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I think the timing chain jumped
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Points & Condenser
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Sep 16, 2011, 3:41 AM
Post #1 of 7
(7605 views)
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I think the timing chain jumped
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Hey Guys, 1974 Ford F100 Pickup with a 302 26,000 miles on a Factory Re-built Long Block, It seems odd that the timing chain jumped a tooth or two with such low mileage but I went to start it one day and it cranked strangely, when it started it was Popping out the tail pipes and when I drove it it had much less power than normal. I pulled the valve cover on one side and noticed a rocker off the valve stem and sitting on the top of the spring instead. I had thought that the lock-nut somehow loosened enough for this to happen so I re-positioned it and adjusted all the valves on that side. When I started it there was almost no difference. So I pulled the cover on the other side and found that 3 Rockers were off the stems and went to re-position them and found one of the push rods badly bent. I installed a new rod and adjusted all the valves on that side. Made sure the timing was set to correctly and ran the engine again. It still cranked weird but idled okay. Which I find unusual if the timing chain jumped why can the idle be fairly smooth? I shut off the motor and lined up the timing mark at (0 degrees) and turned the crank both ways and there appears to be about 6 degrees total of play before the rotor moves. Which seems kind of normal and at the Zero timing mark the rotor is facing the # 1 plug wire. When I run the motor it idles okay but as soon as I put it in gear I get a lot of Valve train noise and it tries to stall out. I also have more than the average Blow-By coming out the breather holes in the valve covers but I have had that for over a year already when everything was running okay other than some Blow-by. Does this sound like the Chain Jumped? Is a Ford 302 likely to have valves hit the pistons when the chains jump? If I find the chain has jumped and replace it with the Cam gear should I try the engine again or go right to pulling the heads to check the valves. Like I said before the motor still Idles good so I'm thinking that the valves are still straight or close to it. Any advice welcomed, thanks, John, Points & condenser
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DanD
Veteran
/ Moderator
Sep 16, 2011, 5:30 AM
Post #2 of 7
(7583 views)
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Re: I think the timing chain jumped
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A 302 unless the block & heads have been decked (machined) to the point of turning it into an interference engine or a healthy sized aftermarket cam has been installed; it shouldn’t bend valves when a chain jumps.
I’ve seen rockers pop off before due to weak valve springs, combined with some very high rpm.
What are the vacuum readings like with the engine running; 18-20” is a normal reading. Is the vacuum gage steady or is the needle bouncing a lot? What is the compression like in the engine?
A 302 timing cover is a breeze to pull; check it out first hand.
Dan.
Canadian "EH"
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Points & Condenser
User
Sep 16, 2011, 9:13 AM
Post #3 of 7
(7571 views)
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Re: I think the timing chain jumped
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I will be able to check the chain in a few days, I am working outside and the weather is bad for the next couple of days. I will get back to you later next week, Have not done vacuum or compression checks yet. Thanks, John
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Points & Condenser
User
Sep 26, 2011, 12:28 PM
Post #5 of 7
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Re: I think the timing chain jumped
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It was only warranteed for 12,000 miles
I tore it down and the chain had jumped I even could make it jump turning it with a breaker bar the chain had 3/4 " of play. Honestly I don't think it was the right chain from the factory rebuilder 26,000 miles even the gears had no wear but the chain was way to lose. The new chain fit well tight but just a slight play. Reassembled and it started and ran ok at timing of 6 degrees BTDC but when I put it in gear it stalls once the engine was fully warmed up I could keep it running in gear by working the brake and gas at the same time. It has plenty of power and sounds good but if you shut it off or it stalls when warmed up it won't start and it sounds like a tight motor or low battery. Once it sits for an hour it starts right up again. Is that a lifter problem or the valves to tight?
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synchro
User
Oct 6, 2011, 9:06 PM
Post #6 of 7
(7448 views)
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Re: I think the timing chain jumped
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Someone tell me how a timing chain jumps time on a "factory rebuilt" Ford 302 dinosaur with only 26k on it? Theres more to it than this!
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