1968 SBO tuning

[Stupidquestionspro]

Transfer slots are now square it was my fast idle screw adjustment that apparent controlled that


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[Stupidquestionspro]

These are the settings required to get a square transfer slot on the primaries.

can’t back out the curb
Idle screw anymore or it doesn’t touch the throttle shaft sooooo.

fast idle which is essentially all the way out to get to this point.

That’s how far out the fast idle had to be out to get square transfer slots why is it that it takes to the limits of my adjustments to do so?

Also I’ve read the transfer slots on secondaries should only be exposed on big cams or motors where the idle mixture screws don’t really work and even then you close the primary transfer slots


So is this set up correct with square primary slots and closed secondary transfer slots.




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[fleming442]

The linkage is probably a little progressive, so the secondaries don't open exactly in time with the primaries to prevent a lean tip-in.

 

[Stupidquestionspro]

Ok so everything with the transfer slots and idle screws look proper? Even though I can’t back them out any farther?


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[fleming442]

Yep.

 

[Stupidquestionspro]

Perfect. I also found measurements in my search to create my own mechanical advance stop bushing with a nut I had laying around and my grinder so that’s in too hopefully tomorrow I’ll have it running and will be able to make sure how close I got to the spec I wanted.

I also changed the springs to the 2 heavy silver because based on the timing curves in the MSD manual reducing the mechanical advance as low as I did causes it to come in pretty early no matter the springs it looks like with the 2 heavy I can expect it around 2800 rpm.

I am also switching to an adjustable throttle cable bracket because somehow I never noticed my throttle cable couldn’t travel all the way to WOT [emoji53]

Found out i have an open gasket on a dual plane manifold and it seems as though I have a fuel boiling issue so I think when I have the funds I’m going to buy a cheap thin heat isolator that also splits the planes in case that is causing me any issues unfortunately I have almost no space between the air cleaner and hood. Maybe I’ll get lucky




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[olds307 and 403]

Since I have to have such high initial timing would it be worth my while to just lock out the mechanical advance and leave the vacuum advance alone?


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Like I said, leave it around 40 and run the full 16 degrees of vacuum advance. I am around 48 degrees total with my 9 to 1 Olds 350 and may add a couple more on my Mallory breakerless either by bumping the base timing 2 degrees or adding another couple degrees of vacuum advance or both. I had 22 base, 14 mechanical and a 30 degree vacuum can. No pinging but had bucking at low speeds. Switching to a 20 degree can, fixed it. I did notice lazier part throttle.

 

[Stupidquestionspro]

Ok so far I made my own 10 degree advance bushing for mechanical and then today I’ll probably time it for highest vacuum and see where that puts my initial and go from there I’m hoping for a curb idle of around 750 in gear so hopefully with that much initial I can make it work.


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[olds307 and 403]

That is a lot of base timing but may work just as well. I still say 20 to 22 base and 18 mechanical with the full 16 degrees of vacuum advance pulling from manifold vacuum.

 

[olds307 and 403]

My 7.8 to 1 Olds 260 powerhouse is running around 70 degrees part throttle from what I can tell. The timing tab bolt is broke off, just eyeballing and using my dial back light. Limiting top end on it is no problem, has none.