cam advance/retard & dizzy timing - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-12-2005, 10:27 PM
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cam advance/retard & dizzy timing

ok, with my timing gear set i got all those little bushings to advance or retard the cam timing. why/when would want to advance or retard my cam timing?

next, i know how to put my dist. in so its lined up and all, but how do i determine how many degrees advance to put it at and how do i physically set the advance?

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Old 12-12-2005, 11:07 PM
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timing the camshaft

The offset bushings are to adjust your cam either to advance it or retard it to get it timed to where the cam grinder recommends.
This requires a Degree wheel, the cam spec card, a pointer, and the camshaft and timing set to be installed on the crankshaft.
The first thing you do is to find Top dead center on #1 cylinder on the bumbustion stroke. With the degree wheel on the snout of your crankshaft, adjust your pointer so it points at 0 TDC.
The way Ive always done this is to first establish when the piston is at .050" before BTDC and .050" ATDC, with the pointer on indicating degrees on the degree wheel. I mark both points, the rotate the crankshaft so its exactly in between those two degree marks. then I loosen the degree wheel and set it at 0 with the pointer, and retighten.This will accurately establish your TDC.
Now the next thing you need is a dial indicator, and you set this on # 1 cylinder intake lobe. Turn the engine over util your dial indicator indicates you have reached the maximum point of lift on your cam lobe. I do the same thing with the cam lobe. Find .050" below maximum lift on both sides of the lobe and then split the difference. the reason I do this is that with a lot of cams, they may be at maximum lift for several degrees. Compare this number of degrees with what the cam spec card says should be the lobe center line degrees. If the pointer indicates that you are reaching maximum lobe lift before the degrees recommended on the spec card you need to retard your camshaft the number of degrees to correct it. If you are reaching maximum lift after the recommended lobe degrees, then you need to advance the cam to correct it.
IE. If your spec card says your maximum lift is at 110 degrees before BDC, and you are reaching maximum lift at 114 degrees before BDC, then you need to retard the camshaft 4 degrees.
If you arent reaching maximum lift til 106 degrees BDC, then you need to advance your camshaft 4 degrees.
Your bushings are marked in degrees of offset, normally in 2 degree increments, from 0, 2,4, 6 and so on.
You can also use those offset bushings to fine tune your power curve of the camshaft. Advancing it tends to focus on improving lower and mid range power, while retarding it focus's on the mid and upper end of the power band.
This is a case where a little bit can make some big changes, so you dont want to just throw a bushing in there expecting miracles. you do need the afore mentioned equipment in order to fine tune your camshaft.
A little bit is good but a bunch aint always better.
As for your distributor, what kind of engine are you running? What mods have you done to it?

Last edited by Max Keith; 12-12-2005 at 11:17 PM.
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Old 12-12-2005, 11:30 PM
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sbc 350 +.030, 230/230, .480/.480 cam, heads rebuilt,roller rockers, intake ports gasket matched, minor-moderate porting in heads, performer RPM, 600 dp carb, 2400 stall converter, a/c delete, electric fan, 50k volt gm hei dizzy, nothing real serious.
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Old 12-13-2005, 08:14 AM
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Distributor timing

Sounds like a good setup, very healthy street machine.
Im presuming you are running lower compression in order to make your engine survive on pump gas.
I would set the initial timing at 10-12 degrees and see how it works there. If it pings, back it off a degree or 2. If you have the means to adjust your total advance, I would recommend 40 degrees total @ around 3000 RPM.
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Old 12-13-2005, 04:55 PM
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are you talking about how far to turn the dist houseing?
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Old 12-14-2005, 08:50 AM
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Quote:
Originally Posted by wayneair
are you talking about how far to turn the dist houseing?
He means check the marks with a light and start the advancing at 10-12 TDC.

If you are unfamiliar with timing and it's functions. There's lot's of reading about it in the boards search functions.
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