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Cam timing gear tooth damage from link chain
https://cimg6.ibsrv.net/gimg/www.off...e0ff7f2e9.jpeg Stock rebuild 330 bottom end, stock style link bar timing chain, stock cam, upgraded pushrods/springs (done by previous owner), less than 10 hours run time most under 2k rpm. I had a timing cover leak, so I pulled it off and went ahead and bought a basic cast cam gear Cloyes double roller timing set to replace the stock one. Once apart I noticed more slack than I would like in the timing chain that was installed, and after pulling the gears off I noticed some pretty significant wear on the cam gear teeth, especially with so little run time and tiny cam. My best guess is a cheap/soft gear that maybe missed heat treat? Anybody seen something like this before? |
https://cimg5.ibsrv.net/gimg/www.off...27c858d61.jpeg Here is the timing set before I pulled it, slack is split on both sides evenly in this pic |
Originally Posted by sailtexas186548
(Post 4671590)
https://cimg5.ibsrv.net/gimg/www.off...27c858d61.jpeg Here is the timing set before I pulled it, slack is split on both sides evenly in this pic most people advance cam two degrees to make up for the slack in timing chain.. my engine builder also has drilled a .020 hole in the plugs behind the top gear. flash ............ |
It doesn't look like that chain fits the cam gear very well ?? could be the pic tho.
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or the contrary
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I have holes drilled in the oil galley plugs.
You make a good point that the chain and gear may be mismatched, glad I had to pull it down otherwise this would have gone unnoticed until it was much worse. I will check the chain and gear compatibly out of the engine when I get a chance. I have a Cloyes billet cam and crank gear coming with a true double roller chain, and a Torrington bearing for the cam gear. |
That chain was so loose that it was on the verge of jumping a tooth or two or more.
I would say that you saved your engine. Did you assemble the engine? was the crank bore align honed? Chain tension is IMPORTANT That wear was caused by the chain riding up on the gear. I would say that it would have blown within another 10 hours at the most. WOW - that was a close call. |
I did not build the engine, I don’t believe it was line honed but I don’t really know. It has stock main caps so I doubt it. I will find out when I install the new timing set. I dodged a bullet for sure, hopefully there aren’t any more surprises hiding from me. |
Line honing has nothing to do with what main caps you have. You cut some off the top of the caps and then re cut the holes by using a line hone.
this causes the crank bores to be slightly closer to the cam bore causing slop in the timing chain. They make a chain that is shorter for blocks that have been line honed and need it. |
I would not be surprised when the past owner "rebuilt" the motor they left the gear on the crank. Either it was worn or not the same exact dimension as the replacement gear and it let the chain flop around. On any motor I open up I dump that single crap and put a double roller on it.
Also there is metal missing and it went somewhere. |
Common wear pattern on high hour/ mileage silent style timing chains and gears.
Someone was just too lazy to change the set. The old school trick of drilling the gallery plugs will haunt you . Dont do it. Those old wet sump motors have so much oil blowing around in the crankcase the extra oil from the drilled holes is a waste. Also the oil coming from around the cam bearing and journal supplies plenty of oil The hole helps create a vacuum break , allows the oil in the gallery to drain back quicker . Results in longer oil pressure build time , especially with hot oil. Clicking hydraulic lifters etc. etc. etc. That old trick came about when roller chains first appeared on the market , metallurgy wasnt quite up to par and the chains would wear prematurely at elevated RPM. The short term fix was the drilled galley plugs. Just like the trick of filing a slot on the distributor lower pilot OD to oil the cam gear! Complete waste of time , and causes more problems than it fixes. |
Originally Posted by Tinkerer
(Post 4671744)
Line honing has nothing to do with what main caps you have. You cut some off the top of the caps and then re cut the holes by using a line hone.
this causes the crank bores to be slightly closer to the cam bore causing slop in the timing chain. They make a chain that is shorter for blocks that have been line honed and need it. new timing set came in today, gonna see how the chain tension is and go from there. Hope I don’t have to pull these out and rebuild them myself it’s about to be boating season! |
Originally Posted by Tinkerer
(Post 4671744)
Line honing has nothing to do with what main caps you have. You cut some off the top of the caps and then re cut the holes by using a line hone.
this causes the crank bores to be slightly closer to the cam bore causing slop in the timing chain. They make a chain that is shorter for blocks that have been line honed and need it.
Originally Posted by f_inscreenname
(Post 4671752)
I would not be surprised when the past owner "rebuilt" the motor they left the gear on the crank. Either it was worn or not the same exact dimension as the replacement gear and it let the chain flop around. On any motor I open up I dump that single crap and put a double roller on it.
Also there is metal missing and it went somewhere. i ran a magnet in the pan and didn’t pick anything up. You are right it’s somewhere, hopefully the filter or in the last oil change I did, and the oil pump isn’t torn up. |
put the new standard length cloyes timing set on, tension is correct now, hopefully that is the end of it.
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