Holley GB Distributor Allowable Tolerances?
- Thread starter cbmind
- Start date
Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
For all IH/Holley distributors (not just gold box), the "new" side play with a force of 5lbs. Applied is 0.002">0.004", with a max allowable of 0.006". This is total side play which includes the slop in the mechanical advance unit as well as the shaft/bushing interface.
Spec for end play is 0.035">0.040". But in my book that is way too much and allows more than 3 degrees variation in timing as the distributor shaft thrusts/loads.
I set up all the distributors I rebuild (either delco cast iron, Holley, or prestolite) with a minimum end play of 0.010" and a maximum of 0.015". End play is adjusted/corrected by the use of shims. I have an assortment of distributor shims from 0.005">0.070" and simply measure the end play with a thickness gauge before removing the drive gear and record what shim (or shim stack) needs to be installed once I've cleaned/lubed the unit and prep for re-installing the gear.
A distributor with the tightened end play provides a much more stable timing signal and adds greatly to idle quality.
If the nylon bushings in the mechanical advance unit are distorted/worn/missing, then timing advance will be all over the place and needs to be corrected with new bushings.
Spec for end play is 0.035">0.040". But in my book that is way too much and allows more than 3 degrees variation in timing as the distributor shaft thrusts/loads.
I set up all the distributors I rebuild (either delco cast iron, Holley, or prestolite) with a minimum end play of 0.010" and a maximum of 0.015". End play is adjusted/corrected by the use of shims. I have an assortment of distributor shims from 0.005">0.070" and simply measure the end play with a thickness gauge before removing the drive gear and record what shim (or shim stack) needs to be installed once I've cleaned/lubed the unit and prep for re-installing the gear.
A distributor with the tightened end play provides a much more stable timing signal and adds greatly to idle quality.
If the nylon bushings in the mechanical advance unit are distorted/worn/missing, then timing advance will be all over the place and needs to be corrected with new bushings.
For terminolgy, when I said end play. I meant grabbing the gear end of the distributor and moving the shaft up and down inside the body. Is this what you were referring to? Also, if shims are needed, where are they placed? How is side play corrected? A new bushing (probably)?
Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
The side play is corrected during a rebuild by installing a new top bushing and then burnishing to size (I can't do that at this point, I send 'em out for that process). If the wear is in the mechanical advance unit, then it all gets tossed out and replaced. The worn advance parts are saved and put to use in "locked timing" distributor conversions for efi setups.
A Holley distributor that has side play beyond spec is somewhat unusual actually, the problem is usually in the trashy condition of the mechanical advance mechanism whether it's a points unit or an electronic trigger. The hall effect trigger in the gold box distributor can tolerate excessive side play, a breaker point system cannot however. Even though a pertronix conversion is also a hall effect system, it likewise can't tolerate excessive runout.
End play is corrected by placing the appropriate shim(s) between the drive gear and the body. The gear is removed, then the entire distributor is gutted/cleaned/inspected/painted/refreshed. After pre-lubing the guts, it's reassembled and the shims are installed and the gear pressed back on and the spring pin re-inserted to lock the gear in place.
If the original vacuum advance can is still working properly, it's cleaned up and re-installed. Otherwise, it gets a remanufactured vacuum can since we can no longer source new ones. The remanufactured items are completely indistinguishable from new ones.
A Holley distributor that has side play beyond spec is somewhat unusual actually, the problem is usually in the trashy condition of the mechanical advance mechanism whether it's a points unit or an electronic trigger. The hall effect trigger in the gold box distributor can tolerate excessive side play, a breaker point system cannot however. Even though a pertronix conversion is also a hall effect system, it likewise can't tolerate excessive runout.
End play is corrected by placing the appropriate shim(s) between the drive gear and the body. The gear is removed, then the entire distributor is gutted/cleaned/inspected/painted/refreshed. After pre-lubing the guts, it's reassembled and the shims are installed and the gear pressed back on and the spring pin re-inserted to lock the gear in place.
If the original vacuum advance can is still working properly, it's cleaned up and re-installed. Otherwise, it gets a remanufactured vacuum can since we can no longer source new ones. The remanufactured items are completely indistinguishable from new ones.
Cleaned up the distributor real good, measured for tolerances, side play nonexistent it seems, whereas end play is at .046" measured with a feeler guage. When pushing the shaft up towards the body, the gear hits on the body and stops. The distance traveled is .046". Do you have the shims to correct this? I got this distributor to use with an efi conversion in the distant future. Not to concerned with the advance. When lubricating the guts inside, what kind of lube? Thanks for the info. Distributors, for whatever reason, have always been a big mystery to me.
Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
This is a source for a starter set of distributor shims, pay no attention to the "chevrolet" designation. I have collected an extensive inventory of similar shims over the years from many sources for all kinds of purposes:
shim kit for msd Chevy distributors - 8495
Pulling the distributor gear on a prestolite or delco distributor is very simple if you have the right tools and procedure to prevent damage. If you damage the gear, you are up shit creek as they are not available from any source though I am currently working with one manufacturer for sourcing some (doesn't look very promising right now).
Pulling the drive gear on any Holley-supply distributor can be somewhat more difficult due to a difference in the interference fit (press fit).
The gear retainer spring pin holes on a Holley distributor are dead center so the gear is fairly easy to orient. The same retaining pin holes on delco and prestolite distributors are obviously drilled as a set at the point of manufacture and must be properly aligned before pressing together. The drive gears for all those IH-pattern distributors are the same p/n.
Michael Mayben
IHPA Tech Moderator - Retired & No Longer Online
During re-assembly of these distributors I use a commercial, copper-base anti-seize lube. Once the units are installed (except for the cast iron delcos), they self-lubricate through engine oil throw-off through the spit holes drilled in the lower body.
The delco lubes the lower portion of the shaft through the spit hole, the upper bush is lubed periodically with engine oil supplied to the oil cup which contains a long felt wick.
The mechanical advance unit also gets lubed with the anti-seize. Part of distributor maintenance on the Holley unit is to add one drop of light oil to the felt under the rotor on occasion. Most distributors I get in for rebuild have never had the advance unit lubed and are therefore frozen and take alotta luv to remove/clean, and repair.
As for the retaining clip...good luck. I have no source for those. It's possible that philbin electric in portland, or might have some on occasion, but the last time I talked to 'em about those they asked me where to get 'em! I salvage those clips from distributors that I do a "lock out" on the mechanical advance unit which does not require use of the retaining clip. At this point, I have no spares. I do have a workaround for the clip but once installed, you will not be able to ever take the advance unit apart again without using a cutting torch.
The delco lubes the lower portion of the shaft through the spit hole, the upper bush is lubed periodically with engine oil supplied to the oil cup which contains a long felt wick.
The mechanical advance unit also gets lubed with the anti-seize. Part of distributor maintenance on the Holley unit is to add one drop of light oil to the felt under the rotor on occasion. Most distributors I get in for rebuild have never had the advance unit lubed and are therefore frozen and take alotta luv to remove/clean, and repair.
As for the retaining clip...good luck. I have no source for those. It's possible that philbin electric in portland, or might have some on occasion, but the last time I talked to 'em about those they asked me where to get 'em! I salvage those clips from distributors that I do a "lock out" on the mechanical advance unit which does not require use of the retaining clip. At this point, I have no spares. I do have a workaround for the clip but once installed, you will not be able to ever take the advance unit apart again without using a cutting torch.