# 1965 389 Camshaft Timing



## oldmanz (7 mo ago)

Hey all! Long time reader, but first time poster! I hope I have this in the right place! 

I have been working on a 1965 Pontiac Bonneville, with the 389 and Carter AFB. No modifications except for what I am going into now.

I have been fighting with IGNITION timing for a while now. It's really hard to find the sweet spot. To advanced, I get detonation like crazy. But set where there is no det, I get a pretty doggy engine that needs the idle screw all the way out just to idle. I can find a sweet spot, but it's real close between the two. I tried running 93 octane, and it helped a tiny bit. But I would like to avoid that. (I will mention that I have tried ALOT of IGNITION timing tricks here. Vacumm advance limited to 10 degree, mechanical limited, points, pertronix, new dist, cap, rotor and coil. I Always have the same results.)

fast forward

This weekend, I did a timing chain replace. While I was in there I swapped out the stock 066 cam with an 068 (melling spc-7). The timing kit I got has VALVE timing degree adjustments for 8r, 6r, 4r, 2r, 0, 2a, 4a, 6a, 8a. I installed the cam straight up (so 0). Got it put back together. Car ran great at idle, but had CRAZY detonation. Can't get the IGNITION timing retarded enough to not get detonation, and also keep the car running.

So, I pulled off the VALVE timing again, and set it to 4r (4 degrees retarded). Now it runs about how it did before! A narrow window of IGNITION timing adjustment between det and idle death / poor performance. 

I am wondering, should I move VALVE Timing down to 6r or 8r? Or is that crazy? I can't tell if I am band-aiding another problem, or if that much degree offset is normal with todays gas? Thanks!!


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## BearGFR (Aug 25, 2008)

I hope not, but it could be that you're fighting a problem of just too much compression for the fuel. The fact that running 93 octane helped is a clue that might be the case. 
Retarding the cam would have delayed the intake closing event, which would have reduced cylinder pressure at low RPM, which would also have helped with detonation. Unfortunately, retarding the cam timing also kills low RPM torque - which is probably why doing that hurt performance.

As luck would have it, just today I ran across some YouTube videos that delve into the subject of ignition timing, modern fuels, and what electronic ignition "kits" (like the Pertronix do and more importantly, DON'T do).

Here are some links:
Orig 70 Pontiac RAIII distributor; why it runs like a dog and why electronic conversion doesn’t help
Recurving a distributor; why it is important to get performance from your engine!
Modifying and custom curving a GM HEI distributor for street performance
Distributor installation tutorial

One point that he brought up in one of the videos, that I personally wasn't aware of, is the difference in fuel today vs. back in the 60's - specifically in how fast it burns, and how that relates to your ignition advance curve.

Fixing a detonation problem by altering ignition timing is at best a band-aid, and will always be associated by a severe hit in performance. 

Sorry to be the bearer of (what may be) bad news, but it's possible that the only viable alternative will be to drop compression with dished pistons.

Bear


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## oldmanz (7 mo ago)

Wow! Thanks for the quick response!
Checking out the videos now. 

Follow up question for you. 
Is dropping the VALVE timing back to 6 or 8 a viable option to drop compression for the time being? It is not a performance machine by any means. Just a cruiser that we travel a bit with. 
I don't have the budget or time to rebuild the engine at this time. I just want to make sure that won't hurt anything long or short term.


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## oldmanz (7 mo ago)

^ I should also mention that I don't actually mind running 93 gas. Just was trying to avoid it if possible. But if that's what it needs, that's what it needs.
Do you have any tips for trying the new gas more scientifically? I can listen for det, but I see a lot of people saying that you can't always here it. 
With todays modern fuel issues, how do you actually choose a VALVE Timing, IGNITION timing, and Fuel octane without sacrificing performance. 
haha. It's too many variables. Do most run 93 in the pontiac motors now?


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## BearGFR (Aug 25, 2008)

That's a lot of 'retard' and I doubt if anyone could predict what effect it's going to have, including me - unfortunately. 

I do run 93 in my '69 GTO all the time. I'm also running aluminum aftermarket heads (which tolerate more compression) and a pretty healthy solid roller cam that has 251/257 degrees duration at 0.050 lift, and a fully programmable ignition. All of that helps keep me out of detonation trouble. My static compression ratio is 10.5:1. If I was running factory iron heads that'd probably still be too much, even with that long duration cam. It'd be safer at around 9.5:1 if I was running iron heads. 

A 'bigger' cam might help you some, but it wouldn't take much change to put you into a snowball situation where in order to make that work and live you'd need different springs, heads machined for different installed height, different pushrods, adjustable rocker nuts, etc.

The money adds up quick.

Bear


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## oldmanz (7 mo ago)

> A 'bigger' cam might help you some, but it wouldn't take much change to put you into a snowball situation where in order to make that work and live you'd need different springs, heads machined for different installed height, different pushrods, adjustable rocker nuts, etc.
> 
> The money adds up quick.


Right! That's why I stuck with the 068 over anything else. haha


I am going to continue putting 93 in and see what kind of effect it has. I will keep looking for anyone else with a stock high comp 389 and what fuel they run. 

The only mystery to me is how the original 066 cam was set. I wonder if it is retarded from the factory? Putting the new one straight up had a huge effect on timing. 
But I suppose the 068 could have raised the compression ratio on it's own. 
Trouble is, I was running 93 pre and post cam swap. So theoretically it had it's best chance with pump gas.

If things don't shape up, I may try to retard a bit more to avoid the dished pistons. I'll see what happens and post about it. haha


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## geeteeohguy (Feb 2, 2008)

You have a 1965 4bbl 389 that will have anywhere from 10:1 to 10:75: 1 compression. You can either run 100 octane fuel or install different cylinder heads if you want to run it on the street and have it perform decently. BTDT with what you are doing, and you simply have too much compression for today's fuels. Simple as that. You can retard it to run without ping, but it will run hot, chug fuel, and drive like a slug. Trust me. You can screw around with camshafts and cam timing and ignition curve all you want, and you won't win this fight. Put some 100LL aviation gas or Sunoco 100 in it and set the timing to stock specs and watch it happily tear up the road. I run Octane Supreme 130 in my own '65 389. It has about 62-63cc heads. (milled #77)


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## oldmanz (7 mo ago)

Great info! Thanks! I think that is what I needed to hear. It's hard to find that info with so many people doing different things. 

So, what is the best route then? You guys have said both dished pistons and different heads. Is there a preferred route?


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> ^ I should also mention that I don't actually mind running 93 gas. Just was trying to avoid it if possible. But if that's what it needs, that's what it needs.
> Do you have any tips for trying the new gas more scientifically? I can listen for det, but I see a lot of people saying that you can't always here it.
> With todays modern fuel issues, how do you actually choose a VALVE Timing, IGNITION timing, and Fuel octane without sacrificing performance.
> haha. It's too many variables. Do most run 93 in the pontiac motors now?


You also dont mention (unless I missed it) *when* you're getting detonation. Base, cruise, or WOT? 

But regardless, trying to run a 60's Pontiac engine, without 93 octane, is like spitting in the wind. In fact, a lot of these guys would be quite jealous of you if you could run 93, without detonation.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> Right! That's why I stuck with the 068 over anything else. haha
> 
> 
> I am going to continue putting 93 in and see what kind of effect it has. I will keep looking for anyone else with a stock high comp 389 and what fuel they run.
> ...


Have you verified TDC? Ive twice recently dealt with members where the dizzy was dropped in a tooth off. In that case, the rotor was pointing at number two when the dizzy was installed, so when you think you're advancing #1, it is already severely retarded before you started. Likewise, if the rotor was pointing at #8 when the dizzy was installed, the timing would have to be retarded, in order to advance #1!

Thats not likely your issue, but I cant think of many other reasons where your setup would require such dramatic retarding... even on low octane, the engine should run at least 6 degrees of advance, without issue.


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## oldmanz (7 mo ago)

armyadarkness said:


> You also dont mention (unless I missed it) *when* you're getting detonation. Base, cruise, or WOT?
> 
> But regardless, trying to run a 60's Pontiac engine, without 93 octane, is like spitting in the wind. In fact, a lot of these guys would be quite jealous of you if you could run 93, without detonation.


Can't hear any at base
Cruise slightly unless really retarded (IGNITION)
WOT less noticeable than cruise when getting it there. But, when even a little too advanced (IGNITION), I get extremely loud det.

But I suppose none of this matters, since I have NOT been taking fuel octane into account. haha 

Yeah, never run a high compression motor before. I was unaware of the fuel challenges. 
It makes total sense, being into it now.


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## oldmanz (7 mo ago)

armyadarkness said:


> Have you verified TDC? Ive twice recently dealt with members where the dizzy was dropped in a tooth off. In that case, the rotor was pointing at number two when the dizzy was installed, so when you think you're advancing #1, it is already severely retarded before you started. Likewise, if the rotor was pointing at #8 when the dizzy was installed, the timing would have to be retarded, in order to advance #1!
> 
> Thats not likely your issue, but I cant think of many other reasons where your setup would require such dramatic retarding... even on low octane, the engine should run at least 6 degrees of advance, without issue.


I have a system with the dizzy, having had it out so many times, where I keep track of where the rotor is in relation to the cylinder wire it was closest too. So, if i am off a tooth, I always get it back on in a place where it will start, and the fine tune from there.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> Great info! Thanks! I think that is what I needed to hear. It's hard to find that info with so many people doing different things.
> 
> So, what is the best route then? You guys have said both dished pistons and different heads. Is there a preferred route?


Climate also matters quite a bit. I live in Jersey and I run closed chamber 670 heads, without dished pistons, on 93 octane, with 16 degrees of advance. Many other guys here could never run that same setup. No two cars are the same, so take the advice with a grain of salt.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> Can't hear any at base
> Cruise slightly unless really retarded (IGNITION)
> WOT less noticeable than cruise when getting it there. But, when even a little too advanced (IGNITION), I get extremely loud det.
> 
> ...


Ah! This is telling. 

If you cant hear any at base, then retarding the timing even more is just a waste. 


You need to set the base timing so that the engine is happy at idle.
If it's pinging at cruise, then you need to install heavier centrifugal springs or limit the vac can further. How are you verifying that you limited your vac can to 10 degrees?
You state that WOT pinging is less noticeable, so if it's not pinging at base, pinging at cruise, and barley pinging at WOT, Im a bit perplexed. I would verify TDC, verify your CCW firing order, run 93 octane, limit your vac advance, install heavier mechanical advance springs, and set the base timing so that the car runs sweet at idle.
Then report back with results


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> I have a system with the dizzy, having had it out so many times, where I keep track of where the rotor is in relation to the cylinder wire it was closest too. So, if i am off a tooth, I always get it back on in a place where it will start, and the fine tune from there.


The problem with that method is that:


If you install the dizzy pointing at #2, and advance it, it will start and run, but act like the engine is retarded.
If you install the dizzy pointing at #8, and retard it, it will start, but act like the engine is seriously advanced.


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## geeteeohguy (Feb 2, 2008)

oldmanz said:


> Great info! Thanks! I think that is what I needed to hear. It's hard to find that info with so many people doing different things.
> 
> So, what is the best route then? You guys have said both dished pistons and different heads. Is there a preferred route?


Depends on the shape of your long block. If I were doing a new build, I would use dished pistons. This is not cheap. Have built a few engines in the past 10 years with dished pistons and they all ran VERY strong on 87-89 pump gas and are still running strong. If I had a tight lower end with good rings, etc. a set of lower CR (2bbl spec) heads in the 8-8.2 CR range would be the choice. My personal deal: I built the 389 in my '65 GTO in 1981 and it only has 50,000 miles on it now. I built it when dished slugs, custom rods, and aluminum heads were not available, but good gas was. It's at 11:1 CR and doesn't leak oil and has 175 psi in every cylinder, and that's with a big cam. With a stock 068 cam it would be about 210 psi compression. I have driven this car less than 10,000 miles in the past 30 years because it needs race gas and I just can't convince myself to bite the bullet and install low compression or aluminum heads, which is what I SHOULD do. It runs like a champ. 
I installed a set of lower compression heads on my '67 GTO years ago and it runs fine on pump gas with a stock carb and stock timing curve and runs like a top. I had owned the car for more than 20 years prior to this, and it pinged and detonated no matter what I did, and I'm a tune-up guy. Retarded timing. Water injection. Carb re-jetting. Nope. Ping City. 

So, in summary: if your engine needs a rebuild anyway, dished pistons are the way to go. If your engine is fresh, swapping heads is easier and cheaper.


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## geeteeohguy (Feb 2, 2008)

I'll add that in 1987 I broke 4 or 5 pistons and blued the crank and pounded the bearings out of a 428 from detonation. And I never heard a thing. Not one rattle until the rods started to knock after a 7000 rpm blast (with the stock cast pistons). But that's another story I've told before.....just because you don't hear it doesn't mean it isn't happening.


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## oldmanz (7 mo ago)

armyadarkness said:


> The problem with that method is that:
> 
> 
> If you install the dizzy pointing at #2, and advance it, it will start and run, but act like the engine is retarded.
> If you install the dizzy pointing at #8, and retard it, it will start, but act like the engine is seriously advanced.


I am attempting to understand this. haha I will reread everything you have posted to try and wrap my head around it.


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## oldmanz (7 mo ago)

armyadarkness said:


> Ah! This is telling.
> 
> If you cant hear any at base, then retarding the timing even more is just a waste.
> 
> ...


Okay, this is good. I have had issues with timing for a while, and I couldn't find anything on vac advance with these engines. It seemed like I would set the initial timing somewhere in the 6 to 12, have a good 34 is with mechanical in, and everything sounded good. Then I would hook up the vac and the timing would jump up like 18 degrees higher and the idle would sound real bad. (like, rich. even after carb adjustment) So, I took off the vac, drilled some holes in the rod, and put in cotter keys to adjust how far it was pulled. Ended up at around 10, but still had rich sounding idle. Just not as bad.


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## oldmanz (7 mo ago)

geeteeohguy said:


> Depends on the shape of your long block. If I were doing a new build, I would use dished pistons. This is not cheap. Have built a few engines in the past 10 years with dished pistons and they all ran VERY strong on 87-89 pump gas and are still running strong. If I had a tight lower end with good rings, etc. a set of lower CR (2bbl spec) heads in the 8-8.2 CR range would be the choice. My personal deal: I built the 389 in my '65 GTO in 1981 and it only has 50,000 miles on it now. I built it when dished slugs, custom rods, and aluminum heads were not available, but good gas was. It's at 11:1 CR and doesn't leak oil and has 175 psi in every cylinder, and that's with a big cam. With a stock 068 cam it would be about 210 psi compression. I have driven this car less than 10,000 miles in the past 30 years because it needs race gas and I just can't convince myself to bite the bullet and install low compression or aluminum heads, which is what I SHOULD do. It runs like a champ.
> I installed a set of lower compression heads on my '67 GTO years ago and it runs fine on pump gas with a stock carb and stock timing curve and runs like a top. I had owned the car for more than 20 years prior to this, and it pinged and detonated no matter what I did, and I'm a tune-up guy. Retarded timing. Water injection. Carb re-jetting. Nope. Ping City.
> 
> So, in summary: if your engine needs a rebuild anyway, dished pistons are the way to go. If your engine is fresh, swapping heads is easier and cheaper.


Thanks! Its an all original engine, aside from the cam and lifters now. It seems that a rebuild is in the cards for it.


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## oldmanz (7 mo ago)

oldmanz said:


> I am attempting to understand this. haha I will reread everything you have posted to try and wrap my head around it.


Oh! You mean for the timing light reading incorrectly?


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## Jared (Apr 19, 2013)

I'm betting you have detonation at WOT and are just not hearing it. Before you drive yourself nuts on this, throw a tank of race fuel or octane boost in there and see if it clears up. Most of the guys who have built these engines recently do so with whatever pump gas is available in the area. I targeted a shade less than 9.5 : 1 with cast iron heads when I built mine and it runs fine on 93 octane pump gas.


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## Jim K (Nov 17, 2020)

Ditto x2 on the octane booster. If it were my engine, I'd degree the cam according the the cam card specs, set timing at the factory setting (to start with. You can play with total timing and when it's all in after you get your pinging issue solved), then get 93 octane and add octane booster. there are several decent brands on the market ( I use VP racing booster). If the knock diminished or lessens, then you can use that as your starting point and make your decision from there. You may end up either deciding on a rebuild, or new lower CR heads or keep with the octane booster. Retarding a cam shaft as much as you are talking about may help a little bit with the knocking issue but for sure it will make your engine a slug on the performance side. Pontiac motors seem to like just a little advance ground into the cam shaft. The 93 octane and booster is a cheaper way to start figuring out which direction you want to go.


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## Jim K (Nov 17, 2020)

the 068 cam was used for several different years in "HO" applications. Stamped S.


S288113.407".447"63302119.407".447"9779068


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## Jim K (Nov 17, 2020)

above is from the Wallace racing web site.


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## oldmanz (7 mo ago)

Jim K said:


> Ditto x2 on the octane booster. If it were my engine, I'd degree the cam according the the cam card specs, set timing at the factory setting (to start with. You can play with total timing and when it's all in after you get your pinging issue solved), then get 93 octane and add octane booster. there are several decent brands on the market ( I use VP racing booster). If the knock diminished or lessens, then you can use that as your starting point and make your decision from there. You may end up either deciding on a rebuild, or new lower CR heads or keep with the octane booster. Retarding a cam shaft as much as you are talking about may help a little bit with the knocking issue but for sure it will make your engine a slug on the performance side. Pontiac motors seem to like just a little advance ground into the cam shaft. The 93 octane and booster is a cheaper way to start figuring out which direction you want to go.


Do you run two bottles of that stuff per tank? It says it treats 10 gallons.


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## oldmanz (7 mo ago)

Update: I haven't touched my cam timing yet, but I did add a few bottles of some additive to try to bring the 93 up. 
I used three 'lucas oil octane booster 15oz'
So far I put about 10 miles on with no real noticeable change. That stuff might not be that great though. 
I'm going to put the cam back at some point soon and see what happens!


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## lust4speed (Jul 5, 2019)

Personally I've never had any luck with octane boosters - even when we went crazy and kept increasing the amount until we ended up at four times what was called for and still had detonation. For testing purposes get the tank near empty and fill with either five gallons of race gas or five gallons of aviation gas. While my current engines now easily run on 91 octane, there was a period where my street engine was at a true 12.8:1 compression and the GTO lived on AV gas for many years. Actually 9-11 was responsible for me having to do something different because all the airports in my area (and probably everywhere) pulled entry passes and gate cards. About the same time race gas quadrupled in price and it was just too costly to use.

For the time being disconnect the vacuum advance. Your problem was not only the total amount of vacuum advance but how soon that advance comes in. Anyway, simplify your problems and take a variable out of the equation. Next forget about the timing light and set your timing by trial and error until you are sure you don't have detonation, and then take another two degrees out of it. Then if you want you can take your timing light and observe what the engine is telling you it actually wants. I've seen quite a few stock high compression 389's and 400's that wouldn't tolerate over 28° total timing on today's gas. Yes, power goes down and temps go up, but at least the bearings won't be pounded to oblivion as quickly.

Have to add that with all the variables, the timing marks on the crank timing chain sprocket usually have very little to do with reality. I've had to use both sides of the zero mark (4R, 2R, 2A, 4A) on different builds to arrive at true straight up cam timing. Crank keyway, crank rod journal index, cam keyway, and ground lobe centerlines all play a part of where things actually end up. Just as well add timing chain length and sprocket teeth to the list of variables. You really need to degree in the cam so you know where you are starting from. The 068 cam is a little more forgiving that the previous 066 cam, and if you are picking up more detonation after a cam swap, then something else has changed.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> I am attempting to understand this


I wouldnt! I barely do... lol... nevertheless, Ive seen it happen twice. A car can run on very bad timing.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> I will reread everything you have posted to try and wrap my head around it.


Well, whats important is that you verify TDC, then drop in the dizzy with the rotor pointing at number one on the cap. Marks on the firewall are okay for ball park stuff, but they dont cut it when tuning.


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## armyadarkness (Dec 7, 2020)

Jim K said:


> Ditto x2 on the octane booster.


X3 I dont like octane booster... unless it's absolutely needed, as a result of extensive testing.


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## oldmanz (7 mo ago)

UPDATE - SOLVED! 
Sooooo, I have fixed the issue! I am updating here so any future lookers can benefit.

It came down to a bone headed move by me installing the timing chain, and the last guy who did the same.

I pulled the timing cover last night with the intention of putting the VALVE timing at straight up. I got to looking at the timing chain paper work and the gears themselves.
With the engine at tdc, the dots on the gears should line up. (either directly, or 180 degrees out on the camshaft side, classic timing stuff)
On mine, the cam shaft keyway was facing straight down, and the crank keyway was facing towards cylinder 1. This puts the cam gear dot abit short of 1 oclock and the crank gear dot straight up.

THAT'S NOT RIGHT!? 

When I had changed everything last, I set the motor to tdc and put everything back the way it was. I didn't even look at dots. Just pointed the keyways back.
It appears that the last guy to change timing chain didn't do it right? And then I made the BIG mistake of trusting him and not using my brain.

So for a while now, the VALVE timing has been advanced by well more than 10 degrees(i don't have a real number). 
When I put in the new cam, that issue was made a bit worse some how. (could be the came, or the old timing gear having been installed the wrong way around, retarding the advanced situation a bit.
When I got back in there and retarded 4 degrees, I was offsetting the advance a bit. But still no where near enough.

So, last night I took the opportunity to spin the cam down by 180 so the dots would match up (left the dizzy in of course), and install the cam properly straight up.
Put her back together and went around the block.

She pulls like she never has. Squeals the tires from a stop. Puts you in your seat. Not a hint of det, and I have a LOT more freedom in the timing adjust before hearing anything! 

THANKS! Everyone for the help and logical troubleshooting experience! I have learned soooo much from these mistakes! It's great! haha

Next steps, I'm gonna continue running 93 with booster, or find some race gas somewhere. I will eventually rebuild the engine and do dished pistons then.


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## armyadarkness (Dec 7, 2020)

lust4speed said:


> For the time being disconnect the vacuum advance.


This is my advice as well.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> UPDATE - SOLVED!
> Sooooo, I have fixed the issue! I am updating here so any future lookers can benefit.
> 
> It came down to a bone headed move by me installing the timing chain, and the last guy who did the same.
> ...


Glad you found it. Wow... thats a mess.


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## armyadarkness (Dec 7, 2020)

oldmanz said:


> UPDATE - SOLVED!
> Sooooo, I have fixed the issue! I am updating here so any future lookers can benefit.
> 
> It came down to a bone headed move by me installing the timing chain, and the last guy who did the same.
> ...


Sounds like a fun car now!


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## Jim K (Nov 17, 2020)

Glad you found the problem! SHould be a joy to drive now..


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## geeteeohguy (Feb 2, 2008)

The only two octane boosters I know of that actually work are Octane Supreme 130 and Torco Accelerator. There may be one more. None of that crap at Autozone works one little bit. (the 0="104" and '108" stuff) Absolute crap.


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## lust4speed (Jul 5, 2019)

Octane boosters that work contain high concentrations of Toluene and while it smells great it is very dangerous in high concentrations (prior to mixing it into gas).

"Toluene (C₆H₅CH₃) is a colorless liquid with a sweet, pungent odor. Exposure to toluene can cause eye and nose irritation, tiredness, confusion, euphoria, dizziness, headache, dilated pupils, tears, anxiety, muscle fatigue, insomnia, nerve damage, inflammation of the skin, and liver and kidney damage. Workers may be harmed from exposure to toluene. The level of exposure depends upon the dose, duration, and work being done..."

One of my early jobs in my life involved manufacturing large pumps and the finished pumps moved down an assembly line and would be dipped into paint tanks. One of the paint additives we added was Toluene and we had to wear full safety equipment when in the paint area and the area needed massive ventilation to keep the fumes from building up.


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## Jared (Apr 19, 2013)

Glad this worked out for you.


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## BearGFR (Aug 25, 2008)

oldmanz said:


> UPDATE - SOLVED!
> Sooooo, I have fixed the issue! I am updating here so any future lookers can benefit.
> 
> It came down to a bone headed move by me installing the timing chain, and the last guy who did the same.
> ...


Wow, it's a wonder it would run at all. Congrats on finding the problem.

Bear


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## geeteeohguy (Feb 2, 2008)

lust4speed said:


> Octane boosters that work contain high concentrations of Toluene and while it smells great it is very dangerous in high concentrations (prior to mixing it into gas).
> 
> "Toluene (C₆H₅CH₃) is a colorless liquid with a sweet, pungent odor. Exposure to toluene can cause eye and nose irritation, tiredness, confusion, euphoria, dizziness, headache, dilated pupils, tears, anxiety, muscle fatigue, insomnia, nerve damage, inflammation of the skin, and liver and kidney damage. Workers may be harmed from exposure to toluene. The level of exposure depends upon the dose, duration, and work being done..."
> 
> One of my early jobs in my life involved manufacturing large pumps and the finished pumps moved down an assembly line and would be dipped into paint tanks. One of the paint additives we added was Toluene and we had to wear full safety equipment when in the paint area and the area needed massive ventilation to keep the fumes from building up.


Some, like Octane Supreme, simply use Tetraethyl Lead. Perhaps ten years ago, I priced out Toluene at the local hardware store. It was something like $30 per gallon, and it required about 3 gallons to treat a 21 gallon tank of 91 octane. Which was about $2 per gallon then, not the $7 it is here now. Cheaper to go with 100LL avgas or even Sunoco in the 5 gallon drum.


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## Rockinindian (Aug 5, 2021)

oldmanz said:


> Hey all! Long time reader, but first time poster! I hope I have this in the right place!
> 
> I have been working on a 1965 Pontiac Bonneville, with the 389 and Carter AFB. No modifications except for what I am going into now.
> 
> ...


First off make sure you are using ported vacuum (no vacuum till engine is off idle accelerating) to run the advance can in the dist.
2nd you got yourself into dark territory installing a cam that’s adjustable , if there is a stock degree cam timing mark use it. Your 389 more than likely has the big valves (for that application & vehicle) with 10.5 or 11 to 1 compression which fuels were 100+ octane 
Back then. Having said all that you can run the timing at -2 and have power loss at high rpm or buy an advance recite kit that come with new weights that are heavier that what is there now, that will slow the advance curve so the low octane fuels won’t detonate as much. You can run the timing +10 and using a timing light with a dial or marking your balancer at 36 deg full advance , make sure your carb is not too lean adjusted properly or you will get the same pinging/detonation while in acceleration , you can use a little octane booster but be careful with stuff you can fry a piston in a heart beat with it. Also those older cars can run 160-170 thermostat which also help rid detonation . Hope that helps,


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## Tlporter (6 mo ago)

oldmanz said:


> Hey all! Long time reader, but first time poster! I hope I have this in the right place!
> 
> I have been working on a 1965 Pontiac Bonneville, with the 389 and Carter AFB. No modifications except for what I am going into now.
> 
> ...


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