To run the vacuum advance with manifold vacuum, you will need to reduce the degrees with a stop fixed into the distributor vacuum advance. If you don't do this, the engine will ping and have too much timing at idle. I have Dave Ray (IgnitionMan, sparkman451@earthlink.net) do all my distributors now, as he is the one that invented, designed and perfected the small body HEI. He has set all of my non-feedback HEI's up for reduced degrees of vacuum advance, and they work well. I think he has pictures he will send you to make your own stopper for the vacuum advance. Just ask him. He is also a moderator over at buickthunder.com as well. You might ask for him, and the fix over there. Regards, Milton
Thanks Milton Thanks Gary My distributor is stock and like new under the cap. Springs are not too soft. They are stock as new. Joe thanks again, i do run 15.5 a gallon at highway speed 60-70mph without vacuum. I am talking about US gallon, (3.5 liters is that right?) I am driving unleaded 98 Octane (European Octane rate). Larry thanks, the springs in the distr. are stock. I will limit the vacuum advance. How many mm or inches has it to be limited? Thanks to all and to you i forgot.
If you're willing to pull the heads anyway, I'll throw one more idea at you. Get yourself a Dremel tool or equivelent and some stones and some of the coarse and fine buffs (Dremel has 1 of ea. in a package, you'll need a few of them) and polish the chambers. Stones first until smooth and all casting roughness goes away and then hit 'em with the buffs. This will lower the compression a little (varies with how much material you remove) and help greatly with detonation. Get rid of any possoble carbon on pistons while there. Doing a basic chamber polish doesn't really take that long and goes a long,long way. Also the next cooler plug maybe? Also cooling and ignition as mentioned earlier. I would try to get it so you can use your full vacuum advance, you'll get a definite fuel economy boost that'll justify all the effort.
I'm with Milton & Larry, Manifold vacuum is the way to go. though we did have a big discussion about it here: http://www2.mgcars.org.uk/cgi-bin/g...ubject=36&source=T&thread=2007041015454227928
I wouldn't limit it.......just get an adjustable one, and set it to where the ping just disappears. Then save yourself all the trouble and expense of trying other things that may not help and are a lot of work. Carmen would sell you one, and ship it to you. His phone # is 716-693-4090.
Do you use your full vacuum advance? Or did you limit it? (I see on your picture that it's not an adjustable kit) Thanks
Bottom line, if you have lighter springs in the distributor, you must limit the vacuum advance. If not, leave it stock, but it should be connected to manifold vacuum.
Joe, i just bought the original one new a couple months back. I am 100% sure that i can use it like it should (full vacuum). I mean my car is stock. No modifications or whatsoever. I think that after almost 40 years of running the carbon is causing my pinging. The engine runs cool. Ignition is tuned stock, TDC/30 Buick says when it's still pinging, carbon is the problem and i know from my own experience with my first Riviera from 1968, it had carbon like you won't believe, but you just don't know until you take off the heads. Don't you think that after 40 years of running it would not have carbon? Thanks again.
Larry, it's all stock, no other springs nothing lighter. Thanks, now i know i can run with full vacuum advance. Buick says too it's carbon. Carbon builts up in almost 40 years don't you think so too? Thanks again.
Not much, i have to check on exactly how many miles, but it's not using excessifly like 1 liter on 500 miles. Why you ask? Thanks
I found out it's more then Carbon.... The original Q-jet....even when it's rich enough at idle speeds, it could be too lean when driving right??? Could that also cause pinging? It pings at part throttle aleady, very early, almost on the same time when moving the throttle pedal.....
before you take this and do it, ill try and get more opinions. Anyone thing that lightly spraying water into the carb might break up the carbon, not enough water to significantly raise the compression?
Get those heads off and clean em up, that is probly most of your problem and the timing is the other part. I agree with the suggestion to pollish the chambers but don't use the felpro gaskets as your actual compression is closer to 9.5:1. The advertised comp is higher than actual. I would limit the vacuum advance to half of its travel ands you'd get about 10 deg
I can't see it being a carbon issue. It sounds to me like the bushing that limits the mechanical advance has fallen off the pin. They use a rubber bushing from the factory and it gets hard and falls off. If you can't get a recurve kit that comes with a brass bushing a your area, in a pinch you can cut a piece off the small od rubber hose used on the windshield squirter's, if it is still the factory lines it should be small enough. Here's a pic. Chris
Most of the actual original parts I've measured have compression ratios in the mid-nines, including some measured for GM engine tests in 1966 while the 400 & 430 were being tested for durability. Devon
Oil in the combustion chamber causes detonation. It was one possibility that came to mind. Also, is your PCV valve good? Does it ping under all throttle positions or just when in the off-idle circuit?
OK, but should i use the original steel gaskets if i will take off the heads or should i use after market like McChord or Fel-Pro? Thanks Robbie
