Big block timing question

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UOP

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Hey got a quick question. I'm helping a buddy of mine with his 383 Cuda and am wondering what a good safe starting point would be timing wise. Specs are:

-69 383
-Stock rotating assembly so not sure of compression but guessing less than 9:1.
-Quick Fuel 750vs street carb
-OOTB 440source heads
-Comp XE275HL cam, 275/287 .525/.525 110
-Edelbrock Airgap Intake
-1 3/4 Hooker super comp long tubes
-MP Igniton, distributor, wires


I originally timed the initial with a vacuum gauge to maximum vacuum. This was just getting it going with the new carb, and this is still a relatively new combo. Later when I threw my timing light on it I was amazed to see that it was set to over 30* advance at idle. I wouldn't have thought it would need that much initial advance, so I just backed it down to 16 initial, and set the total to 35 as a starting point (basically what my sb is timed at). Is it normal for big blocks to want/need more timing than small blocks? This thing really acts like it would love some more timing but I'm afraid to give it any more. What do you think?
 
I'd think somewhere around 20* initial would be in the range.

Low compression will usually handle more initial.

When setting initial using a vacuum gauge, you reset the idle speed every time you dialed in more timing, correct? See where the vacuum was at the constant idle speed. Some just keep twisting in timing and not resetting idle speed.
 
Yes, as I advanced the timing I kept lowering the idle to ~850 rpm. I don't remember what it was exactly but it was over 30*. If it can take more initial does that mean it can also take more total? I know this is something we will need to do actual testing at the strip, but do you think 35-40 would be in the safe range to start?
 
Initial and total are not related.

It might take more than normal total, but, sneak up on that number. Open chamber BB's have been run with 38+ total. so it's not unusual. Run it at the track and keep stepping on it. It'll slow down MPH wise when you've gone too far. Check the plugs if you start getting above 38 would be my suggestion. Look for signs of detonation.

If it starts OK at 30, limit it so you hit a decent total number. Run it and find out.
 
Gotcha. :glasses7:

We still need to mess with it so I guess we'll just see how it goes.
 
UOP said:
Gotcha. :glasses7:

We still need to mess with it so I guess we'll just see how it goes.
Click to expand...
Rob and i agree about 95% of the time about pushing the initial as high as it can tolerate. But i have to question 30*, man that is steep. I have to wonder if the balancer is marked correctly or the compression is alot lower then 9to1. Those heads are more efficient than stockers so they shouldn't require as much total.
I booboo'ed on the ignition system (MSD) earlier so i retracted that comment.
 
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