Timing

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spinman_1949

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Just a quick question re timing and what I am seeing.

When using the timing light, I am noticing that the mark say at iniital will usually be very close to TDC using the dial in advance light I have. But I do see it fluctuate a bit and sometimes I see it move to the advanced side quite a bit. Like as much as 15 degrees. So the engine is warm and idling and I see these bumps in timing. It also seems like I hear the engine lump a bit when this happens. With the cam that is in this 340 I have now set initial to 22 degrees and the advance on the distributor is adjusted to give no more than 6 degrees or 12 on the crank.

So my question is are these jumps in advance normal? Could I have a loose timing chain?
 
Sounds like loose timing chain, but could be a worn distributor also.
Hell, it could be both.

OR, it clould be the mechanical advance.
Might want to at least make sure both springs are on in the distr.
 
TrailBeast,

Distributor is new. See my other thread. Attempt to payback #2. Advance at higher RPM is rock steady at 34 degrees, so my guess is your first response may be correct. Loose timing chain would be more likely to allow the cam to flop around at idle as opposed to when at speed.
 
That was you, oops
Probably the chain then.

Could an ECU cause that also?
I really don't know for sure, but it seems it could.
Hmm

spinman1949 said:
TrailBeast,

Distributor is new. See my other thread. Attempt to payback #2. Advance at higher RPM is rock steady at 34 degrees, so my guess is your first response may be correct. Loose timing chain would be more likely to allow the cam to flop around at idle as opposed to when at speed.
Click to expand...
 
sometimes that light spring will do that,if the idle is low it want to advance than not.If you rev it it should stay steady right.Does yours?
 
If the timing swings are not as severe when the engine is cold but gets worse as it warms up, your chain is shot. That is the Achilles heel of small blocks. The timing chain will stretch so much that the engine will quit running somewhere around 50-60K miles. At least that's been my experience and I've owned a bunch of them over the years. A new chain (preferably a double roller) and a Mopar tensioner will last much longer. Hope this helps.
 
grumpuscreature said:
The timing chain will stretch so much that the engine will quit running somewhere around 50-60K miles..
Click to expand...

I find this a little tough to believe. I've seen stockers with plastic sprockets that ran (poorly) after some of the plastic was gone and they'd SLIPPED a tooth.

Or by "run" did you mean "like a raped ape?"
 
67Dart273 said:
I find this a little tough to believe. I've seen stockers with plastic sprockets that ran (poorly) after some of the plastic was gone and they'd SLIPPED a tooth.

Or by "run" did you mean "like a raped ape?"
Click to expand...

i would agree. ive pulled apart a number of 100,000 + mile V8s that were running great even with their original chains
 
It takes alot for a chain that's intact to stop a engine from running. I've seen brand "C"s with the tin covers running with the chain so loose it wore a hole in the cover.
 
Snake,

I put springs on both sides. So not using the gap spring. I am pretty sure I am not getting any mechanical at idle. When I bring the RPM's up I do not see any advance until around 1300 RPM. I will do some more testing as time permits.
 
My 100k-mile 318 that came in my Duster slipped a tooth and left me stranded, luckily it was close to home but that thing definitely wasn't starting once the timing chain slipped. The cam sprocket looked like it had been gnawed at by a teething puppy lol...

You can pull off the fuel pump and stick a screwdriver or something in the timing cover and see how much play the chain has.
 
67Dart273 said:
I find this a little tough to believe. I've seen stockers with plastic sprockets that ran (poorly) after some of the plastic was gone and they'd SLIPPED a tooth.

Or by "run" did you mean "like a raped ape?"
Click to expand...

No, I mean run period. Learned this with my '74 Charger. The first '18 I owned was in a '73 Van and it doesn't count since it was pulled in favor of a 440 after the first couple of months of ownership. At 58000 the Charger wouldn't start one morning. Had it towed to the shop where I worked and found so much slack in the chain that the crank would turn about a quarter of a turn before the cam started moving. Changed the chain and she fired right up but wouldn't idle worth beans. Dug deeper and found 12 bent valves and 16 bent pushrods. Driving style may have had something to do with it since I treat the accelerator pedal like an on/off switch. I don't baby one by any stretch of the imagination, and a Mopar is the only car I've found that will take the pounding long enough to empty the payment book. Bottom line, if the timing marks are moving around at idle, the timing chain is history. Period.
 
Those plastic gears and chains suck , have 3 hanging on my work bench from the 70's . 50,000 miles or 5,000 hard miles and they stretch bad , plastic also wears . I've seen them go 100,000 mile with grandma metamucil behind the pedal , but a lead foot shortens the life .
Get a double roller set and have peace of mind
 
spinman1949 said:
Jerry,

I suspect this is not a plastic unit. But I will find out.
Click to expand...

as much as a PIA it can be to put a new chain on, i think the end result will be the pay-off. this way, you KNOW everything timing wise internally is sound. i think this is a great decision. plus you wont be questioning the integrity of whats in there now.
 
Abodee,

Yup I think I will do the fuel pump removal to inspect first. I took a look at the manual and it says 3/16 movement on the cam without the crank moving is time for a chain replacement. So after some math I know that on the damper, 10 degrees equals 16mm. Damper is 7.25 diameter. X 25.4 to convert to metric. X 3.1416 for diameter / by 36 = 16.07 mm. So cam is half travel as compared to crank, so 3/16 = 3/8 on the crank. 3/8 = .375 X 25.4 = 9.525 mm. So since I am seeing almost 10 degrees of crank movement before I see diss move, I am thinking that chain is suspect. 9.525 / 16.07 = .592 X 10 = nearly 6 degrees on the crank. So if 6 degrees on the crank is not OK, then 10 degrees sure is an issue.
 
OldmanRick said:
It takes alot for a chain that's intact to stop a engine from running. I've seen brand "C"s with the tin covers running with the chain so loose it wore a hole in the cover.
Click to expand...
lol me too~!lots
 
spinman1949 said:
Abodee,

Yup I think I will do the fuel pump removal to inspect first. I took a look at the manual and it says 3/16 movement on the cam without the crank moving is time for a chain replacement. So after some math I know that on the damper, 10 degrees equals 16mm. Damper is 7.25 diameter. X 25.4 to convert to metric. X 3.1416 for diameter / by 36 = 16.07 mm. So cam is half travel as compared to crank, so 3/16 = 3/8 on the crank. 3/8 = .375 X 25.4 = 9.525 mm. So since I am seeing almost 10 degrees of crank movement before I see diss move, I am thinking that chain is suspect. 9.525 / 16.07 = .592 X 10 = nearly 6 degrees on the crank. So if 6 degrees on the crank is not OK, then 10 degrees sure is an issue.
Click to expand...

nice math, and you are messing with cars ? LOL i have a fresh 360 , and i can tell you im getting maybe 1-2* of fluctuation at the very most. im thinking any more than 5-6 would be enough to cause a shifty idle. i have ran beat up 100,000 mile small and big blocks for daily drivers, and when the front covers came off, i could not believe they were running as good as they were. these engines can tolerate a loose chain , but i would rather have it as tight as i can.
 
To All,

I went and got a leak down tester at HF. Directions were not clear on it's use but luckily some video's on the net.

First I did a check with the engine stone cold. Most of the cylinders are 35 % to
40 % Not great but it is cold. I hear the sound of air and if I missadjust and increas pressure I can tell the sir is escaping via the crankcase. So that would be rings, but it is cold. I think. But I can also hear sound from the exhaust but not sure on that. Could just be hearing the crankcase noise. But 5 & 7 are not good. 5 cold was 50% and 7 is 60%. So I then went ahead and set the valves. Some of the adjusters are not very tight. The valves were all over the place. With gaps as much as .0032 and as tight as .0012. I just set them all to .0030 and hoped for the best. Started up but when it is cold even with the chock it does not like to run. But I held it at around 1500 RPM and after a fairly short time it settled down and went on normal idle at 1000 RPM. So I got it warmed up and went back to leak test #7 . Not fun trying to get at that plug when it is hot. But I got it out and re did the leak test. So it came back up to 45%. Now for where I need help.

I figure cold the improvement was rings and that the other cylinders would offer the same improvement. So they would be in the 20 to 25 % range. But 5 and 7 are still low and that leads me to think that they have valve issues.

Oh and the vacuum is a bit up from before. Still bounces but not quite as much. If I put my fingers like pinching the needle, I can guess that the vacuum at idle is around 10 inches.

Now as to how the engine runs. From 1000 RPM to as much as 3000 RPM there is a definite stumble or miss. If I hold it at around 2000 RPM, I can hear what could be described as a slight backfire. Now I also think the engine is running rich. So I sure would like to do something about that.

But my big concern is those two cylinders. I am wondering if becasue they are next to each other that may have something to do with this. So my next task is to pull the rockers. Then I can make sure that the leak is not across the two cyliniders. Somehow I think I have a head removal waiting for me to get this sorted out.

So any feedback is appreciated, but somehow I think I know what most will say.
 
To all,

I just went back and checked my timing. It is right at 20 initial and what is more interesting is that it is much more stable than it was before. It still moves a bit but not like the 10 degrees as before. So the lumps in the idling are less. Vacuum is still bouncing at idle. Tomorrow I will check the vacuum at higher RPM. I have to quit for the day. Gotta go to a wedding. Whoopteefriggindoo !!!!
 
just wondering, do you have solid or hydraulic lifters?

Since you have issues with bouncing vacuum, have you checked for any vacuum leaks? I swapped my intake manifold a few weeks ago and I couldn't get my idle below 1000 RPM. Vacuum signal was steady but I still had a huge vacuum leak.

The fact that your vacuum is still bouncing might indicate you have a leak somewhere (unless you have a radical cam in there) messing with the way your engine runs. Try spraying some water around the intake manifold and carburetor to see if the engine rpm's change. If they do this indicates you have a vacuum leak.
 
Cuda,

Thx for the input. A bit if a sage going on this car. But to answer your questions.

Solid lift cam and unknown but rumored to be an ISKY and likely over 500 lift 280 duration. So some bounce in vacuum expected. The leak down is still offering some issues as one can expect cold leak down to be lower due to rings being cold no lube. The worst cylinder came back after warn up but stll pretty poor at 45%. My guess is that I have bleed on intake valve or could be exhaust valve. Either one could affect vacuum and cause the bounce. I may need to back off on initial, or recurve the mechanical advance with a bit stronger springs to keep advance from coming in too soon. As far as vacuum leak. Have not found one and besides a stready leak would not cause vacuum to bounce.
 
spinman1949 said:
Cuda,

The leak down is still offering some issues as one can expect cold leak down to be lower due to rings being cold no lube. The worst cylinder came back after warn up but stll pretty poor at 45%. My guess is that I have bleed on intake valve or could be exhaust valve. Either one could affect vacuum and cause the bounce. I may need to back off on initial, or recurve the mechanical advance with a bit stronger springs to keep advance from coming in too soon. As far as vacuum leak. Have not found one and besides a stready leak would not cause vacuum to bounce.
Click to expand...

Hi Spinman,

Is that Harbor Freight LD tester giving you those numbers? I bought one of those and man was it inaccurate and a PIA. They only run 15 PSI to activate the second gauge (Percent Gauge). 45% reading going past the rings sounds really strange (and Bad). I ended up taking the hose off tester and putting it on a tire gauge. That gave me some more accurate numbers and helped me solve a valve issue. Eventually I ordered an OTC LD tester of amazon for $20 more than the HB one and returned that POS. Now with two accurate gauges at 100psi I could really get a reading and was getting an average of 10% past the rings. If your not worried about the percentages and just want to find leaks turn that puppy up past 75psi and have a listen.

Are you sticking a hose to your ear and up the exhaust? Doing the test at TDC where the air isn't moving the crank?

I'm close by if you want to use mine.
 
Seabee,

I can hear air on all cylinders leaking. If I listen at the tailpipes I can hear air. And yes I did do all the cylinders at TDC. So what you are saying is that 45% is not good period. I figured becasue the engine was stone cold and since after I got it hot and the # 7 came back from 60% to 45% that the rest of the cylinders would improve as well. I did increase the pressure which makes the leakdown useless and could hold a piece of tissue in front of the dipstick tube and it moves from the sir escaping. But that is normal from what I understand. Send me a PM and give me your number and I will call you.
 
Like you said, you might as well prep for heads removal and a valvjob from the symptoms you are describing.
 
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