Distributor Drive Gear Misaligned
05-20-2016, 04:47 PM
#21
05-20-2016, 04:51 PM
#22
Melting Slicks
Sry if I repeat anything I just skimmed most those reply's.
1st is this a gm dist with a .491 shaft? Some places like MSD use .500
On the new gear, the toothed part looks a bit thicker(idk if that really matters for this) but pics can be kinda deceiving. You could turn the new gear 90deg then drill a new hole at the proper height. Actually I'd maybe try 45deg so incase you mess up you have another try.
Or you could mod the housing. The easy way would be to remove any shims or spacers that are between the gear and housing. The next solution I can think of would be the have the housing gear end surfaced and material removed from their. You will loose a slight bit of oil pump shaft engagement and maybe even have to not use a gasket or surface the intake or the housing end that sits on the intake.
But all that seems like more trouble than buying another gear, I'd just buy the gm unit I think it was about the same price. Call summit you can prob return it still, they have a 90 day they cover shipping and after it's on you or maybe restocking fee.
GL!
edit: Just saw you posted while I was typing, Summit is cool most of the time.
1st is this a gm dist with a .491 shaft? Some places like MSD use .500
On the new gear, the toothed part looks a bit thicker(idk if that really matters for this) but pics can be kinda deceiving. You could turn the new gear 90deg then drill a new hole at the proper height. Actually I'd maybe try 45deg so incase you mess up you have another try.
Or you could mod the housing. The easy way would be to remove any shims or spacers that are between the gear and housing. The next solution I can think of would be the have the housing gear end surfaced and material removed from their. You will loose a slight bit of oil pump shaft engagement and maybe even have to not use a gasket or surface the intake or the housing end that sits on the intake.
But all that seems like more trouble than buying another gear, I'd just buy the gm unit I think it was about the same price. Call summit you can prob return it still, they have a 90 day they cover shipping and after it's on you or maybe restocking fee.
GL!
edit: Just saw you posted while I was typing, Summit is cool most of the time.
Last edited by BOOT77; 05-20-2016 at 04:52 PM.
05-20-2016, 07:01 PM
#23
Race Director
The GM 84 has a gear that has a rollpin holding it onto the shaft. Look carefully. There should be a small rollpin between the teeth. An old racer's trick and one that I have used is if the distributor housing has a limited area to rotate and moving the gear one tooth over causes the distributor to contact, the gear can be flipped over and the result will be 1/2 gear movement. I have had to do this a few times.
Last edited by 383vett; 05-20-2016 at 07:03 PM.
05-21-2016, 06:48 AM
#24
Race Director
I understood your not really blaming Lunati. Even if you were it wouldnt matter, since they will just say it was your fault.
05-21-2016, 09:03 AM
#25
Melting Slicks
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There is a load on the distributor gear caused by driving the oil pump that keeps the dist gear pinned to the cam gear. A worn dist gear is not the cause of your fluctuating timing issue.
Carbon tracks in the cap, loose coil mounting/ground, poor ignition wires.
Worse case = a loose timing chain.
Check the cap etc first.
No mechanical advance in the distributor it is all electronic. Disconnect the EST wire & set the timing @ 1000 maybe 1200 rpm. If it is steady @ that engine speed the timing chain may be stretched.
We are here to help suggest asking about any issues you may encounter before diving in & getting a tit caught in the wringer.
There are no dumb ??'s.
Good luck.
BTW if the cam you are using has a lumpy idle base timing will be hard to set, for 100% accuracy it will need to be set using the total timing method = another topic.
Carbon tracks in the cap, loose coil mounting/ground, poor ignition wires.
Worse case = a loose timing chain.
Check the cap etc first.
No mechanical advance in the distributor it is all electronic. Disconnect the EST wire & set the timing @ 1000 maybe 1200 rpm. If it is steady @ that engine speed the timing chain may be stretched.
We are here to help suggest asking about any issues you may encounter before diving in & getting a tit caught in the wringer.
There are no dumb ??'s.
Good luck.
BTW if the cam you are using has a lumpy idle base timing will be hard to set, for 100% accuracy it will need to be set using the total timing method = another topic.
Last edited by Churchkey; 05-21-2016 at 09:27 AM. Reason: add text
05-21-2016, 04:12 PM
#27
Drifting
Thread Starter
There is a load on the distributor gear caused by driving the oil pump that keeps the dist gear pinned to the cam gear. A worn dist gear is not the cause of your fluctuating timing issue.
Carbon tracks in the cap, loose coil mounting/ground, poor ignition wires.
Worse case = a loose timing chain.
Check the cap etc first.
No mechanical advance in the distributor it is all electronic. Disconnect the EST wire & set the timing @ 1000 maybe 1200 rpm. If it is steady @ that engine speed the timing chain may be stretched.
We are here to help suggest asking about any issues you may encounter before diving in & getting a tit caught in the wringer.
There are no dumb ??'s.
Good luck.
BTW if the cam you are using has a lumpy idle base timing will be hard to set, for 100% accuracy it will need to be set using the total timing method = another topic.
Carbon tracks in the cap, loose coil mounting/ground, poor ignition wires.
Worse case = a loose timing chain.
Check the cap etc first.
No mechanical advance in the distributor it is all electronic. Disconnect the EST wire & set the timing @ 1000 maybe 1200 rpm. If it is steady @ that engine speed the timing chain may be stretched.
We are here to help suggest asking about any issues you may encounter before diving in & getting a tit caught in the wringer.
There are no dumb ??'s.
Good luck.
BTW if the cam you are using has a lumpy idle base timing will be hard to set, for 100% accuracy it will need to be set using the total timing method = another topic.
But it's been about 5 months since the last time I was home and able to work on it so I'll have to get it back together and get a timing light on it to refresh my memory of what exactly is happening, and then I'll check the stuff you suggested. Thanks!
Last edited by C4ProjectCar; 05-21-2016 at 04:12 PM.
05-26-2016, 08:34 PM
#28
Drifting
Thread Starter
So maybe Lunati gears are just weird? None of this makes sense to me. While it kills me to not figure out what's going on here, I'm thinking I'll just order a Delco gear and hope that it is normal.
You guys have any thoughts? Measurements of other distributor gears would be welcome.
05-26-2016, 09:00 PM
#29
Melting Slicks
Are you 100% sure it is the oem dist?
edit: Not that the new one isn't bad as well. I once got three parts from Jegs that were all bad and on the 3rd they pulled their entire stock to check and found everyone defective.
edit: Not that the new one isn't bad as well. I once got three parts from Jegs that were all bad and on the 3rd they pulled their entire stock to check and found everyone defective.
Last edited by BOOT77; 05-26-2016 at 09:02 PM.
05-26-2016, 09:14 PM
#30
Drifting
Thread Starter
Wow, that's crazy. Maybe tomorrow I'll get a Lunati tech on the phone and see if they can pull up the proper specs of the gear I ordered.
05-29-2016, 12:11 AM
#31
Drifting
Thread Starter
Ended up just going with a Delco melonized gear. Shimmed it to about .023" endplay, and shimmed the distributor housing to properly align the gear using white lithium grease to see where the cam gear touched it. I haven't driven it yet due to other problems I'm working on, but I was able to set the base timing and it seems to run well.
05-29-2016, 02:21 AM
#32
Race Director
05-29-2016, 03:07 AM
#33
Drifting
Thread Starter
I wondered about that but I wasn't sure if that would happen at low RPMs, and I'd read about shimming endplay from so many sources. I figured I might as well shim it while I had the distributor out. It didn't cost much for the shim kit and I didn't want to have any doubt.
05-29-2016, 09:34 AM
#34
Le Mans Master
I wondered about that but I wasn't sure if that would happen at low RPMs, and I'd read about shimming endplay from so many sources. I figured I might as well shim it while I had the distributor out. It didn't cost much for the shim kit and I didn't want to have any doubt.
05-29-2016, 02:33 PM
#35
Drifting
Thread Starter
Is it potentially a concern to have the distributor too high up so it does not fully engage the oil pump drive shaft?