[Greg Reid]

This is a freshly built '68 YS 400 with original 16 heads. I won't go into the build details unless someone wants to know that...I'll just say that it's slightly warmed up.
I wanted to drive it for a while without the vac can in the mix. I've found that it runs to my liking when I set the initial timing at 14 degrees BTDC . Checked the mechanical advance at 3K and it's about 31~33 degrees.
Good, right?

I've been driving it that way for a couple of weeks...So, now that I know the car is pretty reliable and runs well, I decide to hook up the vacuum advance today and do some fine tuning. I have an adjustable can by the way... So I adjust it at idle so that it adds about 10 degrees or so of advance.
I rev the car up to 3000 and the advance is like 42 degrees BTDC. The 10 degrees of vacuum is being added into my initial-plus-mechanical equation.
Bad, right?

I thought it was the new ebay distributor with the adjustable can but when I put a vac gauge on the port I'm using...full manifold port....I see that when I rev the car, the vacuum is remaining at 13 or 14 in. right up to 3 or 4K rpm.
That doesn't sound right to me.....or is it that I just need to limit the mechanical ability of the distributor to advance any further than 30~35 degrees?

[72LuxuryLeMansLa.]

Originally Posted by Greg Reid

This is a freshly built '68 YS 400 with original 16 heads. I won't go into the build details unless someone wants to know that...I'll just say that it's slightly warmed up.
I wanted to drive it for a while without the vac can in the mix. I've found that it runs to my liking when I set the initial timing at 14 degrees BTDC . Checked the mechanical advance at 3K and it's about 31~33 degrees.
Good, right?

I've been driving it that way for a couple of weeks...So, now that I know the car is pretty reliable and runs well, I decide to hook up the vacuum advance today and do some fine tuning. I have an adjustable can by the way... So I adjust it at idle so that it adds about 10 degrees or so of advance.
I rev the car up to 3000 and the advance is like 42 degrees BTDC. The 10 degrees of vacuum is being added into my initial-plus-mechanical equation.
Bad, right?

I thought it was the new ebay distributor with the adjustable can but when I put a vac gauge on the port I'm using...full manifold port....I see that when I rev the car, the vacuum is remaining at 13 or 14 in. right up to 3 or 4K rpm.
That doesn't sound right to me.....or is it that I just need to limit the mechanical ability of the distributor to advance any further than 30~35 degrees?

42 degrees at cruise/light throttle is only bad if you hear it pinging or you are having temp issues. Do you have Jim Hand's book? Go back through his timing section, it should clear that up for you.

Karl

[Sun Tuned]

Greg,
Remember that its sitting there in the driveway unloaded.

The vac should say be at 12 inches (decent size cam we'll suppose) idling, then when you goose it the vac needle should quickly go down towards 3 in. and then it will rise quickly back up above 18 or so at rpm as its not loaded or under a load. Say you keep it at 3500 rpm the vac reading will be high up around 20 inches or higher depending on the free breathing capability of the rest of the combo.

That answer you question??? The numbers you list seem to jive together like they are supposed to.

Put some grease in that ebay dist while your at it.

[Greg Reid]

Karl, I do have Hand's book. I will go back over that part of it.... I'll watch the temp and listen for detonation next time I take it out. I didn't drive it with the vac hooked up yet as I wanted to check here first.
Sun Tuned, your post reassures me that I'm probably OK. It's just as you described it...drops and comes back up.
The advance seems to be 'all in' (at 42 degrees) by 3200rpm or so....If I'm understanding that term right...that is, even if I go up to 4000 rpm, it's still at 42.
That sound OK?
I guess that's why you normally only look at the 'all-in' with the vac disconnected, huh? If you hook it up and start looking at things, it'll scare you.

BTW, the car is pulling 14~15 inches at idle. RA manifolds, 2.5" X-over exhaust, Crower 60342 cam.. (221/229 duration @.050 and .456/458 of lift). TH-400...unsure of rear but it's a highway gear...around 2.90 to 3.08, haven't verified for sure. Unknown torque converter...seems pretty 'tight'. Without the vac advance, the car pulls very hard up to 4K or so. Not pushing it too hard yet.

PS- I did grease the distributor up way back when I bought it. I've read quite a few or your posts. In fact, I have a GM unit I'm thinking of sending you. Some of the stuff I've read about the ebay units make me a little nervous.

[72LuxuryLeMansLa.]

Originally Posted by Greg Reid

Karl, I do have Hand's book. I will go back over that part of it.... I'll watch the temp and listen for detonation next time I take it out. I didn't drive it with the vac hooked up yet as I wanted to check here first.
Sun Tuned, your post reassures me that I'm probably OK. It's just as you described it...drops and comes back up.
The advance seems to be 'all in' (at 42 degrees) by 3200rpm or so....If I'm understanding that term right...that is, even if I go up to 4000 rpm, it's still at 42.
That sound OK?
I guess that's why you normally only look at the 'all-in' with the vac disconnected, huh? If you hook it up and start looking at things, it'll scare you.

BTW, the car is pulling 14~15 inches at idle. RA manifolds, 2.5" X-over exhaust, Crower 60342 cam.. (221/229 duration @.050 and .456/458 of lift). TH-400...unsure of rear but it's a highway gear...around 2.90 to 3.08, haven't verified for sure. Unknown torque converter...seems pretty 'tight'. Without the vac advance, the car pulls very hard up to 4K or so. Not pushing it too hard yet.

PS- I did grease the distributor up way back when I bought it. I've read quite a few or your posts. In fact, I have a GM unit I'm thinking of sending you. Some of the stuff I've read about the ebay units make me a little nervous.

Greg,

You got it. All in means that the weights and springs can't/don't move any further once a given rpm is reached. The reason I suggested you read Jim's book again is he is much more concise than I am when he explains the timing deal.

Karl

[Greg Reid]

Thank you Karl. I'm going to re-read it tonight.
By the way, made a typo in my earlier post. Cam is a Crower 60242

[pugslyx234]

Greg you gonna post some sounds of that new engine?

[Greg Reid]

Not much of a camera...I don't know what it sounds like on your computer but it sounds like crap on mine.
Anyway, here's a clip from back when I was putting the car together....Just click on it.

[PontGuy]

Glad to hear you are finally riding Greg (another Georgia car on the road!) Now you get to play the optimizing/tuning game!

Within 2 years of my initial start-up I upgraded to a Cliff carb, got Sun-tuned to recurve my distributor, upgraded the valve springs, installed a Continental converter, upgraded to a good posi rear, added a RobbMC starter, on and on... the car ran strong to start with, but now it's a whole lot stronger.

It sounds like your timing curve is reasonable for a starting point and as others have already stated the vacuum advance only adds to timing when unloaded, so don't worry much about the numbers you see with it hooked up.

So what's next- engine optimization or finish up with the paint?

Walt

[Old Goat 67]

Originally Posted by Greg Reid

Not much of a camera...I don't know what it sounds like on your computer but it sounds like crap on mine.
Anyway, here's a clip from back when I was putting the car together....Just click on it.

Sounds stout Greg!

[Greg Reid]

Thanks guys. My next priority has got to be paint. I'm having so much fun driving it, if I don't get it painted soon, it'll never happen.