SB overheating
Le Mans Master
Joined: Feb 2014
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From: Richardson Texas
Early last night I ran the engine to get some data. Starting with an ambient temperature of 92*, I ran the car for 25 minutes and shot temps along the coolant path with an IR gun. Upper and lower radiator hoses varied between 6*-8* (198* & 192* after approx 23 min) once the 180* stat opened up. Water pump, outlet, sender and block temps were always hotter than the hoses by at least 10*. Dash gauge read 210* after 19 mins and when I shut it down the upper hose read 204, lower hose read 196 and the gauge was 210+ so it appears it's reading hotter than actual. I shut it down after 25 minutes as the temp gauge began to creep towards the yellow area. I ran out of time to do anything further but today I hope to check the timing. I'm actually relieved that it can idle for nearly a 1/2 hour without getting too hot; but then again it was from a "cold" start without any driving. I still don't know how this will perform in the real world. I'll find out this weekend.
My real interest is the manifold reading. After the engine reached temp, I adjusted the idle to 600-650 rpms at the dash tach. Anything lower and it's lopey; the tach bounces between 500-600 rpms. At 650 it evens out. When I disconnected the vac can from the manifold, rpms went up to 900. I wasn't expecting that. I readjusted the idle back to 650, connected the vac gauge. 14"-15" bouncing between. Still processing this but any input would be helpful.
My real interest is the manifold reading. After the engine reached temp, I adjusted the idle to 600-650 rpms at the dash tach. Anything lower and it's lopey; the tach bounces between 500-600 rpms. At 650 it evens out. When I disconnected the vac can from the manifold, rpms went up to 900. I wasn't expecting that. I readjusted the idle back to 650, connected the vac gauge. 14"-15" bouncing between. Still processing this but any input would be helpful.
Team Owner
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From: Sitting in his Nowhere land Hanover Pa
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When you disconnect the rubber line from the vacuum cannister you need to install a "T" and then reconnect the vacuum line to get a correct reading...do NOT readjust the idle. Once you have a correct reading, and it should be 14-15"hg, you'll know which vacuum cannister to buy...in this case a B26 (available at most auto parts stores...NAPA, for sure). Bring your MityVac with you and test the cannister before buying...they sometimes vary quite a bit. You want to be sure that the B26 you buy pulls all in by 12"hg. Your car is never going to run efficiently/cool until you swap out that useless B1 can that you currently have in there. I don't want to sound like a know it all, but you've been told this by three different members, and you still haven't done it...yet, you keep asking for more advice. CHANGE THE VACUUM CANNISTER.
Race Director
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When you disconnect the rubber line from the vacuum cannister you need to install a "T" and then reconnect the vacuum line to get a correct reading...do NOT readjust the idle. Once you have a correct reading, and it should be 14-15"hg, you'll know which vacuum cannister to buy...in this case a B26 (available at most auto parts stores...NAPA, for sure). Bring your MityVac with you and test the cannister before buying...they sometimes vary quite a bit. You want to be sure that the B26 you buy pulls all in by 12"hg. Your car is never going to run efficiently/cool until you swap out that useless B1 can that you currently have in there. I don't want to sound like a know it all, but you've been told this by three different members, and you still haven't done it...yet, you keep asking for more advice. CHANGE THE VACUUM CANNISTER.
Duke
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Joined: Dec 2009
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From: Flakewood Wrench, FL
When you disconnect the rubber line from the vacuum cannister you need to install a "T" and then reconnect the vacuum line to get a correct reading...do NOT readjust the idle. Once you have a correct reading, and it should be 14-15"hg, you'll know which vacuum cannister to buy...in this case a B26 (available at most auto parts stores...NAPA, for sure). Bring your MityVac with you and test the cannister before buying...they sometimes vary quite a bit. You want to be sure that the B26 you buy pulls all in by 12"hg. Your car is never going to run efficiently/cool until you swap out that useless B1 can that you currently have in there. I don't want to sound like a know it all, but you've been told this by three different members, and you still haven't done it...yet, you keep asking for more advice. CHANGE THE VACUUM CANNISTER.
Team Owner
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From: Sitting in his Nowhere land Hanover Pa
2024 C2 of the Year Finalist - Unmodified
2015 C2 of Year Finalist
Just read Dukes tuning paper over and over and follow to a “T”. It’s really not that complicated
Le Mans Master
Joined: Oct 2000
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From: Santa Ana CA
Maybe you have a vacuum leak in a line or the manifold itself and this is causing things to go a bit lean under a continual load heating the engine.
Race Director
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Disconnecting the hose allows in additional air, which can raise idle speed, If you pinch off the hose, speed should decrease due to loss of advance if it's full time vacuum.
Duke
Duke
Last edited by SWCDuke; Jul 11, 2022 at 08:51 AM.
Le Mans Master
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From: Folsom CA
The car is getting hot in 25 minutes of idle. I should take 15 minutes for it to get warm enough to even open the thermostat and start heating the radiator if he is at idle. I would mist that hot radiator and see if the temp drops like it should. If the temp drops quickly with mist, great you know the cooling system works if it is getting cooling air over the front. Tells you the water pump is circulating the coolant. You can move on to solutions once you establish the basics are working. For timing at this point I would want to know what the basic timing setting is with the Vac Advance disconnected and the line plugged. Proper tuning starts once the base is set and good. The OP mentions he had overheat issues before. It may have compromised one of the head gaskets. I would get the Hydrocarbon test done to eliminate that as a possibility.
Mark
Mark
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Racer
Joined: May 2005
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From: Chicago
C2 overheating
My "overheating" problem, 240+ in hot stop and go traffic ,I solved by replacing belt driven fan with single high flow electric fan, snugly mounted in the shroud, new radiator. Some manufacturing needed. I can run fan on automatic and have a manual override. It will idle all day in 95* weather at around 190*
even gain little HP not having belt driven fan, lol.
even gain little HP not having belt driven fan, lol.
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From: Flakewood Wrench, FL
Thread Starter
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From: Flakewood Wrench, FL
That's a real good question. I'd like to think the cash and effort I put into new cooling system parts had a lot to do with that but maybe the advance helped too. I'm not convinced I've got the timing dailed in; but rather far from it. Not sure what to do next.
Team Owner
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From: Various places in Southern California.
That does seem a bit high. I thought the B26 produced about 8 degrees of distributor advance, or 16 degrees at the crank. So, I'd expect you to see about 24* all in at idle.
But, does the engine perform okay with the B26 as is? If the engine seems happy with it and you don't hear any pinging anywhere, I think you are in a good place.
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From: Flakewood Wrench, FL
That does seem a bit high. I thought the B26 produced about 8 degrees of distributor advance, or 16 degrees at the crank. So, I'd expect you to see about 24* all in at idle.
But, does the engine perform okay with the B26 as is? If the engine seems happy with it and you don't hear any pinging anywhere, I think you are in a good place.
But, does the engine perform okay with the B26 as is? If the engine seems happy with it and you don't hear any pinging anywhere, I think you are in a good place.
8* @ 600 rpm
17* @ 1000 rpm
20* @ 1500 rpm
21* @ 2000 rpm
If I were to guess, it looks like centrifugal was headed for being all in soon. I really wished I had a helper to handle the rpm's to take it higher to find out and next time I will. Is it possible the B26 is too much; adding more crank degrees at idle than I need? Admittedly, I'm not the best student but I do appreciate all help along the way. Thanks guys.
Last edited by Spike66; Jul 17, 2022 at 07:36 AM.
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What's the idle speed set at with the VAC connected? Look at your centrifugal curve. 9 @1000!! That's a lot! Where does is start? Chances are the centrifugal has already started adding advance at a little over 600 or maybe be lower, and if there is no more than 13 @ 2000, then it's too fast and too short.
38 @ 3000 (30 max centrifugal, 8 initial) starting at about 900 would be a lot better. Your idle vacuum indicates a little less valve overlap than L-79 , so an optimized L-79 should work pretty well.
Duke
38 @ 3000 (30 max centrifugal, 8 initial) starting at about 900 would be a lot better. Your idle vacuum indicates a little less valve overlap than L-79 , so an optimized L-79 should work pretty well.
Duke
Last edited by SWCDuke; Jul 17, 2022 at 11:47 AM.
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From: Flakewood Wrench, FL
What's the idle speed set at with the VAC connected? Look at your centrifugal curve. 9 @1000!! That's a lot! Where does is start? Chances are the centrifugal has already started adding advance at a little over 600 or maybe be lower, and if there is no more than 13 @ 2000, then it's too fast and too short.
38 @ 3000 (30 max centrifugal, 8 initial) starting at about 900 would be a lot better. Your idle vacuum indicates a little less valve overlap than L-79 , so an optimized L-79 should work pretty well.
Duke
38 @ 3000 (30 max centrifugal, 8 initial) starting at about 900 would be a lot better. Your idle vacuum indicates a little less valve overlap than L-79 , so an optimized L-79 should work pretty well.
Duke
As I said way early on, the cam is not OEM but rather a little wilder but not as much as an L79. Still, I believe it's too fast and too short and maybe setting 8* @ 850-900 would be a better starting point if it will idle at those parameters. And would I do this initial with VAC in or out of the chain? I did it with it out and found 600+/- rpm at 8* to be stable. I'm obviously missing something elementary.
Last edited by Spike66; Jul 17, 2022 at 01:52 PM.
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If you are using a dial back timing light with the VAC disconnected you are measuring the sum of initial plus added centrifugal. I merely backed out the initial and started the actual centrifugal.
You should select an idle speed with the VAC connected and keep readjusting it to that as you change things, like timing or centrifugal advance. Given the B26 VAC you do not want idle speed less than what it takes to pull about 14" vacuum.
You still have to learn the concept of a "spark advance map". So do a lot of others. Read my tuning seminar. Search for threads stated by me.
Duke
You should select an idle speed with the VAC connected and keep readjusting it to that as you change things, like timing or centrifugal advance. Given the B26 VAC you do not want idle speed less than what it takes to pull about 14" vacuum.
You still have to learn the concept of a "spark advance map". So do a lot of others. Read my tuning seminar. Search for threads stated by me.
Duke
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From: Freedom is never more than one generation away from extinction.
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I experienced some issues with a set of March Under-drive pulleys on my 86 coupe with similar results. It took some tweaking to find the right combination to keep temps and voltage stable.
I know this is a stretch for an answer. What if the water pump pulley is too small or large compared to the crank pulley?? But is it possible that the pump may be spinning too fast? Fast or slow enough to prevent "efficient" heat transfer to/from the coolant? My question to the OP is what are the diameters of the crank and wp pulleys? Also the diameter of the t-stat opening. I've been looking for SB pulley's for my L79. There are a few different diameters to choose from should I not be too concerned about originality.
I know this is a stretch for an answer. What if the water pump pulley is too small or large compared to the crank pulley?? But is it possible that the pump may be spinning too fast? Fast or slow enough to prevent "efficient" heat transfer to/from the coolant? My question to the OP is what are the diameters of the crank and wp pulleys? Also the diameter of the t-stat opening. I've been looking for SB pulley's for my L79. There are a few different diameters to choose from should I not be too concerned about originality.
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From: Flakewood Wrench, FL
The water pump and crank pulleys are the correct size as is the water outlet diameter. As I mentioned above, controlling the temperature is better now that I've replaced the usual suspects.