66 modified 425 wont time

dynamic88builder · July 23rd, 2004, 08:02 PM

i have a 1966 olds dynamic 88 ragtop with a modified 425. mild crane can and bored 30 over. its got about 10k since the build. my problem is it wont stay in time, i reset the the ignition timing (seems to be right at 15* advanced with cam) run around the block and timing is off again. the ignition is fairly stock points and condenser. also looking for advice on where to start with dual exaust mods..this single is killing my horsepower...do they make a bolt on?

jdorour · July 24th, 2004, 07:04 PM

Your ignition timing may be changing as a result of the distributor moving or the points moving. Make sure that you have everything tight. Make sure you have the correct resistor wire from the coil to the points. If you used just a standard length of wire the points may be burning and changing the dwell angle and timing. The least likely problem could be a sheared pin on the distributor gear. I did have this on an Olds 455 that I was running in my boat There was just enough of a burr on the shaft to keep the gear from spinning freely. One more problem I have seen is a bad harmonic balancer. The rubber went bad and the outer shell of the balancer would move around. This caused the timing to appear to change. If this is the case you will not notice any change in dwell angle but the timing marks will move. You will also not notice any change in engine tone or drivability.

About your exhaust question - On the Left you can get the correct dual exhaust manifold (P/N 384893, casting code S) these can be found on all 1965 and 1966 Starfires and some 1965 to 1970 full size cars. You will also need to fabricate a shift link that goes from the frame to the trans if you do not have a floor shift. Or you can keep the single exhaust manifold on the left and have a custom pipe bent for the left side. You will need to do this anyway with the Toronado manifold. On the right side manifold you can just cap off the cross over port. This is what was done at the factory on B and C body cars with dual exhaust. I do not know of anyone that mass-produces headers for the 65 – 70 B and C body cars. You may have some luck having a set of custom headers made.

Some of the others on this site may have better ideas. Maybe we will hear from them?

stuart · July 24th, 2004, 10:56 PM

JDOROUR is quite correct.

Also, do these, listed from easiest to hardest. Do only ONE at a time...

Check the operation of the vacuum advance. First, temporarily disable it by disconnecting it from the distributor and plugging the hose. See if the timing steadies-up. Find a piece of hose, connect it to the vacuum chamber on the distributor and put the other end in your mouth. Start the engine and have a friend watch the timimg mark with the timing light. Create vacuum by sucking in on the hose. The timing should advance as you change the 'amount of suck'. With the engine still running, reconnect the hose to the engine and move the accelerator on the carb. If the timing doesn't change exactly the same way it did with you sucking, you've probably got a vacuum leak.

Next test, remove the cap and rotor and lubricate the centrifugal weights. Occasionally they will bind-up and if you time the engine with them in the advanced position, you'll get 'bad' numbers when they return to a non-advanced position. This actually happens a lot since folks rarely lube these. With the cap off, have someone crank the engine and check if the shaft rotates without wobble. A bent dist shaft (rare) would cause your problem.

With the engine cooled off, pull the coil-to-distributor lead. Position yourself over the radiator and place each of your hands on opposite sides of the crank pulley. Pull up and down alternating on the left and right sides by grasping the belt that goes around the crank. There should be no movement; if there is, then the keyway or key that mates the pulley to the crankshaft is bad. In this case, you really don't have a timing problem, it just looks that way because the timing mark is moving. This rarely happens but I HAVE seen it.

Hope this helps.

[ July 25, 2004: Message edited by: stuart ]</p>

July 23rd, 2004, 08:02 PM	#1 (permalink)
dynamic88builder Junior Member Join Date: Jul 2004 Location: stratford,ct Posts: 14	i have a 1966 olds dynamic 88 ragtop with a modified 425. mild crane can and bored 30 over. its got about 10k since the build. my problem is it wont stay in time, i reset the the ignition timing (seems to be right at 15* advanced with cam) run around the block and timing is off again. the ignition is fairly stock points and condenser. also looking for advice on where to start with dual exaust mods..this single is killing my horsepower...do they make a bolt on? __________________ 1966 dynamic 88 ragtop, modified 424(30 over,edelbrock,crane etc),dual exhaust,TH400, shaved trim moldings, slammed front end crager s/s wheels

July 24th, 2004, 07:04 PM	#2 (permalink)
jdorour Senior Member Join Date: Feb 2004 Location: Atlanta, GA. Posts: 122	Your ignition timing may be changing as a result of the distributor moving or the points moving. Make sure that you have everything tight. Make sure you have the correct resistor wire from the coil to the points. If you used just a standard length of wire the points may be burning and changing the dwell angle and timing. The least likely problem could be a sheared pin on the distributor gear. I did have this on an Olds 455 that I was running in my boat There was just enough of a burr on the shaft to keep the gear from spinning freely. One more problem I have seen is a bad harmonic balancer. The rubber went bad and the outer shell of the balancer would move around. This caused the timing to appear to change. If this is the case you will not notice any change in dwell angle but the timing marks will move. You will also not notice any change in engine tone or drivability. About your exhaust question - On the Left you can get the correct dual exhaust manifold (P/N 384893, casting code S) these can be found on all 1965 and 1966 Starfires and some 1965 to 1970 full size cars. You will also need to fabricate a shift link that goes from the frame to the trans if you do not have a floor shift. Or you can keep the single exhaust manifold on the left and have a custom pipe bent for the left side. You will need to do this anyway with the Toronado manifold. On the right side manifold you can just cap off the cross over port. This is what was done at the factory on B and C body cars with dual exhaust. I do not know of anyone that mass-produces headers for the 65 – 70 B and C body cars. You may have some luck having a set of custom headers made. Some of the others on this site may have better ideas. Maybe we will hear from them? __________________ 1966 Ninety Eight Convertible - 425 Tri-Carb, Factory Dual Exh, Switch-Pitch THM400, 3.54 Posi. 1966 Catalina Wagon - 421 Tri-Power, M21, 4.11 Saf-T-Trac, 8 Bolt Wheels 1989 IROC-Z - 5.7TPI

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July 24th, 2004, 10:56 PM	#3 (permalink)
stuart Junior Member Join Date: Jul 2004 Location: chicago Posts: 6	JDOROUR is quite correct. Also, do these, listed from easiest to hardest. Do only ONE at a time... Check the operation of the vacuum advance. First, temporarily disable it by disconnecting it from the distributor and plugging the hose. See if the timing steadies-up. Find a piece of hose, connect it to the vacuum chamber on the distributor and put the other end in your mouth. Start the engine and have a friend watch the timimg mark with the timing light. Create vacuum by sucking in on the hose. The timing should advance as you change the 'amount of suck'. With the engine still running, reconnect the hose to the engine and move the accelerator on the carb. If the timing doesn't change exactly the same way it did with you sucking, you've probably got a vacuum leak. Next test, remove the cap and rotor and lubricate the centrifugal weights. Occasionally they will bind-up and if you time the engine with them in the advanced position, you'll get 'bad' numbers when they return to a non-advanced position. This actually happens a lot since folks rarely lube these. With the cap off, have someone crank the engine and check if the shaft rotates without wobble. A bent dist shaft (rare) would cause your problem. With the engine cooled off, pull the coil-to-distributor lead. Position yourself over the radiator and place each of your hands on opposite sides of the crank pulley. Pull up and down alternating on the left and right sides by grasping the belt that goes around the crank. There should be no movement; if there is, then the keyway or key that mates the pulley to the crankshaft is bad. In this case, you really don't have a timing problem, it just looks that way because the timing mark is moving. This rarely happens but I HAVE seen it. Hope this helps. [ July 25, 2004: Message edited by: stuart ]</p>