4th Gen ('81-'88): Loss of power at WOT
#11
04-19-2015, 10:52 PM
No, no, no I didn't think you suggested I did!! But I do have a place where I test drive my vehicles after a repair!! 
I think someone else has been there because they keep leaving black marks on the road
I think someone else has been there because they keep leaving black marks on the road
#12
05-19-2015, 08:21 PM
Ok so an update to this frustrating problem!!! This is going to be a novel!! LOL
Turns out that the evap hoses have nothing to do with this.
I had taken the 84 back to the track and I still had horrible loss in power at WOT and then things got worse. It started backfiring through the carb and a more pronounced miss (always had a slight miss since I bought it). So I took it home and changed almost everything spark related (plugs, wires, cap and rotor). Still no change...barely made it back home and the temp shot to 220 QUICKLy and backfiring through carb with ALL acceleration.
Upon further investigation, my #8 cylinder is not firing for some reason as the header right there would not even get hot enough to melt the crayon mark I put at each cylinder. All of the other cylinders melted their crayon marks off evenly and quickly.
Checked for spark at the plug and it is great, checked for spark at the distributor..also great. Checked compression and it is 150. Pulled valve covers off and everything moves and moves the same amount. Gas is getting to the cylinder as there was gas on the plug. Even changed out the plug in case it was fouled and it wasn't and it worked in another cylinder without a miss. Checked the wires and it worked just fine on another cylinder.
So my soon to be son in law and his dad repositioned the distributor so the car would run without backfiring. No backfiring at all at WOT and it has more power than before but the number 8 cylinder is still not firing.
Should they have removed the water pump and all that then the timing chain cover to check the timing chain/gears to make sure the chain had not jumped?? Instead they said they brought #1 cylinder up to TDC and then repositioned the distributor!! I am thinking the sequence should have been #1 to TDC, check rotor position, check timing chain/gear alignment, THEN reposition distributor if needed.
Fact of the matter is that #8 is still not working!!!! ARGHHH HELP!!!!!!!
Turns out that the evap hoses have nothing to do with this.
I had taken the 84 back to the track and I still had horrible loss in power at WOT and then things got worse. It started backfiring through the carb and a more pronounced miss (always had a slight miss since I bought it). So I took it home and changed almost everything spark related (plugs, wires, cap and rotor). Still no change...barely made it back home and the temp shot to 220 QUICKLy and backfiring through carb with ALL acceleration.
Upon further investigation, my #8 cylinder is not firing for some reason as the header right there would not even get hot enough to melt the crayon mark I put at each cylinder. All of the other cylinders melted their crayon marks off evenly and quickly.
Checked for spark at the plug and it is great, checked for spark at the distributor..also great. Checked compression and it is 150. Pulled valve covers off and everything moves and moves the same amount. Gas is getting to the cylinder as there was gas on the plug. Even changed out the plug in case it was fouled and it wasn't and it worked in another cylinder without a miss. Checked the wires and it worked just fine on another cylinder.
So my soon to be son in law and his dad repositioned the distributor so the car would run without backfiring. No backfiring at all at WOT and it has more power than before but the number 8 cylinder is still not firing.
Should they have removed the water pump and all that then the timing chain cover to check the timing chain/gears to make sure the chain had not jumped?? Instead they said they brought #1 cylinder up to TDC and then repositioned the distributor!! I am thinking the sequence should have been #1 to TDC, check rotor position, check timing chain/gear alignment, THEN reposition distributor if needed.
Fact of the matter is that #8 is still not working!!!! ARGHHH HELP!!!!!!!
#13
05-20-2015, 10:02 AM
Barbara:
Did you pull #8 plug and attach #8 wire back to it and ground the plug at the block and check to see if the plug fires? If the plug fires.
The problems in the motor. More than likely valve train.
First I'd pull the rockers off and check for a bent or broken push rod.
I'd also check the rocker stud heights @ #8. Do you have pressed in studs or screw in studs?
Is there any ticking? (Loose rockers)
If none of these things I suggested.. it more than likely a lobe wiped out on the cam for #8 cylinder. Which means the valves aren't opening enough for intake and exhaust thus causing a miss.
If at wide open throttle. You floated/over revved the motor.. it could have also resulted in a bent valve/s.
Did you pull #8 plug and attach #8 wire back to it and ground the plug at the block and check to see if the plug fires? If the plug fires.
The problems in the motor. More than likely valve train.
First I'd pull the rockers off and check for a bent or broken push rod.
I'd also check the rocker stud heights @ #8. Do you have pressed in studs or screw in studs?
Is there any ticking? (Loose rockers)
If none of these things I suggested.. it more than likely a lobe wiped out on the cam for #8 cylinder. Which means the valves aren't opening enough for intake and exhaust thus causing a miss.
If at wide open throttle. You floated/over revved the motor.. it could have also resulted in a bent valve/s.
#14
05-20-2015, 10:24 AM
Maybe also it maybe a broken rocker?
I would dbl check the timing before doing my above suggestions.
Being sure #1cylinder is at TDC and the rotor IS pointing directly at #1! If they pulled the distributor. . It could still be off by 1 tooth/1 cylinder. Hence the popping thru the carb..
Popping thru the carb could be a bad intake valve as well.
I would dbl check the timing before doing my above suggestions.
Being sure #1cylinder is at TDC and the rotor IS pointing directly at #1! If they pulled the distributor. . It could still be off by 1 tooth/1 cylinder. Hence the popping thru the carb..
Popping thru the carb could be a bad intake valve as well.
Last edited by STUMPMI; 05-20-2015 at 10:33 AM.
#15
05-20-2015, 10:35 AM
Did you pull #8 plug and attach #8 wire back to it and ground the plug at the block and check to see if the plug fires? If the plug fires. Yes, did this and it fired.
First I'd pull the rockers off and check for a bent or broken push rod. Have not done this but they all move
I'd also check the rocker stud heights @ #8. Do you have pressed in studs or screw in studs? Honestly don't remember 100% but I think they are screw in
Is there any ticking? (Loose rockers) There was but not anymore. Those were put back to where they were supposed to be.
If none of these things I suggested.. it more than likely a lobe wiped out on the cam for #8 cylinder. Which means the valves aren't opening enough for intake and exhaust thus causing a miss. Could this still be if the pushrod is still moving the rockers and all of them are moving the same way and distance on that side??
If at wide open throttle. You floated/over revved the motor.. it could have also resulted in a bent valve/s. LOL almost always at WOT so this is all quite possible
I will begin tearing in to things in the next day or so and will check those measurements on the pushrods and the stuff you suggested. I guess I am just hoping it is something simple like a missing tooth on the cam or crank gears that caused the timing to jump and the spark, gas, and compression are just not synced up.
Oh BTW...there is NO MORE backfire through the carb at WOT or at all for that matter.
First I'd pull the rockers off and check for a bent or broken push rod. Have not done this but they all move
I'd also check the rocker stud heights @ #8. Do you have pressed in studs or screw in studs? Honestly don't remember 100% but I think they are screw in
Is there any ticking? (Loose rockers) There was but not anymore. Those were put back to where they were supposed to be.
If none of these things I suggested.. it more than likely a lobe wiped out on the cam for #8 cylinder. Which means the valves aren't opening enough for intake and exhaust thus causing a miss. Could this still be if the pushrod is still moving the rockers and all of them are moving the same way and distance on that side??
If at wide open throttle. You floated/over revved the motor.. it could have also resulted in a bent valve/s. LOL almost always at WOT so this is all quite possible
I will begin tearing in to things in the next day or so and will check those measurements on the pushrods and the stuff you suggested. I guess I am just hoping it is something simple like a missing tooth on the cam or crank gears that caused the timing to jump and the spark, gas, and compression are just not synced up.
Oh BTW...there is NO MORE backfire through the carb at WOT or at all for that matter.
Last edited by P343; 05-20-2015 at 10:44 AM. Reason: had more to say!!!
#16
05-23-2015, 06:54 AM
David
I have some answers from your previous post
First I'd pull the rockers off and check for a bent or broken push rod. Checked and neither bent or broken but they are discolored and the one that came off the back of the #8 cylinder has some rough, rusty spots on the end that was in the head. See pic below right about the 7 inch-7.5 inch mark
I'd also check the rocker stud heights @ #8. Do you have pressed in studs or screw in studs? They are pressed in studs
I have some answers from your previous post
First I'd pull the rockers off and check for a bent or broken push rod. Checked and neither bent or broken but they are discolored and the one that came off the back of the #8 cylinder has some rough, rusty spots on the end that was in the head. See pic below right about the 7 inch-7.5 inch mark
I'd also check the rocker stud heights @ #8. Do you have pressed in studs or screw in studs? They are pressed in studs
Last edited by P343; 05-23-2015 at 06:58 AM. Reason: rotated pic
#17
05-24-2015, 07:26 AM
Barbara:
The pushrod appears to be normal.
I would pull #6 rockers off and compare the push rod lengths and wear marks to be sure there even with the 8 push rods.
If there exactly the same.. then the push rods arent the problem.
You said you checked #8 cylinders compression. Said it was 150.
Whats the compression on the other 7? If im not mistaken they should all read 180 on a 70's model 350.
You also mentioned it had a slight misfire since you bought it.
Have you done a leak down test on #8?
While doing the leakdown test..
That would also be a good time to check/compare the stud heights on #8 with the stud heights of #6. To be sure the studs are at the same height. (If the number 8 studs are even slightly higher) your not getting the correct lift. You mentioned you did have a lifter tick previously. Howd you fix it? And was it at #8 cylinder?
Do you know/are you aware of the correct procedure for tightening/adjusting the rockers?
Over adjusting the rocker causes misfires and excessive cam wear.
R u positive that the rotor is pointing @1 cylinder and 5 oclock on the ditributor? When #1 is at top dead center? This is the correct position for early model 350's
Later model 350's the rotor is pointing at 630 .
You also mentioned.. the motor started running hot..
This could also be a sign of an incorrect timing/firing order issue.
(Possibly 1 wire off in sequencing of firing order)
#1 cylinder in #1 position is critical for proper timing and ignition sequencing thru out the power band. Even 1 cylinder off or 1 tooth off of positioning the distributor in the cam at time of reinstallation of the distributor is also critical.
Obviously..
When you changed the intake over the winter.. you had to remove the distributor...
So its pretty obvious to me.. the error in timing may have occured then. Since it ran fine before this change. Im almost positive this is the issue.
To much timing causes poping the carb. To little timing causes it to seem like its starving for fuel.
1 tooth off between distributor position and cam positioning at installation of the distributor can cause this issue. So, i would start with rechecking the position of the rotor @ the distributor and see if its @ number with the piston at tdc on #1 cylinder.
If its not pointing directly at #1 on the cap and pointing at the #1 cylinder.
It maybe a later model motor also. ( maybe try #1 @ 630 position)
You can check this at your local dealer by getting the engine numbers off the back of the block over the flywheel behind the distributor)
Or it could be a worn out (slacked) timing chain. But my moneys on the distributor positioning. Since it ran fine before the intake swap.
The#8 misfire could be overtightened rockers.. cam lobes wiped out. (Just cause the rockers are moving doesnt necessarily mean there opening/closing properly) low compression if all the other cylinders read more than 150 is also cause for misfires.
Hope this helps.
The pushrod appears to be normal.
I would pull #6 rockers off and compare the push rod lengths and wear marks to be sure there even with the 8 push rods.
If there exactly the same.. then the push rods arent the problem.
You said you checked #8 cylinders compression. Said it was 150.
Whats the compression on the other 7? If im not mistaken they should all read 180 on a 70's model 350.
You also mentioned it had a slight misfire since you bought it.
Have you done a leak down test on #8?
While doing the leakdown test..
That would also be a good time to check/compare the stud heights on #8 with the stud heights of #6. To be sure the studs are at the same height. (If the number 8 studs are even slightly higher) your not getting the correct lift. You mentioned you did have a lifter tick previously. Howd you fix it? And was it at #8 cylinder?
Do you know/are you aware of the correct procedure for tightening/adjusting the rockers?
Over adjusting the rocker causes misfires and excessive cam wear.
R u positive that the rotor is pointing @1 cylinder and 5 oclock on the ditributor? When #1 is at top dead center? This is the correct position for early model 350's
Later model 350's the rotor is pointing at 630 .
You also mentioned.. the motor started running hot..
This could also be a sign of an incorrect timing/firing order issue.
(Possibly 1 wire off in sequencing of firing order)
#1 cylinder in #1 position is critical for proper timing and ignition sequencing thru out the power band. Even 1 cylinder off or 1 tooth off of positioning the distributor in the cam at time of reinstallation of the distributor is also critical.
Obviously..
When you changed the intake over the winter.. you had to remove the distributor...
So its pretty obvious to me.. the error in timing may have occured then. Since it ran fine before this change. Im almost positive this is the issue.
To much timing causes poping the carb. To little timing causes it to seem like its starving for fuel.
1 tooth off between distributor position and cam positioning at installation of the distributor can cause this issue. So, i would start with rechecking the position of the rotor @ the distributor and see if its @ number with the piston at tdc on #1 cylinder.
If its not pointing directly at #1 on the cap and pointing at the #1 cylinder.
It maybe a later model motor also. ( maybe try #1 @ 630 position)
You can check this at your local dealer by getting the engine numbers off the back of the block over the flywheel behind the distributor)
Or it could be a worn out (slacked) timing chain. But my moneys on the distributor positioning. Since it ran fine before the intake swap.
The#8 misfire could be overtightened rockers.. cam lobes wiped out. (Just cause the rockers are moving doesnt necessarily mean there opening/closing properly) low compression if all the other cylinders read more than 150 is also cause for misfires.
Hope this helps.
Last edited by STUMPMI; 05-24-2015 at 07:35 AM.
#18
05-24-2015, 09:05 AM
Wow..thanks for the write up David.
Just checked cyl. 6 push rods and they are exactly the same length with same wear pattern.
The compression on all cylinders ranged from 147-150 is what I was told (I did not do that part myself).
Yes, I learned proper rocker adjustment procedure
Well, unfortunately, over the winter I never did change out the intake so I still have the stock intake on it.
Lifter tick/exhaust leak was never really determined and it was near #8.
Getting ready to put my push rods back in and re-adjust the rockers. I will attempt to measure height of the studs while I have the cover off.
I am going to start taking the front stuff off the engine to get to the timing assembly. I will only get so far with it as I do not have the harmonic balancer puller nor crank gear puller. Crank gear HAS to come off as I am installing a double roller assembly.
Once that is done and timing and everything is completely adjusted I will know that at least that part is correct. If there is still a problem, I will strip it all the way down and replace everything (cam, lifters, valves, etc) but then my season will most definitely be over.
Just checked cyl. 6 push rods and they are exactly the same length with same wear pattern.
The compression on all cylinders ranged from 147-150 is what I was told (I did not do that part myself).
Yes, I learned proper rocker adjustment procedure
Well, unfortunately, over the winter I never did change out the intake so I still have the stock intake on it.
Lifter tick/exhaust leak was never really determined and it was near #8.
Getting ready to put my push rods back in and re-adjust the rockers. I will attempt to measure height of the studs while I have the cover off.
I am going to start taking the front stuff off the engine to get to the timing assembly. I will only get so far with it as I do not have the harmonic balancer puller nor crank gear puller. Crank gear HAS to come off as I am installing a double roller assembly.
Once that is done and timing and everything is completely adjusted I will know that at least that part is correct. If there is still a problem, I will strip it all the way down and replace everything (cam, lifters, valves, etc) but then my season will most definitely be over.
#19
05-29-2015, 07:55 PM
Making SLOW progress
Well I have made a little progress on the 84 this week. Finally got the harmonic balancer off, removed the timing chain cover, moved crank to line up the timing markers and they appeared to line up. Chain was loose and there were rub marks on the inside of the timing chain cover.. So I removed the cam gear, then chain, then the never-ending task of pulling the crank gear!!! OMG!! 
It took me over an hour to get that gear pulled off of there!!! So then I began putting the new crank gear on and could only get it on so far. I need to find a bigger socket than I have to put over the end of the crank shaft so I can get the gear on there. So, again, I am at a standstill.
Below are some pictures.
It took me over an hour to get that gear pulled off of there!!! So then I began putting the new crank gear on and could only get it on so far. I need to find a bigger socket than I have to put over the end of the crank shaft so I can get the gear on there. So, again, I am at a standstill.
Below are some pictures.
