I am new to the forum, recently acquiring both a 1991 Land Cruiser and a 1997 Lexus LX450, but this post is about the 1991. I have been searching the forum concerning issues with distributor timing and removal/replacement procedures. I will likely need help with that subject in the near future, but for today I will try and help others who have inquired about the location of the timing inspection window. I have added images that I believe are somewhat self-explanatory; however, for the novice (including myself), locating this window is/was not an easy task.
The first image shows what you will typically encounter (using mine as an example) with air cleaner hoses removed in your search for the elusive timing inspection window. What you are trying to locate behind all that mess, resides between the starter and the engine block, cast into the transmission housing adaptor. It is impossible to see on an aged engine, so I had to get up on a step-stool and reach into the vicinity where the shop manuals show its approximate location. If you are simply looking for an open window in that area, on an unmolested engine, you will not find it. You must get greasy, dirty, and not be afraid of the creepy crawlies or whatever lurks within; feel for it with your bare hands! But still, you will not find the window; what you will find is a very soft black rubber insert/cover that blends in very well with the surrounding area due to layers of grime (see 2nd and 3rd images). Once you have found that soft rubber insert, locate the pull tab and pull it out towards the front of the engine. You will be amazed! The elusive timing inspection window becomes oh so obvious (4th and 5th images). Kind of makes you feel stupid, once found, after spending about an hour with a flashlight, going back and forth between the light and the manual! The rest appears to be relatively easy compared to finding the inspection window. I hope this helps!
The first image shows what you will typically encounter (using mine as an example) with air cleaner hoses removed in your search for the elusive timing inspection window. What you are trying to locate behind all that mess, resides between the starter and the engine block, cast into the transmission housing adaptor. It is impossible to see on an aged engine, so I had to get up on a step-stool and reach into the vicinity where the shop manuals show its approximate location. If you are simply looking for an open window in that area, on an unmolested engine, you will not find it. You must get greasy, dirty, and not be afraid of the creepy crawlies or whatever lurks within; feel for it with your bare hands! But still, you will not find the window; what you will find is a very soft black rubber insert/cover that blends in very well with the surrounding area due to layers of grime (see 2nd and 3rd images). Once you have found that soft rubber insert, locate the pull tab and pull it out towards the front of the engine. You will be amazed! The elusive timing inspection window becomes oh so obvious (4th and 5th images). Kind of makes you feel stupid, once found, after spending about an hour with a flashlight, going back and forth between the light and the manual! The rest appears to be relatively easy compared to finding the inspection window. I hope this helps!