Robert Lewis

Now I'm stuck: took it out to get it warm (it's still overheating @ 204* measured at the upper hose with an IR gun; 164* lower hose) and it was idling too high. Took off the vac advance hose and plugged it, and the engine reverted to its original condition: impossible to adjust idle to 800, with the 12* BTDC jumping like it's scattered, and any idle adjustment near 800 makes the idle speed increase by 300-400 on its own.

The car runs pretty well, but starts to knock under load once it's hot, and runs on when it's shut off. I saw a method of determining TDC by using a vacuum/compression gauge on the #1 cylinder, so I'll try that and see where the rotor is. Any other suggestions?

Gary's '66

First, 204° is NOT overheating! If your getting readings above 225-230° OR its puking after shut down then THAT'S overheating!!!
Second the run on and pinging is timing related and can be just one issue or ALOT of different issues combined, but usually things wrong within the distributor. I suggest you read "Lars tuning secrets: The Common Tuning Tour Observations and Fixes" in the search this forum section. He's also a forum member and for a VERY reasonable rate can get it all dialed in for you.

Gary

Mike Ward

I didn't think that all would be well given the above saga.

May I ask where you got the 12* initial timing @800 RPM figures from?

BTW- forget the rotor orientation and TDC for now. It's got no relevance to your problem.

lars

Why don't you just send me an e-mail request for my Distributor Installation Paper, and I'll send you the complete instructions with photos of the correct installation and procedure. It also has the procedure that I call "walking the rotor" for moving it a tooth over.

Lars
V8FastCars@msn.com

Gary's '66

Speaking of the devil! How ya doing Lars? Just to let you know you did a fine job on my distributor. The car has never run better.

65tripleblack

I agree there's absolutely no reason to waste your money on a new crankshaft. Have it drilled/tapped after removing the dampener and radiator and shroud.

If your camshaft is a flat tappet then it, along with the distributor drive gear are nodular iron. If your aftermarket distributor's driven gear is steel, then there's a good chance that it chewed up the cam's drive gear which is causing the timing to jump around.

Read post #30. Oops.........I forgot, you only read one guy's posts.

Robert Lewis

How do I tell the difference between nodular iron and steel?

Robert Lewis

Mike, 12* BTDC and 750-850 RPM idle is from the 65 Corvette Shop Manual Supplement.

65tripleblack

I don't think there is a way. I would get a GM iron gear anyway since you don't know what you have. It will have the dimple, which MUST point in the same direction as the rotor electrode, so that will take the guesswork out of that part of your problem.

Before buying a new dist driven gear, you should examine the distributor drive gear on the camshaft as best you can with a pencil beam flashlight, to check for wear on the drive surfaces of the teeth.

Robert Lewis

That's the kind of direction I need: specific. Thank you!:Thumbs Up:

FWIW, I did check the drive gear carefully when it was out, and I couldn't detect any wear at all on the drive gear.

Robert Lewis

Here is what I ordered:
Note that it says it doesn't fit my vehicle, but Amazon may not be the final authority on Corvettes....

Robert Lewis

Also note that it doesn't have the dimple.

DansYellow66

I wonder if this might not be a better choice?

http://www.rockauto.com/catalog/more...355&cc=1322132

I think the 10456413 is for a later HEI distributor. Are you running an original distributor or a later HEI unit?

Robert Lewis

An original distributor.

65tripleblack

IF the distributor gear (the driven gear) is melonized steel, it will cause wear on the CAMSHAFT GEAR (the drive gear).

Check the camshaft gear for wear before you buy anything.

65tripleblack

I'm sorry. I edited my post and deleted the part number, so you were very quick to pull the trigger if you got that part number from my post. 10456413 IS A STEEL GEAR, and you need an iron gear.

I have tried but cannot find a GM part number. If someone doesn't get it for you, I will look further and post it for you.

Interestingly, the GM iron gears and the GM steel gears have the dimples located in a slightly different alignment! The iron gears have the dimple coincident with one of the roll pin holes, but the steel gear has the dimple OFFSET from the drive pin holes.

Robert Lewis

How do you feel about this: http://www.summitracing.com/parts/su.../applications/

65tripleblack

Yes, that looks correct!
The GM part number is 1958599.
You can also buy it here: http://www.parts123.com/parts123/yb....5Z50000050B~~~
Dansyellow66 part reference is correct as well.

Again, I can't emphasize strongly enough..............examine the cam's distributor drive gear because if it's damaged, then the cam must be replaced!

ghostrider20

Robert, for now, pull the hose off the carb to the vacuum advance. Cap the nipple on the carb off so you don't have a vacuum leak.

We need to get your base static timing set and verified.

Start the car and use the idle adjustment (curb idle screw) to set the idle at about 1000-1100 RPM. I was never able to get a stable idle at 750-850 in either the 30-30 or the LT-1 cam. 950-1000 min RPM for the LT-1 and 1050-1150 for the 30-30. You get better idle quality and the timing is not bouncing around (mechanical weights).

Some like a real low idle with shake and lope. I like a smoother faster idle. I idle my LT-1 cam 327 at around 1200 RPM.

Steps.

- Hook up timing light
- Start car and let it warm up.
- Pull of the vacuum advance hose from the carb.
- Cap off the carb nipple that the hose came off of.
- Set idle screw to about 1000 - 1100 RPM.
- Record what the timing light reading is.
- Turn idle down as low as it will go without stalling the engine.
- Record what the timing light reading is. (It may be jumpy)
- Turn Idle up to 1300-1400 rpm
- Record what the timing light reading is.

You have 3 timing values to record and post back with.
Note if the timing line was jumpy or not.

- Mark

Robert Lewis

This is great, Mark. Thanks!
Does it make any difference that I'm using manifold vacuum rather than ported vacuum?