I have a bone stock 80,000 mile 70 GS stage 1 that is finally getting back on the street.Currently,I have my initial timing at 10 degrees BTDC and with full mechanical advance of 30 degrees in by 3500 RPM.With Sunoco Ultra 94 Octane I am getting detonation! For the street using this fuel what have you guys found to best timing setup? Thanks This car is totally original including mechanical distributor weights and springs
i asume you disconect vacum advance. 10-12 initial, 32-34 total at 2000-2500 is recomended. i use xylene as octane boost, a 4 to 1 blend gives you 97 octane when mixed with 92 octane. just adjust with air temp, AIR TEMP IS A BIG FACTOR, the hotter it is the more octane you need my 11-1 moter wont knock at 60 degrees with 92, also polished pistons and cobustion chamber helps,AVGAS is the cheaper way to go if its avalable where you live
Just use some avgas which is leaded and about 112 notwithstanding the name 100ll (low lead). Go to a small rural airport and they wil gladly make the sale.
I think the "Bone Stock" part is what's gonna be your limiting factor. With the carbon of 80K miles in the cylinders and the relatively small overlap numbers of a stock Buick cam, you probably have too much low rpm cylinder pressure to run much 10* initial timing. Longer duration cams tend to bleed off low rpm cylinder pressure so we can run upwards of 18* initial. You could try to clean some carbon out of the cylinders...o No:
Make sure the advance limit bushing hasn't deteriorated and fallen off. If this is the case you may be getting more advance after you think it's all in. Also I find a little race gas mixed in with the 94 helps alot. Even a gallon or two mixed in to a full tank may be enough to stop the detonation. Also running a high speed retard will help, like the Stinger S-4. I run an MSD Digital 6. It has a retard feature. I'm able to run 20* initial, 36* total all in at 2500, and I kick it back 4* at 4400 RPM and up.
Good tip and a heads up on that Larry :TU: ...I have the same kind of a problem with mine..way too much advance...I have to check that out later on in the week as well :TU:
Wow Thanks for all of your replies so quick! This is a car I just take out once a week late Sunday afternoons for an hour (if I'm lucky). Currently,I do not race the car although I will this fall at which time I will buy high octane fuel ,bump my timing and go for it. Until then,I am probably going to drop my initial timing off until detonation goes away.I feel that putting a curve kit into my mechanical advance to have my 25-30 degrees in by 2500 will increase detonation.What do you guys think? Is 104 octane boost going to increase octane with 94 Sunoco ultra or is it a waste of money? Also,what experiences have you guys had with Pertronix's Igniter II electronic ignition? Yes Vacuum is plugged when timing is set. As I mentioned before this Stage 1 455 has never been opened stock cam ,heads,intake ,exhaust ,carb and distributer and my advance bushing appears to be fine Thanks for your feedback
Larry70 GS I just looked to see if my advance limit bushing was still on my distributor as your attached pic shows and mine does not have any bushing on that peg,just a bare peg with a small groove around it's top.It looks as if it is just a plastic bushing that presses over that peg from what I can see in your pic?Where can one get another bushing and what is the proper thickness for a stock application? Will any curve kit with weights ,springs est come with these advance bushings that one could purchase through a speed shop? Thanks again Rich
There's the problem Rich, Got to have that advance bushing. Without it you are getting way too much advance. Also, if it is a stock Stage1 distributor, with stock springs and weights, your advancve isn't all in until 4600 RPM. Those are the stock specs as per the 70 Chassis manual. If you are timing your engine at 3500 RPM, there's still more advance left in the distributor, and that's why you are detonating. Advance bushings(they are plastic rings) commonly come in spring kits. My experience with the commonly available spring kits, is that they really don't give you a performance curve. They do give you the bushing though. The best spring kits I've seen, come with the Crane adjustable vacuum advance. It comes with 3 sets of springs that let you bring in your total advance from as low as 1600RPM to 3200 RPM by mixing the springs as per there instructions. Well worth the money. My advice is to get the spring kit, and the bushing, set your advance to be in by 2500, and set the total timing at 30-32* Hope that helps.
Jim, I didn't know that. I use AvGas ($2.65/gal.) whenever I go racing and figured it to be as the name.. 100. :beer Maybe I can get more than 14-16* timing out of mine, too. When I couldn't find a bushing for my distributor, years ago, I used 1/4" vacuum tubing as a stop.. worked fine until I got the real thing.
Gary: Despite the name it is highly leaded which as we say the way it was back then anyway. The number is not based on the same test method as used for auto gas. As I posted before I used to use 130 plus in another aircraft which was tinted green. The 100 ll is tinted blue but that is just to let us know that it has not been contaminated with say jet A in which case it will change color. There are also websites that survey the price per location for avgas. I bought some for about 2 recently. Survey your local small GA fields and avoid the commercial fields. I enjoyed your articles on George's website. They were some of the first things I read when first getting into Buicks.
Jim, That's good stuff to know. Out here in Elko, Nevada we have only one airport and it's pretty small. One of the casinos (Red Lion) does fly 727s in, loaded with contributors to our education fund though (gamblers). Other than that, just Skywest (Delta Connection) and their small planes. FYI, I modified the oiling article on the BPC website after considerable input from those who know more. If you remember I always had a disclaimer at the bottom of that one requesting folks to talk to more experienced Buick folks. Still there but I'm more confident it's better than before. Of course, with a new block coming out that article will be moot except for the stock block folks. At any rate, glad you could use the articles or at least get some entertainment value from them. There's a new one now on installing a fast-ratio Monte Carlo SS steering gear.
Just getting ready to have the ratio reduced on my 66 442 L69 which has the old endless feel ratio . You know what I mean about that. By comparison the Buicks of the 70 vintage are already pretty quick. You will like the avgas solution for allowing more timing. I use it all the time in engines with the higher compression. It is much cheaper than the race fuel.
