Need advice on Tuning a Quad

[SirRobyn0]

Thank you all!
If I remember correctly my vacuum advance adds about 20deg. But I will re-measure it tomorrow as well as the mechanical advance and report back. I think it is the original stock distributer, but I don't know for sure.
What is a "safe" limit for total timing at ~3000rpms? I am afraid of hurting the engine, is that a concern?
@SirRobyn0 you are completely correct, since I gave up on using this truck as a trailer hauler, I mainly want to learn with it, and gain some sort of basic understanding of how to work on an older vehicle. So I really appreciate all the advice and explanations.
By the way, what exactly does a ping sound like? will I know if my engine starts pinging?

I think you'd be better off looking up a video on youtube, like SBC pinging, so you can hear it vs one of us attempting to describe it.

I remember the thread on the trailer. I'm heading out on Saturday in my 84' C20 for a nearly 400 mile journey with the trailer. And I will return with 2 tons of corn. That will be enough to last the bird farm for 6 months. I want to do it before there is much of a chance of having to deal with snow or seriously bad ice in the passes as I will need to go over Snoqualmie pass, and Manastash ridge pass.

 

[Velder]

@SirRobyn0 Wow that is a pretty big load of corn. If you don't mind me inquiring, where do you buy your corn? 400 miles and the passes you named, you seem to be headed for Idaho? mainly interested because we will be moving (Lord willing) to northwest Montana next spring, and I am hoping we can find more affordable feed grain for our animals. The little truck will probably have to pull a trailer for that move.

 

[SirRobyn0]

@SirRobyn0 Wow that is a pretty big load of corn. If you don't mind me inquiring, where do you buy your corn? 400 miles and the passes you named, you seem to be headed for Idaho? mainly interested because we will be moving (Lord willing) to northwest Montana next spring, and I am hoping we can find more affordable feed grain for our animals. The little truck will probably have to pull a trailer for that move.

I'm going to tag you in the farming thread and answer your question there if that's alright.

 

[Velder]

@SirRobyn0 That would be great! I didnt know there was a farming thread. See you there.

 

[Ricko1966]

There are like 100 different hei combinations GM took into account all kinds of factors. Anyway Robyn gave you good advice I didn't read everyone's because I already saw where things were going. I would tell you to setup the distributor by trial,error and testing. What works best for total,ignore initial,then how fast can we bring the mechanical in,then what are your vacuum readings and how much Vacuum advance can we add at cruise. Unless you're willing to do the work to set up the distributor that your truck wants,then set it up like factory, the initial that worked for so and so. What weights were in his distributor?,what eccentric?,springs?vacuum advance cannister? What was his total centrifugal? Etc. Etc. The best total wouldn't even be the same between 2 absolutely identical cars and engines if one only had different heads.

 

[75gmck25]

Every engine is different, but a common guideline is that base plus mechanical should not exceed about 34-36 degrees for a mild build, usually measured at about 3000 rpm. However, this is just a guideline. It’s common for mechanical advance mechanisms to add about 20 degrees, so 12 degrees base plus 20 mechanical (32 total) is usually a safe range.

However, you also have to watch out for stock vacuum advance cans that add 20+ degrees, because that can put you up to 52 degrees at lean cruise. That may lead to light throttle pinging.

Make sure when you measure base timing that the vacuum advance is disconnected and the line is plugged, and you set the idle down low so there is zero mechanical advance. You should also use a piston stop to measure TDC and ensure that zero on your timing tab is really zero.

 

[fast 99]

Know I am getting a little ahead of what the original question was, these engines were designed to operate as a system. Here's few things to check at some point.

If needed there are vacuum units with much less advance. 20 degrees is about the most I have seen. Way to tell is look at the distance between there the hook in the rod goes through the hole punched out in the mounting bracket. Longer the slot, more advance.

Depending on what is still on the vehicle and emissions configuration could be a TVS and or vacuum check valves in the advance circuit. Operation should be checked.

Another thing that is often overlooked is the valve for air preheat in air cleaner snorkel. If that doesn't open when motor is hot it can create problems and of course that pesky EGR should work.

 

[Velder]

Hi @Ricko1966 thank you for the input, I am very willing to put the work into setting up the distributor. Do you mean setting up using the distributer and vacuum can that are currently in the truck? or replacing them with new ones of known value?
I will get the timing measurements and post them here tonight.
@75gmck25 I think that just the vacuum can I have, it adds right at 20 deg. if I remember correctly. Could you elaborate on using a piston stop?
@fast 99 I was wondering about that air preheat system, I will try to check that, I don't know if my EGR is working or not, I have thought about replacing the valve just to be sure. But other than the A.I.R. system, which I have temporarily disabled, All the emissions are intact.

 

[Ricko1966]

It's complicated,busy but will get back to you.Search for threads between me and @Squirrely Brother I walked him through it. Yours will be the same deal. Find what total gives best mph in a measured distance with vacuum advance disconnected and plugged. Time low bring it up 2 degrees at a time for best mph,that's called total. Use a landmark you can pass about 3/4 through 2nd gear look at your speedo. Mph is more accurate than ET for what we are doing. then how fast can we bring it in. Then we deal with vacuum. Something just occurred to me. You are running a stone stock 305 with knock sensor right? Time it like factory. They are a breed of their own

 

[75gmck25]

You can buy a piston stop from summit, or make your own from an old spark plug.

General process ( from memory) for finding TDC is:
- Remove plugs and turn the engine over until you are a little short of where you think TDC is. Check rotor to make sure you are on #1, not #6.
- screw piston stop into #1 spark plug hole until it stops, then back off a little.
- gently turn engine over a little more until the piston hits the stop again. Put a mark on the balancer that lines up with 0 on the timing pointer.
- now turn the engine backwards slowly until #1 hits the stop again. Mark the balancer again to match 0.
TDC for #1 will be exactly halfway between the 2 marks, so make a mark/line there on the balancer. Adjust or remark the timing tab or balancer so the balancer 0 lines up with 0 on the tab.

This article suggests how to make one. https://www.johnheard.com/how-to-find-tdc-and-make-your-own-piston-stop/

 

[Velder]

Thank you both. @Ricko1966 yes I am running a completely stock engine, And I belive it has knock sensors.
I got home late, so didn't have time to get the timing measurements tonight. will try to get those tomorrow.

 

[Ricko1966]

Thank you both. @Ricko1966 yes I am running a completely stock engine, And I belive it has knock sensors.
I got home late, so didn't have time to get the timing measurements tonight. will try to get those tomorrow.

Time your engine to the stock reccomendations,I seriously doubt you need a piston stop If you time it with your factory marks,to factory spec and it doesn't run good,then we can start trying to reinvent the wheel but right now try what you have at stock specs. Here's the deal with the guys twisting the distributor,giving it more advance 1/2 of them don't know what they are doing in the first place,there dad did it his dad did it so they do it,not realizing sometimes its not the right thing to do. Your engine has esc,it retards timing when it senses detonation.Your engine has esc because the factory has already put in more timing than your engine can use. It senses detonation and pulls out some timing. The guys twisting there distributor are twisting it until they detect detonation then backing it down to get rid of the detonation,the bad is that's a fixed value it's never going to advance beyond that point. Your esc ignition will run as much timing as the engine can use and will pull some timing as needed,when needed,not pull it forever and lock it out like the non esc guys are doing.

 

[Ricko1966]

I also rebuilt and tuned my Quadrajet with a kit from Cliff Ruggles. Mine shows similar AFR readings as yours, and it seems to run fine. Not sure why it goes so lean at cruise.

I’ll have to disagree on 4 degrees being enough base timing. 4 degrees made my engine really lethargic. When I had iron heads I used 8 and then 12 degrees, and with aluminum heads I’m at about 15 degrees base. Aluminum heads will tolerate more timing than iron heads.

For timing
- I disconnect and plug the vacuum advance, and set the idle down to about 600, and then set base timing to 15 BTDC.
- my mechanical advance adds about 20 degrees and it comes in quickly, by about 2200 rpm
- my vacuum advance adds 17 degrees

I’ve been running this timing setup for about five years, with no issues.

I would assume you are not running a 305 with knock sensor ignition. Not poking you just want Velder to know yours is not an apples to apples comparison. Or so I assume.

 

[Velder]

@Ricko1966 thank you so much for the explanation on the ESC, I didn't realize what it really did.
I don't know if it makes any difference or not, but here is what my timing is currently.
5 deg. @ 750rpm Vacuum advance disconnected
25 deg. @ 750rpm with Vacuum connected
22 deg. @3000rpm Vacuum disconnected
40 deg. @3000rpm Vacuum connected
While doing the timing, sometimes it seems a little irregular, meaning the timing mark jumps a little to either side, Is this normal? And occasionally the timing light does not flash, as if it did not detect a spark. Don't know what any of that means, but thought someone here might.

 

[Ricko1966]

@Ricko1966 thank you so much for the explanation on the ESC, I didn't realize what it really did.
I don't know if it makes any difference or not, but here is what my timing is currently.
5 deg. @ 750rpm Vacuum advance disconnected
25 deg. @ 750rpm with Vacuum connected
22 deg. @3000rpm Vacuum disconnected
40 deg. @3000rpm Vacuum connected
While doing the timing, sometimes it seems a little irregular, meaning the timing mark jumps a little to either side, Is this normal? And occasionally the timing light does not flash, as if it did not detect a spark. Don't know what any of that means, but thought someone here might.

My advice to you would be quit looking for something wrong,and enjoy your truck,yes there's going to be little moments where timing skips a beat it stumbles on a 33 degree day from a 10 mph punch only if it's raining out. These little things are just the nuances of these old trucks. If it runs good drives good,does what it's supposed to your job is done. Seriously I learned this the hard way years ago, I'd fix all the bog problems,now the smaller problems were now the big problems,now the even smaller problems were the big problems,now the smaller problems were the big problems. Until I ended up with a vehicle I couldn't enjoy. I didn't want the sun on it,or rain,can't park it anywhere it could get stolen etc.etc. etc. Fix the big stuff,don't sweat the small stuff and enjoy,quit working on it and drive it somewhere.