Hi folks, I have a 1983 308QV that has an airpump that will need to be smogged soon (CA-ugh). The pulley that drives the airpump is attached to the camshaft through a coupler (119215) that snapped. I purchased a replacment new coupler and a new retaining pin (100279). The problem I'm having is that the 3mm pin that secures the coupler to the camshaft is a bit too small. It should be a press fit but slides through the end of the cam and the coupler fairly easily. I found out the hard way - the pin worked its way out and gouged the end cap housing on the cam!! Any ideas from you master mechanics on how to solve this problem? Will Loctite work (e.g. 609) or a threaded machine screw with nut? Other types of cotter hardware? How about "peening" or widening the end of the pin? Thanks in advance for any advice you can offer.
you can try using the retaining pin for the 328 it is 4mm instead of the 308's 3mm pin. I do not have the part # handy but I am sure Daniel at Ricambi can hook you up. Wade
I would save "potting" the pin as a last resort and secondary to using the proper size pin. Nothing special about that pin --- so no need to pay "Ferrari parts price" for one. Go to McMaster-Carr, http://www.mcmaster.com/# and you will find nearly any diameter & length of pin you could possibly want. They will cost peanuts, so if you are unsure about the exact size you need, order several different sizes and use the one which gives the best fit ---- ordering a dozen or so pins from M-C will still cost you less than one Ferrari pin from a Ferrari parts supplier
I admit to not knowing how this setup works, but in the years of reading Fchat something jumps into my head here. Is this pin a shear pin to protect the engine in the event of a seized smog pump? There are stories of cars' smog pump seizing, stopping the cam and valves are bent and many tears are shed. Is this pin designed to fail and free the cam drive? If it is, I'd be very careful what I used to replace it! This same sort of system is common on outboard boat motors. If you hit something with the prop like a rock, the pin shears saving the prop and other drive parts from damage. Just a thought about using a McMaster replacement that may or may not apply.
To 308 Nut: Thanks for your comments. A 4mm pin would probably be too big but the aforementioned source for hardware probably has what I need. The pin probably only needs to be .001 to .002 mm bigger to make it work. Brian Harper: Your warning is well taken. Yes, the coupler does have a narrow neck along its shaft that will snap and serves as a safety valve in the event of a frozen air pump which is what happened on at least 2 occasions. This is probably a consequence of not "using" the air pump except every couple of years . The problem is the replacement Ferrari parts don't seem to fit properly even though they were obtained from reliable sources. The coupler is NOS and the pin looks pretty generic. It is probably a matter of tolerances - maybe a couple of hundreth's of a mm would make it work. Thanks again guys for your input!
Yes, it is a shear pin --- McMaster has those as well. Some shear pins are designed with an area of reduced x-section or are notched to act like a "mechanical fuse", if you will. But, the type used on the smog pump pulley is simply made from mild steel with a uniform, smooth profile and of sufficiently small diameter to shear when needed --- so any mild steel pin of the proper size will work in this application Plus, as lem321 states, the primary shear function is taken up by the coupler shaft ----- the pin, in this setup, has a secondary (backup) shear function.
