I have a 305 with 126,000 miles that puffs blue smoke when I start it. I just changed it to Mobile 1 synthetic. Would it be a good idea to change the valve seals or wait until the engine change is necessary? I have heard of these engines going 250k?

How involved is the valve repair? Can it be done in the car? Any comments?

Thanks

 

Sounds like your valve guide seals are worn out. Pull the heads and have new seals and a 'valve job' done on the heads.... or replace the heads.

 

The need for a "valve job" has decreased dramatically since the mid-70's due to hardened seats and valves for unleaded fuel.

90% of "smoke at start up" is hardened, cracked valve stem seals. Replace them, which can be done with the heads on the car, and the likelihood of needing any further work is very slim.

I have an '82 305 sitting in the garage with 300,981 miles on it (probably more than that because it also has 15" wheels instead of the stock 14", and the speedo is slow). It made it from Sacramento to Denver without needing to add any oil, did not smoke at start up, and passed the enhanced dyno emissions test with a "fast pass". The only reason it's sitting in the garage and not in the engine bay is the car was purchased for an LS1/T56 swap.

Yes, these engines can last a long time with proper (not even "superior") maintenance.

 

can new seals be put on without taking the engine out?

 

Yea its possible, its the fastest way. Ive only done one "valve seal" job and I removed the heads and did a valve job since I had free access to valve cutting machines/stones. But if you get an adapter to hook up compressed air to the cylinder you can do it that way...Like maybe a leakdown tester would do it plus you can use it in the future for diagnostics. Maybe someone else can chime in with the procedure without removing the heads.

 

I've used a sparkplug with the electrode hollowed out and about 4 psi of compressed air attached to do valve adjustements on a Ducati Desmo valvetrain. I would expect it would work equally well on just about any motor. I'd make sure both valves were closed and the air pressure was applied before compressing the valve springs and removing the retainers.