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1971 Cutlass 350 timing

1971 Cutlass 350 timing

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Old August 12th, 2018, 03:53 PM
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1971 Cutlass 350 timing

Hi guys,

My new timing light has arrived and I am exited to get the timing adjusted and then the new carburetor installed.

This is the light:
https://innova.com/en-US/Product/Detail/3568

The light is at work so I haven't had a chance to read any instructions yet but I am sure they will set me off in the right direction. Is there anything specific to these cars or any better procedure that I should be aware of? Probably a dumb question but I haven't adjusted timing for about 15 years and even then was just a plain old light, nothing fancy.

Second part of the question is what the timing should actually be. The car is basically bone stock, including the carburetor that will be going on after. Should I just look up the original manufacturer recommendations or are there better settings to use?

Thanks for the help and knowledge, like I said it has been a long time and I have never used a light with any kind of advanced features.
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Old August 12th, 2018, 07:27 PM
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Assuming it still has the points distributor, use the factory timing procedure and settings.
If it has a GM of similar HEI, you need to use different initial timing settings.
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Old August 13th, 2018, 06:51 AM
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Originally Posted by Fun71 View Post
If it has a GM of similar HEI, you need to use different initial timing settings.
Why? The engine determines what the timing requirements are - cam, CR, etc. The engine neither knows nor cares whether the spark is triggered mechanically with points or electronically with an optical or Hall effect sensor. All the engine cares about is when the spark plug is fired. Yes, the mechanical and vacuum advance curves in the distributor have an effect on the optimum initial timing, but given how much variability there is among HEI distributors, that needs to be figured out no matter what.
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Old August 13th, 2018, 01:40 PM
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I say that because points distributors have more mechanical advance than GM HEI distributors, which translates to a higher initial setting in order to achieve the same amount of total advance.
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Old August 13th, 2018, 05:11 PM
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Originally Posted by Fun71 View Post
I say that because points distributors have more mechanical advance than GM HEI distributors, which translates to a higher initial setting in order to achieve the same amount of total advance.
Then you adjust accordingly, per Joe’s statement. The engine combination dictates the correct amount of advance etc., not the distributor.

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Old August 13th, 2018, 06:07 PM
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So the numbers I have dug up say 12° at 1100RPM. It also says the idle should be 600RPM in drive. Does that sound reasonable? Seems OK to me, but again I haven't adjusted this type of stuff in a lot of years, lol.

With that said, I guess the best way to do this is to use the idle adjusting screw to get the engine to 1100RPM, adjust the timing to 12°, then adjust the idle back down to 600RPM in drive? It just seems like it would be difficult to be accurate with either opening the carb manually from under the hood to get to 1100RPM and move the distributor or have someone in the car raising the rpm and holding it steady.

The website also gives me "point gap" and "dwell angle" but I am not even entirely sure what those mean or how to adjust them so I think I will just stick to the timing for now, lol.
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Old August 13th, 2018, 06:45 PM
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Run as much base timing and vacuum advance as the engine can handle at curb idle without preignition. Don't worry about what the book says. Ive been doing this for many years and never have set my timing above curb idle. 11-1200rpms makes zero sense to me for performance tuning.

A starting point for you could be 12-14* base timing with the vac advance disconnected.
Add another 10-12* with the advance can hooked to unported vacuum. Get an adjustable limit (not rate) advance canister if yours is not right.
Then the centrifugal should bring in the rest at about 2700 rpm for a total of 36-40* at 2700-2800 rpm at sea level with good non-ethanol gas. If it spark knocks under load back off the base 2* and limit the vacuum to 8* vs 10 and road test.
Use a vacuum gage hooked to manifold vacuum to tune. Turn the air/fuel screws in/out to obtain the highest vacuum signal possible. Tweak the timing and A/F mixture adjustments in unison to obtain the highest vac signal possible. You don't really need a timing light tuning with a vac gauge. The light helps dial in each of the three events so you can see the actual numbers. I always go to the vac gauge.

Point gap is a static gap measured with a clean feeler gauge between the points on the highest spot of the crown of the cam (distributor cam). .016" to .018".
Dwell is the same adjustment but measured with a tach/dwell meter. 30* of dwell = .017" point gap but is measured running.
If you have a QuadraJet you will likely need to mess with the AVS valve. We'll save that for another discussion.
Follow this recipe you'll be rewarded with a great running engine and might smell some rubber.

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Old August 14th, 2018, 05:29 PM
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Thanks droldsmorland, is this still a wise thing to do if you are just looking for fuel efficiency and proper running condition and not too concerned about performance? It isn't a performance car and we don't try to use it as one.

I also have a fully restored quadrajet rebuilt by Ken at Everyday Performance. It should be all setup and ready to go other than the fuel mixture screws from what I understand so hopefully that part will be fairly straight forward.
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Old August 14th, 2018, 06:55 PM
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With the tweaks I mentioned above you will get performance and economy...if that's even possible with a 71. 13-14mpg downhill with a tailwind is about it. Possibly more with a 2bbl but I've never owned a 2bbl Olds.
Its simple to tune with a vacuum gauge. Plug the gauge into intake manifold vac source either the carb base or a nipple on the intake(preferred). Adjust the A/F screws until you obtain the highest reading. Have the distributor somewhat lose enough to turn while it's running and again observe the vac gauge and shoot for the highest vac reading. Go back to the A/F screws then back at the timing at least twice both times achieving the highest vac reading. Done. Test drive. If it pings back off the timing a degree or 3.
Verify the point gap/dwell is spot on too.
Verify zero vacuum leaks too.
91 or better non-ethanol gas as well.
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Old August 14th, 2018, 07:11 PM
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Ok, and when making these adjustments shooting for the highest vacuum, is there a tipping point where it will actually start going down or is it just the pre-ignition sound I am listening for? I am just concerned about going too far and damaging something.

I am guessing I would want to check the point and dwell before doing all this, or it doesn't matter?

Thanks!
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Old August 14th, 2018, 07:19 PM
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On my street/strip SBO 355 I ran 14 intial 22 mechanical for a total of 36. car ran 12.2's more than that didn't help . as far as people who say you need as much initial as possible it can become a balancing act because of hot starts. They can be slow sluggish and you wont be happy. I run a really aggressive curve so as soon as its off idle the timing is climbing fast coming . Just Fwiw. Even on my much milder sbo powered B body Pontiac it likes a fast cruve with only 12 degrees initial all in by 2800. This is just my experience on my setups.
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Old August 14th, 2018, 08:18 PM
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Originally Posted by 71OldsCut View Post
Ok, and when making these adjustments shooting for the highest vacuum, is there a tipping point where it will actually start going down or is it just the pre-ignition sound I am listening for? I am just concerned about going too far and damaging something.

I am guessing I would want to check the point and dwell before doing all this, or it doesn't matter?

Thanks!
Yes, the vac signal will drop so will RPM when too lean or too rich. "Just right" on the A/F mix will produce the highest vac signal. Additively so will timing. That is why you need to do small tweaks to both....one at a time.

Beware of any vacuum leaks, poor ignition components or fuel delivery problems as it will make these adjustments canted lean or rich. Always verify everything is in good service before making any adjustments or you will go off into the weeds.

Post your results so we know we all helped you and your Olds.
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Old August 14th, 2018, 08:25 PM
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Originally Posted by coppercutlass View Post
On my street/strip SBO 355 I ran 14 intial 22 mechanical for a total of 36. car ran 12.2's more than that didn't help . as far as people who say you need as much initial as possible it can become a balancing act because of hot starts. They can be slow sluggish and you wont be happy. I run a really aggressive curve so as soon as its off idle the timing is climbing fast coming . Just Fwiw. Even on my much milder sbo powered B body Pontiac it likes a fast cruve with only 12 degrees initial all in by 2800. This is just my experience on my setups.
Good point. Each engine is slightly different. So are ambient conditions such as elevation (air density), temp etc...Same for fuel and driving style. Your specs are what I always recommend as a starting point. 12-14, another 10ish on the can and all of it in at 2700 2800, 36-38-40* total.... Its an Olds thing. My Chevys like a bit more(small block 327). Cadillac a bit less (8.2L!).
Bottom line is super tunning is a technique of using all of your senses to super tune to dial in just what it likes...arent modern self-adjusting cars boring?

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Old August 15th, 2018, 06:28 AM
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Alright guys, I will see what I can do.... hopefully this Friday, if not sometime Saturday and Sunday. Should have some results by the end of the weekend.
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Old August 17th, 2018, 01:58 PM
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Hi guys, one last question here - after base timing is set, do I reconnect the vacuum line to the distributor? I know it is mentioned above about have an adjustable vacuum canister but I don't have one. Will reconnecting the vacuum line be good enough? Or maybe I am misunderstanding this entirely.... I get that the line should be disconnected and plugged at idle but am unclear of what to do when checking the total timing.

I am also confused about what the timing advance buttons on the timing light do. Do I even need to use them?

Also... do I have to plug the port on the distributor too or just the line that goes on there? (as I sit and think more questions keep coming to mind, lol. As usual I tend to overthink things...)

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Old August 18th, 2018, 10:30 AM
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Hi guys,

Thanks for all the help, I think I got a lot figured out by just getting in there with the knowledge that I had from here and figured some out along the way.

It was apparently just tuned up before I got it, but I still wanted to verify all of the settings. It looks to be pretty close. It could maybe be advanced a degree or two but it isn't out too much if anything. The dial back feature on the timing light is very nice, once I figured out how it works. While I was there with everything hooked up I decided to play around with the fuel mixture screws just to get a feel for it. With the car off I wound them all the way in, then back out 1.5 turns. car wouldn't start and stay running so I gave them another .5 turn. It then ran, so I kept backing them out slightly until the vacuum and RPM seemed to stop increasing and then back in a little bit.

It actually runs fairly good now. It seems like the main thing that was far out of adjustment was the idle speed. It was low. Even when I first got it, it just felt and sounded too low so I raised it a bit based on sound. Even after raising probably 75-100RPM, it was still off by about 150RPM or so. After all that my vacuum went from about 14.5" to 16". Still not up around 20" like I would like it to be, but it is progress.

Tomorrow I will put the new carb on. I am hoping that alone will get me some more vacuum pressure and then after maybe giving it that extra degree or two of timing as well as dialing in the new carb maybe the pressure will be where I want it.

I also found a used dwell/tach meter for $20 that I am going to pick up and check that as well.

That is my update. Thanks again for all the help and suggestions.
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Old August 19th, 2018, 12:08 PM
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Originally Posted by 71OldsCut View Post
Hi guys, one last question here - after base timing is set, do I reconnect the vacuum line to the distributor? >>>>>Yes and see how much it advanced the timing. That's how many degrees the non-adjustable can adds on top of the base number.

I know it is mentioned above about have an adjustable but I don't have one. >>>>Likely not.

An adjustable can lets you dial in how much timing the can adds. It's for super tuning. If you decide you want one down the road I suggest an adjustable travel, not an adjustable rate. The adj. travel lets you limit the travel. An adj. rate will still go to its max just at a slower or faster rate. It doesn't let you limit the total travel.

Will reconnecting the vacuum line be good enough? >>>>>Yes, if not, you won't have any vac advance.

Or maybe I am misunderstanding this entirely.... I get that the line should be disconnected and plugged at idle but am unclear of what to do when checking the total timing. >>>>>You want it connected to check total. Your total is the base number added to the vac advance number added to the centrifugal number. The weights under the rotor add in another 10-15* as RPM climbs and the springs are overcome by the inertia of the spinning distributor weights ( so they fully open at a given RPM, usually at or before 3000 RPM). Make sure the weights and springs are clean and the springs are in good shape.

I am also confused about what the timing advance buttons on the timing light do. Do I even need to use them? >>>>>You figured this out it sounds like?

Also... do I have to plug the port on the distributor too or just the line that goes on there? >>>>>>No,

just disconnect the vac source to the can and plug it off so you dont have a vac leak. I disconnect the hose from the advance can and plug the line off there. Or you can disconnect at intake (or carb base) and use a nipple plug at that port. Either way, you don't want a vacuum leak as it will throw off the timing and A/F settings....essentially it would be the same as a vacuum leak.
A stock or near stock Olds 350 should be north of 18 Hg of vacuum. 16Hg is a little bit low. With the timing and A/F set right you should be able to see a steady 18-22Hg or inches of vacuum. If all is well with the engine's valves, no vac leaks timing right etc...
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Old August 19th, 2018, 12:16 PM
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Thanks for all of this. I think timing-wise I am in good shape. I put the new carb on and found that the metal line that connects to the back of the carb through a short rubber hose was in bad shape. The rubber piece was basically rock hard and falling apart so I think that was likely contributing quite a bit to the lack of vacuum pressure. I am just waiting on one more piece to get here before firing it up. Hopefully with that new piece of tubing, new carb, and dialing in the fuel mixture on the new carb will get that vacuum reading into the 20's. Then I can for sure rule out a vacuum issue causing me to not have third gear. I have my doubts, but it would be really nice if that fixed it. If not I will have to dig into the valve body.
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Old August 19th, 2018, 12:41 PM
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No third gear could be a few things.
1. Low oil level
2. low oil pressure(quickest way to verify a trans health is pressure checks in all gear ranges)
3. The shift linkage is out of adjustment.
4. A bad or out of adjustment servo band
5. Sticking valve in the valve body
6. Cross leak in the servo coupling case cover or governor.
7. Bad reverse clutch.
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Old August 24th, 2018, 01:50 PM
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Alright, update number 2.

After the new carb was installed, and that broken piece that goes to the choke fixed, I fired it up. Before I could really dig into anything the heater core sprung a leak, and the problematic valve covers were smoking a bit too. So, I shut it down, replaced the valve cover gaskets, and bypassed the heater core for the time being. So now the good news is that it runs without leaks and smoke which is nice, but still doesn't run well yet.

It seems to run OK cold, but after it gets kicked out of high idle would stall right away. I had the mixture screws where the builder said would be a good starting point already so I wound the idle screw in until it would run on its own, which had to be around 900-1000RPM. I then started winding the fuel mixture screws out half a turn at a time until the vacuum stopped increasing, but I have to keep the idle up around that 900-1000 mark or it would still stall where before it would run in the 500's idling in park and still run on its own.

Before shutting it down, I quickly just rechecked the timing which leads me to my main question - does the factory balancer have a small groove cut into it where TDC is? That was the line that conveniently was right about where it should be when I checked the first time, but now that line is nowhere close. Could it be that when the timing was adjusted using the old, leaky carb that was in bad shape, now that a new carb is on, the timing is in a completely different spot? I am not sure if that is possible, but could explain why it is running like it is....
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Old August 24th, 2018, 04:24 PM
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My neighbor happened to stop by while I was trying some things and said the reason the timing has moved is probably because I had the vacuum line to the distributor connected. Stupid me, he was right so at least that is answered.

I was kind of hoping the timing was out, at least that could be a reason it runs bad. I still can't get it to idle much lower that 900 RPM or so. One strange thing that might help people who better understand this stuff why it is running like this is when I shut it off the last time, it made a noise and kinda puffed something out of the carb. I don't think it was gas because I didn't see any wetness anywhere so I think air. Either way, is that a sign of too rich or too lean? I start with the fuel mixture screws 1.5 out like it says and after backing them out another 1-1.5 turns the vacuum stops going up, but it never really runs good. I am not too sure what else to check
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Old August 26th, 2018, 11:52 AM
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You still have a vacuum leak.
What did you torque the carb down with? Over torque distorts the carb and will destroy it. It doesn't need much. The correct method for tightening the 4-bbl carb bolts is: Tighten one diagonal set of bolts to 36 in-lbs (3 ft-lbs); tighten the other diagonal set of bolts to 36 in-lbs (3 ft-lbs); tighten all four bolts to 144 in-lbs (12 ft-lbs).

P.S. After operating the car for a few days, retighten the bolts to 12 ft-lbs, as the gasket will compress some under load and with heat/use.

What base gasket are you using? One hole, 3 hole or 4 hole? The base gasket must match the carb spec/requirement.

Disconnect everything attached to the carb throttle base and intake manifold and plug them off, yes this includes the trans modulator, brake booster, PCV and any other item with a vacuum line on it from the carb and intake. Does it run better? Yes? then book up the vacuum advance can. Does the timing advance? Verify the vac advance can is holding vacuum.

Connect the things you disconnected above one at a time until it starts to run poorly. A bad brake booster hose, check valve or the booster itself can leak. Same deal with the PVC system. Not all PCV valves are created equal. You need the right one for your application.

Come to think of it...the trans modulator vacuum line could be causing the trans shift problems as well as this carb issue. A broken vac line will cause high shift points(and a leak).
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Old August 26th, 2018, 05:34 PM
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Hi drolds,
I did find one more fairly significant vacuum leak. There was a capped tee fitting on the vacuum line going from the carb to the distributor, problem is that cap had a huge hole in it. I have replaced it, as well as all the other rubber lines with new today. I removed the tee and just have a solid line to the distributor from the carb now.

After reading up on torque for the carb, I opted to go with the method most seemed to use - grip the top of the ratchet and snug it up. I tried 12 FT LBS on the torque wrench but it seemed to tight and wouldn't click so either I chickened out or my torque wrench isn't accurate. Either way, they shouldn't be overly tight.

I did notice that the gasket that came off was slightly different than the gasket the new carb came with. The old one had two 1/8" notches on the small holes and there was only one large hole that covered both the larger holes. This is what rockauto.com shows for the right gasket. The one it came with didn't have those 1/8" notches and had two holes for the larger ones instead of one oval shaped one. Not sure if any of that matters too much, but I did try the old one and it seemed to be an improvement so I left it for now.

I now have it back basically exactly where it was before the carb change. It idles at 600RPM in drive, and runs basically the same so I guess I will call that progress. But, the vacuum reading is also exactly where it was before. 15.75" or so, just under 16". Before I started looking into this, the initial reading was 14.5 so it is better but still not great.

I did plug all the vacuum related items off and it seemed about the same. I have also before any of this, tested the vacuum at the manifold where the modulator line connects, and then checked it right at the modulator and got the same 14.5" reading so I think the line itself is fine.

One thing I am not clear on is how to check if the vacuum can holds vacuum. I have confirmed that the vacuum advance works, and when I disconnect the line from the distributor there is little to no suction on the line, but when I rev the engine it increases which I think is what is should be doing...

Thanks for all the help. If all of this checks out, as far as I know there are only a couple of other things it could be. Either the intake manifold gasket needs to be redone, or there is something wrong with the valves...

Is there any test that I can do to rule those out?

I also just want to be sure it isn't the brake booster since it is a large vacuum source it seems - when the line is disconnected from the booster, the engine gets rough, but then when I plug the hose with my thumb it returns to normal. Does that mean it is ok?
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Old September 9th, 2018, 06:02 PM
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Hi guys, I have one more question, or clarification about some of what was discussed above. I have advanced the timing and readjusted the fuel mixture and it definitely seems to be helping. I am up t 17" for vacuum, and the timing is at about 14 degrees at the 1100 RPM. I am going to pick up some different springs tomorrow to make sure that mechanical advance isn't messing with those numbers at all. Alternatively, I have heard an elastic around the weights will work, I am just not sure if that is a good idea...

My new question is, at the idle of 750-800 or so RPM, what would be a safe range to up the timing to? I think that would be easier than the 1100 RPM I have been using. I keep coming across some posts saying that olds engines like lots of timing, some claiming they are at 20-22 degrees for initial timing. Would this be at that 800ish RPM? Seems like a lot. But seeing as how I am at roughly 14 degrees at 1100 RPM, if the engine can handle 12-14 degrees at 800ish RPM that should get the vacuum up where it should be.

I think I would be more comfortable with this is I knew what pre-ignition sounded like. I just worry about being deaf to it and hurting the engine...

Thanks!
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Old September 9th, 2018, 06:47 PM
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If the engine is stock, use the stock settings. Do not confuse what you read for HEI settings vs the points distributor that you have. Set your dwell first and then your timing. If you want to advance it a few degrees the engine will probably tolerate it.
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Old September 9th, 2018, 07:30 PM
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Ok, thanks. I think one other thing that plays into my favor is that this car never gets driven hard. The worst it will ever see is passing a slow car on the highway. If I understand correctly, if the timing is too far advanced it can hurt the engine under high RPMs.... But I guess the springs on the distributor wieghts play a role in that too where it could start hurting the engine under moderate use too. So much to think about and learn, lol.
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Old September 10th, 2018, 11:27 AM
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You'll be fine with setting the initial timing a couple degrees higher than the factory setting. Your 71 engine has low compression so it can tolerate more initial timing than a high compression engine. If you connect the vacuum advance canister to manifold vacuum instead of ported vacuum, it will increase the timing at idle which will help increase the vacuum and allow the engine to run smoother.
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Old September 10th, 2018, 05:19 PM
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Thanks. I was unable to find somewhere locally that had a spring kit, so I have some on order. I went out to just familiarize myself with the weights and springs and have a question about them - do the weights have a bit of play in them before the spring is activated? It looks like mine move a good 1/4" or so before the spring gets involved.

Also, I think I know what pre-ignition sounds like, but how loud is it? I would assume fairly loud if you can hear it while accelerating from in the car, but just want to be sure. I heard a faint noise but to me it sounded more like lifter noise or something. I could only hear it with my head right under the hood. Even with the hood closed you wouldn't be able to hear it.

Using the dial back feature and with the vacuum line to distributor plugged, it looks like I am at 20 degrees at 1100 RPM and 12 degrees at 800RPM. Ken who built the carb actually suggested 12 at 800 so I think it is safe and not causing pre-ignition, I just want to be sure I know what I am hearing. But again, with the weights a springs possibly not being in good working order maybe it is getting those numbers with some level of mechanical advance and I am actually well under with room to go still.
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Old September 11th, 2018, 07:12 PM
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You will not get pre-ignition or detonation at idle or just reving the engine, it needs a load.
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