well, ive been running synthetic since I got my Z a couple years ago b/c i always pushed that car pretty hard.

Anyway, i recently did a head swap along with a bunch of other mods and blew up the stock bottom end.

I dont want to run synthetic anymore and dont have to as far as the NEW bottom end goes, but the heads have already seen synthetic for about 3,000 miles.

Would running regular motor oil be an issue with valve guide seals, etc etc in the heads? Should i replace them(seals) or just run 'em as they are?

They are Vortec heads BTW
I dont want any futur problems due to the change over. I know synthetic softens everything up pretty significanlty compared to regular....

THOUGHTS!?!?!

 

Just go straight to dino juice. You don't need to change any seals.

 

you wouldn't want synthetic in a new engine for the break in, but after that synthetic would be vastly superior to conventional oil. it'd be a step backwards to not continue running synthetic. there is no danger to any parts switching from one to the other or even mixing oil types.

 

i have heard to not break an engine in on syntheic but what about the LS1 cars...they had synthetic right out of the box did they not? BMW Mercedes and several others use synthetic during break in..what make other engines different ...what gives ? why can't you run synthetic in a brand new engine?

 

How long is the break in period for an engine? 500 miles??

 

roller cam engines can run synthetic, if you have a flat cam break it in with dino. i break all mine in on 30w dino.

 

Wouldn't breaking in a roller block with synthetic take longer than breaking it in with dino juice?

 

For over a decade, the factories have been doing a very good job with their machining and ring technology, along with such things as roller follower cams, so the "break-in" isn't as critical as it was in days of yore. But, with a rebuilt, you're typically back to old-school.

From http://www.gmgoodwrench.com/crate_eng/startup.shtml :

Start-up instructions:
1. Always put safety first. If your car is on the ground, be sure the emergency brake is set, the wheels are chocked, and the transmission cannot fall into gear.
2. Be sure to check the engine's oil level and prime the oil system.
3. Run the engine between 2,000 and 2,500 RPMs, with no-load on the engine for the first 30 minutes.
4. Adjust the distributor timing roughly by hand for a quick start-up and the smoothest idle possible.
5. Adjust the carburetor settings, if necessary.
6. After the engine has been running for 30 minutes, set the ignition timing (see install ignition section for timing specifications).
7. Drive the vehicle with varying speeds and loads on the engine for the first 30 miles. Be sure not to use a lot of throttle or high RPMs.
8. Run five or six medium-throttle accelerations to about 5,000 RPMs (55 to 60 MPH), then let off in gear and coast back down to 20 MPH.
9. Run a couple hard-throttle accelerations up to about 5000 RPMs (55 to 60 MPH), then let off in gear and coast back down to 20 MPH.
10. Change the oil and filter with 10W30SG oil and PF1218 ACDelco oil filter (PN 251605610).
11. Drive the next 500 miles normally, without high RPMs (below 5,000 RPM), hard use, or extended periods of high loading.
12. Change the oil and oil filter again.
13. Your engine is now ready for many happy cruising miles.

With roller cam, you can eliminate the cam run-in part. With a rebuilt engine, you can change to synthetic at Step 12.

 

i started out with Kendol 50wt dino, with the freash engine, and im still running it, never had a problem and i change it every 2.5 months. :lala: