total timing and I mean total.

[62goldenrodvan]

Ok, Can any one tell me how much timing is too much?
The motor is 204" ford six with the fspp aluminum head clifford header 2.25" exhaust dura spark II msd and a custom intake I made with three 44 idf webers 264 csc and all the whammy shit.

My Question is if the timing is 14 int 20 in the dist totaling 34 deg with the vac distconnected how much timing will the motor see?
With the vac connected @ 3000 rpm my dial back light is telling me 54 deg. yeah 54 deg.

So when every one says 32-36 deg is that really total timing or does the vac advance over lap centifical advance when the rpms are low? and the weights are not all the way against the stops?

At this point I have 14 initial 20 in the dist and 20 more with the vacuum advance hooked up. :

Any info,
Thanks,
Kevin.

 

[66 Fastback]

Sounds about right. The 34 deg is your wide open throttle timing figure when manifold vacuum is low because the throttle plates are open. Under that condition, there is little to no vacuum advance.

The 54 deg could possibly be seen on the highway during cruise conditions. Under those conditions, the tthrottle plates may not be open much under llight throttle and there could be a significant vacuum component that will advance the timing beyond the 34 deg seen at WOT. The key is that the engine is not heavily loaded and the the rpm's are relatively high, so it can handle additional vacuum advance.

When you see the 54 deg of advance in the driveway, the engine is not under any load and engine vacuum is relatively high. It really is not a realistic picture of what would be going on when motoring down the highway and you see more load and less vaccum advance.
Doug

 

[62goldenrodvan]

Thanks doug,

So Im not too far off base.
I understand the no load in the drive way,and the loaded road condition,
but the classic inline web site suggest that you check timing both ways,
With vac disconnected for a centrfical reading and connected @ 3500rpm
for a total? reading.

So for my next question does the vacuum canister (on the distributor) adjustment limit the travel as well as the sensitivity of operation? or is that adjustment strickly for when timing is needed. not how much is needed.

Thanks,
Kevin.

 

[66 Fastback]

Typically, it is supposed to just change the vacuum level when the timing is advanced. From what I have read, it may depend on the vac cannister. I think I have heard that the Crane Units may limit the travel too. I had some Accel units that were not very consistent on or repeatable.
Although nothing is being changed on the slot to limit the advance, I can see where the vac cannister can limit the travel in some cases. It seems to me that the spring in the diaphram could limit that amount that the diaphram can travel under the vac levels to be normally encountered.
Doug

 

[62goldenrodvan]

Ok, thats what I was thinking but was not sure,It is ford dura spark unit with the ford vacuum can from a 78 granada.

Now if I have my 34'deg and the only real way to tune the vacuum advance is by driving it and noting the load conditions, If it pings back out the adjustment until it doesnt ping?
I think the classic site said two turns at a time to get some results.

Kevin.

 

[CZLN6]

Howdy Kevin and Doug:

I just wanted to add a couple of FYIs to Dougs thorough explanations.

The 32 - 36 total is a generality. Given your combo you will have to experiment to find what is ideal for you. Again, given your cam and the Alloy head, you will likely find that you can safely use more. To what effect- ????

Also, driving with a manifold vacuum guage hooked up and plumbed so you can watch the vacuum level fluctuate as you drive will be a good insight to what your engine is really doing.

Finally, ignition timing and A/F ratios are very closely related. Getting your carb combo tuned close to ideal will need to be done before you can feel safe with max ignition advance. Once you're close, you will likely find that you will reach max power with somewhat less than max advance. Less advance will also generate less heat.

Adios, David

 

[62goldenrodvan]

Thanks David,

I know an a/f gauge would be nice so I could be spot on.
but what I do have is pyrometer in each primary tube 2" away from the header flange and reading ranges from 800-900 at an idle to 1200-1350 at freeway speeds light load to moderate load respectively.

Kevin.

 

[Hot 6t Falcon]

Howdy from the other brother,

Just an FYA, so you can visualize this better. Remember that the camshaft runs at 1/2 the speed of the engine crank - that's what the cam gears and timing chain do.

That why the 20 degrees in the distributor is showing up as 40 degrees on the crankshaft.

You are doing it right.