My IROC has over 220,000+ miles on it and it puffs on the start up every now & then.

I have a 383 stroker motor in the works right now, but I was wondering if switching to a synthetic oil would help prolong engine life or wear & tear?

I curently use Castor oil 20w/50 in the engine. If I switch to a synthetic oil, what wieght would I use then? I dont know much about the synthetic oils so any info would e great.

Thanks

I have a 305 4bbl LG-4 now

Since it is a new engine you're not going to need to use such thick oil because you really shouldn't have any burning after it is broken in. I would use 5w30 or 10w30 mobil 1 synthetic. There have been many arguments about oils, try searching for some.

I assume you're talking about what to use in the LG4 until the 383 is ready to go.

The issues with synthetic in a high-mileage engine are:
Existing deposits from the petroleum oil - the synthetic will likely desolve them, and they'll contaminate the synthetic;
Usage - add-oil between changes will cost you a little more (of course, changes are going to cost you more, too).

The puff of smoke at start-up is probably from your valve guide seals. Replacing them can be done with the heads on the engine if you have access to compressed air. While replacing them, you can clean some of those deposits off of the valve covers, reducing both the contamination and usage problems.

You will reduce wear by using synthetic (a general statement that may not apply to all available brands, certainly not equally). The 20W50 probably isn't necessary, either in petroleum or synthetic versions.

Yes it is when you are trying ot control oil smoking...esp when you only need 9,000 miles out of the engine....I use Super Tech 20w-50......WAL-MART

Point being, if the smoke is only at start-up, the 20W50 isn't going to provide any benefits a 10W40 or 10W30 couldn't. And, being thicker, it will "tend" to obsorb more power, reducing mileage, etc.

It will smoke less with synthetic oil. If you want a 50w oil mobil 1 has 5w-50 available so go for it. I dont change my synthetic oil for 10,000 miles if your car uses it pretty fast you wont need to change it just keep adding.