I steam clean ( real steam,not hot water), then when dry I use a wire brush and get all the loose paint off. When the block is clean and nothing loose, I shoot with PPG MP-170 Epoxy Primer. I then Top Coat with Genuine Cummins Beige. I have never had a peel problem. I just just brush on BBQ Black High Temp on the Exhaust manifold. In about a year the exhaust manifold needs a re-coat.
PPG, MP-170 is a Two Part Catalized primer. My PPG Supplier suggested its use on a bare block prior to top coat. I have 3 engines now shot with PPG, MP-170 and then Top Coat with no effect of heat seen. I also use the PPG, MP-170 as base primer on my trucks. Its tough stuff. This primer has a 3 day top coat window or it must be lightly sanded and more primer shot. Shooting topcoat should not be a problem in a 3 day window. However the window must be adhered to. I only use it on Blocks, heads and all bolt on accessories. Exhaust manifold just gets high temp BBQ Black.
there was a really awesome thread of a guy in Sweden with a suburban, he did painted basically every surface inside and out of the engine, I just wish I could find it, I it was on TDR....not a member tho.....
If you really have a good 2 to 3 hours to kill go to the TDR site and read all 38 pages of "-90 Burb is going to get the C". This man's ingenuity and flawless execution will inspire all, this guy does custom work that is practical not for Bling. Hint to all non-members, if a member makes a comment, the entire thread is viewable to all for 5 days. http://www.turbodieselregister.com/forums/forumdisplay.php?s=&forumid=30 this will get you to the Cummins swap forum then search for the above title
Check frequently, you won't be disappointed. I've been following it for years.
I have use the POR and Eastwood exhaust paint for manifolds. Both do a pretty good job. These have been semishow cars though so did not see a lot of driving.
I use the PPG Epoxy primer on motors then cover with urethatne. Single stage is less trouble. The clear coat works but you have to fight with more painting.
CAUTION! Use a respirator with these paints. This stuff is wicked and will put you in the hospital if not the funeral home.
The ceramic coatings for exhaust are top notch. Had a complete exhaust system for a rod done a few years ago. $700 plus shipping. It was pricy but super to look at.
This coating is typically exhaust only. I see they do valve covers also. This would not work for the block. Earlier it was mentioned to powder coat the engine. Again this isn't very practical, not that it couldn't be done. The block would have to be powder coated before assembly.
I used the epoxy primer and single stage urethane on Harley engines. It did discolor right at the exhaust port where it enters the pipe on the head. The same happened on a Kohler engine in a pulling garden tractor. On a small block chevy you can see a bit of discoloration right at the exhaust header. This paint will deffinately not hold up on exhaust manifolds. For manifolds 1st choice is ceramic coating if you can handle the $$, 2nd choice is one of the exhaust manifold paints (POR 15 or Eastwood), 3rd choice BBQ black spray bomb OR Exhaust paint from your local auto parts store.