Which oil for '84 GM 366?

[Alex_V]

No reason to be afraid of carbureted engines - the more you know about them the better off you'll be, and when it lets you down (which it's bound to) you'll be able to do something more than call a service or tow truck. Getting it in good tune may save some fuel, but just as importantly if it's not currently in very good tune it'll only help that hard-working engine and get you down the road with less fuss and more vroom.

They're a little pricey, but Schaeffer's has products to fill all your sumps (not sure about SAE 50 but they'll surely have something to go in that gearbox) and it's stout stuff - I believe their marketing statements about savings from less friction and longer drain intervals. With the number of miles you're putting on it couldn't hurt.

 

[BrocLuno]

Tuning that engine is not rocket science. The thing about most BBC including the 366 is that they are way under-timed.

You may want to pull the distributor and go through it. Shim the shaft to about 0.015" clearance near the drive gear, make sure the fly-weights are operating smoothly, etc. I'd tap the distributor body out the bottom on the condenser clamp hold-down screw hole and run a longer screw out the bottom, then run a dedicated ground wire from the block to that extended screw.

Change the vacuum advance to a real Delco 15* unit and set the initial timing at 8* or so. If it'll start hot, you can add a bit more. It'll help with mileage - a lot ... If it's all smooth that way and no signs of ping, you can swap to an 18* vacuum advance. It should ping once in a blue moon on cheap regular. It's sometimes hard to hear in a truck, but you'll hear it if it's not too loud in the cab. No regular pinging allowed.

Good plug wires are a must. Not expensive, but good. I use Moroso spiral core. They hold up to heat well and won't buzz your radio bad. Carbon core wires are not your friend.

Make sure all the grounds from the battery (-) are good. Add one to the firewall. Maybe add one say #8 wire to the alternator mount. That will make sure there is no false signal for the regulator.

If the factory resistance wire from the rubber block to the coil is frayed, look to replace it with an external ceramic resistor and new plain wire. Make sure the non-resistor 12v lead from the stater is in good shape. That supplies the coil when cranking. If all the ignition wiring is good, it'll run for ever.

May have gummed rings a bit depending on how it was maintained ... I'd throw two full cans of BG109 in with the oil change. Big filter is a good idea.

Look at the fuel lines and make sure they are staying cool. It's easy enough to have vapor lock if you are working hard at slow speeds ...

 

[c502cid]

If it is a Quadrajet in-carb fuel filter I bet it hasn't been changed in a while. Change it (and watch for stripping it out.. snug is enough!. If that is the only one, add an in line filter too. If you show any signs of vapor locking in the heat, add a cheap-o electric fuel pump.

Big blocks are easy as long as the basics are covered. Second the importance of good grounds too.

Any oil will work, really. It might, and probably will, use a quart of oil every 1000 miles, perfectly normal.