WHY IS MY TIMING SO FAR ADVANCED? [ADDED July 20th The Problem Was Valve Too Tight!!!! Read on...]
After replacing my Valve Stem Seals on my 87 Stock vert a timing problem has come out of nowhere; the engine with 161K mi has been great up to now, I have owned it for 12 years.

PROBLEM: I can't set the timing at 6* BTDC and can't get to run smoothly! Could my timing chain slipped? I did not have that off. Or is something else wrong?

SITUATION: With crane at 0 and TDC on the compression stroke of Cyclinder #1 I had the rotor at the #1 wire position. BTW I'm sure about this since I had the valve covers off.

EST and distributor tach wires disconnected. With the slot for the Distributor at 5 o'clock engine ran very rough and to keep it running I had to advance it off the plate.

I set the slot for the distributer with a long screw driver to 4 o'clock, I could not get it to run.

I then went the other way, distributor set to 5:30 and also to 6 o'clock, runs very rough and again had to advance the timing off the plate for the harmonic balancer marks. Must be about 25* BTDC & no codes are set.

The timing chain cover has never been off, when I first tried to start after the new valve stem seals I had a lot of vacuum leaks. Until I got the vacuum leaks taken care of it ran so bad I thought it would break a motor mount.

I look through a lot of CF threads on timing, but could not find answer; hope someone could help. THANKS

 

The outer ring may have spun on the damper, so the mark is no longer in the correct place. Have you had a timing light on it recently ?

 

are you sure the plug wires did not get crossed.

 

The mark is where it has been for 12 years and I have set the timing before, so that is not the solution. Thanks for the suggestion though.

 

I have re-check the plug wires, that is not the problem. But thanks for your suggestion!

 

Does anyone know whether it is likely that after 161K mi of wear that the timing chain could have skipped the gear on the cam or crank and be causing the very rough running?

 

If you only replaced the seals, my guess is that the valves are not adjusted correctly. A valve that is too tight will cause the car to run rough and trying to adjust timing to specifications will be difficult at best. I doubt that your chain slipped or that you spun the balancer. This is especially true if you just replaced the seals and really have not run the car any distance.

One way to check this is to start the car and pull one plug wire off to see if the idle changes, then replace. If you pull the plug wire and there is no change, you have found the cylinder with the problem. Another way would be to do a compression check. A valve that is too tight will show a low compression. Compression testing with our cars is a B***H since there is little or no room on the passanger side.

Here is the link to a post that Joe C put out about adjusting valves outside the normal thinking and practice. It works like a charm and you can tell when you have reached zero lash (+.0015). I have been adjusting valves on Chevys for 30+ years and this is the best practical way that I have come across yet.

http://forums.corvetteforum.com/show....php?t=2039702

Let us know what you find.

 

Thanks for your reply, actually I adjusted the valves on the loose-side, at the recommendation of a very experienced C4 mechanic.

Instead of tighten the nut on each rocker arm one full turn after rotate of the pushrod stopped (per the factory Service Manual), I actually only gave it three-quarters of a turn and was checked by another friend who has adjusted values on a number of Chevy Small-Blocks.

Could my valves be too loose and cause the rough running? They doesn't sound too loose. Also, if they are too tight that would not make running only possible at very advanced times, would it?

I tried your suggestion to pull a plug wire, since my idle so erratic and rough, I be picking up a compression meter and checking within the next few hours, then back to you. Yes compression tests are difficult, but since I have part of my fender liners out it is not as bad on my C4.

 

I only tighten my valves 1/2 turn. I have always used the rotate the rod method until recently. When I changed out the block to the ZZ4 the runners of the SuperRam were so close to the rod with the new Roller Rockers that I didn't get a good "feel" on one of the rods. I thought I had them adjusted correctly (especially since I have been doing this for 30 years). But I got one (1) too tight. One out of 16 isn't a bad percentage..but it was like I was running on 7 and not 8! Anything less than 100% just isn't good enough

Just happened the Joe C was having a problem close to mine and he tried the feeler gauge method (his own). I tried it and it worked better than twisting the rod. I could feel the resistance better than twisting the rod.

It is hard to trouble shoot engine problems via long distance, but at least you have more experience of this Forum than any Chev dealer you take it to. You just have to weed through all the suggested solutions given and see which one fits your specific case. But at least you are getting information and checking out possible solutions.

In the "old days", if your car had gas and spark it would run. Now, it can have both, but a sensor is telling it something else and therefore it doesn't run!

Good luck. - John

 

John,
Your guess is golden, apparently the valves are too tight. Hope I did not mess them up; while trying to solve this rough running and out of time I did take the car out and drove about 2 miles. It would not go faster than 20 mph.

Here is today's compression test results:
Cyl / 1st Stroke / 4th Stroke / Pressure Build Up
#1 0 psi 0 psi none
#3 0 psi 0 psi none
#5 145 psi 150 psi fast
#7 150 psi 150 psi fast
#2 150 psi 150 psi fast
#4 145 psi 150 psi fast
#6 150 psi 150 psi fast
#8 0 psi 0 psi none

Please check the link Joe C's post about adjusting valves. When I click on your post, it does not come up.

Thanks for sharing your experience on adjusting valves, I am looking forward to learning more practical means of getting my car running right.
Gene

 

Try this:

http://forums.corvetteforum.com/show....php?t=2039702


Tested the link and it works. Basically you can boil this down to place the feeler gauge between the top of the valve stem and the rocker, tighten the nut as you pull the feeler gauge away from the valve. When you feel resistance, you have reached zero lash plus the thickness of the gauge. Joe has added his logic to the amount of additional turning of the nut to take up this additional .0015" of the gauge.

At .0015 for the thickness, that is not much. I then tightened the nut 1/2 turn. I have roller rockers with a lock inside the nut. I turned the lock screw until it was tight then turned the lock screw AND the nut about 6-8* together to get a good lock. So this is a hair more than 1/2 turn. If you do a search you will find FSM telling you 1 turn and other members set theirs from a 1/4 to the full turn. My wifes uncle used to race in the 60's and 70's and always set his at 1/2 turn. So that is what I do, worked for him.

For your car, line up the timing mark to zero with compression on #1. Now adjust Exhaust 1, 3, 4, 8 and Intake 1, 2, 5 and 7. Then turn the engine over by hand 360 degrees so the timing mark lines up again and adjust Exhaust 2, 5, 6, 7 and Intake 3, 4, 6 and 8. Your DONE.
-John

 

Thanks John, that link works.

Ok, I am convinced to follow your and Joe C suggestion; however, given what I have on the schedule I not be able to remove the vacuum lines, valve covers, etc. and put the distributor back at 5 o'clock, until later this week or next.

Thanks again, I am on the right track and will get out the feeler gauges!
Gene

 

The critical step is making sure the lifter is on the base circle of the cam.

 

Gene,

Know exactly where you are. I usually work 12+++ hour days and most of the weekends. I have been trouble shooting my 85 since the end of May....a day here and a hour there. I will get it done soon.

 

John & Others,
After 10 days I removed the valve covers and distributor. I followed the 0.0015 inch feeler gauge valve adjustment procedure on 19 July and put the slot for the distributor at 5 o'clock. With the caps on each rocker arm over the pushrod, I started it up. SMOOOOOTH, hitting on all 8!!!!

After warm up and there was no need to do any additional valve adjustments, just twisted the distributor to what sounded best, then I hooked up my timing light. Wow, only 1 degree off! Just a little more of a twist to get to 6 degree BTDC.

I now swear by Joe C's "unconventional" hydraulic valve adjustment! Now on to other problems...

Thanks Again, Gene

 

Yep, too tight. "after rotatie of the pushrod stopped . . ." is wrong, I believe you mis-read that part. Using the "rotate the pushrod" technique you only want to feel SLIGHT resistance/drag when the rod is turned.

That procedure is so error prone that I always advised against using it; what's "slight" to one person isn't "slight" to another.

Up and Down is more error proof.

Jake

 

When using the feeler gauge method, why doesn't the bowl-shaped indentation into which the valve stem fits cause a problem?

What I mean is that the top of the stem is rounded and it fits into a rounded indentation. Wouldn't the gauge fail to fit the contours of the bowl shape--bridging the indentation?

 

Your thinking of the wrong end of the rocker arm. You want to place the gauge between the VALVE STEM and the rocker, not the push rod and rocker. The top of the valve stem is flat and the rocker will be flat if it is stamped or if you are using roller rockers you will have a flat surface to place the gauge between. I have RR's and placed the gauge at a 90* to the wheel on the end of the RR. I didn't want to have the wheel roll when I pulled on the gauge, which is why I put the gauge at a 90*.

Works great, try it.