The Stovebolt Site Forums The Shop Area Engine Shop Distributor Question

Hi guys,
The vacumm advance is shot on the 235.
How do you remove it to put a new one in?
Is it hard to do, and what is all involved in replacing this part?
Thanks in advance.

Chevyboy62

Chevyboy62,

You might want to consider buying a shop manual. The sponsor of this site and most parts vendors sell them (and they can be found on eBay).

http://www.americanclassic.com/

You have to remove the distributor to remove the vacuum advance mechanism. This is not a diffucult job - just be slow and careful.

1. Take off the distributor cap after disconnecting the ignition lead (if you disconnect the plug wires, mark them).

2. Mark on the block the location to which the rotor is pointing (I rotate the engine until the rotor points to the block and then put a chalk mark on the block).

3. Disconnect the vacuum line from the advance mechanism.

4. Take out the bolt that holds the mechanisim to the ledge in the block.

5. Pull out the distributor - you might have to jiggle/rotate the rotor a little.

6. Unclamp the advance mechanisim from the shaft of the distributor.

For installation:

1. Put new gease (lithium or chassis grease) in the grease cup on the distributor.

2. I set the points (put in a new condensor, if its been a while since it was replaced).

3. Loosely clamp the advance mechanism around the distributor shaft.

4. Insert the distributor into the block. You might have to do this a few times before you are able to line up the rotor to the mark you made on the block.

5. Connect all wires/leads. Put the cap back on the distributor.

6. Connect the vacuum line to the advance mechanism.

7. Bolt the mechanisim to the block with the bolt in the middle of the Octane Selector scale.

8. Loosely clamp the advance mechanism's collar around the distributor.

9. Restart the engine (and check the dwell, if you have a meter).

10. Set the timing.

11. Go for a drive.

I trust that others will correct (or add to) what I outlined above.

Tim

A slightly related question I have been thinking about. So, we have four stroke engines, so the engine fires every other stroke? But the distributor, it doesn't skip a fire when it comes around does it? It fires every time the rotor is underneath a wire right? So, does the distributor make one revolution for the engine making two?

The reason I ask is because when doing some ignition or valve work you need to put the engine on TDC, but wouldn't putting the rotor on wire #1 be sufficient? That is when the cylinder fires right?

That might do it. Been laying awake at night thinking about this...

Tony M,

I hope these help you sleep better at night:

http://www.k-wz.de/vmotor/v_omotore.html

This site is great - be sure to check out the camshaft section, too:

http://www.howstuffworks.com/engine4.htm

Tim

Tony, I know some people start reading and go right to sleep. So I'll make it short.

The distributor gear ratio makes the distributor turn at 1/2 the speed of the cam, so you're right! Now, the best way to set the engine at the #1 firing position, especially if the distributor is out, is to remove the plugs, hold your finger over the number one plug hole, and turn the engine by hand (I use the fan blade on a clutchless fan) until the pressure starts to blow your finger off the hole. Then turn the engine until the timing mark is lined up.

Good night and sweet dreams. :p

I'd like to add : _NEVER_ change the condenser if the points are burning evenly ! usually they'll burn a tit on one side and a valley on t'other , once in a blue moon you get lucky and find a perfect condenser that burns the points evenly , it's _gold_ as it'll make the points last about forever so don't change it !.

Actually, the distributor turns at the exact speed as the cam, which is half the speed of the crankshaft.
Finding TDC with the rotor pointing at #1 is inaccurate at best..... doesn't account for base advance, chain slop, and eyeballin' it.
Sounds like you have a running engine..... if there's room, I'd swap that vac advance with dist. IN the truck, that way timing is still close!

Also compare the price of the advance module by itself to a rebuilt distributor. Some motors the advance unit is $25-30 while a complete rebuilt dist. is only $40.

The 235 vac advance canister is getting hard to find. And you do have to remove the dist to change it, as it clamps around the base of the dist. The vac advance can be removed on the newer engines (230-250, etc) w/o removing distributor, but not on a 235.
Johnnys right, the cam turns 1/2 as fast as the crank, and the dist turns the same speed as the cam. Ergo, the dist turns 1/2 as fast as the crankshaft.

Really want yer mind blown? The cam in a I-6 chevy turns opposite crank rotation, yet the distributor still turns clockwise like a V8. The trick? Reverse cut distributor drive gears.


chip