When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
The EGR can be very important to some engines. When you disable the EGR the temperature of the combustion process can go up causing pinging or detonation. From that point on the engine will want / demand a higher octane fuel to keep it happy and quiet.
For testing I use a handheld vacuum pump to operate the EGR to work on the C4's L98 while the engine is running. After getting the EGR replaced my L98 idled so smoothly it was amazing.
New plugs in and took a stab at timing. I will make a separate thread for better dialing in once I have a Lars Qjet back on her.
Seems like it is back to running how it was when I bought it. I cannot explain my elation.
I routed the plug wires better but a few of them could still be shortened. But it seems like the biggest change was timing.
After all that. Went for a drive. She’s a little touchy but the bad stutter, rough idle, hesitation, all gone.
Initial timing with vac disconnected was like 30-something!! I had it at 36 (all in by 2500) with vac disconnected but when added the vac back in it was 56-58. I dialed it back to 52 at 2500 with vac can hooked up. Pretty sure the B26 vac can should only be adding 16 deg, I’ll figure that out later.
I took it for a 20 minute drive and couldn’t stop smiling.
This is why I bought the car. Thanks to everyone here. From this point out it’s about tinkering with improvements as opposed to just getting back in the road.
TDC should be at the 0 mark (the deepest notch) What you show indicates the harmonic balancer at 9 or 10 degrees AFTER top dead center (ATDC).
I see that the zero mark on the harmonic damper is between the sharpie marks, but either the outer damper has slipped, or the marks are in the wrong place.
While you are all set up, perhaps do the test again using the 0 mark? Hopefully it is just a transcription error that my brain can't process.
EDIT: Perhaps everything's fine, and you just happened to take the photo at 10 deg ATDC? I just saw your followup post.
New plugs in and took a stab at timing. I will make a separate thread for better dialing in once I have a Lars Qjet back on her.
Seems like it is back to running how it was when I bought it. I cannot explain my elation.
I routed the plug wires better but a few of them could still be shortened. But it seems like the biggest change was timing.
After all that. Went for a drive. She’s a little touchy but the bad stutter, rough idle, hesitation, all gone.
Initial timing with vac disconnected was like 30-something!! I had it at 36 (all in by 2500) with vac disconnected but when added the vac back in it was 56-58. I dialed it back to 52 at 2500 with vac can hooked up. Pretty sure the B26 vac can should only be adding 16 deg, I’ll figure that out later.
I took it for a 20 minute drive and couldn’t stop smiling.
This is why I bought the car. Thanks to everyone here. From this point out it’s about tinkering with improvements as opposed to just getting back in the road.
It would be useful to know what you timing is now at idle w/no vac can.
Then again w/ vac can.
It sounds like you are getting 22* out of the vac can, and will need to reduce it.
That sounds to me like a typical vac can designed for old school gas, on ported vac. You will need about a 12* can to work with new school gas, on manifold vacuum.
It will be worth it when you figure it out.
The Timing Curve is THE most important thing to get "right" during a tune-up, on a carb engine.
A little off and it runs horrible quickly.
You already know how big a difference a small adjustment makes.
And you still have room for improvements!
You may not have a lot of initial timing now, which is not ideal.
1st:
You want to set the total timing to 36*, and leave it there.
2nd:
You can get a new can, or an adjustable can, or a VAC Limiter from Lars to fix that. Or make your own. 12* is what you want. You can measure it with your mity-vac or timing light at idle. Then it should drive OK. Better even.
3rd:
Depending on where your initial timing is (no vac), alter the bushing stop in the distributor, or the bushing, to limit the centrifugal advance to about 24*. Somewhere around 12* initial is good, but that # is not that critical. If single digits, you are leaving improvements on the table.
If you get half-way thru this process it may ping.
Do not drive it "that way" until the pinging stops, or you are finished making your 3 changes.
It should not ping after all 3 changes.
TDC should be at the 0 mark (the deepest notch) What you show indicates the harmonic balancer at 9 or 10 degrees AFTER top dead center (ATDC).
I see that the zero mark on the harmonic damper is between the sharpie marks, but either the outer damper has slipped, or the marks are in the wrong place.
While you are all set up, perhaps do the test again using the 0 mark? Hopefully it is just a transcription error that my brain can't process.
EDIT: Perhaps everything's fine, and you just happened to take the photo at 10 deg ATDC? I just saw your followup post.
the photo was just where I was finding TDC with a piston stop and all plugs out.
It would be useful to know what you timing is now at idle w/no vac can.
Then again w/ vac can.
Limiter from Lars arrived this weekend. Will be installing soon! Honestly not sure I know what knock/detonation/ping even sounds like so I'll have to hit up YouTube.
I would redo my timing readings per your request but since it's "good enough" for now I'm leaving it alone until after I swap on my new-to-me Lars rebuilt Qjet.
As for the plug wires someone mentioned before, I bought a crimper and new terminal ends. Honestly the PO did an okay job on terminating, unless you make a notch in the insulation that wire is going to be somewhat visible. Either way, PO left the wires too long and I plan to clean that up a few projects later.
