dyno diagnostics

[Paul Tesone]

 Some months ago , I had the engine of my 1957 Biarritz completely rebuilt . After less than 500 easy going miles and never exceeding 65 mph , puffs of white smoke could be seen upon starting the car. The smoking would stop after the initial puff . The smoke did not occur on every start up , but became more frequent until it finally did occur every time the car was started and the puffs became clouds which persisted as long as the car was running . A second rebuild was completed last week . I was told that the valves were "bad" and that the cause of the problem could have resulted from the engine overheating which occured as a result of the heat riser getting stuck in a closed position or an improper break-in of the newly rebuilt engine .The truth is that neither the person who reassembled the engine after getting it back from the first machine shop nor the second machine shop can or wants to say for sure what happened . Now , the new machine shop is advising that I have the dual quad carburetor jets "adjusted" on a dyno machine . The reason I have been given is that the new gas often runs lean , and this will cause the engine to run hot. However , during the few miles I put on the car before the problem became evident , the car never overheated and performance didn't seem to be affected when smoking .  Now , I don't know much about engine mechanics or the new gas ,; but it seems to me that if the new gas and carburetor adjustments were really an issue , these dyno machines would be very busy testing our old cars . Any thoughts as to the validity of going thru the expense of a dyno evaluation will be appreciated . Thanks , Paul Tesone ..CLC # 6876

[Scot Minesinger]

Bad carburetor adjustments are unlikely to cause harm or overheating of the engine, especially since you were monitoring that and probably were careful to break it in properly.  Probably the first re-build was a poor valve job, replacement rocker arms are very poor quality for example.  Now they are really running scared and taking more precautions. 

Let the buyer beware unfortunately.  It seems to me that in general many service/parts entities that work on our classics do not provide a degree of durability, and that the work/parts are good for about 500 to 1,000 miles which is a lifetime for many classics (trailered?).  I drive my 1970 Cadillac 5k miles per year, and have found that durability is a huge problem and have resorted to performing all repairs, oil changes and etc myself out of necessity (rather write a check, but no one is deserving of the payment that I have found yet).

[Wayne Womble 12210]

Someone didnt install the valve seals correctly. The gas didnt cause the failure. Heat didnt cause the failure.

The little puffs you saw at start up was oil sucked into the valve stem.  As the seal got worse more and more oil is burned and the smoke becomes constant.

[Dave Shepherd]

Some months ago , I had the engine of my 1957 Biarritz completely rebuilt . After less than 500 easy going miles and never exceeding 65 mph , puffs of white smoke could be seen upon starting the car. The smoking would stop after the initial puff . The smoke did not occur on every start up , but became more frequent until it finally did occur every time the car was started and the puffs became clouds which persisted as long as the car was running . A second rebuild was completed last week . I was told that the valves were "bad" and that the cause of the problem could have resulted from the engine overheating which occured as a result of the heat riser getting stuck in a closed position or an improper break-in of the newly rebuilt engine .The truth is that neither the person who reassembled the engine after getting it back from the first machine shop nor the second machine shop can or wants to say for sure what happened . Now , the new machine shop is advising that I have the dual quad carburetor jets "adjusted" on a dyno machine . The reason I have been given is that the new gas often runs lean , and this will cause the engine to run hot. However , during the few miles I put on the car before the problem became evident , the car never overheated and performance didn't seem to be affected when smoking .  Now , I don't know much about engine mechanics or the new gas ,; but it seems to me that if the new gas and carburetor adjustments were really an issue , these dyno machines would be very busy testing our old cars . Any thoughts as to the validity of going thru the expense of a dyno evaluation will be appreciated . Thanks , Paul Tesone ..CLC # 6876

Paul, what a pile of false science mumbo jumbo, nothing stated by anyone who touched your engine is technically correct.  if the smoke was oil, which would have been blue this is always an issue with bad valve seals, rings or a leaking intake manifold on some engines.  Whiteish vapor is coolant entering the cylinders, so you still have no definitive diagnosis as to what the root cause is. I hope you didn't pay 2x for this headache.

["Cadillac Kid" Greg Surfas 15364]

Paul,
I second Dave's comments.  There is some validity in what Scott says regarding "cheapie" parts, however it is usually evidenced by decreased lifespans.
Your description of the "puffs of white smoke" is not a definitive diagnosis warrenting engine tear down without further clues.  What did the first machine shop say?
IF the motor was machined, clearanced and assembled correctly, and if the quality of the parts (specifically pistons and rings) is up to par (i.e. major manufacturer, not off-brand "bargains"). you should be able to break the motor in in a hundred miles or less.  Ask the machine shop what proceedures they suggest for cam and ring break in, and follow them.  Even though I too feel a "Dyno" carb "setting" is over the top, you might find a service agency that has an Air Fuel Meter to check your mixture just as "insurance" against another claim from your machine shop.
As Dave's note, I hope you have enough warrantee from your mechanics not to have to be paying again.
Greg Surfas

[dplotkin]

  Even though I too feel a "Dyno" carb "setting" is over the top.

The ideal way to break in a fresh motor is to do so on a dyno and if not a dyno, a test stand. The first start of a fresh engine is a critical point in which severe damage can be done to cylinder walls and other parts if a first start and cam break-in are failures. An engine rebuilder is correct in wanting a carburetor to be in good operating condition and its adjustments as close to optimum as possible. You want a fresh engine to "light off" and run as quickly as possible, you want cranking to be at a minimum. Too rich and the cylinder walls could be washed down. Too lean could burn a valve. Over heating a fresh motor is dangerous as the motor is already tight and generating more heat than it will once run in. Extra heat is not helpful.

I realize that many an engine is rebuilt and re-installed and broken in on the road and this works most of the time. Yet given the monitary committment to the rebuild why would you scoff at a run-in and carb setup on a dyno or test stand? It's the best way to do it, and for many of the better engine builders the only way they will do it and warrantee the job.

It is not at all over the top. It is best practice.

Dan

[Paul Tesone]

Thank you all for your responses . Let me say that the smoke was definately white , not blue ; and my restorer did inform me that that was an indication that coolant was getting into the cylinders . I have been using this partcular restorer for a number of years . In addition to a complete frame up restoration on my 57 , he has done a similar complete restoration on my 47 as well as  mechanical  and cosmetic restorations ( except for engine rebuilds ) on my 37,55 & 61 . So I do have a history with this person and I really do feel confident in his abilities . I think too many people were involved in this 57 engine rebuild . Years before I started working with my present restorer , a different person did some "engine work" on this car . He turned out to be an incompetent thief and I was lucky to get my car back before he skipped town and disappeared . When my present guy started the frame up restoration , I told him to have the engine rebuilt . He sent it to a machine shop , had the shop do what was needed  and reassembled the engine himself . I have to assume that whatever the thief had done a few years earlier was redone either by the machine shop or my guy . Between the time that my engine was rebuilt and the time that a problem became apparent , my restorer had problems with two other engines ( one was another Biarritz ) rebuilt by this same machine shop . At that point he refused to deal with that shop again and sent my engine to another shop . So , yes , I am paying twice . I purchased american made valves from Egge and the machine shop charged me $2265 for the new rebuild . This time my restorer had the machine shop reassemble the engine . I'm sure his feeling was that he wanted the shop to take full responsibilty for the proper functioning of the engine . I don't know if my guy plans to charge me for removing and reinstalling the engine . I don't know why the machine shop didn't dyno test or dyno break-in the engine before returning it to my restorer . I would have gladly paid for the service if it were necessary . I just thought it would be a good idea to get the readers opinion about this dyno test .I'll talk to my guy about a dyno break-in as suggested by Dan .Then we'll see how the new rebuild performs . I don't like paying the extra money for a second rebuild , but if the problem has been corrected , I can live with the added expense . What still worries me is that ,other than telling me that the valves were "bad" , no one has given me what I consider a satisfactory explanation of why the valves were or went bad . We will see what happens . Thanks to all for your suggestions and advice . ...Paul Tesone CLC # 6876