1992 350 crate Smoke after switching to synthetic

Do a dry and wet compression check on all cylinders. If wet compression check is much higher than dry you probably have ring issues. But if both checks have about the same psi then it's probably just time to put valve guides seals in.

The synthetic..especially if you used 5W20 or 5W30...sounds like its slipping past piston rings on that side.

hi dandy..Doug if you are not familiar with the difference between a wet and dry compression test here is a really good essay http://www.freeasestudyguides.com/compression-test-injecting-oil.html

I used 10w-30 synthetic just like I did with conventional. From what I understand you can't go back to conventional. Sorry im not the best mechanic I only know so much. Since it's smoking from the driver side exhaust wouldn't that mean that it's coming from the left cylinders? That's where the exhaust is hooked into the manifold on the side it's smoking.

Good evening fordnut

You CAN go back to conventional

And yes to your question...that's correct, probably only one of the cylinders though on left bank. Left is looking at engine from rear, drivers side, standing in front of truck looking at engine it's on your right but it's left bank

So you can go back to conventional? Only reason I believed that was I had heard from other people. What reasons would there be why you couldn't? So do you think I should change it back to conventional?

I am a firm believer in never changing oil types or brands. Every time I have changed I ended up with issues. Only tried different twice and Once blew a motor(slung rod right thru oil pan) and once spun a rod bearing. Both times was within five days of the oil change. Now did it cause my issues. Probably not but its kinda hard to make this old red neck believe that it didn't. I won't try different ever again. Don't care how much better they say it is. If I was in your shoes I would change oil back over to what you was using before.

Okay that's probably what I'll do then. It ran damn good with just catrol in it but I wanted to go longer for oil changed because I drive 80 miles a day to work getting 9 miles a gallon so any expenses gone would help but I'll just change

Agreed. There are no reasons you couldn't switch back. Yes, change it back and change again early..like 1000 miles or less

Thanks guys I'll change it today and see if does it any better. BTW 350 crate motor has less than 15000 on it. Brand new when I put it in shouldn't have any ring problems but it hasn't been babied so it could very well. Thanks guys

From my experience syn s tend to find the smallest flaws in seals, rings and gaskets on older vehicles. Where as conv oil will not. Changing the oil back will not fix the root problem causing the smoking but it might not be noticeable with conv oil.

I use Mobil1 in my Corolla but that's all it's ever had....and USE A QUALITY FILTER! They are not all the same. Wix, Purlator, there are other good ones. this is one case where more expensive is worth every dime

I've always ran Castrol 10w-30 with a wix filter

Well that not old at all. For giggles might want to pull your spark plugs out on that side to see which one or ones is burning the oil.

And 10W40 in my 1976 F250w/ 390..

Wix is one of the best..good choice

Just slung a rod motors locked up.

No you kidding right? The crate motor when been talking about?

Yep. She's locked up.

Damn. I hate that. Have you called your friend yet to tell him how much you appreciate him talking you into changing oil types?

Oooohhh nooooo say it ain't so...

I appreciate it soon much this shit sucks

Whoever flagged that..sorry I seldom use that language and shouldn't have here. My apologies..you know what I mean