Timing Chain Slack
 

I have a 1988 Toyota 4runner with a 22r engine. The engine has a maximum of 10,000 miles since it was rebuilt by a local machine shop. The engine started making a loud tapping sound and everyone who heard it said it was my valves needing adjusting so I removed the valve cover and the valves were slightly out of adjustment. I adjusted them to the proper specification but before replacing the valve cover I was looking at everything to be certain it all looked good. While looking down into the engine where the timing chain is I noticed a small bolt about 6" from the top of the engine going into the engine itself. About half of the bolt head had been worn off. The only thing that could cause this is the timing chain. The timing chain has a lot of slack but the chain and all the components were supposed to be replaced when the engine was rebuilt, It does not look like anything is broken and if this is a new chain it should not be stretched this much. I have read online that when the engine is not running some slack is normal but enough slack to allow the chain to wear the head off of this bolt is too much. Does anyone have any idea as what the problem could be? The guy who rebuilt the engine has been in business for over twenty years and has an excellent reputation when it comes to rebuilding engines so I do not think he would have use my old parts during the rebuild but I can not be 100% sure that he did not. The engine runs great, just very noisy from what now appears to be the timing chain flopping around.Any advice will be greatly appreciated. My guess would be to replace the timing chain and guides even though they are suppose to be new ones... ,,???

If he over-torqued the tensioner bolts, it may be binding up.

Take a photo of the bolt you are describing and post it here and send it to the shop. If they goofed up, I would want them to fix it.
They may have been in business a long time but not specifically building Toyota engines.

Thanks for the replies. It may be this weekend before I get to look at it again but i'll try to get a picture of the bolt before then.It would be great if he just over tightened the bolt. The bad thing is they were in business for over 20 years but shortly after rebuilding my engine he closed down due to starting to have trouble with his eyes. Hummm,,,.