| Author |
Message |
magoo (Magoo)
| | Posted on Tuesday, August 28, 2001 - 10:35 pm: | |
Opps, David you answered my question just before I posted mine. |
magoo (Magoo)
| | Posted on Tuesday, August 28, 2001 - 10:32 pm: | |
Also David, Make sure the carbon buttons in the caps are riding on the rotors. It does sound like you have the wrong rotor. Are they exactly like the old ones? |
David Harris (Dakharris)
| | Posted on Tuesday, August 28, 2001 - 10:26 pm: | |
The rotors are Magneti Marelli Made in Italy with an "R" on them (NOS). No part number on them. They appear to be identical to the old ones. They don't appear to have any protective coating on them. The old rotors are definitely worn as the new ones have more length (distance from plastic to end of rotor where it contacts the distributor). One would think that the new ones would have a more efficient spark than the older, worn ones. Is some other component of the system compensating for the stronger spark? Understand that the car runs fine again with the old rotors. I only changed them as I have an annoying minor surge/miss at low speed and am searching for a cause/solution. |
Steve Magnusson (91tr)
| | Posted on Tuesday, August 28, 2001 - 5:12 pm: | |
David H. -- Do the new and old rotors have the same metal contact width at the end? If not, your power loss could be related to the mechanical phasing between the rotor contact and the outer cap contacts (not a trivial thing to get right with the rather narrow 2-valve 308 rotors). It's also possible that the new rotor length is just not right so the rotor contact -to- outer cap contact distance is too large. Is the rotor PN you're dealing with 124288? |
Herbert Edward Gault (Irfgt)
| | Posted on Tuesday, August 28, 2001 - 4:10 pm: | |
I have seen rotors that would erode and arc through the center of the rotor to the shaft that they attach to. It is quite visable on an ignition scope. |
david schirmer (David)
| | Posted on Tuesday, August 28, 2001 - 2:58 pm: | |
Could the rotors have some sort of film/oil on them that needs to be cleaned off? Just a hypothesis. |
David Harris (Dakharris)
| | Posted on Tuesday, August 28, 2001 - 12:06 pm: | |
O.K. I put two new correct rotors in the old distributors and used emory paper to knock the film of green crud off of the contacts. She fired right up but the car had no power. All 8 cyls. fired, but the car idled at 800 rpm and wouldn't rev past 5000. Throttle response was sluggish. I put the old rotors back in and everything was back to normal. Wires are all firmly connected. Anyone wish to pose a hypothesis? |
Nick Scianna (Nick)
| | Posted on Tuesday, August 28, 2001 - 3:36 am: | |
Hi. Peter and Warren are correct,just check your wires and your plug extenders at the same time to be safe,check the resistance values,check for hairline cracks,that is common.Good luck. Nick Scianna |
'75 308 GT4 (Peter)
| | Posted on Tuesday, August 28, 2001 - 3:14 am: | |
Lightly dress the contacts in the dist. cap with emery cloth and that should be fine. Magoo is right, unless the contacts are pitted, scarred, or arced, they can still be reused. The caps are made out of a Bakelite material and are delicate, so treat them gently and they'll last a long time.
May be a good idea as well to replace the centre carbon button in the cap when changing the rotors. |
magoo (Magoo)
| | Posted on Monday, August 27, 2001 - 11:10 pm: | |
David, In my opinion If the contacts in your caps aren't eaten up by corrision or spark deterioration why should you replace the caps. I would have no problem replacing the rotors seperately. They are not a matched set that has to be replaced together. |
David Harris (Dakharris)
| | Posted on Monday, August 27, 2001 - 11:02 pm: | |
Is it ok to change worn rotors without changing the distributor caps if the caps look to be in good shape but the rotors appear to be worn out? My shade tree mechanic friends are evenly split. What do the Ferrari experts say? By the way, I'm talking about a 308QV engine with what I believe to be original ignition parts (no records of their being changed). Spark plugs changed two days ago, wires changed two years ago. The clock is at 41,500 mi. |