question on total timing

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blk00rt

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I know mopar small blocks like around 32 to 35 degrees of total timing. Is that initial plus mechanical or Initial+ mechanical + vacuum advance.
right now my engine is set at 8 degrees initial, 24 with the mechanical in full, and around 44 with the vacuum advance connected. It sounds like its breaking up at high rpms...do I need to bump my initial up to get more initial + mechanical or should I lower it so that mechanical and vacuum is around 34?
I am thinking the first but just want to confirm.
Thank you in advance.
 
BLK,

You want 34 to 36 total mechanical. The vacuum is not involved except for high vacuum run. Like cruising in high gear. You can check out this thread I did on my experience with timing issues. I had some serious ping that was due to the fact that the cam in my engine likes 20 degrees initial. So I had to recurve my diss to limit the mechanical advance. I will edit this post and give you the link for the diss discussion.

But right now we need more info.

What engine. Is it stock? What induction. What ignition. Stuff like that.


http://www.forabodiesonly.com/mopar/showthread.php?t=198096
 
blk00rt said:
I know mopar small blocks like around 32 to 35 degrees of total timing. Is that initial plus mechanical or Initial+ mechanical + vacuum advance.
right now my engine is set at 8 degrees initial, 24 with the mechanical in full, and around 44 with the vacuum advance connected. It sounds like its breaking up at high rpms...do I need to bump my initial up to get more initial + mechanical or should I lower it so that mechanical and vacuum is around 34?
I am thinking the first but just want to confirm.
Thank you in advance.
Click to expand...

Vacuum enters the picture, but, not in full throttle situations.

I'd put more initial and less mechanical on the engine. Not knowing your set up, I don't even run factory 318's with less than about 14 initial.
 
To explain this another way, it's say, 36* with the engine revved so that the mechanical advance is "all in" and after you "think" it's where you want, blip the engine up so you KNOW it's "all in." This is a direct reading, with vacuum unhooked. No need to add initial.

If you are nervous about that fan, then do this when the engine is just barely warm, and unhook the fan belt. You won't hurt the engine for the 1 minute or so you need to check.

THEN after you idle down again, still with vacuum unhooked, check to see where the initial has "landed." The intitial plus the amount in the distributor (the "curve") should equal the total you just set at high RPM.

After you get this where you want, then you can check vacuum, but again, with a caveat. Make sure you are generating enough vacuum at the port at some RPM to pull the vacuum clear in. Determine how much is "in" the can, and at what vacuum it's supposed to be "in"

And be aware that many spec books, including the Mopar shop manuals, list distributor both vaccum and mechanical specs in DISTRIBUTOR degrees, which much be doubled to "get" crank degrees

That is, 12 distributor degrees means 24 at the crank.
 
spinman1949 said:
BLK,

You want 34 to 36 total mechanical. The vacuum is not involved except for high vacuum run. Like cruising in high gear. You can check out this thread I did on my experience with timing issues. I had some serious ping that was due to the fact that the cam in my engine likes 20 degrees initial. So I had to recurve my diss to limit the mechanical advance. I will edit this post and give you the link for the diss discussion.

But right now we need more info.

What engine. Is it stock? What induction. What ignition. Stuff like that.


http://www.forabodiesonly.com/mopar/showthread.php?t=198096
Click to expand...

the engine is pretty much stock, has an ld48 intake, a 600 cfm holley and a cam a little larger than stock.
thanks for the link
 
Blk,

No problem. Oh and re the fan? LOL I was timing my engine and I set the light on the radiator and it dropped down into the fan. Luckily I have a viscous fan so my light survived. Luckily when it happened I was on the way to shut it down. But if you do take the belt off, keep in mind that the water pump is not running so you don't want to run it long. You could get some serious hot spots in the engine. I decided to just take off the fan. Made it much easier for me to do the other tests I was doing like cranking it around to do leakdown tests.

You might want to get some input from Crackedback re tuning with vacuum guage. He taught me a lot re that.
 
spin,
thanks I set the timing at 16 initial and about 32 total. It runs strong now...I found out that I have bad wheel hop too. oh well it never ends.
 
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