i am new to this post so first of all, hello all.....

my question is about this engine that i bought from an old man who had a friend that bought a 1970 chevelle in 1970 and totaled it in 1980. my friend got the engine and tranny from the wrecked car and has had it in his garage for the past 23 years. it is a complete engine carb, intake, distributor, starter, brackets, alt, and tranny, all connected as one assembly, and its not locked up. he wanted 200.00 for the engine and i bought it and brought it home. i own a 1970 chevelle (art in progress), and wanted to put this engine in my car later on, but i am hearing of some problems that i will have because of this engine.

finally my question......

the numbers on my engine are as follows...

engine #VO903CNR 350ci/300hp

block #3970010 4 bolt mains, steel crank

heads #3927186 camel hump with 64cc chambers,202 intake ,165 exhaust valves

i have asked quite a few people about rebuilding this engine back stock except for an alluminum intake and HEI ignition and headers , and maybe a bigger than stock cam..... approx. 350 hp after i am done

and the answer i get is that a premium fuel engine of 1970 will not run on 93 octane fuel without pinging my ears off, and that i can not adjust the timing enough without losing much power to compensate for the pinging....... octane in 1970 was 110 rating and now its 93 at our pumps. i understand i could buy racing fuel at $4.00 a gallon but i am not interested as i plan to use the car as a semi daily driver. octane boost is around $5.00 per can and it only gives approx 3 octane per can plusout to the tank. has any one used a engine like this using the stock heads in todays gasoline world?

thanks...............................

You should have no problem with your rebuilding plan. The hotter cam will actually reduce low rpm cylinder filling which will make the engine a little less ping prone when lugging around town. Of course the reverse happens at higher RPM, but as RPM goes up octane requirement goes down simply because random explosions simply run out of time to occur.

If your uncomfortable with the compression you can do a couple things. When rebuilding the heads, kiss 'em a little with a die grinder to open up the chambers a bit. Shop for pistons with enough dish to lower the compression (wouldn't be my choice as a flat top with a tight squish is more resistant to detonation and gets better efficiency out of the burn ie more power and better fuel mileage) . Be aware that for a few bucks piston makers will fiddle the tops for you. Or put the engine together with a thicker head gasket, you can find a range from steel shim at .015" compressed to composition at .040, or so, compressed. So there's plenty of play space here.

Plus you can fiddle the timing, as was suggested to you, you can also fiddle the mixture. Timing can be a reduced in the base setting which will kill some power through-out the RPM range but a more elegant advance curve can be employed, less up front more/faster later. The carb's fuel curve can be modified and complicated to supply a richer mixture in places where the engine may want to ping. And my God I haven't even talked gear ratios and tire sizes, etc, etc.

So hopefully you see that you can get at the pinging issue from a bunch of ways that doesn't require throwing 4 dollar a gallon race gas at it.

Last suggestion, you need more knowledgeable advisors.

man thanks for the list of how-to's and they were great . maybe i will keep the engine and get to work soon..... by the way.... what did you mean by gear ratio and tire sizes affecting the possible pinging in the engine?  

I'd just like to add that with the unleaded fuel you'll be needing hardened seats on those exhaust valves. you also can have your distributor recurved and modified to get more advance. depending on the cam, 34 degrees total would be a good start. I like to tune to mph in quarter.  

flat top pistons w/ 64 cc heads is less than 9 & 1/2 :1 compression.  that compression will run on pump gas w/ no trouble at all.  the 186 casting 350 heads are getting rare so hang on to those. stock later model 350 heads have a 76 cc chamber.  so those 64 cc chambers help your compression ratio quite a bit. flat tops w/ 76 cc heads only give you about 8.3 :1 compression.  put the hardened exhaust seats in them for sure.  also I can tell you unless someone has been through those heads already they do not have 2.02 & 1.6 valves in them.  them came stock w/ 1.94 & 1.5 valves.  everyone thinks they have 2.02 valves until a machine shop sees them & tells them otherwise.

Compression, cam timing and the speed (RPMs) and load on the engine have a large effect on detonation and preignition. Too much compression, too little cam, too high a gear too heavy of a load conspire to ping the engine.

You have to look at the car as a total system. A reasonable set of comprimises from the engine to the tires will be faster than optimizing something at the expense of everything else. I say that around the thought of the engine. So many guys blow their life savings on the engine. Then there's no money left for the right transmission, driveshaft, rear axle, tires, wheels, suspension, etc. They end up with a car that isn't nearly as quick as it could have been with a set of thought out comprimises.

Bogie

Gearing controls engine loading. This is the old lever principle. However, engines and cars are a bit more complicated than the simple lever because there's a bunch of simple levers from what's inside the engine down the driveline to how the car transfers weight under acceleration, deceleration, and turning.

The overall gear ratio is changed to optimize different characteristics. The factory chooses a high ratio (low numerically) like a 3 to 1 rear axle ratio (small lever) to maximize fuel economy. This is where the driveshaft turns 3 revolutions for one of the rear axle. Years ago, before overdrive transmissions, the final (high) gear ratio in the transmission was 1 to 1 so the engine was turning the same rpms in high gear as the drive shaft. The drag racer chooses a low ratio (high numerically) like 5 to 1 to maximize the amount of force (way bigger lever) applied to the rear tire, this minimizes the time it takes to go 1/4 mile, but gives really bad gas mileage on the street. You have to realize that speed (terminal velocity) is not what wins drag races, it's lowest time that gets there first, speed is an incidental compoment to a drag race.  The circle track racer is in a much more complex situation needing a comprimise between good fuel economy, quickness, and a sustainable high speed. He/she will pick a ratio between that of a street machine and a drag racer. But the track will have a great influence on that ratio. Short track needs a low ratio for quickness out of the corners; a long track needs a higher ratio for good top end and reasonable fuel economy. The road course needs something in between to deal with a combination of tight to wide turns and short to long straights. Basically the circle track car needs enough lever to quick (time) but also needs to be fast (speed) the end ratio is of course a comprimise as each situation cannot be idealized.

Gearing includes all the ratios in the transmission and the rear end plus the distance from the axle center to the tire tread resting on the ground. That distance is again a lever. You can adjust the overall gear (lever) ratios by changing tire size. This is easier, faster, and cheaper than gear changes. A taller tire creates a high ratio (low numerically) situation, where the car goes a further distance per revolution, this is akin to a short lever. A shorter tire creates a low ratio (high numerically) situation, where the car goes less a distance per revolution, this is akin to a long lever.

This is all  to say that with a short lever you generate less torque in a longer distance  and with a long lever you can generate more torque over a shorter distance.

Gearing is a very complicated subject which in it's complete exploration creates chapters in books if not complete books. This is where physics and mathmatics meet reality. Those who master this go fast, those who don't, well they don't go fast.

Since gearing determines the load on the engine, it is a direct contributor to the forces and temperatures in the engine's cylinders; gear ratios have a significant affect upon an engine's sensitivity to pinging whether it's from detonation (explosion) or pre-ignition. A high compression engine running a mild cam and a high ratio rear gear set such that the engine is turning rpms low in its power band is subject to pinging because the absolute cylinder pressures and temperatures are too high for the available fuel octane. You can fix this by increasing the octane rating of the fuel, or reducing compression ratio, or putting in a longer duration cam, or putting in a low ratio (higher numerically) final drive, which includes fiddling with the tire size, or some amount of all of these.

But each set of circumstances has an optimum solution depending on what you want the car to do. And every change to solve one problem creates a new optimum solution that cascades into other changes. This is whay it's so hard to set up a car and keep it competitive. Everything affects everything else from the weather to the tires to the track surface.

Bogie 

hello!!
I realize this is an old post, but I've been away for a bit and I came across this post and I had to reply. I have virtually the exact same set up in my '72. I've been SLOWLY rebuilding the motor, chassis, drivetrain, body, et al over the last 10 years or so. As for your engine, I've never really had a problem with detonation except when the timing was set too advanced, the motor has the stock style dished pistons which don't allow for exessive compression even with the .015 head gaskets, and my block and heads have been milled appox. .010 each, but then again I live @ 6000ft + alt. However with your engine and heads I would bet that with a little more cam, some simple minor bowl work on the heads, headers, ignition up grades, etc, you should end up very happy with your engine, I know I am. It's not a 10 sec car, not even a 12 sec one, but she'll give the imports a thing to think about. Have fun with your project!!!