Valve Guides or something more?

[aphaynes]

Here's a rookie question
I have blue smoke at startup but not when driving. The 305e really doesn't use much oil. When I do have to add oil I attribute the loss more to the leaking rear main than anything else. So is the blue smoke at startup due to valve guides or something else? If valve guides, where is a good source for those for the 305e?

[LEWISMATKIN]

you have diagnosed correctly. However, the valve guides are cast intragal in the heads. If you don't want to remove the heads and have the guides knurled, you can purchase the "umbrella" type valve stem seals, and install them w/o removing the cylinder heads. You will need an air hold fitting, a valve spring compressor, and a lot of patience. If it isn't using a lot of oil, you might want to postpone this job and drive the truck for a while, it won't hurt the engine to have a little oil on top of the cylinders at start-up. I hope I have been helpful in this matter. As a side note, check the drainage on the cylinder heads to see if the heads are draining good. If oil is remaining puddled up on the cylinder heads, oil will leak down the guides. If this is the case, simply clean the drains on each head and you will have eliminated the greatest cause of the problem.

[TJ's GMC]

If these engines aren't burning some oil you know you don't have any left. They used to say if they weren't burning about 1/2 a quart between oil changes something was wrong.