Heat Issues - New to me 70 Chevelle - Page 17 - Chevelle Tech
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post #241 of 409 (permalink) Old Jul 18th, 17, 9:19 PM
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Steve
 
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Re: Heat Issues - New to me 70 Chevelle

Quote:
Originally Posted by ghoticov View Post
Wow, thats a lot to take in. lol The thing I am trying to get my head around is how if you are at 16 initial and them = 14 vacuum advance, how does it only go up to 37 when the engine revs up?
Because when you open the throttle wide open, the vacuum goes to 0, so the vacuum advance goes away, and then the mechanical advance kicks in.

Quote:
And then if you are at part throttle why does it go up to 51? Which is 21 over your 30 (16+14). Where is that 21 coming from?
The 21 comes from your mechanical advance since the engine RPMs are still higher than 3K. When you let off the throttle, the vacuum goes back up and kicks the vacuum advance back on. As the rpms come down, the mechanical advance will slowly go away.

Remember, the mechanical advance comes from centrifugal forces. As the engine spins faster, the weights on the distributor spread out and increase the advance until it hits the limit - 21 in my case by the time you hit 3K rpms. Once I get down to 750 rpms or so my mechanical advance goes to 0.

Quote:
I know I will get this but I am having a hard time wrapping my head around it.

And for me, right now... my only real choice is to advance my timing from 10 (where it is now) and try maybe 14 or 16 and see where my timing is once it revs to 3000...right? Since I have no vacuum advance. I would think the more advanced I can get it without pinging, the better?
Yes, within reason. You don't want to get your initial plus mechanical much above 36 degrees (in my experience.)

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post #242 of 409 (permalink) Old Jul 18th, 17, 9:20 PM
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Re: Heat Issues - New to me 70 Chevelle

Why not work on your initial problem instead of your initial timing. Your timing is probably close enough that it is not effecting your temp. Fix the cooling problem first and drive the car for a while and make some changes as you go. Get your air cleaner to fit right and the bad hoses changed once you get the thing to cool properly. Get out there and drive it.
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post #243 of 409 (permalink) Old Jul 18th, 17, 9:31 PM
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Re: Heat Issues - New to me 70 Chevelle

If you checking the timing check the dizzy gear also. My car has been running hot and it always stayed at 180 like clockwork. Found the gear torn up causing way retarded timing. I got two temp gauges also and noticed the head temp was always 20deg hotter than the intake temp. Runs a hell of a lot better now with the timing on.

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post #244 of 409 (permalink) Old Jul 18th, 17, 10:39 PM
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Re: Heat Issues - New to me 70 Chevelle

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Originally Posted by zombie1969 View Post
If you checking the timing check the dizzy gear also. My car has been running hot and it always stayed at 180 like clockwork. Found the gear torn up causing way retarded timing. I got two temp gauges also and noticed the head temp was always 20deg hotter than the intake temp. Runs a hell of a lot better now with the timing on.

dizzy gear
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post #245 of 409 (permalink) Old Jul 18th, 17, 11:15 PM
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Re: Heat Issues - New to me 70 Chevelle

"...dizzy gear..." Yeah, I remember when I first joined this site, I made the "mistake" of saying "the dizzy" instead of "distributor" and was immediately admonished by someone here for such a heinous digression! Oh my!

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post #246 of 409 (permalink) Old Jul 18th, 17, 11:45 PM Thread Starter
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Re: Heat Issues - New to me 70 Chevelle

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Originally Posted by lucifershammer View Post
Because when you open the throttle wide open, the vacuum goes to 0, so the vacuum advance goes away, and then the mechanical advance kicks in.

The 21 comes from your mechanical advance since the engine RPMs are still higher than 3K. When you let off the throttle, the vacuum goes back up and kicks the vacuum advance back on. As the rpms come down, the mechanical advance will slowly go away.

Remember, the mechanical advance comes from centrifugal forces. As the engine spins faster, the weights on the distributor spread out and increase the advance until it hits the limit - 21 in my case by the time you hit 3K rpms. Once I get down to 750 rpms or so my mechanical advance goes to 0.

Yes, within reason. You don't want to get your initial plus mechanical much above 36 degrees (in my experience.)
Ahhhhh, ok. I am starting to understand more. I think I was getting confused by the manifold vacuum timing advance and the mechanical timing advance. I thought they were the same thing but now I understand its not so it makes more sense.

Since my initial timing is currently at 10 and my mechanical+intital goes up to 32 at 3000rpms, is it safe to say that my mechanical timing is 22?
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post #247 of 409 (permalink) Old Jul 18th, 17, 11:51 PM Thread Starter
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Re: Heat Issues - New to me 70 Chevelle

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Originally Posted by Bonkerman View Post
Why not work on your initial problem instead of your initial timing. Your timing is probably close enough that it is not effecting your temp. Fix the cooling problem first and drive the car for a while and make some changes as you go. Get your air cleaner to fit right and the bad hoses changed once you get the thing to cool properly. Get out there and drive it.
Well, that's basically what I am going to do since I have no choice right now since I don't have a vacuum advance on my distributor.

I am going to install the new t-stat, finish sealing the shroud as much as possible, fill with distilled water (to get more distilled water in the system versus rad fluid), then check the timing and raise it if I can without it pinging and then drive it and see how it goes.

Like others have said, raising the timing at idle via the vacuum advance directly relates to cooling because of it being lean so if I can raise it as much as possible, without going over 36 overall (right now I am at 32 overall) I would think it would only help at this point.
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post #248 of 409 (permalink) Old Jul 18th, 17, 11:52 PM Thread Starter
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Re: Heat Issues - New to me 70 Chevelle

Quote:
Originally Posted by zombie1969 View Post
If you checking the timing check the dizzy gear also. My car has been running hot and it always stayed at 180 like clockwork. Found the gear torn up causing way retarded timing. I got two temp gauges also and noticed the head temp was always 20deg hotter than the intake temp. Runs a hell of a lot better now with the timing on.
Quote:
Originally Posted by Dean View Post
dizzy gear
Quote:
Originally Posted by Brownd3max View Post
"...dizzy gear..." Yeah, I remember when I first joined this site, I made the "mistake" of saying "the dizzy" instead of "distributor" and was immediately admonished by someone here for such a heinous digression! Oh my!
WTH is a dizzy gear? lol

I WISH mine would stay at 180 !!
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post #249 of 409 (permalink) Old Jul 18th, 17, 11:57 PM
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Re: Heat Issues - New to me 70 Chevelle

Go to the "Performance" section of Team Chevelle.
At the top of the forum when you open it will be: Sticky: Ignition 101
All your timing questions will be answered! It is a great article.
Keep working at it. You have the right attitude, and there are lots of people here to help.
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post #250 of 409 (permalink) Old Jul 19th, 17, 7:12 AM
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Re: Heat Issues - New to me 70 Chevelle

Yup

Quote:
Originally Posted by ghoticov View Post
Since my initial timing is currently at 10 and my mechanical+intital goes up to 32 at 3000rpms, is it safe to say that my mechanical timing is 22?
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post #251 of 409 (permalink) Old Jul 19th, 17, 11:10 AM
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Re: Heat Issues - New to me 70 Chevelle

ghoticov,

Steve pretty much covered everything about timing I would have replied with. Great answer!

Now, back to the cooling system related stuff, did you get your t-stat drilled & installed? How about the clutch fan assy?
.

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post #252 of 409 (permalink) Old Jul 19th, 17, 11:20 AM Thread Starter
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Re: Heat Issues - New to me 70 Chevelle

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Originally Posted by Kirby10 View Post
ghoticov,

Steve pretty much covered everything about timing I would have replied with. Great answer!

Now, back to the cooling system related stuff, did you get your t-stat drilled & installed? How about the clutch fan assy?
.
Yes, Steve did a great job at explaining it all! I am also currently reading over the Ignition 101 thread in the Performance Section. I started to read it weeks ago but I didn't understand enough of the basics to understand most of the post. It is all starting to make sense now and now knowing that I don't even have a vacuum canister installed, it makes sense why the timing was the same whether we plugged or unplugged the line (in which the line wasn't going to a vacuum canister). And also goes back to trusting guys at Car Shows. lol How in the world did they not know whether my distributor had or didn't have a vacuum canister is beyond me. They seem to know so much about timing and so forth.... to miss that fact baffles me. But I digress...

I am going to install the new AZ 15356 t-stat this afternoon. I was waiting to get the 2202 Flexpro Water Outlet Gasket from Amazon. I have a standard gasket but read many places that the 2202 gasket really helps prevent leaks.

I have the 772 fan and 2747 fan clutch installed... as well as the new 71 shroud. The fan seems to sit a little high in the shroud and its pretty much all the way in the shroud (versus 1/2 in and 1/2 out like some suggested). There is about 1/2 clearance on the top of the shroud about about 1-1/2" on the bottom. I am not sure how to change that since it sits in clips on the bottom and if I try to raise the shroud, it will come unclipped and no hold at the bottom. So I decided to run it like it is (1/2" clearance on top and 1-1/2" on bottom) because it seems like its moving a lot of air and it is drawing it through the radiator (tested using a piece of paper all over the rad).
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post #253 of 409 (permalink) Old Jul 19th, 17, 1:48 PM
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Re: Heat Issues - New to me 70 Chevelle

Quote:
Originally Posted by ghoticov View Post

I have the 772 fan and 2747 fan clutch installed... as well as the new 71 shroud. The fan seems to sit a little high in the shroud and its pretty much all the way in the shroud (versus 1/2 in and 1/2 out like some suggested). There is about 1/2 clearance on the top of the shroud about about 1-1/2" on the bottom. I am not sure how to change that since it sits in clips on the bottom and if I try to raise the shroud, it will come unclipped and no hold at the bottom. So I decided to run it like it is (1/2" clearance on top and 1-1/2" on bottom) because it seems like its moving a lot of air and it is drawing it through the radiator (tested using a piece of paper all over the rad).
Your fan not being center (top to bottom) in the shroud is due to 1 of 2 things or both.. Engine is sitting too high, core support is sitting too low. If your fenders and doors line up correctly and no one has shimmed the fenders up off of the core support then I would say it is most likely worn core support bushings. As long as the fan doesn't hit the shroud, I wouldn't be overly concerned about that right now. Might be something you want to look into later though. Fixing it could be as simple as removing the 2 large bolts that attach the core support to the frame, raise the core support enough to center the fan blade, add large washers between the frame and the rubber mount, reinstall the bolts. NOTE, don't let the nuts and washers fall down inside the frame rail. They can be a bear to fish back out with the bumper installed.
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post #254 of 409 (permalink) Old Jul 19th, 17, 2:05 PM
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Re: Heat Issues - New to me 70 Chevelle

I had a old Race friend change my Timing for my 468
he changed Bushing in Dist. / took out Blue & put in Bigger Black one / New Spark Plugs
Moved the Distributor some and changed the Timing
from 11* Initial & 35 Total with Vac 6 in Drive & 8 in Park
to 15* Initial & 34 Total with Vac 8 in Drive 10 in Park

Car is much more responsive

Still waiting for a Track day to do some Testing

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60' = 1.664
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1/4 = 11.814 et / 115 mph
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60' = 1.547
1/8 = 7.311 et / 91.76 mph
1/4 = 11.595 et / 114.28 mph


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post #255 of 409 (permalink) Old Jul 19th, 17, 2:14 PM
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Re: Heat Issues - New to me 70 Chevelle

I run my 462 with about 20-22 initial, that where it likes it and runs cool/starts easily. On my 289 1/8 mile drag car i used to run it locked out at 42.
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