Timing / advance
OK guys I thought this topic deserved its own thread. I am having some trouble and If you look at my other thread "motor hard to keep running in gear" you will see what all I'm talking about.
Basically I've been told that for for my cam 300 adv. 246/246 @050" .515/.515 lift i need to lock out my mechanical advance and set the base timing to 36*. But I have also been told that i need to set it to 20*+ vac advance.
Is this 2 different methods or just 2 different ways of explaining it. If I set my base timing to 36* and still ran 15* vacuum advance, wouldn't that give me 51* total?? I have used the search feature and googled this topic but I am yet to find something that completely explains It. I need your help......
I was also told another methed is to limit my centrifugal adv. to 8* and add 28 to eliminate hot starting trouble.
My questions are, How do i lock out the weights in for the mechanical adv.?
Would 21*base + 15deg vac adv. give me the 36 i need?
How do you limit the mechanical adv. to 8* or limit it any for that matter??
Here are some copy's from the other thread so you can get any Idea of what I've been instructed to do.
"That cam needs a lot lot lot of timing at idle to idle properly.
The short method is to simply lock out the mechanical advance and reset the timing at 36° BTDC at idle.
You can find 36° on the balancer by wrapping an length of masking tape around the balancer. mark where the two ends of tape meet.
Remove the tape and lay it out flat say on a counter top. measure the length of your two marks you make on the tape while it weas on the balancer.
1/10th of that length is 36°. Mark the tape at 1/10th the length of the circumference and reinstall the tape around the balancer referencing the circumfrence marks at TDC. Mark off the 36° point on the balancer using the 1/10th length you made on the tape.
Now you can set the timing at 36deg BTDC.
Once you have done this readjust the carb idle mix screws.
It will never idle right with the stock stall converter.
With you young family you'd be much better off with a mild hyd cam and stock converter and gears as all you'll achieve is burning a lot of gas for nothing.
Summit #K1102 is just right for your situation. A lot lot easier to change the cam and lifters than change the gears and converter."
"No it is not too much. It is exactly what the motor requires to idle correctly with that cam. The exhaust delution caused by the increased cam overlap slows the combustion speed down so much at idle and low rpm that you need much more timing at idle to compensate. Lock out the mechanical advance and set the timing at 36deg BTDC. It will not move with rpm.
Vacuum advance is a separate thing and is in addition to the fixed 36deg mechanical advance. (10 to 15deg additional cruise vacuum advance)
Mechanical 36deg fixed..... Vacuum 10 to 15deg at part throttle hiway cruise.
Use ported or full timme vacuum source, which ever works best for your.
I use ported.
If the car is hard to start when hot with fixed 36deg timing, install a ignition power interupt switch on the HEI distributor power wire to disable the spark during initial hot cranking. it will fire easily.
This is the correct way to set up the engine with this camshaft for an automatic trans car. You still need the converter.
You'll need a 3.5 or 4.5 power valve and will need to reset the carb throttle blade opening at idle to expose just .030" of idle transfer slot on both the pri and sec throttles. Remove the carb and flip it over and have a look."
"Sorry about that. Yes the 3000+ stall will fix the idle issue. You should be able to idle at 1000 rpms in park and in gear. I doubt you will feel the car go into gear from park.
And yes, you need a bunch of timing (at least 20 degrees at idle) and a lower power valve number. (like 4.5). Total mechanical timing should be around 38 or 40 degrees with old iron heads.
Vacuum advance may not even work with that cam. You need to check the vacuum while driving down the road. It would help mpg if the vacuum advance would work.
I would use the RPM intake. Much better low rpm torque.
Don't expect too much power with that 3.08 gear. And be careful not to over heat the trans with that loose convertor on the street (try to run it above the stall).
"If you are going to put the stall converter in this weekend I would wait to do any setup additions until after the converter goes in it will make all the difference in the world. Even if you don't put the gears in till later. After the converter goes in then work on the idle. Your chasing you tail otherwise. As far as the timing tape idea you could also consider buying a inexpensive timing light with advance dial on the back. Just keep in mind that if you fix your mech advance and set it at 36 deg it may be hard to start when its hot. sometimes you have to limit your mech advance say to 8 deg then set the base at 28 deg which will help with hot starts. But I agree with the previous post that you need more."
I was gonna do what fbird said but If there is a way for my to attain the same adv. with out having hard hot start issues I'm all for it. Now these other guys gave me some Ideas and I don't know whats the best way to go. I guess I could try them all and see which is to my liking, but I need to figure out how. PLEASE HHHEEEELLLLPPPP!!!!!!!
I have locked out timing on my race engine and have no hard start issues at all even with high compression I use a stock starter with no problems. MSD distributors have a provision to be locked out. If your dist doesn't I would think you could take the weights/springs off and tack weld or brase the advance in place.
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