What is needed in a rebuild on a '70 Buick 350, to make sure that I can run it on unleaded gas without having to hear that annoying knocking sound I get when I don't put lead additive in the tank often times?o No: Do I have to harden the valve seats or somethin? It's not the spark plugs, already went through several sets of those to figure out that that's not the problem...not timing related I am sure...and if I recall, 1970 was a year that leaded gasoline was the only kind available, and if I recall again, it doesn't hurt to run a leaded gasoline engine on unleaded, but still the knocking sound I get from the engine is annoying sometimes. It doesn't do it all the time, just some times, and it's only got a little over 70 thousand original miles, so it can't be a rod about to go out or anything like that........I am planning on a rebuild though soon, and when I do I was wanting to make sure I know what I need to do to actually eliminate problems on down the line, as well as adding some goodies too.:Brow:
1. The knocking sound is probably an octane-rating issue rather than an "unleaded gasoline" issue. Buy premium and see what happens. If that doesn't help, you might have to lower the compression. 2. The use of unleaded gasoline (of a suitable octane rating) requires nothing except hardened exhaust valve seats. Don't let anyone tell you Buick has "high nickle" cast iron, and hardened seats aren't needed, either. God, I can hardly wait for that myth to go away.
1. The knocking sound is probably an octane-rating issue rather than an "unleaded gasoline" issue. Buy premium and see what happens. If that doesn't help, you might have to lower the compression. i agree. a simple solution for this is to stop at your local FBO / airport and buy 100LL AVGas or 100 octane Low Lead Aviation Fuel. it normally runs quite a bit cheaper than 110 octane race gas. just don't pump it directly into your car. AVGas is designated for "off road use" only. not timing related I am sure you've tried backing the timing off and it didn't go away?
when does it knock acceloration,cruise,turning off?what is your timing set at? do you have a temp gauge? could it be running hot? dwell good? these can all affect this also and i think you could have a combo of running a bit hot along with timing or carb(lean) issues plus the lead and carbon already built up in your cylinders already i think a cleanup on heads and top of pistons and proper tuneing/test radiator you should be ok
Your 10.0 (or so) engine can run just fine on unleaded premium... if you are having detonation issues, simply put your initial timing at 0* and drive the car. When you see it doesn't knock, you can adjust your timing (upward) for max power and economy. It will be fine!
So, I think premium is 91 octane here, and should I try putting in 91 to see if it goes away? I usually go with 87 or 89, but what's 2 more octane ratings anyhow? Worth a try I suppose..
should I try putting in 91 to see if it goes away yes, this is what we're saying. try the highest octane you have convenient access too. AvGas would be better but it's also a bit more expensive than premium. if necessary, back the timing off a little bit. Alec has good points about a the motor running warm and carbon build-up aggravating the situation. run something like Sea Foam through the gas tank and do you have your car plumbed for an actual temp gauge or are you just using the factory gauge/idiot light?
most motors will run without hardened seats, the myth is what the machine shops push that they are needed
My engine will run fine as-is on 87 or 89 octane, 87 it knocks the most on, 89 octane keeps it mellow, and I tried 91(premium) today and it ran the best on it compared to either 87 or 89. Even though 91 is a bit more costly, it may very well be worth the extra few cents.:dollar: No knocking or black smoke coming out the exhaust while running it. Like I said, 87 or 89 it will run fine on, but I don't like the sound of knocking. Black smoke is irritating too, when I rev it or mash the gas down. Well, I am not sure but it won't be too long now and it'll be time to take the trans./engine out for a rebuild on both. Gonna be sure and get some things done on both that I won't regret. Even if hardened valve seats are not a must, while it's getting rebuilt, why not have them hardened!?
That's REALLY EASY. Buick DID "install" them beginning in '71; as a metal-hardening process done by heat-treating the parent metal. This, of course, saved about a dollar a head casting as opposed to shoving in hardened inserts but required a large outlay of cash for the specialized equipment needed--easily justified on the sort of production runs that GM did. Most machine shops don't have induction hardening machinery--so the procedure "in the field" is to punch in inserts. Yes, it takes skill, and yes, sometimes the casting is thin and things go bad. It would have been better if GM had put inserts in during the production of the head--but they didn't, and now we have to live with the results of them pinching pennies. Of course they will run. The question has always been "how long". And that "how long" becomes an unacceptably short length of time when non-hardened exhaust seats are run with unleaded gasoline in any environment that builds a lot of cylinder pressure--fast driving, trailer towing, racing, etc. But it's your money, and if you drive like Grandma, you can get by without hardened seats for quite some time--usually.
I have driven all of my Buicks.... on unleaded gas for the past 30 years, with hundreds of thousands of miles. Never have I had a problem with valve recession. I just went over my heads on 70 350, and only had to clean and relap the valves in..... can't say I've ever been able to to that with a Chevy motor. And I can assure you I drive em pretty hard.......... well, harder than grandma anyways! :laugh:
Thanks for the input everyone regarding the hardened valve seats. I would have to think that the nickel content being higher in our heads must contribute to the success of most of us without the hardening. Other brands seem to 100% need the hardening, from what I can tell. Keep up the input everyone! Inquiring minds want to know!!!!!
my 65 v6 still running,never been opened, have never put in additives driven daily and in winter,pulling around a 65 special is work enuff my 72 convert with 430ci had since 89 my fathers 72 electra 150000 plus the knock is your real problem right now before you damage bearings or pistons, or valves/seats due to detonation worry about the valve seats unless you lose compression thru them if you are really worried about unleaded fuels get a 75-80 350 engine and rebuild that
Hardened seats are a waste of money. Dennis Manner said you don't need them - why should I disbelieve the guy that spent half a century designing Buick engines? He said "the only time you need hardened seats, is if you're towing a load and running the engine at 4000 RPMs for hours." He also said additives are a waste of money:laugh: A properly tuned engine will not detonate/ping with pump gas.
This is going to sound stupid, but I'm currently doing this on my own vehicle (after hearing about it from someone who's been doing it for a while now) and it does seem to have some affect. If your engine has some carbon build-up, pour a bottle of ATF (yep, tranny fluid!) in your tank, at your next fill-up. You should notice a little nicer drivability, get better milage and will give you a slight power bump (more noticed, than felt). If you find your car starting to run rough while doing this, check the plugs. Could be some chunks of carbon have gotten wedged in the gap. ATF is one of the "tricks" mechanics have used for years, for cleaning out carbon without having to perform a full-on engine rebuild (water and diesel fuel are the more common treatments, though). I've always seen it trickled down the carb while the engine is set at WOT, but adding it to the fuel in the tank seems like a easier way to go about it. I know, you guys are probably thinking "WTF?! This guy's an idiot!", but really, it does seem to make a small difference. You'll see it mostly in the gas milage (at least I did) and it may help cure some of your knocking, as I've noticed it seems to act as a mild octane booster. Try that in combo with readjusting the ignition timing and you should be good to go. ...btw, on the subject of hardened valve seats, I've seen both sides of the argument in action. No two castings are going to be exactly the same and I'm sure this has an impact on how well the heads will hold up. I figure the way to look at this situation is to have it done on the reasoning that its good insurance against uneccessarily wasting a perfectly good cylinder head. Bob
