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.
Not to sound like a jerk but PLEASE get rid of that glass fuel filter. I once saw a beautiful 69 Camaro burn to the ground because of one. I don't want to ever see anyone go through that again.
I like your carb. It looks like something I would build. I would cut the choke tower off especially if using a drop base air cleaner.
Quote directly from the manual - Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle (WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to achieve the correct timing curve.
Oh I believe you. Just cannot imagine what the writer was thinking. The only reason to do something like that on the street is if you just don't think you are burning enough gas.
Not to sound like a jerk but PLEASE get rid of that glass fuel filter. I once saw a beautiful 69 Camaro burn to the ground because of one. I don't want to ever see anyone go through that again.
I like your carb. It looks like something I would build. I would cut the choke tower off especially if using a drop base air cleaner.
I agree. The glass filter is temporary though. This car sat for 20+ years. When it was resurrected, a new tank, fuel lines, etc were put in. But not a new FP. I experienced junk in my carb that was clogging up float valves after I had to cut the filter off. (it was installed directly on the Holley FP when the motor was out and could not be removed in car. Don't ask me how they thought that was a good idea) The glass filter is to see if any more junk is still in the system before I switch over to the Holley aluminum one. Going to run it a few more times before I switch over. Not a fan of these filters, at all, except for this one purpose.
Using a drop base, but with the K&N filter top. Debating on cutting the horn, or installing a choke. Surprisingly even in winter starting was not to overly bad without a choke. Will probably just cut that sucker off.
Quote directly from the manual -
"Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle (WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to achieve the correct timing curve."
GM's lazy. It uses the same, tired instruction guides for every dang 'performance' motor --- word for word --- verbatim.
As for priming oil system, GM repeats same typo error ad infinitum --- admonishes user to employ a dill motor (sic), repeat dill motor. Every engine, every install guide, every time.
GM's lazy. It uses the same, tired instruction guides for every dang 'performance' motor --- word for word --- verbatim.
As for priming oil system, GM repeats same typo error ad infinitum --- admonishes user to employ a dill motor (sic), repeat dill motor. Every engine, every install guide, every time.
HA! Your right! Here it is!
"The engine should be primed with oil prior to starting. Follow the instructions enclosed with the tool. To prime the engine,
first remove the distributor to allow access to the oil pump drive shaft. Note the position of the distributor before removal.
Install the oil priming tool, part number 141-955 from our licensed partner www.factoryperformanceparts.com. Using a 1/2" dill motor, rotate the engine oil priming tool clockwise for three minutes. While you are priming the engine, have someone
else rotate the crankshaft clockwise to supply oil throughout the engine and to all the bearing surfaces before the engine is
initially started. This is the sure way to get oil to the bearings before you start the engine for the first time. Also, prime the
engine if it sits for extended periods of time. Reinstall the distributor in the same orientation as it was removed."
* check around your local area, especially the community of circle track, there's likely someone local who's using a SUN or similar dist machine-tester to recurve racer's distributors. Ask the auto machine shop operators who do circle track work. They'll know who does distributors.
Do you have an adjustable timing light?
It's not that hard to do yourself.
I see you have a 2016.
Perhaps you would prefer the smart phone adjustment option:
It is crazy powerful.
It's $569 with the small cap tach drive corvette version.
Includes full timing map, vacuum advance, rpm limiter, launch retard, start retard, security disable, multiple timing curves, and much more.
By far the best way to tune vacuum advance is on the road, under varying loads. Not by mail.
This lets you change it, even while you are driving, one cell at a time, or load a new curve with a one button push.
I will keep both a 93 & 89 octane timing curve loaded & ready for my cross country trip.
I am a believer in the power of this fully computerized distributor.
I helped one guy tune his car via cellphone MAP screenshots, from 600 miles away.
IMO a full timing MAP is one of the biggest advantages of an EFI system.
Cold start runability and altitude adjustments are a distant second.
Ease of AFR tunability is third.
HA! Your right! Here it is!
"The engine should be primed with oil prior to starting. Follow the instructions enclosed with the tool. To prime the engine,
first remove the distributor to allow access to the oil pump drive shaft. Note the position of the distributor before removal.
Install the oil priming tool, part number 141-955 from our licensed partner www.factoryperformanceparts.com. Using a 1/2" dill motor, rotate the engine oil priming tool clockwise for three minutes. While you are priming the engine, have someone
else rotate the crankshaft clockwise to supply oil throughout the engine and to all the bearing surfaces before the engine is
initially started. This is the sure way to get oil to the bearings before you start the engine for the first time. Also, prime the
engine if it sits for extended periods of time. Reinstall the distributor in the same orientation as it was removed."
"Remove the distributor. Rotate the engine. Reinstall the distributor in the same orientation."
What could possibly go wrong? Who writes this stuff?
I rest my case. Circular file!
Do you have an adjustable timing light?
It's not that hard to do yourself.
I see you have a 2016.
Perhaps you would prefer the smart phone adjustment option:
It is crazy powerful.
It's $569 with the small cap tach drive corvette version.
Includes full timing map, vacuum advance, rpm limiter, launch retard, start retard, security disable, multiple timing curves, and much more.
By far the best way to tune vacuum advance is on the road, under varying loads. Not by mail.
This lets you change it, even while you are driving, one cell at a time, or load a new curve with a one button push.
I will keep both a 93 & 89 octane timing curve loaded & ready for my cross country trip.
I am a believer in the power of this fully computerized distributor.
I helped one guy tune his car via cellphone MAP screenshots, from 600 miles away.
IMO a full timing MAP is one of the biggest advantages of an EFI system.
Cold start runability and altitude adjustments are a distant second.
Ease of AFR tunability is third.
I like it. Just saw the version with mechanical tach.
Last edited by Redhook98; Mar 24, 2026 at 09:57 AM.
Quote directly from the manual -
"Set spark timing at 32º before top dead center (BTDC) at 4000 RPM with the vacuum advance line to the distributor disconnected and plugged. This setting will produce 32º of total advance at wide open throttle (WOT). The HEI vacuum advance canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to achieve the correct timing curve."
First, I strongly recommend you email Lars for the latest copy of his instructions. He updates them all the time, and they are absolutely the best practice for a street driven car. Whatever you found online is likely out of date, and possibly a forgery.
Second, speaking of out of date, I know exactly what the GM tech writers were thinking. They were thinking that for an off-road engine, 32 degrees of max advance will prevent pinging, and therefore prevent warranty returns. What is in the instructions you found is NOT up to date, and is not best practice for a street driven engine. Can you find a new ZZ4 for sale from GM?
As others have stated, get your timing sorted out before buying more parts (though you might need a new distributor, or at least a working vacuum advance).
Follow up. Seemed to be timing. Used Lars paper from 2005 and all went well. The major bog is gone. Going to re-calibrate the carb to same specs as the GM spec-d Holley and will see where I am. (purple accelerator cam, 70 jets in Primary and 82 in secondary). For a "stock" 355hp motor in a 50 year old car, it is surprising quick once 85% dialed in. Vacuum advance hooked back up too. Initial time before messing with was 12 degrees with no vacuum advance. After adjusting for 36 degrees with no vacuum advance at 2500-4000 RPM, idle timing was at 20. With vacuum advance hooked up, I am at 52 all in. In line with what others have posted. Thanks all for re-calibrating me.
Yes, glass filter is on the way out. I no longer see sediment from old filter.
Do you have an adjustable timing light?
It's not that hard to do yourself.
I see you have a 2016.
Perhaps you would prefer the smart phone adjustment option:
It is crazy powerful.
It's $569 with the small cap tach drive corvette version.
Includes full timing map, vacuum advance, rpm limiter, launch retard, start retard, security disable, multiple timing curves, and much more.
By far the best way to tune vacuum advance is on the road, under varying loads. Not by mail.
This lets you change it, even while you are driving, one cell at a time, or load a new curve with a one button push.
I will keep both a 93 & 89 octane timing curve loaded & ready for my cross country trip.
I am a believer in the power of this fully computerized distributor.
I helped one guy tune his car via cellphone MAP screenshots, from 600 miles away.
IMO a full timing MAP is one of the biggest advantages of an EFI system.
Cold start runability and altitude adjustments are a distant second.
Ease of AFR tunability is third.
Do you have an adjustable timing light?
It's not that hard to do yourself.
I see you have a 2016.
Perhaps you would prefer the smart phone adjustment option:
It is crazy powerful.
It's $569 with the small cap tach drive corvette version.
Includes full timing map, vacuum advance, rpm limiter, launch retard, start retard, security disable, multiple timing curves, and much more.
By far the best way to tune vacuum advance is on the road, under varying loads. Not by mail.
This lets you change it, even while you are driving, one cell at a time, or load a new curve with a one button push.
I will keep both a 93 & 89 octane timing curve loaded & ready for my cross country trip.
I am a believer in the power of this fully computerized distributor.
I helped one guy tune his car via cellphone MAP screenshots, from 600 miles away.
IMO a full timing MAP is one of the biggest advantages of an EFI system.
Cold start runability and altitude adjustments are a distant second.
Ease of AFR tunability is third.
What a difference! Wow! This thing runs incredible now! The difference between the Dragonfire and the Progressive Ignition is night and day. I installed new plugs (old still looked new) and wires. Need to tweak the profile a bit, but wow! Thanks!
Of course this was all AFTER I pulled the pan to find the missing washer. That was fun. Idler arm was directly against header. Mechanic who changed the oil used a long filter which sat about 1/2 inch above the header. That was fun too. Lol!
Still installing the GM ZZ4/6 tuned Holley 770 later and changing out the fuel supply side. Hey, its paid for so why not.
