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post #31 of 148 (permalink) Old Apr 24th, 19, 2:56 PM
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Re: Overheating sbc

Thumper cams, with narrower lobe centers, cause the exh valve to open later, keeping the combustion heat in the block as opposed to letting it out the exh system sooner. It makes it a little harder to cool

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post #32 of 148 (permalink) Old Apr 24th, 19, 3:52 PM
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Re: Overheating sbc

If you have a digital dial back timing light and the RPM is 3950 at idle then you set the timing light up wrong.If you have a dial back timing light you can use it but make sure to keep it set at its base 0 degree setting. Then just use the light to read the base timing off of the stock timing indicator that's on the timing chain cover.
A dial back timing light will get confused by a Multi-spark (MSD) box if you have any of these then just use a basic timing light to set timing.
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post #33 of 148 (permalink) Old Apr 24th, 19, 3:53 PM Thread Starter
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My distributors part number on jegs is part number 121-8365 ...MSD Ignition Pro-Billet Distributor GM HEI

Bosch-Actron Digital Timing Light Designed with Advanced Features
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post #34 of 148 (permalink) Old Apr 24th, 19, 8:24 PM
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Re: Overheating sbc

Use your laser temp sensor on the thermostat housing, hoses and the radiator if it isn't shiny aluminum. Going into drive or OD only says that you have a wiring issue. You are either really overheating and putting it in drive gives you a false reading where somehow you are getting a ground through the electronics of the transmission or you are not overheating and your gauge is wrong when not in gear.. Check your grounds as a priority with a meter from the chassis, cowl, engine and from the gauge itself to the battery. It should be 0 ohms or just a hair higher. Nothing above a couple ohms is acceptable and really it shouldn't be higher then .5 ohms. AND WHEN YOU LAST MODIFIED THE CAR DID YOU DISCONNECT THE BRAIDED WIRE FROM THE COWL TO THE VALVE COVER?????
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post #35 of 148 (permalink) Old Apr 24th, 19, 11:25 PM
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Re: Overheating sbc

Quote:
Originally Posted by Mrfresh352 View Post
My distributors part number on jegs is part number 121-8365 ...MSD Ignition Pro-Billet Distributor GM HEI

Bosch-Actron Digital Timing Light Designed with Advanced Features
Your MSD HEI distributor is not a multi spark unit if you are still running it with the module that came with it. https://www.jegs.com/i/MSD-Ignition/121/8365/10002/-1 The timing light you have should work. Your timing light will not work properly with a multi spark ignition system or module. If you're still getting funky readings, try it on another car and see how if it works.

https://actron.com/sites/default/fil...lish_16313.pdf

Make sure you set the 2/4 button so the 4 is lit up on the face. If the 2 is lit up, toggle the button 2/4 until the 4 lights up. Your car is a 4 stroke. Make sure your pick up lead is isolated from other plugs and wires.

I could have sworn you said you had a mechanical water temp gauge. There are no wires that go to your sending unit, right? Just a tube that runs to the sending unit that can't be removed or cut.
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post #36 of 148 (permalink) Old Apr 25th, 19, 5:28 AM
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Re: Overheating sbc

Narrower lobe centre causes exh valve to open sooner, not later.
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post #37 of 148 (permalink) Old Apr 25th, 19, 5:39 AM
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Re: Overheating sbc

Ignore my post above, it is wrong.
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post #38 of 148 (permalink) Old Apr 25th, 19, 2:26 PM
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Re: Overheating sbc

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Ignore all my posts, most are wrong.
We try to but its hard since you post alot of bs.
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post #39 of 148 (permalink) Old Apr 25th, 19, 5:30 PM
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Re: Overheating sbc

Where is the vacuum advance line going? Is it into a ported or manifold vacuum source? If it's ported(high up on the carb) I would put in on the port on the baseplate of the carb which is full vacuum....

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post #40 of 148 (permalink) Old Apr 25th, 19, 7:19 PM Thread Starter
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Initial timing is 19 but advance timing stops at 30 and doesn’t keep going to 36. Do I need springs for my curve? Took it for a drive and it doesn’t do much at wot like it use to. Still responsive but I didn’t hear the roar that I use to. Temp went up to 240 again and as soon as I was going to shut it off it drops to 185 and stays there.

I put the initial at 16 but it still wouldn’t climb to 36 any lower on the initial and it shakes and is about to shut off. Vac advance is ported from the carbs small port top left corner if your facing the carb from the front. It’s a Holley 650 with out the fuel float bolt. I can do a video if anyone wants me to upload it to YouTube.
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post #41 of 148 (permalink) Old Apr 25th, 19, 9:19 PM
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Move vacuum to bottom port
Using Long Chevy water pump ?
Are you setting timing w/vacuum advance plugged ?
Forget idle timing.
Use distributor springs for about 3400, you can see this on dial back light.
Assuming you run at least 91, set timing for 36 @ 3400.
If starter kicks back, work w/dist bushings, put a good starter on or wire separate ignition switch.
Be sure your carb isn’t lean @ idle or jetted lean. Try 68 & 70 just to start.

You should be able to hold 160.

Good luck
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post #42 of 148 (permalink) Old Apr 26th, 19, 12:48 PM Thread Starter
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Okay I will Switch it this weekend. Yes my water pump is long. And yes I plugged vac advance when setting the timing.
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post #43 of 148 (permalink) Old Apr 26th, 19, 10:32 PM
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Re: Overheating sbc

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Originally Posted by Mrfresh352 View Post
Okay I will Switch it this weekend. Yes my water pump is long. And yes I plugged vac advance when setting the timing.
If you say it's only overheating or changes when you go into drive or OD then its electrical. If you are overheating sitting in traffic or running it hard then you might have a timing issue. Putting it in gear shouldn't immediately change your temp gauge. Can you clarify what the problem is again! I do not understand your initial post?
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post #44 of 148 (permalink) Old Apr 27th, 19, 1:39 PM Thread Starter
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Okay I’ll try and explain it again. I’ve turned it on yesterday and it takes a while for it to fully warmup about 7-10 mins. Once it get to 160 it will stay there for about 5 mins and then it starts to climb slowly. 180, 200, 230, once it hit 240 for 2 minutes it immedialty starts to drop.

I did this without changing the gear. Still in park. It drops to 185 and stays there. I will provide a link to my YouTube to get more help later. I’ve never seen this so it’s hard for me to explain.
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post #45 of 148 (permalink) Old Apr 27th, 19, 1:53 PM
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Re: Overheating sbc

Sounds like it is low on coolant. If it gets that hot and then finally cools down, I would assume the cooling system is capable. Or something like thermostat upside down. I'd have to go back and re-read the thread.

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