is this at all possible weird

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cudaboy 67

cudaboy 67

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hello all, is this possible?firstly heres my settup, 440ci 68 A body,manual 4 speed, 750 four barrel vac sec, msd streetfire,new o/e elec dizzy,coil,leads..........car starts,somtimes bit reluctant kicks back,flames thro top of carb, idles fine, runs real boggy under load then suddenly like a switch picks up, carb fine, plugs spot on colour.... < revs up real sweet when stationary, timed up twice and still seems to run advanced, bastadized number one spark plug,cut out ceramic bit,threaded in 10mm studding protruding into heads ,refitted plug, cranked by hand till piston stopped,checked rotor, bang on number one on cap,looked at balancer..............no sign of timing mark in relation to fixed pointer on block.................. can somthing have slipped? know the balancer keyed on but this odd, cheers in advance, nathan.
 
Your TDC method was unclear or missing something. The piston stop you have made should be long enough to stop the piston Before TDC then rotate back around until it stops again, your true TDC mark will be between these two.
If you turn your crank back and forth to feel slack, before the valvetrain moves. will show timing chain looseness.
 
Sounds like the timing chain jumped a tooth.
Fire out the carb means timing or valve issues.
 
cudaboy 67 said:
hello all, is this possible?firstly heres my settup, 440ci 68 A body,manual 4 speed, 750 four barrel vac sec, msd streetfire,new o/e elec dizzy,coil,leads..........car starts,somtimes bit reluctant kicks back,flames thro top of carb, idles fine, runs real boggy under load then suddenly like a switch picks up, carb fine, plugs spot on colour.... < revs up real sweet when stationary, timed up twice and still seems to run advanced, bastadized number one spark plug,cut out ceramic bit,threaded in 10mm studding protruding into heads ,refitted plug, cranked by hand till piston stopped,checked rotor, bang on number one on cap,looked at balancer..............no sign of timing mark in relation to fixed pointer on block.................. can somthing have slipped? know the balancer keyed on but this odd, cheers in advance, nathan.
Click to expand...

your half right... the inner hb is keyed on, the outer (talking stock dampner) has a rubber ring between the inner and outer rings... they can break lose and spin... just had this happen on my slant and upgraded to a Romac SFI one...
 
To summarise the above, I would:

Check your timing marks with a piston stop. The way you do this follows:

You need a stop that you can adjust, and you are NOT trying to stop the piston "at TDC" but rather DOWN into the bore some amount, not critical. The reason for this is that as the piston aproaches, goes "over" and down again, the piston slows down, and becomes difficult to resolve near the top

So make sure the no1 piston is "down a ways" install the device, and unhook the battery. Wrench the engine until it stops, and you may have to adjust the length the first time around. When the engine stops against the device, make a temporary mark exactly under TDC of the timing tab, onto the balancer

Now turn the engine left (CCW) and do the same thing.

You will have two marks some distance apart, and true TDC will be halfway in between----if the original is correct, that is where it will be

Determining if the cam drive has "slipped." "Depends." If there is some wear on the drive, and ESPECIALLY if it is one of those @*@($&*@#&$*)@#$!%#^_&U#$# plastic sprockets, be suspicious

You can get some idea of chain wear/ play by watching the rotor, and wrenching the crank back/ forth against the "slop" which you can feel with practice. If the crank moves 10* before the rotor moves, it's too much

Determining if the cam is in time can be a little more difficult. If you have specs for the cam, you can see where one of the timing events happen.

MSD---I'm not intimitely familiar with MSD stuff, I don't use it. But SOME of them have advance/ delay stuff built into the box, and if your's does, this might be an issue --changing the timing when unwanted

If you don't have your balancer degreed, either do so, or buy the proper timing tape. IF you are using a "dial up" timing light, SUSPECT it might be inaccurate and round up a conventional light to double check
 
67Dart273 said:
To summarise the above, I would:

Check your timing marks with a piston stop. The way you do this follows:

You need a stop that you can adjust, and you are NOT trying to stop the piston "at TDC" but rather DOWN into the bore some amount, not critical. The reason for this is that as the piston aproaches, goes "over" and down again, the piston slows down, and becomes difficult to resolve near the top

So make sure the no1 piston is "down a ways" install the device, and unhook the battery. Wrench the engine until it stops, and you may have to adjust the length the first time around. When the engine stops against the device, make a temporary mark exactly under TDC of the timing tab, onto the balancer

Now turn the engine left (CCW) and do the same thing.

You will have two marks some distance apart, and true TDC will be halfway in between----if the original is correct, that is where it will be

Determining if the cam drive has "slipped." "Depends." If there is some wear on the drive, and ESPECIALLY if it is one of those @*@($&*@#&$*)@#$!%#^_&U#$# plastic sprockets, be suspicious

You can get some idea of chain wear/ play by watching the rotor, and wrenching the crank back/ forth against the "slop" which you can feel with practice. If the crank moves 10* before the rotor moves, it's too much

Determining if the cam is in time can be a little more difficult. If you have specs for the cam, you can see where one of the timing events happen.

MSD---I'm not intimitely familiar with MSD stuff, I don't use it. But SOME of them have advance/ delay stuff built into the box, and if your's does, this might be an issue --changing the timing when unwanted

If you don't have your balancer degreed, either do so, or buy the proper timing tape. IF you are using a "dial up" timing light, SUSPECT it might be inaccurate and round up a conventional light to double check
Click to expand...

to help 67 streetfire box only has top end rpm limiter
 
So it runs like crap then suddenly fixes itself ? Bad lifters or valve(s) sticking in the guides.
 
hello and cheers for all the input, i did my piston stop thing just to give me a ball park figure,not ideal but the rotor pointer on dizzy <when it was inserted into spark plug hole> was bang on the number 1 on the cap and when checked balancer no marks anywhere near to be found,i have no tacho wired up<i should> but bet you where the stumble clears its at the same increased rpm point every time give or take i think timing chain out would run crap right thro, as would sticking valve etc, the transition is so precice like its running with several plug leads off then they all reconect at same time.for piece of mind im going to swap out the balancer for the potential damage can cause if is slipping which im sure is the problem.stationary the car revs up sweet,only under a bit of load, it has run very well in past so im leaning on it being an ignition timing problem. ps any suggestions on a brand/supplier of balancer? have to get one stateside for sure
 
Backfire thru the carb is a timing issue.
Bog on acceleration than clears up, something is not right with the accelerator pump or cams in the carb.
Did this happen all at once or have you been fighiting it for a while?
 
Maybe the coil is on it,s way out?Symptoms lead me to believe it,s ignition related.If the dampner slipped,she,d be vibrating/shakin like a :shaking2:
 
hello, site been down all day, have tried identical carb and same symptoms, going to recheck tomorrow with a timing light and my new mark on harmonic balancer, 12 degrees and 36 total?
 
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