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Discussion Starter #1
My 70 XR-7 went out with a bang thismorning. It was running funny, real low idle and little backfires out of the intake. Then as I got on the freeway onramp and punched it, it made a series of very loud backfires. There was alot of smoke out of my pipes and then the engine died. The engine still turns over and sounds healthy, but it won't start and there's alot of little backfires out of the exhaust and the intake.
I have an Edelbrock performer intake with a 600 cfn carb that's only 2 years old. And my ignition has a pertronics chip replacing the points. Could it be the ignition? Or timing chain? I've had the car for 4 years and never had a problem with the engine, which is a Cleveland. Could it be the intake?Please help, this is my daily driver and it's sitting on the lot at my work.
 

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Sounds like chain. Is it the original chain, they used nylon teeth on those. If you cant afford a true roller, get a replacement chain and turff the nylon gear. Also check dist. gear, it might of went south too.
Sorry to hear about the Cougar, it still has 8 lives left.

Rick
 

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Check the dist cap to make sure its not cracked. If its not I would look for a bad timing chain like Dark said. Pull # 1 plug and get #1 cyl to top dead center on the compression stroke. Then pull your dist cap and check to see if the rotor is pointing to the #1 plug wire on the cap. If its not then you jumped a tooth on the chain (or dist gear went bad) and now would be a good time to put that performer cam in you have been wanting!!! (had to through that in) mm
 

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get one of the cheap rollers on ebay for like 37. cheap enough eh?
 

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Discussion Starter #5
Thanx for your replies. It's not the dist cap, so maybe it's the chain. I heard that blowing the timing chain can do internal damage like a piston hitting a valve. This really sucks, Thurs is my B-day and I have to spend it without my baby.:( I know a guy that works on old fords and he's going to look at it on saturday, his day off from his shop. I'm trying not to have it towed to a shop and pay all kinds of money when I know 2 mechanics that will help me work on it. I work all day and study martial arts at night , so I don't really have time to work on it myself untill this weekend. Plus I don't even know what to do without some help. Good thing I live 3 miles from my work. If I do have to tear the engine apart I will put a performer cam in, anyone have suggestions on how wild of a cam for a daily driver?
 

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It's not that tough changing the chain, but it's time involved. More so if you change the cam at the same time. Check the chain first as modified mark says. If it is the chain, ask your buddy for help, need to drain oil, take off the whole front engine stuff (water pump, cover, drop pan, take off balancer, etc) time consuming, so check first. Changing cam reguires alot more involvement, (take out rad, rockers, lifters, intake, etc.) but a good cam without changing springs would be around 260-280 degree advertised for good get up , anything more than it's a whole new ball game, (convertor, valve springs, carb, exhaust, rear gears, etc.).
Hopefully it's the chain, so just replace that until you gather all the nessecelery pieces then change cam, and reuse the new chain. Good luck and keep us posted.

Rick
 

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I had a Torino in college with a 302, nylon teeth on the timing chain gear went south and skipped a tooth. Engine kept running long enough to pull up into my driveway from the street, but no more. It did bend a valve, too, which meant pulling the heads off and having a valve job done. I did the work myself as that was the sort of budget I was on in college, learned lots about such things. I was told that a 302 should be a non-interference motor, meaning piston should never occupt the same space as a valve, no matter how out of whack the timing is. I definitely had piston-valve contact with my deal. We'll trust that it's just your timing gear, at worst, but it would give you a marvelous excuse for the cam, since the intake, heads, etc... would all be off anyway!

Ron.
 

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Dead Kitty

Believe it or not, you might have actually experienced a little good luck. Let me 'splain it to you Lucy...

When those darned nylon covered timing gears get old, say 80k miles plus, the teeth get brittle and break off. Most of the time, the engine will continue to run, but you'll have a devil of a time keeping the timing in spec with that loose chain.

OK, now what has happened to more than a few engines I have known. Those little bits of nylon gear sit in the bottom of your oil pan. Normally, the pickup screen on the oil pump will keep them contained, but sometimes they don't. I have personally seen several engines where the bits of gear have gotten past the screen and up into the oil pump. The pump then gets jammed.

The design of the engine is that the oil pump is driven by a shaft off of the distributor, which is driven off the camshaft which is driven by the timing chain to the crankshaft, right?

OK, so what happens when that oil pump jams up? Ooops! Sometimes, if you're lucky, the distributor gear will strip, or the timing chain will strip off the rest of its nylon gear. Another 'lucky break' is if the roll pin that holds the distributor gear to the shaft will shear and the distributor shaft just stops turning. Why are these two scenarios lucky? The engine just stops. WTF? But the absolute worst thing that can happen when the oil pump gets jammed is that the oil pump driveshaft will break. The next thing you know you have no oil pressure. Do you think you'll notice that gauge at zero before any real damage is done? Think again! How long do you think your engine will run with zero oil pressure? Just think of the damage that this last option can cause!

Ty, just count your woes as a blessing in disguise because now you have a good reason to pull the motor and do a complete rebuild! I know, I know, this may not have come at the best time, but at least nothing is seriously broken!

Let us know what happened!
 
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