Timing Chain stretched - needing replacement?

  • Hi all -


    This may have been addressed before so please bear with me for the long post, I could not find the same issue in a previous thread that had a resolution. :)


    I had to replace my oil pan last Spring and when I was at it, I had a look at my timing chain from below. It looked pretty sloppy with a lot of slack on the fuel pump side. I was surprised seeing this, because about 25K miles ago, I had a local restoration shop replace it because it had more than 1/2" deflection reaching through the fuel pump mounting boss. Shop manual said that is the limit for deflection of the chain.


    I didn't know as much as I do now and had asked the shop to install a double roller timing chain set. They called me and told me it was not possible because of the hatchet counterweight requiring a narrower crank sprocket. They said they would have to install set with a "regular width" chain. So, that's what they said they did. I saw the hatchet weight there when I changed out my oil pan so I presumed they did what they say they did. The restoration shop no longer exists of course.


    Now I'm wondering, would the chain have stretched that much after only 25K miles? Yes, I get on it once in awhile, but not that often. I'm wondering now if they even did the job they said they did. I took them at their word and never checked.


    I've attached a snap of my timing marks and pointer. The space between 12 BTDC and where the pointer is (at about 4 BTDC) is how much I can rotate the crank before the distributor rotor begins to move. I understand the limit should be about 6 degrees whereas mine appears to be 8 degrees. That seems to also confirm that I should change my chain. I also included a snap of the front crank area showing the chain and hatchet counterweight although you can't see the slack in my chain from the angle of the picture.


    What I'm wondering, if I can figure out what chain to buy that is, can I just replace the chain and retain the existing sprockets? I have no idea what chain to buy and would like some advice if possible. I understand that for pre-66 engines (mine is 1965 six bolt) the change level is good info to have handy. Unfortunately, my engine tag is missing but I can provide the engine build date off the block boss in front of the LH cylinder head - 5F15P. That translates to June 15, 1965. I don't know what the "P" signifies.


    Also, if it helps, the VIN stamp on the block is 5F07K778037. Not sure if this will tell you the change level.


    Any help steering me in the right direction to get this sloppy chain addressed is greatly appreciated.


    Thanks,

    Rob


    Timing slop.jpegChain and hatchet.jpg

  • You are correct that change levels are important in 1965. Based on the late date of your engine build your engine is probably change level 8. The difference from change level 6 to change level 7 is mostly about the different camshaft sprocket and camshaft retainer plate. The difference from change level 7 to change level 8 is the change from an aluminum water pump to cast iron and the timing cover change for the water pump. None of this will affect the chain getting loose. There is always a very short time where the chain begins as tight. In a short period of time the chain can show looseness. There are a couple of possible causes for what you are experiencing. The most obvious would be wear on the upper and lower sprockets. The other subtle issue could be that, at some time, your block main cap saddles could have been line bored or line honed. If a shop is not careful when doing this, the crank will end up slightly closer to the camshaft creating a loose chain from day one. The front main cap has the proper configuration for a Hipo cap but I am unable to get a really clear view. Does if just have the numeral one and an arrow?


    -Fred-

    65 Koupe early San Jose Phoenician Yellow 4 speed
    66 GT Koupe Dearborn Blue 4 speed
    66 KGT San Jose fastback pony interior Silver Frost 4 speed
    64 Falcon sedan delivery 289 4 speed
    65 Ranchero 289 4 speed
    66 Corvette roadster 427/425 4 speed

  • Here's another shot of the front main cap. Yes, it is numbered "1" with an arrow. The other caps are all numbered in sequence. Why do you ask? The engine has never been apart to my knowledge, except for the possible timing set replacement I mentioned so no line bore. Good to know the change level.

    Is it difficult to find a replacement timing set complete with both sprockets now that I have the change level? Thanks!

    IMG_6578.jpg

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