|
#1
|
|||
|
|||
Hi,
I've got a dial back timing light and I'm trying to set my 340 to 35 degrees total advance with vacuum disconnected. This is with the MP elec. ign with orange box. At idle I get a fairly consistant signal from my timing light but it still misses about 1 out of 10 times. When I try to set total at 2000 RPM the timing light is firing all over the place with only about 1 in 10 hitting where I think the timing should be. It gets worse as I go up from idle in RPM. I haven't physically tested the harmonic balancer, but I don't think its a problem there since sometimes for a few seconds the mark stays right where I think it should be then its all over the place again. I've changed plugs and plug wires. It seems to ping a little bit under heavy load no mattter where I set the timing, so I think that means that the spark really is jumping around? Could it be the timing light? Any other suggestions? Thanks, Keith |
#2
|
||||
|
||||
The only time I had that happen was when I used 8.8mm wires. The timing gun couldn't pick up the signal. I'm not too sure what it could be. What kind of gun is it?
|
#3
|
|||
|
|||
It could be the intermediate shaft bushing is worn or maybe the distribitor. It is also possible to be the timing light.
|
#4
|
||||
|
||||
I have the same problem in by newly rebuilt 383. It has under 200 miles on it. My wife's wagon has a 383 in it all orginal 'cept for the electronic conversion kit. I set the timing in that with my Craftsman timing light and the mark was rock steady. It did however miss in about a 1 in 10 as stated earlier. My rebuilt 383 timing marks jumps around. I'm at a lost with this also. Only thing I can think of was that the block had a spun main bearing and the machinist had to align hone the block which will slightly raise the crank in the engine bring it closer to the cam increasing slack in the timing chain causing the jumping timing mark. Since align honing takes a little metal out of the bottom end of the block in order to realign the mains. The block I sent out to be built didn't have a spun main that I know of.
|
#5
|
|||
|
|||
I have that kind of a 'problem' too, and I'm not too worried. And I mean it just doesn't vary a few degrees, but it's everywhere. I think it because of the weak signal of the 300+ wires. Usually inside a garage in the dark I can get consistent results. If the timing is only varying a little, there may be several reasons for that. One 'major' thing is usually that the distributor connection to the oil pump drive shaft is very loose. This can cause erratic readings at steady throttle.
|
#6
|
|||
|
|||
TRY CHECKING YOUR TIMING CHAIN IT MAY BE STRETCHING ON YOU. REMOVE THE FUEL PUMP AND PUSH THE CHAIN IN SIDEWAYS IT SHOULD NOT MOVE MORE THAN 1/4" AT THE ABSOLUTE MAX. YOUR MARKS SHOULD BE STEADY AT ALL RPM'S YOU HAVE A PROBLEM SOMEWHERE. IF IT DOES HAVE MORE THAN 1/4" YOU HAVE A BAD CHAIN GOOD LUCK
|
#7
|
|||
|
|||
The timing light is an "Inova" brand ???.
The problem does seem worse now that I've changed plug wires. They are just Accel 8mm through, so I don't see how that could really be a problem unless my timing light is just really crappy. Which it may be since if plugs really were not firing as often as the gun misses my car would be running pretty crappy instead of just pinging a little. The mark isn't just wandering around, its missing quite a bit and all over the place when it fires. Maybe it gets worse as the advance is set higher on the gun. I'll check that out. Anyone remember how many inches around the balancer is 35 degrees? Then I can try without the digital advance. |
#8
|
|||
|
|||
I would check the value at 2500rpm, or a bit more. Your MP distributor may not be fully advanced at 2000 rpm. If not, then small variations in engine speed would show up in the timing. Also, make sure your vacuum port on the carb is well sealed when you do this. I use 34 degrees total in my 360/380 crate motor, and find good power and easy starting. I read that MP recommends 38 degrees, but I'm happy with a few less HP and smoother running.(also, I never have fuel quality problems. If racing is all you want, ignore my last two comments..)
|
#9
|
|||
|
|||
I spent a day mapping out my orange box a while ago, and if you have not played with the distributor (allen wrench in the vac. horn) then it will max out around 2200 rpm with 36 degrees total if you have an inital around 6-8 BTDC. This wont really help until you figure out the light problem first, but I'm pretty sure you will have to advance the curve to get the mechanical all in by 2000. Of course this sounds silly, but have you tried a buddy's light to be sure it is/isnt the light? Also, I dont remember if you said if it was an inductive pick-up? My buddy's light is an old one that is not inductive, and it dances as well, but my inductive light works great as long as the wire is sure to lay on the pick-up. Although, I only have the stock wires, so I get signal coming through the insulation with no problem!
[This message has been edited by dartboy71 (edited July 27, 2000).] |
#10
|
|||
|
|||
I was out playing with the timing again today and I decided to pull the cap off the distributer. There was some scoring on the contacts in the cap which I cleaned up a little just by rubbing them with my fingers. Also I cleaned up some junk that was on the rotor contact. This seemed to improve the situation quite a bit! But not completely. I realized that it has been about 3 years since I put in the MP conversion kit distibuter. Should I be replacing the cap on these periodically? How about rotors? Can you grease the contacts?
I also realized that I used the same gun to time a different engine and had no problem. Smaller plug wires on that one though. One last thing. I noticed that there was about 1/8 inch of free play on the rotor before it felt like it hit the spring. Is this normal? Keith |
#11
|
|||
|
|||
You should not have scoring on the contacts..they are magnetic..Anything dirty in there is cause for alarm. You should take it all apart, clean it, replace the springs(maybe with lighter ones while you're at it..)and put it all back together. If you're not up to that, and want to eliminate the distributor as the source of your troubles, buy an MSD unit($190) or a replacement MP($125).
If you decide to clean it up, make sure to check the contact gap with a non-magnetic guage. Check all ribs on the rotor, as it may not be symetrical. If one rib is too close, it will throw off the timing. This MAY be the "1 in 10" miss that you're having...1 in eight is pretty close, eh? That close rib will fire off too soon, disrupting the readings as well as your timing on that cylinder. I'm not sure how to fix a non-symetrical rib, but I would use that as the reference rib for the gap. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
timing problems | RAMROUGH | Slant Six Chat | 9 | 02-06-2005 08:04 PM |
400 timing problems | Chrism_73 | Performance Talk | 3 | 02-17-2004 05:38 PM |
383 timing problems | kingjr | Performance Talk | 6 | 07-15-2001 08:48 PM |
Timing Problems Fix | ChristianCuda | Performance Talk | 4 | 03-08-2001 12:25 PM |
318 timing problems...please help | dart_gt_67 | Performance Talk | 2 | 03-06-2000 09:10 PM |