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Old 10-29-2011, 11:46 AM
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454 peanut port timing

Recently installed 1997 454 peanut port with edelbrock 2.0 intake and 650 AVS in my 65 impala, 700R4, 4.11 rear end.

I can set the total timing at 33, with vacuum advance unplugged, and initial at 4, but when I plug in the vacuum advance, initial goes to like 14, and total is still at 33.

It seems like it drives fine, not super power, but good. the problem is that the smell of fumes is very strong, and I just feel like I should be able to adjust initial timing better.

any ideas or suggestions?
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Old 10-29-2011, 08:54 PM
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yeah. Disconnect the vac advance and plug it. Move the base timing up to 12 degrees before top dead center. Reconnect vacuum advance, make sure you connect it to a full time manifold vacuum source, one that pulls vacuum at idle. Recheck timing. It should be 20-24 degrees before top dead center.
The idle will go up when you do so. Idle it back down on the idle speed adjustment then reset the idle mixture screws. If you use a vacuum gauge to set the idle mixture, set it to it`s highest vacuum. If doing so by ear, go for highest idle speed. Test drive. Report back results.
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Old 10-29-2011, 11:41 PM
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I just read your thread and will take your advice, but here's what I did this afternoon;

I connected vacuum advance to NO vacuum at idle, because, if I were to do your suggestion, my total advance will be close to 50. Right now it's like 8, and than total is about 38. It takes a few rotations to get it started, and MAY sputter when turned off.

I have an adjustment allen nut in the vacuum advance but turned either way, doesn't see to change anything. If I connect vacuum advance to vacuum at idle, set timing to about 8, and then plug in vacuum, it goes to like 22, but then total advance seem so high, near 50, isn't that too high?
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Old 10-30-2011, 12:45 AM
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Total timing is initial plus mechanical- no vacuum advance is added. Also, turning the adjustment usually only changes the tip-in point of where the vacuum advance stops/starts- not the total amount of advance it supplies.

Now, 48-50 advance under light throttle cruise conditions w/the vacuum advance hooked up and working is fine. The vacuum advance drops out when the engine is under a load, so it will not be that high when you are accelerating hard, or climbing a hill, etc.

You want somewhere around 12-16 initial, the rest comes from mechanical. Keep the total timing to about 38 or so, depending on the cam, gas quality, etc. This may mean you will have to modify the distributor to give you the right amount of mechanical advance.

You want about 10-12 to come from the vacuum advance. If your vacuum advance is giving more than that, you will need to physically limit the vacuum advance can's travel w/a vacuum advance limiter plate like the Crane #99619-1. Or you can make one.

DETERMINING TDC will allow you to be sure the timing tab and damper are correct for TDC.

MAKE A TIMING TAPE to see what the total timing is, w/o needing to use a dial back timing light.
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Old 10-30-2011, 08:07 AM
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it smells rich (like gas) because it doesn't have enough base timing and the carb throttle blades are open past the idle transfer slots.

Good advice posted above.
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Old 10-30-2011, 05:09 PM
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good info guys, I have read all these things, but I am still a little confused.

What should I set initial timing at, with the vacuum advance unplugged?

What should initial timing be when I connect the vacuum advance?

When I throttle to 3,000 rpm's, what should the total timing be safely(and do I test this total timing with or without the vacuum advance connected)?


I think once I know that, I can determine if I need to change anything on the distributor, or not.
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Old 10-31-2011, 06:16 AM
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I would unplug the vacuum advance and rev the engine to 4000 to 4500 rpms and see how far the timing mark moves (max mechanical timing). Then set the max timing to between 38 and 40 degrees. I would guess the timing at idle would need to be around 14 to 16 degrees to get 38 to 40 max mechanical.

then plug the vacuum advance into a manifold source and the timing should increase at idle to 26 to 30. if the timing goes more than that, then you should either put a stop on the vacuum advance or buy an adjustable vacuum advance canister.
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Old 10-31-2011, 06:21 AM
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What should I set initial timing at, with the vacuum advance unplugged?
Stock cam? 12 or so. This is not written in stone. NONE of the timing figures are- they are a safe place to tune from. NOT the exact setting that the engine has to have.

What should initial timing be when I connect the vacuum advance?
Initial is W/O the vacuum advance added in. Initial PLUS vacuum advance should be somewhere around 22-24 (12 initial PLUS 10-12 vacuum advance). This is IF the vacuum advance is hooked up to manifold (aka "full time") vacuum.

When I throttle to 3,000 rpm's, what should the total timing be safely(and do I test this total timing with or without the vacuum advance connected)?
Providing the mechanical advance springs are allowing full advance to come in all the way at 3000 RPM, the timing will be initial plus mechanical, or 12 plus 26 = 38 total, w/o vacuum advance. To get 26 (or whatever it ends up needing), the distributor will probably need to be modified to limit/extend the mechanical advance to give you the mechanical advance required. There are dozens of threads that deal w/limiting the mechanical advance.

WITH vacuum advance hooked up and giving you 10-12, on top of the initial and mechanical advance, you will see about about 50, give or take- if the engine is under no load, and the vacuum advance is adjusted so it will give full advance at the vacuum the engine is making at 3000 RPM.
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Old 11-01-2011, 10:26 AM
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I did as you instructed, and the 'blow by' or 'exhaust' smell is very strong, any ideas on that?
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Old 11-01-2011, 11:11 AM
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Originally Posted by hotrodcommuter
I did as you instructed, and the 'blow by' or 'exhaust' smell is very strong, any ideas on that?
Is the cam stock? Did you adjust the idle mixture screws to give the highest vacuum/RPM at idle? What is the vacuum at idle?

Are you getting the "eye burning" kind of exhaust 'smell'? Are you in the open or a garage, closed in, or what? I mean, a running engine is gonna smell like exhaust, so give us an idea of what you're experiencing.

If you're getting the eye watering kind of thing happening, do the idle mixture screws work? By that, I mean does adjusting the IM screws cause the engine idle to change if turned a half turn to a full turn, or are the screws basically unresponsive except maybe at the extremes like all the way in or out?

Will the engine stall out if you turn the screws all the way in?
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Old 11-01-2011, 02:19 PM
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Is the cam stock? yes

Did you adjust the idle mixture screws to give the highest vacuum/RPM at idle? yes

What is the vacuum at idle? 22

Are you getting the "eye burning" kind of exhaust 'smell'? yes

Are you in the open or a garage, closed in, or what? outside

I mean, a running engine is gonna smell like exhaust, so give us an idea of what you're experiencing clothing stinks and smells burnt .

If you're getting the eye watering kind of thing happening, do the idle mixture screws work? By that, I mean does adjusting the IM screws cause the engine idle to change if turned a half turn to a full turn, or are the screws basically unresponsive except maybe at the extremes like all the way in or out? they resond well, and will affectively adjust the vacuum

Will the engine stall out if you turn the screws all the way in?
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Old 11-01-2011, 02:41 PM
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Well, the vacuum reading of 22 is high if anything. That smell is usually from unburned hydrocarbons like from an overly lean mixture caused by a high-overlap cam or a stuck EGR (are you using an EGR?), or even from a vacuum leak that's diluting the idle mixture causing incomplete combustion.

The idle screws should cause the engine to die if screwed in all the way. If there's not a vacuum leak (this needs to be ruled out- try removing all the vacuum lines to the carb and intake except the vacuum advance and plug the ports. If it improves, find which vacuum line is leaking), the primary throttle blades could be open too far because the initial timing isn't high enough- but if you've set it up w/the vacuum advance hooked to manifold vacuum, that's not too likely to be the problem because the timing would be at least 22 degrees (12 initial plus 10-12 degrees from the vacuum advance). And even more if the vacuum advance is supplying more than 10-12 degrees- which it almost surely is if it's like most vacuum advance cans that haven't been limited.

If you're using ported vacuum, try manifold instead. You'll need to lower the idle speed by using the curb idle screw- this will close the butterflies and that's what you want to lessen the transition slot exposure.

Another possibility is the secondary throttle blades are adjusted too far open, or they are hanging up for some reason (warped base plate, throttle blades fouling on the gasket or intake casting, etc.).

Might be a good time to CONFIRM TDC. This will allow you to be sure the timing tab and damper are correctly indicating TDC.

MAKE A TIMING TAPE to see what the total timing is, w/o needing to use a dial back timing light. You can also buy a timing tape, get one that matches the diameter of your damper.
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