[1957willyman]

how can i prevent my initial timing and centrifugal timing coming in at sametime my engine idles about 1200 rpms has about 23 degrees timing msd distributor with whatever springs and weights came in it

[cobalt327]

Originally Posted by 1957willyman

how can i prevent my initial timing and centrifugal timing coming in at sametime my engine idles about 1200 rpms has about 23 degrees timing msd distributor with whatever springs and weights came in it

If you're saying that the mechanical comes in at idle speed, you need stiffer springs. Typically you want the mechanical all in by around 3000 rpm (this is just a rough rule of thumb- every engine combo is different).

Why is the idle so high? You usually can idle lower than that, even w/a stout cam.

Besides the mechanical coming in at idle speed (if that's the case), I'm wondering if this might be a case of not enough initial timing and the carb is trying to idle on the transfer circuit...

More on timing here. The page was originally on the GM HEI but the timing info still applies. The main difference between the GM HEI and the MSD distributor is the MSD distributor uses bushings to limit the mechanical advance. In some cases, the 18 degree bushing is not enough. If you need more initial and less mechanical timing- like is often the case w/big cammed engines- you need aftermarket bushings.

[vinniekq2]

why is your engine idling so high?

[MouseFink]

This is a old problem with engines that have been equipped with radical camshafts. Those type camshafts have long valve duration, high valve overlap, the engine has low manifold vacuum and sometimes will not idle below 900 RPM. The mechanical advance mechanism starts advancing the timing at 900 and is fully advanced by 1100 RPM. The timing advance on engines equipped with radical camshafts should be checked after the mechanical (centrifugal) advance mechanism is fully engaged , meaning at 2000 RPM .

Engines equipped with radical camshafts do not need or use a vacuum advance and require the mechanical timing advance checked at 2000 RPM or more with the total timing advance from 35 - 40 degrees. The RATE of the timing advance can be tailored by changing the advance springs and weights or you can install an electronic ignition system that is designed for engines with radical camshafts.

[Greg T]

Originally Posted by 1957willyman

how can i prevent my initial timing and centrifugal timing coming in at sametime my engine idles about 1200 rpms has about 23 degrees timing msd distributor with whatever springs and weights came in it

I think a lot more info is needed. Complete parts list of the engine would be nice.

[1957willyman]

gregt i have a 454 - 10-1 compression 527 lift cam 292 312 duration 320 cc heads quickfuel 750 carb msd street fire off the shelf disributor 93 octane gas will not idle the same everytime i crank it cold or hot got about 23 degrees initial timing 40 overall

[vinniekq2]

hope thats not a hydraulic flat tappet cam?

[1957willyman]

yes it is a comp hydraulic flat tappet cam i dont think its the cam something in the distributor

[1957willyman]

give me some ideas or things to look for as far as having a flat cam some times it will fire up and idlejust fine sometimes it want i think its something to do with timing but iam kinda new at this stuff so iam learning by listening to you guys and whoever how can i check for a flat cam

[MouseFink]

The 23 degrees you are seeing is not initial timing. The way you have it now is the initial timing advance is 14 degrees (7 degrees on the crank x 2) with an additional 9 degrees of centrifugal advance by 1200 RPM and an additional 17 degrees of centrifugal advance by 2000 RPM for a total timing advance of 40 degrees.

It seems to me the centrifugal timing advance needs to be limited 5 degrees with bushings under the weight plate (or however MSD does it) and the initial advance raised from 7 degrees to 12 degrees on the crank. About the only way you can set the initial advance if the engine will not idle below 1200 RPM is by increasing the initial advance until the engine is difficult to start and then back it down.. Initial timing 12 degrees "on the crank" (12 x 2 ) = 24 degrees initial advance + 12 degrees centrifugal advance = 36 degrees total advance. After the initial advance is increased to 12 degrees on the crank, you must readjust the engine idle to 1200 RPM.

You cannot observe the initial timing advance with a timing light when the engine is idling at 1200 RPM.

[1957willyman]

if i need to change springs in distributor do i need to go a stronger spring? do i need to change bushing and weights to? or do i need to limit travel of weights

[cobalt327]

Originally Posted by 1957willyman

if i need to change springs in distributor do i need to go a stronger spring? do i need to change bushing and weights to? or do i need to limit travel of weights

Your question was answered at post #2, is there something you do not understand in the linked-to info?

[cdminter59]

Why do you have the idle set to 1200 rpms? I have a Crower mechanical roller cam 641/636 lift and 256/266 duration at .050. I have Edelbrock Performer RPM heads #60559 with 315cc intake runners. My carburetor is a Holley 850 DP. My distributor is a MSD Pro-Billet 85561. I have my idle set at 900 rpms. My initial is 12* btdc and the total is 37*. Looking at that Streetfire distributor and the MSD 8428 advance kit they recommend there is really no easy way to set up the mechanical advance. Even when using a medium spring the advance curve will start with 8* @ 1000 rpms. The advance curve will be at 20* @ 3500 rpms and you will have to use a stop at this point. Even then you are looking at 16* initial 20* mechanical advance. You will have to use the vacuum advance stop provided with the distributor also set at 11*-14*. Try backing off the curb idle screw on your carburetor to see what the lowest rpm is. I don't want to piss you off but IMO that distributor is junk. It is to be used with a completely bone stock engine. A GM HEI is easier to setup for a performance camshaft.

[cobalt327]

Originally Posted by 1957willyman

if i need to change springs in distributor do i need to go a stronger spring? do i need to change bushing and weights to? or do i need to limit travel of weights

The bushings are the things that control how much mechanical advance there is. The stock bushings only go to 18 degrees- if you need less mechanical advance- which you will- you need to either make or buy bushings that will limit the mechanical advance more, or use some other method to control how much mechanical advance the distributor supplies.

The stiffer spring will keep the advance from starting so early, but you still need to get control of your idle before getting into the mechanical advance.

You can use a vacuum advance, no problem. Connect it to a ported vacuum source and limit the amount of vacuum advance to about 10 degrees.

[1957willyman]

what if itake the weights and springs out try to lock the assembly from working atall