what is causing smoke on start ups?
TECH Senior Member
Joined: Jun 2016
Posts: 22,288
Likes: 3,615
From: Central Cal.
TECH Addict
Joined: Dec 2017
Posts: 2,153
Likes: 959
I didn't ask if the heads are aluminum; they are; we all know that.
Are they Castech? A particular GM supply plant in Mexico?
https://www.google.com/search?q=castech+706+heads&tbm=isch images
https://www.google.com/search?q=castech+706+heads info
This is an EXTREMELY common problem. In fact one of the photos that will come up in the Image search, is probably MINE. (it usually does... this morning, for me, it's the left-hand-most one on the 5th row, shows a single head bolt with a bunch of coolant-related gunk, and a steam-cleaned strip right below the bolt)
Next most common problem is, not putting sealer on the rocker bolt threads. The intake ones are exposed to the intake port, and oil can wick right straight into the ports. The Permatex/Loctite (same company) "hi-temp automotive thread sealer with Teflon" is my preferred spooge for this.
I'd look into those 2 things before worrying about "shop".
DO NOT run 20W-50 in one of these motors if it's stock. That's just WRONG. Run what's supposed to be there; 5W-30 I think. 10W-30 at the thickest.
Are they Castech? A particular GM supply plant in Mexico?
https://www.google.com/search?q=castech+706+heads&tbm=isch images
https://www.google.com/search?q=castech+706+heads info
This is an EXTREMELY common problem. In fact one of the photos that will come up in the Image search, is probably MINE. (it usually does... this morning, for me, it's the left-hand-most one on the 5th row, shows a single head bolt with a bunch of coolant-related gunk, and a steam-cleaned strip right below the bolt)
Next most common problem is, not putting sealer on the rocker bolt threads. The intake ones are exposed to the intake port, and oil can wick right straight into the ports. The Permatex/Loctite (same company) "hi-temp automotive thread sealer with Teflon" is my preferred spooge for this.
I'd look into those 2 things before worrying about "shop".
DO NOT run 20W-50 in one of these motors if it's stock. That's just WRONG. Run what's supposed to be there; 5W-30 I think. 10W-30 at the thickest.
11 Second Club
Joined: Dec 2016
Posts: 665
Likes: 5
Sometimes, ported heads will leak thru the rocker bolt depending on how much the roof of the intake runner in the head is ported, I used almost 2 quarts in 400 miles. I finally put thread sealer on the rocker bolts and my issue stopped. My plugs told the tale.