383 Overheating when at idle. - Team Camaro Tech
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post #1 of 27 (permalink) Old Jun 12th, 11, 08:38 AM Thread Starter
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383 Overheating when at idle.

I have a 383 motor in a 74 Camaro. Its got a stock radiator, stock water pump, 16 inch flex-a-lite pulling fan and a stock fan shroud. I am not running a thermostat right now. When I am driving at 25-30 + mph the car stays about 180-190 but when I stop in traffic it slowly starts to rise and then will hold steady when moving again but will not lower. Then everytime I stop it rises more. Timing is at 6* BTDC and I have a Moroso advance kit in the Dist. The trans cooler is in the side of radiator also. I bought this car with the motor in it so I am not sure on all the internal options it has. I am getting very frustrated with tryin to get this problem fixed any help would be great.
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post #2 of 27 (permalink) Old Jun 12th, 11, 08:57 AM
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Re: 383 Overheating when at idle.

First thing would be tunning and if all is good... Then that flex fan needs to go, plus you need a 180* T-stat... Try a thermal or non-thermal clutch fan. If not go electric.

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post #3 of 27 (permalink) Old Jun 12th, 11, 09:04 AM Thread Starter
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Re: 383 Overheating when at idle.

Tuning is good just got it back about 2 weeks ago from the shop and had it tuned up. I also had a 195 thermo in it at that time and it still overheated. My other question is Ive heard timing can play into heating issues. Whats a good overall timing for a 383? like I said I have it at about 6* BTDC and I get great throttle responce and power but did notice last night when It heats up and I try to restart it I get some kickback. Overheating also a head gasket issue maybe?
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post #4 of 27 (permalink) Old Jun 12th, 11, 09:22 AM
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Re: 383 Overheating when at idle.

A properly set up stock cooling system and correctly tuned motor will cool your engine efficiently. Lately every other day there is a cooling problem here and on others sites as well. All the result of improperly set up systems. Read these and "Timing 101" posted on here numerous times.
http://www.camaros.org/pdf/corv_cooling2.pdf

http://www.chevelles.com/forums/showthread.php?t=351262
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post #5 of 27 (permalink) Old Jun 12th, 11, 09:58 AM Thread Starter
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Re: 383 Overheating when at idle.

Quote:
Originally Posted by Sauron67MM View Post
A properly set up stock cooling system and correctly tuned motor will cool your engine efficiently. Lately every other day there is a cooling problem here and on others sites as well. All the result of improperly set up systems. Read these and "Timing 101" posted on here numerous times.
http://www.camaros.org/pdf/corv_cooling2.pdf

http://www.chevelles.com/forums/showthread.php?t=351262

Ok so everything I read says timing should be as high as 16* in these cars and you say to read Timing 101. But I cant find the section "Timing 101".
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post #6 of 27 (permalink) Old Jun 12th, 11, 10:28 AM
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Re: 383 Overheating when at idle.

does your distributor have a vacuum advance can?
with the correct vacuum can, it will pull in that additional timing at idle.

I agree with Skip, you really need a thermostat and try the factory 7-blade fan with clutch

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post #7 of 27 (permalink) Old Jun 12th, 11, 10:33 AM
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Re: 383 Overheating when at idle.

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Originally Posted by Stroked74 View Post
Ok so everything I read says timing should be as high as 16* in these cars and you say to read Timing 101. But I cant find the section "Timing 101".
If you do a search here it will come up. There are two versions, this is one. http://www.camaros.org/pdf/timing101.pdf You need a B-28 vacuum can.
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post #8 of 27 (permalink) Old Jun 12th, 11, 01:15 PM
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Re: 383 Overheating when at idle.

Quote:
I am not running a thermostat right now.
Mike
Quote:
A properly set up stock cooling system and correctly tuned motor will cool your engine efficiently
The stock setup is way over built, so over built that anty issues like timing leaning will not be picked up with a sysytem in good condition
So damn good that if any changes are made...clutch fans, shrouds, thermostats removed one gets problems....yes a thermosts removed will cause running hot...not over heating.
It is not the thermosts but the restiction of the thermstat opening....Smokey Yunick did a lot of 'work on this subject, and published.....which is how I sort my engine decades ago and many since.

Nothing wrong with your timing, and not a cause of the problem.

PS Check that u have the correct 12 or 15lb radiator cap and it seals correcly.

My Spelling is not incorrect...it is creative

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post #9 of 27 (permalink) Old Jun 12th, 11, 03:21 PM
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Re: 383 Overheating when at idle.

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Originally Posted by Steptoe View Post
Nothing wrong with your timing, and not a cause of the problem.
I think John timing advice and how it affects cooling is correct. You don't? True it's not the cause, but it adds to an existing problem.
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post #10 of 27 (permalink) Old Jun 12th, 11, 07:34 PM Thread Starter
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Re: 383 Overheating when at idle.

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Originally Posted by Tom P View Post
does your distributor have a vacuum advance can?
with the correct vacuum can, it will pull in that additional timing at idle.

I agree with Skip, you really need a thermostat and try the factory 7-blade fan with clutch


I do have a vacuum can hooked up. I tried resetting my initial timing today at about 10* BTDC but when I hook the can up it sky rockets off the chart. Rev her up to about 3000 RPM and I hit about 24* on the timing tape with the can hooked up. Does this sound right for a 383? I am new to this old motor stuff. I will be buying a 180 thermostat and 7 blade this week. Do I need a fan clutch or can i mount to just an adaptor. I am running a 15lb cap also on the radiator. Sure hope this fixes the problem. Really wanna driver her.
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post #11 of 27 (permalink) Old Jun 12th, 11, 08:02 PM
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Re: 383 Overheating when at idle.

Quote:
I think John timing advice and how it affects cooling is correct. You don't?
No because as I stated above
Quote:
The stock setup is way over built, so over built that anty issues like timing leaning will not be picked up with a sysytem in good condition
Assuming no blocked or partly blocked cores.

When one gets into more modern engines/cooling systems where radiators are built to basic requirements...not overbuilt...then timing leaning etc become very apparent....
Which is where the confusion comes in...modern principles applied to old building...

On the other hand..which has now come to light....yeah something is not right there BUT it doesnt effect the hot idle.
Quote:
I tried resetting my initial timing today at about 10* BTDC but when I hook the can up it sky rockets off the chart. Rev her up to about 3000 RPM and I hit about 24* on the timing tape with the can hooked up. Does this sound right for a 383?
Get the stock fan/clutch, NEED the radiator shroud if havnt got one

My Spelling is not incorrect...it is creative

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post #12 of 27 (permalink) Old Jun 13th, 11, 05:15 AM
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Re: 383 Overheating when at idle.

not all vacuum cans are the same. You should determine your vacuum at idle and steady cruise and then match the can to your needs. pulling in 16 degrees of crankshaft timing at idle is not unusual.

When you "rev it up", the vacuum can drops out and you are then seeing the mechanical advance in the dizzy.

Definitely run a clutch - a good Heavy Duty Thermal clutch is the Hayden PN 2747 for our cars. http://www.haydenauto.com/upload/Hay...fan-clutch.pdf

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post #13 of 27 (permalink) Old Jun 13th, 11, 08:42 AM Thread Starter
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Re: 383 Overheating when at idle.

Quote:
Originally Posted by Tom P View Post
not all vacuum cans are the same. You should determine your vacuum at idle and steady cruise and then match the can to your needs. pulling in 16 degrees of crankshaft timing at idle is not unusual.

When you "rev it up", the vacuum can drops out and you are then seeing the mechanical advance in the dizzy.

Definitely run a clutch - a good Heavy Duty Thermal clutch is the Hayden PN 2747 for our cars. http://www.haydenauto.com/upload/Hay...fan-clutch.pdf

Fan clutch, Fan ordered. Will go buy a thermo today. Now you say 16* of crankshaft timing. Do you mean without vacuum hooked up or are you talking about after the can is hooked up. Sorry like I said Im new to all this. I have 11* without vacuum as my initial. When i hook the vac up I cant read it since its off the charts then when I hold 3000 it reads 24-25ish which would be about 36* overall corect? It runs great at 11* and the original owner had it at 6* and it ran good also. Thanks for all the help
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post #14 of 27 (permalink) Old Jun 13th, 11, 10:49 AM
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Re: 383 Overheating when at idle.

Vacuum cans are typically referenced in distributor degrees. you need to double that number to get crankshaft degrees or what you will see with your timing light. for example a vacuum can having 8 degrees of max. advance will yield 16 degrees of ignition advance in relationship to the crank. I am talking about when the can is hooked up. Heres a useful link on this topic.

http://www.corvette-restoration.com/...c_Adv_Spec.pdf

if you disconnect and plug the vacuum line, thats your initial advance. then hook up the vacuum advance, the difference, at idle, no other changes is how much timing the vacuum can is pulling in.

If you are seeing 24-25 degrees at 3000 rpm - that is your total timing. Total timing is a result of the initial plus any centrifugal - any vacuum advance drops out under WOT or heavy load. So you have 11 intial with 13-14 degrees centrifugal for a total timing of 24-25 degrees. How much centrifugal advance and how fast it comes in totally depends on the moroso springs, stops etc that are installed in your dizzy. Generally - most engines like total timing to be all in between 3000-3500rpm.

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post #15 of 27 (permalink) Old Jun 13th, 11, 03:20 PM
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Re: 383 Overheating when at idle.

Quote:
When you "rev it up", the vacuum can drops out and you are then seeing the mechanical advance in the dizzy.
Well sort of ..no
When u intially rev, the vac drops , VA cuts out...as the engine speed catches up with the throttle it pulls a vac and the VA actuates...a good rev up is is too short a time to establish any VA in or out or reliable advance numbers.
Follow toms post above...except..to clairfy
Quote:
if you disconnect and plug the vacuum line, thats your initial advance.
Correct
Quote:
then hook up the vacuum advance, the difference, at idle, no other changes is how much timing the vacuum can is pulling in.
When the VA is connected it advances, the advance increases the rpms, IF it has a reasonbly quick curve the cent advance could also be advancing....it is important that both measurements are taken at the same idle rpms

It does sound very much another case of an old school engine designed for manifold vaccuum being run on a dizzy with specs designed for later model (about post 1974) ported vac dizzy specs.....which are very different...as discussed many times over and over.....they run, the often run "well" but are still way off any potentual of power or economy.
There is a narrow range between about 15 and 18 degs after TDC that the max explosion must reach its peak.....about +- 2 to 3 degs. at any given rpm.,, and varies as to how much load the engine is under (and a few other things)

you have a low intial...longer battery life, less loading of started stops the dreaded so called heat sink....dry, melted solder joints on armitures
Engine fires, engine Vac established in the manifold...the VA is sucked in and activated
This is the idial advance...determined by cam, fuel type, dynamic compression etc, usually 12 to 18 degs.
The engine accelerates the rpms increase which requires more lead time....this is usually a curve untill around 3000 rpms is hit ..there is no need for more timing after this point because the milli secseconds required to time are far to small to at these rpms and therefore too small to make any significant change (over simplified)
More load requires less advance...changes in compression ..lot of stuff....less load more advance...can run leaner mixtures, less compression, the VA kicks in to provide this.

My Spelling is not incorrect...it is creative

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