Where can I find a timing curve for a factory 1971 olds 455?
I cant seem to find one.

I have a edelbrock perofrmer dual plane intake. Holly 4160 carb 750 cfm. And C heads. Stock cam stock bottom end.
Does that change anything?

 

Page 6C-11 of your Chassis Service Manual.

- Eric

 

Unfortunatly I dont have that service manual.

 

Ahhhhhhhhh.

That's rather another story.

You should get one. They're all over eBay.

Get a real, original copy, not a crappy scanned CD.

- Eric

 

She owns a 1980s Caddy with a 455 swapped in place of the original 307.

 

So... 1980s Caddy Service Manual and 1971 Olds CSM should do the trick.

They wimped out and didn't go for the 501, eh?

- Eric

 

Hmmm. Wouldn't the timing depend upon which distributor was used - the original 307 HEI distributor or the '71 455 points distributor?

 

I think we're ASSuming the '71 455 distributor, but you're right.

- Eric

 

The 307 distributor doesn't have any provision for changing the advance curve in the distributor - it's all done in the ECU.

 

Thanks for the pdf.
With me running mechanical only, it looks like my spark is advanced too far.
Initial on my 455 is around 13 degrees at about 650-750 rpm.
I forgot what it was on the higher side.
But it runs fine though with mechanical only.
I will do some checking and see about re-adjusting it if possible.

This is the 3rd car this engines been in, Im the first to remove the heads thats for sure. It might have a bit of a cam but its hard to tell, it kinda sounds like it might. Stock bottom end though.

 

You should check the RPM and degree of advance when it maxes out - it should be about 36 degrees at about 3,000 RPM.

And you will probably benefit from a vacuum advance. One of the adjustable units will give you the most flexibility.

OldCutlass Eric loves to give people advice about how to dial in their advance settings.

- Eric

 

I will look for that.
If it maxes out sooner that means there is to much advance so I should retard the timing to compensate right?

Here is an image I found online, it is just like the one in my 455:
http://i.ebayimg.com/23/!BgjrUP!CGk~$(KGrHqIH-EIEsK7W1tc+BLFvY+k46!~~_35.JPG?set_id=8800005007

The carb is a holly 4160, I plugged my VAC advance into the port on the side of the Holly, I believe this is the ported vacuum, is this the wrong port to be using?
Should I be using the manifold vacuum instead?

Is that why I get to much advance with vacuum and its fine without, because the ported vacuum is adding vacuum when the throttle opens, when I should be using manifold vacuum so that the vacuum goes away when I press the throttle?

 

What do you mean by "too much advance"? Depending upon the specific vacuum canister, it can add as much as 24º advance (as the original on my '78 HEI did). This is where the adjustable canister comes in as you can tailor the amount of vacuum advance. Seems the general consensus is ~10º is optimal.

Ported and manifold vacuum will end up being the same once you open the throttle; it's just at idle when ported has no vacuum.

 

You can use ported or manifold vacuum, with a relatively stock engine it won't make much difference. The argument has been going on for decades.

 

Reason I asked is because i thought it was right, then I held RPM up, and when I let off the throttle, I had an intake backfire.
That was with vacuum advance on.
With it removed, I think it happened but it was less prone to happening.
This was in park and when letting off throttle after a rev.
In drive while driving, no problems with mechanical only. Never tried it with vacuum as well.

It was repeatable. Is it possible the carb needs adjusted and my timing is fine?
The holly 4160 @ 750 cfm is currently as-is from the box, I never went adjusting anything on it yet.

 

Do you have an adjustable timing light? What is your timing set to?

 

Backfiring through the carb sounds like a carb related issue and not so much a timing issue.

 

What would cause a brand new holly 4160 @ 750 cfm to do that?
To lean?
I never adjusted the carb yet.
Maybe my spark is/was fine and the carb is what I should be adjusting?
I dont recall anything like this with the factory carb.

 

What is the part number of your 4160? I'll ask again, what is your timing set to?

 

I remember a friend's engine would backfire and shoot flames out the carb when letting off after revving. There was a plug missing either in the rear of the carb base plate or the intake manifold, either way it had a big vacuum leak.

 

Holly 4160 part number: 0-76750BK
I havent adjusted anything on it, I was told it should be fine out of the box.

I remember the 750 ish idle timing was about 12 degrees advance mechanical only.

I forgot what the max was, I will check it again and see.

 

If you are running 12* at 750 rpm its most likely too low. I'd set it to 16-18* and tightened the distributor down. With the engine running and timing light hooked up, connect our vacuum advance line to manifold vacuum and note how much more timing you get.

 

0-76750BK is a double pumper(mechanical secondaries) and 4 corner a/f adjustments. Not a simple carb and a bit extreme for a mild 455 with an automatic.