Ok I was at a car show this weekend and I was looking at a 64 Ford something (forgot now I didnt buy it). Had a 289 with auto.
Here is the question.

When the engine was started it had some valve noise. Like one of the rockers was loose. SO I asked him about it and he said that he loosened up the rockers because he was running UNLEADED gas. The engine was designed to run on LEADED gas.

Is this correct? I have never heard of this and I have been a Mechanic for the past 5 years.....


I assume just put an additive in it .....


Thanks

Running unleaded in an older motor can cause burnt valves unless the heads have been redone with hardened valves and seats. I ran my 67 Vette on unleaded for years back in the 80's and never had a problem. With that said I think he was blowing smoke, but I could be wrong.

Keith

The guy is :smokin:

Having the rockers loose is going to do nothing but hammer the valve tips into a mushroom shape and loose some lift and duration.

Originally posted by Old Scout
The guy is :smokin:

Having the rockers loose is going to do nothing but hammer the valve tips into a mushroom shape and loose some lift and duration.

boy ask for a oldtimer and get a REAL old one huh!!
:flipoff2:

yes newbie they are right - being loose is only gonna give valves/guides less stress during the "loose stage" and then when they hit the rockers IMO it will make them have more stress..not to mention the above stated problems..

weather the guy is Lyeing or not is a different story he may belive this is what you should do when not running lead..

Weather he has put enough miles on hte motor this way or not to hurt it is what you need to find out if interested in car!

I have just experienced what happens when you run cheap unleaded gas in an older engine that was engineered for leaded fuel. I bought a 72 Commando with an AMC 304 that was hitting on 5 cylinders. Pulled the heads and found three exhaust valves had actually worn down the (non-hardened) valve seats and were sitting nearly 1/4" down from where they should have been. The machine shop called it 'Tuliped' valves. The man said it was due to the cheap unleaded gas. Loosening the rockers is not gonna solve the problem. I can't believe anyone would try that. The only real solution is to have new 'hardened' valve seats put in. Or get later model heads that already have them. In my case, I had the seats replaced with hardened ones, new valves, guides, springs, etc. Total cost was about $600. but now they are just like new... :D:D

Wait a minute now.... I could be :smokin: too, but what he said does make a bit of sense to me. Now if the valves were adjusted soooo loose, (I am assuming a 64 289 had hyd lifters) that they made noise, now that sure cant be good for all the reasons you guys mentioned, plus it would make for some nice flat cam lobes. Now without lead as a lubricant to help keep the exhaust valves cool enough to keep from burning, reducing the seat pressure may help to keep the cool as well. If the valves were just loose enough to to take off a bit of spring pressure, but still keep the lifters in contact with the cam, then it would be the same as putting a lighter spring in, wouldn't it? Less spring pressure means less heat and less wear on the valve seats.

Originally posted by Keith
Wait a minute now.... I could be :smokin: too, but what he said does make a bit of sense to me. Now if the valves were adjusted soooo loose, (I am assuming a 64 289 had hyd lifters) that they made noise, now that sure cant be good for all the reasons you guys mentioned, plus it would make for some nice flat cam lobes. Now without lead as a lubricant to help keep the exhaust valves cool enough to keep from burning, reducing the seat pressure may help to keep the cool as well. If the valves were just loose enough to to take off a bit of spring pressure, but still keep the lifters in contact with the cam, then it would be the same as putting a lighter spring in, wouldn't it? Less spring pressure means less heat and less wear on the valve seats.

The only way to lessen the seat pressure is to use a weaker spring. Seat pressure is how the valve cools it's self. Your valves will burn if they loose there seat pressure! A loose rocker will have no affect on seat pressure!:flipoff2:

But if you loosen the rocker, wont it then raise the spring height, and therefore lower the spring pressure. How does a high spring rate cool the valve? Does it use the head as a heat sink, and requires good contact with the seat to drop the temp?

no because the valve height is determined by the length of the valve when it is closed, the rocker being loose will only open it for less time.
I suppose you could pull any shims from under the springs if applicable but less seat pressure isn't gonna help much, the valves are gonna close hard no matter what as it seats down it will wear into the seat, two solutions, lead leaves a small deposit there to lubricate the action, or seats hard enough to take the contact

Originally posted by Keith
But if you loosen the rocker, wont it then raise the spring height, and therefore lower the spring pressure.

NO. The spring height is set by the spring retainer and keepers, not the rocker. There is a gap (lash) in between the tip of the valve and the rock face. The only time these two touch is when the cam is pushing the valve open.


Originally posted by Keith
How does a high spring rate cool the valve? Does it use the head as a heat sink, and requires good contact with the seat to drop the temp? [/B]
YUP! weak springs will not seat the valve against the seat and it will overheat and burn.

Yeeeup. I am a dumbass. Of course the retainer and keepers set the spring height. Valve stem is only so long, and the spring is already under pressure with the valve closed. Sheeese! Thanks for setting me on the road to recovery!:D

I think he came up with one of the best excuses for an engine that needs new lifters that I have ever heard.

Needless to say I didnt buy the car. I just didnt like the overall picture.....