Keep cracking heads!
FWIW there are 2 different designs...
1st design 12558081 I believe these are 15mm tall
2nd design 12570326 I believe these are 13mm tall
The 2nd design is what you should have installed from factory.
2 things come to mind, 1 make sure there not damaged from removal.
1. Clean the block register where they sit and verify there is not an old set stuck in the replacement heads... Some times they come off with the head and some guys just pound them in to the head. They must be removed if they are stuck in the head.
2. Clean the threaded holes in the block with a proper chase tool. This is often over looked and is a very important step in achieving the proper torque value.
Other than that, make sure the head is fully seated before you start the tightening process. If you have to pull it down with the bolts, there may be an issue and it could be causing un do stress.
While You checked the deck of the block, did you check straight across, criss cross and so on?
These blocks are almost never 100% perfectly flat. I have on so bad I was called and told to pick up my block and locate a new one for performance use. The core is shifted to one side and that side has a low spot in the center.
It would require cutting the deck alot to fix properly. Then the other side would have to be cut to match. It would also require running a thicker Cometic gasket to achieve proper quinch. The piston is already . 013 out of the hole in the lowest spot, which is almost unheard of on these. There typically in the .005 - .008 range on most iron blocks I have dealt with.
Thread Starter
Teching In
Joined: Nov 2017
Posts: 17
Likes: 0
Ok I changed my plan. I hope it’s my best option. So I was talking to the head shop and they suggested maybe putting some 243 heads on the truck. Said they are a much better casting. I’m sending the new gm Head that I ordered back because when I received it i noticed it was a 706 castech Head. The worst gm head possible. I understand the 243 heads have a larger intake valve and a slightly larger combustion chamber meaning I might lose some compression. But I’m wondering if it will be enough to notice on a stock application? Am I going to lose some hp numbers? Really I just want the truck to run another 150k miles and not have to touch the heads ever again. And no I didn’t want to shave the head down and spend more money on pushrods on this daily driver.
Replace the engine, cheap, easy, simple. Get a yard engine with a 90day warranty and lowish miles or buy a trashed up rot box cheap or pick n pull yard etc. Not worth all this time and hassle imo
