1984 Chevy Monte Carlo jumped time.

Eric1974

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#1
Make
Chevy
Model
Monte Carlo
Year
1984
Miles
67,000 original
Engine
305
Last year got stranded just out of town the car just died on me and would not start back up. Finally got the time to tear in to it and my suspicion was correct. It jumped time. And unfortunately that year and who knows what other years GM saved a few pennies by using the plastic nylon cam gear and it must have jumped a couple teeth. Hopefully they took that engineer out back and shot them, but probably not, they more than likely got rewarded with a bonus. But anyway back to the post. Got everything back together with the new chain and gear, the car runs but not very good. Is this engine a non-interference engine or is there a chance of engine damage? Valves, push rods ect. Few things need done yet such as possibly needing to move the distributor(which has never been taken out or even loosened), checking with the timing light, and or doing a compression test. Newer plugs were installed but could be fouled out yet again I don't really know. Does not back fire through the carb or anything like that but she really smokes that's for sure. Thanks much for any advice very much appreciated.

Eric
 

grcauto

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#2
As for bent valves it depends. Even non interference engines can bend valve if they are floating during the event. How much foot did you have into it when she puked?
 
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#4
those plastic gears go WAY back - late 1960's my GTO Chevelle days.

305 was a good engine non interference but as grcauto mentioned shix happens.

Think positive - to calm the negative neds remove valve covers for a look-
 
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#5
If you have a timing light and the dist "has never been moved", I would check timing first, because that may be an easy way to confirm that the chain is properly installed. That engine could have ten other reasons to run bad, but the timing should still be set to a good spot unless something crazy happened like the cam got twisted or the dist shaft bound up and dist gear jumped a tooth.
 

Eric1974

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#6
Sounds good. The old timer I'm working on it with said there's been a few times he had to move the distributor because it jumped a tooth there as well. When we first put the new cam gear on something wasn't jivin with where the rotor button was pointing. It was not pointing at #1 cylinder, it was pointing the opposite direction with the marks on the crank gear and cam gear pointing toward each other. Crank gear at 12 o-clock and the cam gear at 6 o-clock. Did a little more digging on you tube and found that the after market were showing to both face 12 o-clock. I would have never guessed that. Why would they even do that? I hope that is correct because that's how it is right now. I'm guessing it would not even run at all if it was that far out anyway.
 

Eric1974

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#7
This may be irrelevant but I figured I'd add that I sold the car to the person I'm working on it with with them obviously knowing what had happened to it and that the mechanic that he occasionally have do work on some of his cars had seen the video with that alleged after market differences. I've looked up other video's and it's mixed as far as the marks facing each other and or away.
 
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#8
So. you don't just "line up the dots"? 1555778375378.png Disregarding any position that the dist may be pointing, let's consider the crank/ cam relationship. Cam turn at 1/2 the speed of the crank. Cam timing has two "happy spots". Dot on cam sprocket could be at 6 or 12 o'clock, the valves would still open/close at the right time (but it matters to the dist). Problem with using the 12 o'clock position is the greater chance of getting the chain "off a tooth".
Like math? Crank at 2000 rpm means that cam will be at 1000 rpm and dist will be at 2000 rpm. Any error with cam timing will cause twice as much spark timing error.
 
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billr

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#9
Wow, what a mess! I think you are getting some bad info.

1) I'm pretty sure all those old SBC engines are "interference", there just isn't enough room in the wedge-shaped combustion chamber for the valves to open adequately without going down into the piston bore a bit.

2) I just saw Dan's recent post. Yeah, on the factory Chevy parts (and all other after-market I have seen) the dots go close together. That's the way it was in '66, 69, 73, 79, and '97, so I expect '84 was the same.

3) "Twisting the dizzy" is a favorite way to get spark timing/rotor pointing all confused, that's what has probably happened here over the years. Worry about the dizzy config after the cam timing has been verified and compression checked.

4) I have never heard of a dizzy skipping teeth on its drive gear. A sheared pin, yes, but not the gear.

5) The plastic sprocket is for quietness, not cost. I have seen broken plastic covering on cam sprockets, but the chains tend to stay in time because the root of the tooth is high enough to engage the chain still. That's assuming just one or two teeth have lost their cap. 1960s for this "cheapening? No, long before that. My '29 Ford A engine had something the consistency of particle-board for a cam gear. We called it "pressed horse-shit". A softer material for the larger gear/sprocket is common practice and many gear-trains of all kinds.

6) What is the brand and P/N of this aftermarket cam chain set? Maybe we can verify that it really is a non-standard alignment.
 

Eric1974

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#10
I always thought the dots on the gears had to go that way as well as in the pic. I will get the info about the after market timing set and post what it is. It's not available to me right now. Thanks for the info and I'll re post soon.
 

grcauto

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#11
I think the OEM has two dots on the cam and one on the crank. The two dots on the cam are 180 degrees apart. If I remember right the one dot was for TDC for number one and the other for TDC number six. At least I think that's right.
Now I'm second guessing myself. I'll fire up my service info PC and report back.
 

nickb2

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#12
GRC wins. PDF here, one for six o clock. No need GRC, my service info was already up. @ bat auto, we pulled out an old Studebaker yesterday. What a trip to see one still very well alive and running. 8119965-1950-studebaker-champion-std.jpg
 

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billr

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#13
Well, let's think about this seriously... Two dots on the cam gear/sprocket, 180 degrees apart, can work fine; and either can be lined up with the crank gear. It makes no difference which mark on the cam gear is used, since it rotates 1/2 turn for each crank revolution. Both cam marks will line up as the crank is turned twice.

I guess my only question is: why, oh why did anybody think it was a good idea to put two marks on the cam gear; just to invite confusion???
 

grcauto

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#14
Well, let's think about this seriously... Two dots on the cam gear/sprocket, 180 degrees apart, can work fine; and either can be lined up with the crank gear. It makes no difference which mark on the cam gear is used, since it rotates 1/2 turn for each crank revolution. Both cam marks will line up as the crank is turned twice.

I guess my only question is: why, oh why did anybody think it was a good idea to put two marks on the cam gear; just to invite confusion???
They are circular indentations with a 6 in one and the 1 in the other. The two would actually cause more work if they were not identified.