That's it, pg, up the hill, Gramps was in the gas, and the vacuum dropped away. Vacuum wiper systems were around until '58. ('58 is the year when most of the cars and even trucks went from two to four head lights also) Rambler/AMC until '72. The later vacuum systems had tanks for reserve and vacuum pumps so the speed of the wipers was steady and not stopping at the worst time, when in the gas.

 

Hi there,

PG. the green line is the best mech advance I can have when I'll get the new springs set ( at least a couple of weeks ) but now I have to work with what I have ( the grey slowest curve, as 73Shark says). So i think I'll make a temporary tuning with my standard distributor setting ( I hope my mech will be available in these days)

the max advance values for the GM V8 ( 52-54° at cruise mode) 36-38° at WOT are intended with how many octanes gasoline? here the gas is at 94 oct , with 98 oct available only in very few places .how many octanes in the US? because if my gas has less octanes than GM stated , I need to retard the advance

From what I have understood , the vacuum advance worksproperly when the engine is at steady operation and mid-throttle,so what happens when I push hard on gas pedal reaching max rpm quickly? I suppose the vacuum advance is less effective...

engine pinging. What I hear when this happens? Ifear a bit this. I don't want to destroy my engine. I want to keep acertain safety margin ( 2-4° retard in respect to max values) because an engine is not a perfect stable machine and the advance needed will vary under many circustances : from the MSD tech lit , RETARD theadvance if
-lowfuel octane
-lean air-fuel mix
-hot temp
-heavy load

 

Hi Again, my engine is low compression and low power but in an effort to get the most power I use 93 oct gas.
The Vacuum: my car produces 17in HG at idle at the rubber line that connects to the vacuum can.
The reading here varies, high at idle, low or none at WAT and high at steady part throttle.
Myvacuum can gives no advance below 6in HG and a maximum of 16* advance at 14in HG.
Here's my tune up results from 01-15-08.
Initial timimg 8*
with vacuum can connected 24* ( adds 16* )
Centrifugal at 3,000 adds 24*
48* total
So if I were driving down the road at a steady 3,000 rpm the max I will get is 48* of advance.

You can use more initial timing and limit the centrifugal advance by changing the limit bushing, you will have to test the alternative ways by trial and error, but start with the conventional guide lines and go from there.

My car is never pushed above 4,000 rpm ( I'm a wimp ) but you showed 6,000 rpm, you might consider shifting a little sooner.

Enjoy your day and your Vette, PG.

 

Aldo,
Evidently, if the rating for octane is figured the same as it is here in the USA, you guys have a significantly higher octane fuel than we do. Sounds great!!! We have only 93 octane fuel here anymore. The days of "Sunoco 260" are gone.
As for any pinging that you're getting, what octane fuel are you using? I may have missed it if you've already told us the answer to my question. I'm thinking that your mechanic took care of the timing and fuelmixture, no? From your postings, I see no indication that your 'Vette is overheating.
In all honesty, Aldo, it's too bad that you're not here in the states, and in Texas for that matter, LOL as I'd enjoyworking on the 'Vettes w/ you. Like I had said in another post, my brother and I, when we visit each other, anywork, from minor maint. to major engine work, we save for our visits as we really enjoy working on our rides w/ one another. Weboth are into vehicles, cars, trucks, bikes, etc.and it's cool turning wrenches w/ someone who's well versed in the field, and not bragging, but I'm not too bad on rides and neither is my brother. This reason is what's so cool for site members to get together. Ofcourse the time wouldn't be there to do any significant work, but atleast to discuss theories and brainstorm topics would be, like the forum here, but "in person." It's great w/ some people who are into it and knowledgable. I really hope that the relay happens. I'm sure it will to some extent, I'm down to "kill the weekend" if need be. Anyway...Sorry for getting side-tracked.
And Aldo,the "octane fuel" you use is???

 

Hi there.

Texas Jim.
I have checked right now. the gas here is at 93 octanes. So same as in the US.
But 2 brands makes gas at 98 and 100 octanes . these gas are expensive and not everywhere. One day I'll try them ( even if I should reduce the advance or at least have a certain safety margin in the standard advance setting)
My engine is not pinging now , because I think that my advance has been kept "quiet". But since I'm going to increase the advance , I have to be careful and immediately realize when my engine is pinging. But I'll have my mechanic on my side and he will understand immediately...
Thanks texas Jim for all the appreciations you made about me.
Ah..overheating.I have still my temp gauge working bad( it measures less than reality) but made a measure atmech with a temperaturegun after 1 hour ride and temp was 180°F. I have discovered anyway that my auxiliary fan on the radiator is permanentlyON because its switch is gone and the former owner of my car connected the fanON always ( California). Probably this the reason for non overheating. I have disconnected now the auxiliary fan because it's quite cold in these days. I'll check soon what happens with the auxiliary fan OFFin hotter days.

PG
thanks so much for all the details about your engine. I will use them as reference. I see that you have a certain safety marginin your advance ( 6°-8° below max value).
your cruise mode advance is 48° ( max 52-54°) , your WOT is 32° ( max 36-38°)
that's my same idea too. I'll keep my advance about 4-6° below max

Unfortunately still no time to go tomech and make a first tuning with my heavy spring distributor. But I think that I'll make the final setting only when I get the lighter springs.
It seems that my MSD street fire distributor has no bushing to stop the max advance. Just the spring replacement...

personally I go over 4000 rpm when pushing hard. Even if my peak of power and torque is at 4000 rpm ( I think... I feel an all of sudden power peak at 4000 rpm ) , I shift at 4500-5000-also a bit more...( I think my tachometer is faithful , replaced the printed circuit 2 weeks ago)

 

Aldo:A way to check for pinging is to be in 4th gear or Drive at about 30-35 mph and give it a moderate amount of gas (not enough to downshift if an automatic) and listen for a rattling/pinging sound. If you detect any, then you can retard the timinga little. If not, then you're OK. Small blocks will tolerate a fair amount on initial advance.