If you set to total timing as many above have mentioned, it will make a huge difference. Your sputter just off idle could be the accelerator pump in the Quadrajet. It should squirt a steady flow in to the primaries when throttle is opened.
Like John said, you can easily check the vacuum advance with a manifold source of vacuum. On your Q-jet, that would be the nipple on the passenger side of the carburetor, towards the top. To check vacuum advance function, you don't even need a timing light. If you pull the hose off the carburetor end, at idle, a manifold source will hiss, and the engine will run rough. If you take the hose leading to the vacuum advance, and place it on that manifold vacuum source, the timing will advance, and the idle will increase very noticeably. That will confirm that the vacuum advance canister is functioning. If you have the original distributor that came with that engine, it will be part number 1111984. Initial advance will be 6* BTDC. The specs for that distributor say it has 19-23* of mechanical advance at 1800 RPM, and 30-34* at 4600 RPM. Not really sure if that is a typo in the chassis manual or not, but if you do the math, the total advance (without vacuum advance) could be as much as 40* at 4600 RPM. That is too much IMHO. Your distributor may have less than that. Manufacturing tolerances were not as exact as they are today, so some 1111984 distributors might have 34* of mechanical advance, others may have 30*, or somewhere in between. Most Buick V8 engines will like somewhere between 30 and 34* total advance at wide open throttle. That is why setting your total advance with a light is so important. You can set it exactly, and the amount of mechanical advance in the distributor is less relevant. To do that though, you must install lighter springs into the distributor. The stock springs don't allow the weights to extend all the way out until 4600 RPM, and you don't want to have to rev the engine that high in your driveway. It isn't good for the engine, and your neighbors will not appreciate it.:laugh: What you need to do is buy the Crane adjustable vacuum advance kit. It comes with 3 sets of springs that are ideal. If you use the yellow ones, it will allow all the mechanical advance in at 2200 RPM or less. With a standard timing light, you can make a 30* mark on your balancer. Then rev the engine until that 30* mark stops moving up. If it lines up with the timing tab, you can see what the total advance is. All this is in the Power Timing thread. You can use the same technique to measure how much vacuum advance you have as well. The stock canister has between 14 and 18* at 16" of vacuum.
The vacuum advance on mine is connected to the manifold vacuum tee on the front of the engine. I checked it with a vacuum pump and it held vacuum. My distributor is the 984. I marked the 30 degree mark 1.75" from the initial timing mark. Car idles about 1,000-1,100 since I reset the timing to 6 and dwell at 30. I pulled the air cleaner off so I could see better, but left all vacuum hoses hooked up and checked manifold vacuum off the tee in the manifold that runs to the air cleaner and it was right at 16 at 1,100 rpm with a little fluctuation between 15 and 16. Is that normal? The car has a stage 1 spec factory cam. Anyway when I would rev it up to around 1,800 rpm the 30 degree mark went up to where 6 is marked. I guess that's 36? Revving it up to 2,000 or a little more and it didn't move any more. I didn't go much higher in the RPMs because I don't trust the factory tach and my tach/dwell meter only goes to 2,000. Is this what I should expect or do I need to do more adjusting on the timing?
Like I said, until you get a set of lighter springs in there, you can't be sure of what the total advance is. The stock springs won"t allow the weights to swing all the way out until 4600 RPM or more. Lots of guys make the same mistake of revving it up to 2000 or 2500, measuring the advance and calling it a day. You can be sure when you nail it that all the advance will come in. Get the lighter springs in there to be sure you are seeing the total. Your vacuum may be normal for the cam you have. Without knowing the cams specs, no way to know for sure. A stock cam will make more like 20".
So I get the lighter springs it will bring in total advance earlier so I will be able to read it at around 2,000-2,500 right? Would you happen to have a part number for the lighter springs? Are they something I could get at a local parts store? Also are the springs all I would need to change? Cam specs from another thread on here: IN. EX. IN. EX. IN. EX. IN. EX. TA Stg 1 * .406" .441" .419" .456" 210 226 260 276 113 1100-5500
It's all in the Power timing thread. Yes, the lighter springs will let the weights go to full travel at around 2000 RPM or so. Your stock springs don't let that happen until 4600 RPM. Up until then, you are only seeing PART of the mechanical advance. This is the kit you need. http://www.summitracing.com/parts/crn-99601-1/overview/ Vacuum is normal for that cam.
Great, thanks. What would be your thoughts on something like this that has just the springs for less $ ? http://www.oreillyauto.com/site/c/d...k=Search_N0613_1379763_876&pt=N0613&ppt=C0150
Sure, but I believe those springs are not as light as the Crane springs. It also includes the bushing for limiting the mechanical advance, a good thing. You can really boost the low end performance by bringing all the mechanical advance in by 2500 RPM. Selecting the right springs to do that is easier with a variety of springs. You can mix and match them until you get the desired result. If you choose to do that, remember that you must limit the amount of advance in the stock vacuum advance canister. The stock springs, as I have stated, only let part of the mechanical advance in at cruising RPM. The vacuum advance supplies another 14-18* of advance for a total around 40* or so. When you nail it, engine vacuum drops to near 0, and whatever advance was in the canister disappears. At the same time, increasing RPM causes the weights to go full travel, so you are left with your initial advance + the full mechanical advance. Bringing all the mechanical advance in at cruising speed and then adding the stock amount from the canister can cause overadvance, and the engine will surge. Limit the stock vacuum advance to 8-10* maximum. Again, all this is in the Power Timing thread. http://www.v8buick.com/showthread.php?63475-Power-Timing-your-Buick-V8 I suspect lots of guys are reluctant to read it being it is many pages (24) long, but it is worth doing so. All your questions were answered long ago in that thread.
I bought these springs and they do not work as well as the ones in the crane kit. I myself found that the stock vacuum advance worked better than the adjustable one in the kit. I don't remember for sure but I think I used 1 light spring and 1 heavy spring from the kit or possibly 1 light and 1 stock spring. I also used the little brass bushing from the kit. I run a little bit of initial advance but its still around 26-28* mechanical with close to 50* at cruise with vacuum advance. I do not have any audible pinging and since I have adjusted the APT on the carb the throttle response is near fuel injection type snappy and crisp. If you haven't already please check out Larry's power timing sticky (dude knows his stuff)
Why is the engine idling so fast with that mild cam??? Inaccurate tachometer? Messed-up idle/off idle fuel curve? Inaccurate timing?
I haven't reset the idle yet since I re-timed it. It was idling around 700 to start with. My tach is accurate according to the tach/dwell meter at least up to 2K rpms. When I reset the timing the idle went up and I haven't addressed that yet. Maybe this evening.
I read several pages into it and decided that the initial post was all I really needed, but I guess I need to read more. I've read and re-read that several times. Printed it off, highlighted etc. A condensed version as a sticky with just the pertinent info would be really helpful and would likely cut down on posts like mine here. A cliffs notes version/quick reference if you will. I'm probably not alone when I say I find it much easier and less time consuming to just go ahead and ask a question (that may have already been answered many times) as it arises rather than to weed through 24 pages of posts to find or potentially not find that needle in a haystack answer at the moment you need it. I apologize for asking things that have been answered before. I ordered the Crane 99601-1 kit. [h=1][/h]
If you've noticed, I do answer all your questions. I don't say, go read the thread, I've answered that before:grin: All of the questions you have asked are covered in that first post, and page. Ignition timing seems to be a confusing aspect of engine tuning for many, which is why I wrote the thread years ago. You don't have to read the entire 24 pages at once, read it in stages. Others have contributed their ideas to it, and there is a lot more to the thread. You don't need to apologize for anything. I will answer any question you post if I can.
step 1: acquire timing light with adjustable advance step 2: acquire spring kit step 3: clean timing marks on engine block and on balancer so it may be seen easier step 4: remove cap and rotor to install lightest springs step 5: re install cap and rotor step 6: connect timing light to battery and spark plug wire on #1 cylinder (closest to the front on the driver side) step 7: start engine and let idle to get warm (upper hose is tight) step 8: remove and plug off hose from the vac advance. step 9: set light to 38* (im guessing your real timing will be closer to the 20's mind you) and point dat bad boy at the timing marks on the block taking note of where the line indicates while revving the snot out of the engine (say bout 4k) if the line is not near the 0*mark on the block turn the dial until it lines up with the 0* the number on your light indicates your maximum mechanical advance timing. I guess the goal is 30-32* (mine is 26-28*)but the actual real world amount will vary due to gasoline and weight factors etc.. step 10: shut off engine remove cap n rotor. step 11: replace the springs with the medium ones. step 12: re install cap n rotor and vac advance step 13: test drive the beast. if it pings in the lower rev range replace one of the springs with the next heavier one. If it pings up top you may need to retard the total timing by adjusting the distributor.
it can be a fine line between pinging and a taught n tuned engine. You will have to experiment a little to get the right combination of springs. Another factor is making sure your carb is properly tuned as these two systems play off each other BIG time.
just from my own experience when my car has ran out of steam in the mid-high range it has been either an ignition issue (in my case a corroded cap) or a vacuum leak. I found probably a dozen places where it was leaking at some point.
Thanks for all your answers. You are truly a wealth of knowledge and an asset to this community. I don't meant to get argumentative, but all of my questions weren't answered in the first post of that thread...for example manifold vacuum, crane cams advance kit part number, how to check dwell... Anyway, I do have another question, how do I limit or change vacuum advance with a stock/original vacuum advance diaphragm?
Well - you really have learned a great deal. I did see one piece of early advice you apparently didn't take - and I'm glad for you. There was an early suggestion to replace plugs and wires; an expensive and often fruitless act - no disrespect to the gentleman offering that advice is meant. If you ever get to the point where you "think" parts replacement is your answer, do yourself a favor and learn how to diagnose suspect parts before a wholesale replacement. The last time I had a misfire and suspected a plug wire, confirming the bad part was as simple as checking the resistance with an ohmmeter. The bad part was obvious and I didn't waste a dime replacing perfectly good parts. I've been running the same spark plugs for twenty years; they get a rare checkup and go right back in. Heck, my lawn mower spark plug has thousands of hours on it in 23 years of service; still works like a champ. You'll find the adjustable vacuum advance is a great addition and an excellent way to fine tune for drivability.
Does it have the original exhaust pipes on the car? here is a problem My dad had on his "70 stg 1. the original exhaust pipe is a dual wall. so what happen was that he drove it through a big puddle of water and the outer pipe cooled and the inner pipe shrunk and the inner pipe stayed hot and looked like a horse shoe. you couldn't even drop a 3/8" nut down it. ran good at lower end of rpm but fell on face in mid rpm and upper. took a motor change to find that problem. if the exhaust has been changed then you don't have to worry about that.
No, you are right, I don't mention dwell in my post, but few still use points these days. I'll see if I can edit the post to include it. As far as limiting the vacuum advance, have a look at the pictures at the bottom of that first post, specifically 3 & 4. 1 & 2 deal with the Crane adjustable unit. I think what I will do is create a sort of index in that first post mentioning where to find specific timing topics in those 24 pages.
