stock 302 stumbles bad/weird noises

[BorderBronco]

Hello Guys and Girls,

I need your advice and help on an engine issue.
Stock 1974 Bronco w/302 and 3 spd
I drove the Bronco Monday to work and back home and parked it. It ran great.
Did not use it yesterday. Went out to start it up to take it to work tonight and on first crank it sounded like the belt came loose and was hitting metal. I stopped and popped the hood and saw everything intact. Cranked it again and sounded like something hitting metal. Tried again and it fired but sounds like its firing on 2 or three cylinders. I shut it down and now am worried to run it again. It's got me worried since it ran great Monday and two days later it does this.

What should I check next? I wonder if the dizzy gave up the ghost? Or God forbid there is internal damage to valves or pushrods....

I appreciate the help in advance.

Josh

 

[Lawndart]

Timing chain jumped a tooth or two??

 

[BorderBronco]

Timing chain jumped a tooth or two??

Thanks. If the timing chain got loose enough it could be hitting inside the cover, right?

 

[B RON CO]

Hi, it could be the timing chain. You can turn the motor until the balancer mark lines up with the timing tab, #1 TDC, and see if the rotor points at #1 wire in the distributor cap, or 180 degrees off. It should be pointing at about 1 o'clock. If the timing skipped the rotor will be way off. Good luck

 

[blubuckaroo]

Is the neighbor's cat missing?

 

[BorderBronco]

Is the neighbor's cat missing?

LOL! That was the first thing I thought of. I was like "OH NO!!! I just sliced up the cat!" Thank goodness it wasn't a cat.

 

[blubuckaroo]

The timing chain is a suspect. If was loose enough to jump, it'll still be loose. Put a wrench on the crank, and rotate the motor in both directions while someone watches the rotor. That should give you some idea of the chain slack.
Do you know the history on the motor?

 

[JAFO]

I'll will x14 timing chain. Easy enough to see if the timing is off. I had the timing chain break in my old 72 Chevy Blazer back in the 80's. I was accelerating sort of quickly. Actually bent one intake valve even though the old 350 is not suppose to be an interference engine. Changed the chain in my 96 Dodge a couple years ago. 150K miles. Chain had some slack in it when I got the timing cover off. Probably ready to be changed. People don't give them much thought, but they do wear out.

 

[BorderBronco]

The timing chain is a suspect. If was loose enough to jump, it'll still be loose. Put a wrench on the crank, and rotate the motor in both directions while someone watches the rotor. That should give you some idea of the chain slack.
Do you know the history on the motor?

How much play in the rotor am i looking for?

The motor is the original 302. Bought new in 74. parked in a garage around 1985 where it sat for about 28 years. second owner put a new water pump and fuel pump on it, not sure about the timing chain. We acquired it in 2012.

 

[blubuckaroo]

How much play in the rotor am i looking for?

The motor is the original 302. Bought new in 74. parked in a garage around 1985 where it sat for about 28 years. second owner put a new water pump and fuel pump on it, not sure about the timing chain. We acquired it in 2012.

If you don't know all the vehicle's history, you really don't know how many miles are on it. The odometer starts over at 100K. Mine has been reborn three times.

The OEM timing set had a nylon clad top sprocket. When I replaced mine at 80K miles, the nylon cap was all missing. The metal teeth were badly worn too. The nylon found its way to the oil pump pickup screen. The new timing set really woke up the motor.
If your engine already has a lot of miles, I'd just replace the timing set with factory type. (but without the funky nylon cap) No use springing for a double row set on a used motor.

This is what I found on checking timing chain slack.
https://www.youtube.com/watch?v=4_f5ukZVri8

 

[DirtDonk]

That guy's numbers seem to agree with what we've been using for a long time now.
At less than 5 degrees, you're good to go.
At 7 degrees it's effecting performance and it's time to start figuring out when you're going to be changing it out.
At 10 degrees you should have done it long before that and be in the middle of changing it right now!;D

I've heard of some brand new chain sets with about 5 degrees, but I'm thinking that a good tight one is more in the 3 degree range. But that's not based on recent testing of that theory. Just what I "think" I remember. And some of that could have been slop in the distributor too for all we knew.
I think the book describes how to deflection in fractions of an inch, but doing it the degrees of distributor rotation is a cool way to do it with the engine still assembled.

You would have to take into account possible wear of the distributor and mating cam gear surfaces too. That's going to skew the readings if they're worn.
Luckily they're usually in better shape than the chains!

I replaced a double-roller chain one time with only 25k miles on it. I was inside the engine for one reason or another and noticed it had a lot more slop in it than when new. Was a shame too, being such low miles. Figured it should stay tighter longer than that.

Paul