Shaking and backfiring. 360

-

kickywow

Well-Known Member
Joined
May 6, 2008
Messages
113
Reaction score
0
Location
Delta, B.C.
1971 Dart Swinger

Last year I spent many many hours in my garage swapping out my 318 to a 1978 360. When it was all in and hooked up I took it out for a drive. When it was at idle it all seemed well, however when I put it into drive or reverse and lightly pushed the gas the engine would shake and backfire.In the 904 transmission I had a B&M balanced flexplate.

Today was the day where I had finished working on it to get ready for this year, I took the balanced flexplate out and put in a properly balanced torque converter for a 360 with a cast crank. however drive up and down the street.... and backfiring and shaking continued.

I am confused, exhausted, and don't know where to go next... Suggestions on what could fix my problem?:|

Nick
 
Do you have the plug wires on correctly?? Out of time??
 
What are you running for a distributor? Crossed wires, wires backwards around the cap, open wire, open/ broken plug, valve hanging open (run a compression check) cam out of time, timing retarded................
 
My guess is you crossed #5 and #7...and now,one i firing to soon and one is to late.
 
externally balanced incorrectly can cause a vibration this is true..... but you could hang a 5 lb lead weight on it and that will NOT make the engine backfire. Externally balanced means you have to have the correct converter AND the correct harmonic....only ONE correct will cause vibration ....BUT again that will NOT cause backfiring....you either have an ignition issue ( first choice ) OR a Carb issue (second choice)
Make certain your distributor is NOT 180 out and then start walkin the wires...my guess is you will find a crossed set.... Incorrect firing will cause BOTH Vibration AND backfiring
have at it and good luck
PS check for vacuum leaks also
 
The above assumes that the engine is a fresh build and that all the internals were assembled correctly esp the timing gears & chain...... if the engine has miles on it, depending on how many....your chain might be sloppy and you may have jumped a tooth or three.....
jumped tooth can be easily checked by taking the dist cap off and marking where the rotor is facing then turn the damper bolt to turn the engine over and watch the rotor they should move one to one then switch direction on the damper and watch the rotor....if you can move the crank a significant amount before the rotor responds....your chain is SLOPPY enuf to jump a tooth
 
This all helps. I will check and reply, the last post by 66cuda i may not understand 100% but re read and try
 
I'm going to go through the list of suggestions and explain what i found after a quick check. Only thing I did not check was a compression test because I do not have a compression tester.

The engine does have miles on it I did not build it. came out of a 78 cordoba, which I purchased of a friend.

What is the easiest way to tell whether or not the distributor is 180 out? I found top dead center and it points forward where number one is on the distributor cap.

I followed each wire to the plug from the cap and it was all correct, only one contact inside the silicone boot was kind of far into the boot itself. Each wire was also good there was no breaks in it. All the plugs are new and did not see any breaks or cracks.

For the timing issue and the timing being retarded, I timed the car today, plugged the vacuum advance line, and set the timing to 5-7 degrees advanced.

The distributor is an Autoline rebuilt product, for electronic ignition. Carb is a brand new Edelbrock Thunder series 650cfm, however I'm not the best tuner?? With the new intake and carb there is minimal Vacuum lines and everything is plugged in.

The last thing to cover would be... The sloppy chain, How much is a significant amount? when is switched directions there was some play where the rotor would not react to the movement. However this movement wasn't that large and I don't know what "Normal" movement is.

On a side note interesting thing I found in the distributor cap on the contacts for each wire I found a plastic formation maybe from the factory on 3 of the 8 contacts. but only one contact had quite a bit of plastic on it... It is too late to fire my car and check tonight, but I will think about it all day until I can get home to check these issues.

Thanks for reading

Nick
 
I'm going to go through the list of suggestions and explain what i found after a quick check. Only thing I did not check was a compression test because I do not have a compression tester.

The engine does have miles on it I did not build it. came out of a 78 cordoba, which I purchased of a friend.

What is the easiest way to tell whether or not the distributor is 180 out? I found top dead center and it points forward where number one is on the distributor cap.

I followed each wire to the plug from the cap and it was all correct, only one contact inside the silicone boot was kind of far into the boot itself. Each wire was also good there was no breaks in it. All the plugs are new and did not see any breaks or cracks.

For the timing issue and the timing being retarded, I timed the car today, plugged the vacuum advance line, and set the timing to 5-7 degrees advanced.

The distributor is an Autoline rebuilt product, for electronic ignition. Carb is a brand new Edelbrock Thunder series 650cfm, however I'm not the best tuner?? With the new intake and carb there is minimal Vacuum lines and everything is plugged in.

The last thing to cover would be... The sloppy chain, How much is a significant amount? when is switched directions there was some play where the rotor would not react to the movement. However this movement wasn't that large and I don't know what "Normal" movement is.

On a side note interesting thing I found in the distributor cap on the contacts for each wire I found a plastic formation maybe from the factory on 3 of the 8 contacts. but only one contact had quite a bit of plastic on it... It is too late to fire my car and check tonight, but I will think about it all day until I can get home to check these issues.

Thanks for reading

Nick
Sounds like maybe time for a new cap and rotor,this will help eliminate this plastic looking formation on 3 and 8 cyl.Good luck.
 
Before we go to the timing chain........do you have a volt/ohm meter?
you can pick up a cheap one for for less then $20

put it on ohms and check the resistance of each wire. the long ones will have more then the short ones But if you have a bad one it will be obvious, as it will be way hire then the rest.

take a good look at your cap and rotor....in fact i might be best to just replace them.


Now, that you have done all of that, here is how you check you timing chain.
role the motor over to tdc then remove you dist. cap. Rotate you motor in the other direction watching the ign rotor until you see it move. if the crank has moved 12* it need replaced. if it's more.......It probably has jumped.

I don't think it's you chain.
 
FIRST REREAD WHAT THIS GUY POSTED:

........do you have a volt/ohm meter?
you can pick up a cheap one for for less then $20

put it on ohms and check the resistance of each wire. the long ones will have more then the short ones But if you have a bad one it will be obvious, as it will be way hire then the rest.

take a good look at your cap and rotor....in fact i might be best to just replace them.


Now, that you have done all of that, here is how you check you timing chain.
role the motor over to tdc then remove you dist. cap. Rotate you motor in the other direction watching the ign rotor until you see it move. if the crank has moved 12* it need replaced. if it's more.......It probably has jumped.

I don't think it's you chain.

To clarify the above, rotate the engine with a wrench CW, then CW, watching the rotor for movement. The timing mark should not move more than 10-12* against the "slop" in the chain








. Only thing I did not check was a compression test because I do not have a compression tester.
Nick

You NEED a timing light, dwell/ tach if you have points, vacuum gauge, and compression checker. You NEED to get these

What is the easiest way to tell whether or not the distributor is 180 out? I found top dead center and it points forward where number one is on the distributor cap.

The engine won't run at all if "180 out" but one easy way is you need the "compression stroke" for no1, not just bringing the "mark" up. So you remove no1 plug, stick your finger in the hole, and bump the engine with a remote start switch. You might have to "go round" a couple of times before you get this. AS SOON AS you start to feel compression on your finger, look at the timing marks, they should be "coming up." Bump/ rotate the engine to about where you run the timing, IE 8* BTC or whatever, and be sure the rotor is approaching/ at the no 1 plug tower

I always scribe a line on the dist. rim centered below the plug tower so I know where to look. Then rotate the dist RETARD (CW on smallblock) AND BACK CCW (advanced) slowly, until the points open, or until the relutor tip is centered on the core of the pickup coil. THIS SHOULD BE close enough for the engine to start right up.

(Obviously in your case, just "check" it don't move it, but you've already checked it with a light, right)


only one contact inside the silicone boot was kind of far into the boot itself. Each wire was also good there was no breaks in it.

Not sure I get this---wire just may have slipped, but this kind of thing can also break connections. You MUST check them with a meter Shake them around as you check them, looking for intermittent spots inside the wires

For the timing issue and the timing being retarded, I timed the car today, plugged the vacuum advance line, and set the timing to 5-7 degrees advanced.Nick

OK, but what have you done to insure that both the mechanical and vacuum advance are actually working? To do that you either need the balancer degreed, or timing tape, or a "dial up" delay timing light. You should be able to rev the engine, vacuum disconnected, and see the mechanical move. You should also be able to remove the dist. cap, and "spring" the rotor CW, and it should freely 'spring back' showing the advance is not sticking.

You should be able to jack up RPM by jamming a screwdriver in the idle cam or just jacking up the fast idle, then disconnecting / connecting the vacuum advance. You should both hear the engine speed up, and be able to see the timing move up

Also, check your timing marks for accuracy. Very very easy. Get, build or buy a "piston stop."

http://www.jerrybramlett.net/images/pic_installation.jpg

Remove no1 plug, determine that the piston is "down a ways", and disconnect battery ground. Install the stop. If you've made it or first time use, you'll have to adjust it so it's long enough to actually touch the piston at some point

Gently wrench the engine over CCW until you stop the piston "on the stop." Make a temporary mark on your balancer under TDC on the timing tab. Do the same thing rotating CCW. Now you'll have two temporary marks some distance apart. True TDC will be halfway between the marks, and if the original is still accurate, that is where it will be.


ONE LAST THING. Something I've found incredibly usefull is what many call a "cylinder balance test" which can QUICKLY find a dead/ weak cylinder.

CAREFULLY pull the dist. boots up off the towers a small ways. If you have a 12V test lamp with a nice slim probe, use that. Otherwise, jam paper clips or small nails (brads) down into the towers right beside the wires. Now with the car at a fast smooth idle, use your test lamp or a probe to ground one plug tower at a time. Use your tach if possible, or just your eyes and ears. EACH cylinder should "drop" the same RPM and "wiggle" the engine the same as the next. A weak/ dead cylinder will become fairly obvious most of the time.
 
Thanks I will keep checking it out. Im going to go see if what i did last night with those plastic bits fixed it
 
I replaced the # 5 wire, the boot on the distributor wasn't very good, as for the extensive list provided above I will print out and try tomorrow. I work this evening and will make an attempt at that tomorrow. I checked the timing chain slack again and there is no way it is more than 5 degrees on the balancer.
 
check the gap on the points if it has points, if it has electronic ignition check the air gap on that.....if its not that then pull a plug wire at a time until you find the bad cylinder....from there pull the valve cover and see which pushrod went trru the rocker arm and if that isnt the problem take the rocker shafts off and lay a straightedge down the tips of the valves to make sure the heads were done properly
 
I narrowed it down to cylinder #3 and replaced the cap, rotor, and the spark plug. Then the shaking stopped! Thanks for all the help and suggestions!

Nick
 
-
Back
Top