
OK, so which engines does this affect? What model years? | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2999 Registered: 12-2000 |
Jay, I had three bent ones in mine, replaced all eight with the ones from Superformance. Another GT4 F'Chatter had one break on him while driving  . He's back on the road again  . | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2182 Registered: 11-2002 |
>>JRV my mechanic said he had dropped a valve once (not mine) and it shattered like glass!<< Jay, exactly...it's actually awe inspiring cool to simply tap the edge of a valve head and see the stem shatter like glass. Creepy, Scary to knowing it was revving like crazy only days before inside a FERRARI engine. { } Verrel, the 4v's don't use sodium valves , everyone (i think) had wised up by the time 4V motors came along. Plus the 4V stems are to thin for sodium. Some claimed back in thedays that Ferrari Manu'd their own sodium valves which was the problem, but the truth is Porsche used ATE sodium with the same embrittlement/snapping results. The idea originally was that due to increased exhaust temps something was needed to cool the valve stems near the transition from head to full diameter point on the stem, and that by filling a portion of the stem this could be achieved. It was, but with one serious side effect, the thinner steel became work hardened (embrittled) right at the thinnest point turning the steel to glass. Todays valves are of different steel and one piece so modern engines no longer use sodium that I know of...at least not Ferrari or Lamborghini. | ||
| Jay Grande (Jay)
Intermediate Member Username: Jay Post Number: 1476 Registered: 10-2001 |
JRV my mechanic said he had dropped a valve once (not mine) and it shattered like glass! | ||
| Verell Boaen (Verell)
Intermediate Member Username: Verell Post Number: 1071 Registered: 5-2001 |
Which 3x8 engines have these failure prone sodium filled valves? I'm particularly interested in the early QV engines since my QV was built in Oct'82. | ||
| Mitchell Le (Yelcab1)
Member Username: Yelcab1 Post Number: 628 Registered: 11-2001 |
I replaced mine with all new exhaust valves at $40 each from Superformance in the UK. Nice valves. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2179 Registered: 11-2002 |
>>If you have a healthy low mileage 1975 motor, do you do a pre-emptive strike and replace the exhaust valves, or wait for the kaboom? << You pull the heads and ditch the sodium valves. I used to show clients a little trick..... When a head would come off..while on the bench open an exhaust valve and with a small wrench "tap" once on the edge of the valve and lo & behold plink the head would fall off . What happens is the valve heads stay on by luck as long as they are seating squarely, but if a small piece of trash or carbon gets between the seat & valve face the tilt snaps the stem...plink. | ||
| Hans E. Hansen (4re_gt4)
Intermediate Member Username: 4re_gt4 Post Number: 1660 Registered: 4-2002 |
But, Jay, the question is what if you have a healthy, running motor still in the car. Do you pull the heads on an engine that is otherwise running fine and not burning oil (VERY expensive) and replace the valves for no other reason than they MIGHT break, or wait? | ||
| Jay Grande (Jay)
Intermediate Member Username: Jay Post Number: 1475 Registered: 10-2001 |
Hans, I'm replacing. The aftermarket valves are about $50 each compared to OEM $500 each(Canadian). Like I said, I'm glad this happened while doing a valve adjustment with the engine out and not while I was driving on the road. That would have been catastrophic! | ||
| Hans E. Hansen (4re_gt4)
Intermediate Member Username: 4re_gt4 Post Number: 1658 Registered: 4-2002 |
If you have a healthy low mileage 1975 motor, do you do a pre-emptive strike and replace the exhaust valves, or wait for the kaboom? For a betting man, this would depend upon the likelihood of failure. If it's not too common, wait. If it's very common, replace. So......??? | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2177 Registered: 11-2002 |
The intakes aren't sodium. Doesn't mean they're not worn out, but the heads don't fall off. | ||
| Jay Grande (Jay)
Intermediate Member Username: Jay Post Number: 1471 Registered: 10-2001 |
Understood, but the previous owner had the engine "rebuilt" (yeah right!) I'm glad I opened it up to make sure. The valves "looked" okay and were within spec. How about the intakes? | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2176 Registered: 11-2002 |
>>Anyone else had this happen?<< Actually it is common on the early motors. Seen it numerous times. The sodium valves sounded like a good idea at the time, of course 25 yrs on your valves is about as long as any valve would last. Just think, 355 valves only last 10K-20K miles and a few years. | ||
| Jay Grande (Jay)
Intermediate Member Username: Jay Post Number: 1469 Registered: 10-2001 |
Well, my GT4 engine was getting back together nicely until Friday... When my mechanic was doing the valve adjustment on the exhaust valves one would not come into spec. even with the shims. Upon closer exam, the valve had broken inside. I was told that this is not an uncommon problem with the exhaust valves in the early 308's due to their "hollow" construction. I've since given the go ahead to buy 8 new aftermarket exhaust valves and have the guides machined. I will take pictures once the heads are removed. Boy am I happy this happened before the engine went in and was started! Anyone else had this happen? How are the intake valves? Same construction? |