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Old 07-24-2011, 09:14 AM
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383 overheating

Hi there guys I hope someone can help me out with an overheating issue on a SBC 383 that is new. Specs: 86 block bored .030, eagle rotating assembly, ProComp 72CC aluminum heads, MLS head gaskets , Comp Cams #113821—advertised duration is 288/296, and lift is 458/473, cam is not degreed, 1.6 roller rockers , Autoline AP106 plugs gapped at .030, timing is set at 26 deg advance , Weiand 142 street blower with a 2.5” pulley so overdriven , Weiand single plane intake , 170 deg thermostat , 4 core aluminum radiator, 1 5/8” headers, electric fan, mechanical fuel pump, 3 “ K&N air cleaner, I am unsure on the carburetor as it does not have a LIST # on the choke tower, it only has 4778-8 stamped there and Holley has no listing. I would guess it is a 700CFM, but not sure. I know the jets were increased from stock, but I don’t know what the sizes are as it was quite a while ago they were changed.

The engine is heating up to 230 so I don’t want to drive it much at all until I figure this out. I am thinking the carb may be too small and I am running too lean or the timing is also too far advanced. It seems to want that far to idle and run hard. It has a lot of power and really no lag at all when I stomp the pedal, the issue is it heats up and that scares me as I spent too much to burn up a piston.

Any ideas will be much appreciated.

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Old 07-24-2011, 09:25 AM
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Is that 26* initial timing or full advance timing? If it's initial, what is the full advance and @ what RPM?





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Old 07-24-2011, 09:37 AM
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Timing

Initial timing is 26* @ 900rpm, didn't check the total yet. Just finally got it running yesterday and didn't check the total. It has a Mallory Unilite and I am running Taylor 8mm wires also.
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Old 07-24-2011, 10:10 AM
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Total is much more important than initial. You don't have an overheating problem until you're certain the timing, jetting, etc, is all okay. Once you've set all the specs, and you're still running too hot, then you have an overheating problem. You could very well have a timing problem that is causing it to overheat. Or, you could could be running way too lean that causes it to run hot. Know what I mean?
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Old 07-24-2011, 10:49 AM
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2x on previous poster thoughts..

Hey,

Are you for most certain:

1. the thermostat is operating correctly?

2. the water-pump is operating correctly?

3. the radiator is not ever so slightly clogged? even if you see lots of flow?

4. the bottom radiator hose is not collapsing under suction?

5. the engine coolant passages are not clogged.. no matter how slight?

6. the sender and gauge are correct?

Does this help any?
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Old 07-24-2011, 10:54 AM
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also,

Flex fan, clutch fans, or electric fans?

Fan shroud or no shroud?
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Old 07-24-2011, 10:56 AM
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Most aaftermarket distributors Ive dealt with over the years come preset at 22-24* advance. So you are probably at 48-50 degrees all in, which is definitely way too high. Get that checked and adjusted properly.

Are you sure your timing marks are correct? There are several different timing tabs available, and balancer timing marks have been moved over the years.
Any idea how much boost youre achieving?
What type of fuel are you running?(octane)
Are you sure your gage is correct.
At what point does your fan turn on? Is it shrouded? What CFM?
Is anything being forced out of the overflow? If not, you are not overheating, just running hot. Outside temp makes it harder to keep things cool. Have you tried adding a house fan in front of the radiator to see if that cools things off. If it does, you may need more fan.
Have you looked at the plugs?
Any audible detonation/pinging?
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Old 07-24-2011, 12:56 PM
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Answers

Total timing is 46* at 3K rpm
Thermostat is working as I checked it before install
no hoses collapsing or air bubbles in the lines
Electric fan--17" puller that comes on at 190 deg--no fan shroud and not sure of the CFM but it seems to move a heck of alot of air through the radiator when running.
carb is adjusted for max vacuum--holley (700CFM ? )
Supposed to be 7.2lb to 7.4lb of boost with these pulleys
No radiator clogs
Sending and receiving units are working

I used this this same setup on the 355 and it always ran around 190*. I had it dyno'd and they changed the jets on primaries and secondaries but I have no idea what they went up to. Everything I find says that with a blower you need to run rich and on the other motor you could always tell as you smelled it.
Right now I smell nothing and I found a formula online that helps get a ballpark on a carb --cu in x max rpm / 3456 x ve%: I used 383 X 7K / 3456 x .90 (good head flow/intake and blower) and it says I should be at around a 739CFM. So my thinking is that with the overdriven blower on here I should be around an 800CFM for the amount of air being pushed into this thing.
When it overheats when I am driving it is spitting fluid out of the overflow some--running 50/50 mix water and glycol
Also running 93 octane.

FmrStrtracer--- you mentioned I am too far advanced--would you have an idea what I should be initial and total timing by chance? Also since I have the 400 balancer I had to buy the different timing tab and I bought one from summit that is adjustable. Not too sure why it is adjustable but I have it zero'd and am using that 0 mark to go off of with the advance timing light.
What do you think on the CFM of the carb?
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Old 07-26-2011, 05:04 PM
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any other ideas?

I checked timing and adjusted and I am at 10* initial advance and 26* total at 3K now. I rejetted the carb from 75 on the mains to 78 and from 84 on the secondaries to and 87. Adjusted for max vac on the carb and not much help at all. Took it out to the hwy and it still ran at 220 at 70mph. Have to let it cool down so I can open the radiator and see if it spit out a bunch or what, nothing is in the driveway or garage right now, but I want to check the radiator--the overflow looks normal.
Anyone have any other ideas? Someone mentioned running without a thermostat but I have never done that and am unsure how it would affect. Also has anyone had a car that ran at this temp and lasted any amount of time?
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Old 07-26-2011, 06:53 PM
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Did you verify TDC when you put the adjustable pointer on? You say you have it "zeroed" and don't know why it's adjustable. How did you zero it?
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Old 07-26-2011, 08:02 PM
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We cranked it over by hand with a straw in the hole and when it came up to max lift on the piston we considered that TDC. It was pretty much right on the zero mark on the pointer also so went with that. We used that mark to time the car. May try to go a little less tomorow on the timing and see if that helps. Also gonna see about maybe a higher volume water pump (?) and I have an aftermarket Alum radiator from Jegs so I am gonna see if they may have some type of shroud like was mentioned from someone else trying to help me out. Don't know how much that will help though as the thing is heating up while moving and I would think that with that much air hitting the front of the car a shroud would be a moot point--but I don't know.
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Old 07-26-2011, 08:13 PM
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Serptine drive or old v belt? I had same deal on my 383 cause I had serp drive system and a non reverse rotation pump. Also my 383 runs 18 deg int timing 26 seems like a whole lot. Are you maybe fighting a vac leak somewhere or carb issue ? My bad I missed that your running a blower also my best advice for tunning drop the coin on a wideband setup from aem . I am a Hybrid car owner v8 muscle and boosted four bangers are my game.

Last edited by stroker00s10; 07-26-2011 at 08:18 PM.
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Old 07-26-2011, 08:25 PM
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You need to be a little more (a lot more) precise on finding true TDC.

Get or make a pistons stop and do it right.
Ya it matters.

You will need to find true TDC accuratly and fix the pointer.
Recurve the distributor mechanical advacne and vacuum advance to work correctly with the blower.
You can do this with or with out a boost retard box.
The set up is a bit different , depending
.
You will need to "boost reference" the carbs power valve
so it reads and works off intake manifold vacuum BELOW THE BLOWER.

Some of the vacuum hoses that hook to the carb base will need to be hooked to the intake manifold instead. Some 1 way in line vacuum check valves may be needed.

You need to fix the cooling system.

What is the real compression ratio of this 383?

Must be less than 8.5:1 to run any kind of boost on pump gas.
Flat top pistons and 72cc heads isn;t going to work.

You may have popped a head gasket already by running it to hot with incorrect timing.


Do a compression test on all cylinders to start.

What is the diameter of the blower pulley and the crank pulley
( blower drive ratio ) Don't get all carrieed away with boost, yet.

Last edited by F-BIRD'88; 07-26-2011 at 08:31 PM.
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Old 07-27-2011, 10:22 AM
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I am running the odler style V belt on the motor.

I am going to order one of the piston stop tools just to be sure I am at absolute TDC. In the meantime we are going to put the stock size top pulley on the blower that we were using on the 355, to give right at 3psi of boost --BTW it is a Weiand 142 street blower with max boost of 8psi. Also going to try no thermostat and back off the timing another degree or 2 (as of now) and see what happens.

F-Bird I have no idea how to Recurve the distributor vacuum advance. Can you give me some direction or a website I can go to to get some schooling. I definitely don't have a boost retard box, so will have to do it without if possible.

This intake setup was a direct swap off of the 355 that ran at 190* also. It was connected up with the vac lines and all as the tech directives said to do at install--but if I need to move them now with the cu. in. upgrade can you give me a site I can go to that gives different scenarios and configurations I can try?
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