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After some driving sessions, I noticed small drops under the car, either oil or antifreeze. I took it to my friend's garage and lifted the car on a hoist — in the end, the picture was clear: there was fine bubbling of antifreeze along the joint between the cylinder head and engine block; nothing blew into the radiator expansion tank. Decided to replace the gasket — found one locally for 600 rubles.

The cylinder head was checked for flatness with a special ruler — it turned out to be perfectly flat.
I installed (tightened according to the manual to 130 newtons) and drove off, but the joy didn't last long — air blew into the radiator expansion tank.
In the end, I put it in the garage for a year without thinking about this problem again. Recently, on Drom.ru, I saw an ad selling a Laurel from 1986 with two engines similar to what I needed (LD28)! The car was not operational; one engine was next to it, and the other had been dismantled for major repairs and completed (new pistons, rings, chain, bearings were installed — all that was left was assembly). The price wasn't high, so I wanted to buy it just for the engines. As a result, I almost missed out on this deal. Additionally, the block condition there is excellent compared to mine.

In the end, I intended to install an overhauled engine but then decided to take the easier route and only replaced the cylinder head.

Upon removing the cylinder head, it turned out that gases were blowing due to insufficient tightening — as I had easily loosened the bolts (125 newtons is too little for used bolts). Nevertheless, I still decided to install another head immediately. Transferred my fuel injector and camshaft from my car since the purchased ones were of unknown condition — the valve was dirty with surface rust — I didn't want to clean it.
This time, I tightened with a higher torque — 15-16 kilograms (previously, I had been tightening at 13 kg). Installed another cylinder head gasket that came with the engine. The old bolts easily held this tightness so if you're using old bolts, tighten them to 15-16 kilograms (as 13 is insufficient and may cause a blown head like mine did. By the way, the gasket was blown on the cylinder head side between the third and fourth cylinders and along almost the entire length towards the manifolds.
After installing an alien cylinder head, pay attention to make sure that the plate between glow plugs does not touch the cooling system block-off plugs (I missed this point and almost burned out wiring — upon turning on the plug heater, smoke immediately appeared; I reacted quickly and nothing was damaged. Bent the plate away from the plug — everything is okay.