I had to have my old truck smog tested today. It passed in flying colors. I was planning to change the motor because of a leaking rear main seal. Can anyone tell by these numbers if it might be worth my time to just change the rear main seal and keep the motor? Here are my numbers with a 160 degree t-stat. It is a sbc.

..................... Old truck .....standard
Hydrocarbons(HC)........0.69 ..........4.40
Carbon Monoxide(CO)....12.23 .........48.00
Oxides(NOX) .......... 4.09 ..........7.00

By the numbers is it worth my time to change the rear main seal or is this motor shot? Do these numbers mean anything? Am I too rich?

thanks for your expertise



[ 02-04-2002: Message edited by: flyfast ]

If I'm reading your numbers correcly, your engine is real clean. The numbers, if my memory is right, are in parts per million (PPM) and are listed as maximums. Contact your state vehicle inspection department or DMV for clarification.

As for the rear main seal, depending on the year of manufacture (80's and up) you probably have a one piece seal. In which case the trans and flywheel have to be pulled to fix it. If it's a two peice type, all you have to do is drop the oil pan and rear main bearing cap.

If I remember correctly:
High HC values=poor combustion, too rich, bad spark, low compression.
High NOX= high combustion temps, too lean, too much spark advance.
Dont remember what CO indicates.
That's about all I know you can get from the emmisions values. I think the number of miles, oil consumption, and doing a leakdown test would be a better way to make your decision.
BTW, I just got rid of an 89 chevy with nearly 300K miles on it and it passed emmisions.
Gary

CO looks a little high and I doubt the cat converter is working anymore. The low HC means the engine is well tuned and running evenly. Usually this means that the compression and spark are good. But the high CO can help an older engine run better so the HC might go up if the CO is adjusted down. NOX is low enough but that is also a function of low compression. If you are thinking about the condition of the motor, do a compression test wet and dry and post here-that will tell the story.