SBC 350 with overheating issues

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Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Thu Oct 08, 2015 6:24 pm

glades cat wrote:It looks like your thermostat housing is the highest point in the cooling system. Drill and tap a 1/4" pipe thread and install a 1/4 turn brass valve on top to get rid of the air. Bleed air until coolant comes out. Be sure and drill a 1/8 hole in the thermostat to bypass coolant until it opens.
Also test the coolant for products of combustion with a kit. I suspect a blown head gasket. It's very cold where you're at. Make sure you do a good warm-up before running the engine hard. Things contract and swell a lot more than they do in S FL.
Good luck Bruce.
Thanks Rick,
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Re: SBC 350 with overheating issues

Post by terrible ted » Thu Oct 08, 2015 7:48 pm

glades cat wrote:It looks like your thermostat housing is the highest point in the cooling system. Drill and tap a 1/4" pipe thread and install a 1/4 turn brass valve on top to get rid of the air. Bleed air until coolant comes out. Be sure and drill a 1/8 hole in the thermostat to bypass coolant until it opens.
Also test the coolant for products of combustion with a kit. I suspect a blown head gasket. It's very cold where you're at. Make sure you do a good warm-up before running the engine hard. Things contract and swell a lot more than they do in S FL.
Good luck Bruce.

I did something similar put a small 3/8 hose out the top to the fill bag- can what ever you call it then it vent the air always

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Re: SBC 350 with overheating issues

Post by terrible ted » Thu Oct 08, 2015 7:52 pm

Hardtail wrote:Question: So you don't think the overheating and the engine RPM's going to idle and almost quitting are the same problem?
Could be 2 different problems, I would like some tips on how to get the air out of system,
I'm going to put on a New water pump, Fresh Fuel, Fuel water separator filter, New Belt for the water pump/alternator...anything else???
I'm not sure if the radiator has a cap, I think the only cap is on the little tank (overflow reservoir) that is on the cage above the engine, which that small hose you see in the picture goes up to.
a fuel water separator will work - fuel filter with the drain at the bottom

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Re: SBC 350 with overheating issues

Post by wildcard » Thu Oct 08, 2015 8:35 pm

from what I"ve read on here you have a problem listening to people that can"t read what you posted.get rid of fuel junk,clean carb,you're expantion tank will eliminate burp,but first take t stat an drill 2 or 4 1/8 inch hole around outside of housing for water flow or put 3/4 or 7/8 restrictor plate washer for t-stat , check water flow in motor a lean fuel which is junk gas will run HOT if you have bubbles in radiator you have a bad head or gasket good luck I personaly do not run a filter here, in florida because all fuel has water in it . have had no issues in in fuel in probable 20 + years :stirpot:

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Re: SBC 350 with overheating issues

Post by terrible ted » Fri Oct 09, 2015 7:51 am

He's running in the north he need the t-stat motor need to stay warm. You do not want to run that in the winter without the t-stat.
Also as for the expansion tank will not always fix trapped air. He should be checking things first always evaluate the problems what do your plugs look like. Like mention checking for blown head gasket. looking at his fuel filters (if small black grains in the filter this could be hoses degrading due to ethanol).

Diagnosing from reports is not always right on the spot take you time and don't jump to conclusions

I expect the plugs electrodes are burned away some due to lean running.

I seen a similar problem were a motor would rev up the drop and idle for a wile then rev up. Filter at carb was clogged I want to say chewing tobacco was in the fuel tank.

Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Fri Oct 09, 2015 10:53 am

terrible ted wrote:He's running in the north he need the t-stat motor need to stay warm. You do not want to run that in the winter without the t-stat.
Also as for the expansion tank will not always fix trapped air. He should be checking things first always evaluate the problems what do your plugs look like. Like mention checking for blown head gasket. looking at his fuel filters (if small black grains in the filter this could be hoses degrading due to ethanol).

Diagnosing from reports is not always right on the spot take you time and don't jump to conclusions

I expect the plugs electrodes are burned away some due to lean running.

I seen a similar problem were a motor would rev up the drop and idle for a wile then rev up. Filter at carb was clogged I want to say chewing tobacco was in the fuel tank.
Thanks for all the help, at this point I do believe the gas is bad, I know it's old, so going to start with fresh gas, new filters and new fuel lines, and new spark plugs.
Question? Has anybody ever had a water pump just stop pumping water, assuming no air in system? ??
I replaced both hoses to and from the radiator and new coolant before i took it up there,
also ran it with and without T-stat, still over heated, that is why I already bought a new water pump, I also thought the expansion tank would always take care of the any air in the system,
So with everything that has been said in this thread, If it were a blown head gasket, one of the spark plugs would have coolant, be wet, not firing?

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Re: SBC 350 with overheating issues

Post by terrible ted » Fri Oct 09, 2015 12:55 pm

The problem is air rises to the top of the motor if the pump get and air pocket it can stop pumping. I have had 4 sb boats.ex ASE Mech But i to may be wrong, evaluate everything. Great on gas compared to cad or my 540.
Also with out a t-stat or a restriction plate it will over heat too much flow, best to flow at correct rates. If you just want to restrict the flow people will cut the spring and plunger out of the t-stat. To me i say find the problem just don't replace parts. You what to know why at least i always do.
Also if it ethanol it will go bad if AV gas is can sit over a year and be good. Av gas has a shelf life of 1 year but seeing its a car motor probably not av gas.

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Re: SBC 350 with overheating issues

Post by terrible ted » Fri Oct 09, 2015 1:07 pm

It may show
if the plugs are all the same or could be red or clean
Are any discolored - ethanol can make them brown. They can melt when lean.

test use the checker also compression test YOU BUILD YOUR EVIDENCE. This is long distance diagnoses can be like the blind leading the blind because we only can see what you describe.
I say take your time get all the facts


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Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Fri Oct 09, 2015 8:20 pm

Thanks Ted, I'm ordering one now to take up with me.

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Re: SBC 350 with overheating issues

Post by Ol Yeller » Sun Oct 11, 2015 7:39 am

Have you had your belt drive off and on recently. I ask because if don't let the lower belt drive pully float on it's shaft you'll put a lot of pressure on the rear main crank bearing on you engine. This will cause overheating that's hard to figure out and also eventually wipe out the crank bearing leading to a loss of oil pressure. Don't ask me how I know this. :cry:

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Re: SBC 350 with overheating issues

Post by Hardtail » Sun Oct 11, 2015 5:40 pm

Ol Yeller wrote:Have you had your belt drive off and on recently. I ask because if don't let the lower belt drive pully float on it's shaft you'll put a lot of pressure on the rear main crank bearing on you engine. This will cause overheating that's hard to figure out and also eventually wipe out the crank bearing leading to a loss of oil pressure. Don't ask me how I know this. :cry:
So I should let off the pressure and turn it over a few times? Care to give me some instructions on how to do that? I bought it set up this way and have only done maintenance to it,
Overheating was a little problem from day one but has got worse until last time I ran it. Problem #1 the boat is in Minnesota and I am in Miami. So when I first bought it the temp gauge would go to 200 - 210 even with the 180* T-stat but didn't boil it out the relief/ blow over hose until the last time I ran it last November. So now with all the help and comments, I have a few things to check out when I get back up there. First the gas,,, cause I first thought the 2 things were related, RPM loss and overheating, so now I can see if new gas fixes one problem,
and the tester Ted recommended should rule in or out the blown head gasket, a valve on top of the T-stat housing should clear the air,
Just a note: This weekend I was looking at a friends SBC 350 dd that had a Radiator cap mounted on top of the T-stat housing with no expansion tank, so that cap was the high point in the cooling system, we rode all day and he had no problem.

1. First I tried no T-stat, then new T-stat 180* (3 years ago now) ran over 200* then...
2. Put a wrap on the headers to try get more heat out away from the engine. not much change with that either...
3. Changed all the hoses and flushed the system and put new antifreeze.
4. So this year I bought a new water pump, thinking maybe it was degrading and going bad, which I haven't gotten to do yet...
5. Then I've been told Headgasket could have started with small leak and gotten worse to now gets over hot real quick.
6. Maybe when I flushed it I didn't get all the air out when I put back in new coolant and the old gas got water in it,,,and no longer combustible enough
I'll Let you all know what I find when I know more.
I may have more questions when I start working on it in 3 weeks.

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Re: SBC 350 with overheating issues

Post by Ol Yeller » Sun Oct 11, 2015 6:49 pm

I would remove the 4 three eights inch bolts holding the lower bearing to the belt housing. See if it Springs out. If it does that would indicate that is pushing on the engine crank bearing. Century Bell Drive has detailed instructions on their website to do this. I had a similar problem and did everything that you did. Drove me nuts. The problem is the Bearing freezes to that lower shaft overtime. You have to pull it apart sand it and grease it to free it up. You put it together with the clamp loose And run your region so the crank has no pressure either way. The tighten the clamp.

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Re: SBC 350 with overheating issues

Post by Ol Yeller » Sun Oct 11, 2015 7:03 pm

Hardtail, to test your head gasket you simply pressurize your cooling system and see if it loses pressure over a certain amount of time. If you're cooling system will not hold pressure, it's probably your head gasket is leaking. If it does hold pressure then I would rule out your head gasket. To pressurize your cooling system there's a pressurization kit that's available at most part stores. Hopefully you can rent or borrow one. The instructions are inside the kit.

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Re: SBC 350 with overheating issues

Post by Hardtail » Sun Oct 11, 2015 10:06 pm

Ol Yeller wrote:I would remove the 4 three eights inch bolts holding the lower bearing to the belt housing. See if it Springs out. If it does that would indicate that is pushing on the engine crank bearing. Century Bell Drive has detailed instructions on their website to do this. I had a similar problem and did everything that you did. Drove me nuts. The problem is the Bearing freezes to that lower shaft overtime. You have to pull it apart sand it and grease it to free it up. You put it together with the clamp loose And run your region so the crank has no pressure either way. The tighten the clamp.
Ol Yeller,
Thanks, I printed the instructions out, not sure how many hours on it, but can't hurt to take a look,

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Re: SBC 350 with overheating issues

Post by Striker543 » Mon Oct 12, 2015 12:46 pm

Is your radiator getting enough airflow? Are hoses connected properly (hot line to the top of the radiator/return line from the bottom of the radiator)?

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Re: SBC 350 with overheating issues

Post by akblackdawg » Mon Oct 12, 2015 5:01 pm

you seem very concerned about possibility of cracked head/head gasket. might be worthwhile to have a local mechanic up there go over and do a compression test, that would provide good information. shouldn't cost over $100 and would save you a lot on gas if the 2nd boat isn't necessary.
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Re: SBC 350 with overheating issues

Post by Hardtail » Sun Oct 18, 2015 2:12 pm

Just found out that I already have a valve on top of the T-Stat housing, so a good chance it was put there because of past overheating issues,
I am guessing that if I open the valve and pour coolant in the expansion tank this should let all the coolant in to replace the air, Do I need to run engine
when valve is open?
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Re: SBC 350 with overheating issues

Post by bkmail » Mon Oct 19, 2015 4:11 am

I use the valve like yours to burb air out of my system. Run it till she starts to warm up, crack the valve open till antifreeze exits. Shut the valve and keep an eye on the temps. Repeat as necesary.
Also helps if the thermostat has a small hole drilled in it as mentioned earlier.
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Re: SBC 350 with overheating issues

Post by Hardtail » Mon Oct 19, 2015 7:35 pm

bkmail wrote:I use the valve like yours to burb air out of my system. Run it till she starts to warm up, crack the valve open till antifreeze exits. Shut the valve and keep an eye on the temps. Repeat as necesary.
Also helps if the thermostat has a small hole drilled in it as mentioned earlier.
Bk
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Re: SBC 350 with overheating issues

Post by glades cat » Mon Oct 19, 2015 7:52 pm

Hey Bruce, the point where you fill the cooling system should be the highest place. It looks like you could install an in-line radiator hose filler neck, like this one…
http://www.summitracing.com/parts/mor-6 ... AqFy8P8HAQ
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Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Mon Oct 19, 2015 9:44 pm

glades cat wrote:Hey Bruce, the point where you fill the cooling system should be the highest place. It looks like you could install an in-line radiator hose filler neck, like this one…
http://www.summitracing.com/parts/mor-6 ... AqFy8P8HAQ
Thanks Rick, I'm heading up there soon, counting the days, My son in law (Marine) is driving his pickup up there, so I'm taking my AC airboat up with me, and if that car motor boat
doesn't behave I'll tow it back and fix it right this time before taking it back up there, but if it behaves and I can get it running right, then maybe we will race them car motor against
AC motor just for Sh*** N giggles, After we get our limit of Deer,,, of course : ) :reindeer: :reindeer: :reindeer: :reindeer: :reindeer: :reindeer: :reindeer: :reindeer: :reindeer:

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Re: SBC 350 with overheating issues

Post by Hardtail » Wed Nov 04, 2015 10:14 pm

Ok so when I open to let the air out of the pepcock the over heating
Fixed, but the the fresh gas didn't help the engine issue, still goes to 5000 RPM's for about 20-30 seconds then drops off to idle or quits.
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Re: SBC 350 with overheating issues

Post by Rich Andrews » Thu Nov 05, 2015 10:34 am

Your overheating issue is solved U think?

Have you drained your oil and made sure no water/radiator fluid in it?

Have you manually grabbed your inlet and outlet hoses to make sure they are both heating at the same rate to ensure your water pump is flowing properly?

Is your water pump cavitating? Have you really fixed the overheating issue?

Rev your motor up and down, get it hot then see if it still overheats. If it does your exhaust is probably leaking into the block and your not seeing it because the outer part of the head isn't cracked or blown out.

You could have a lot of corrosion inside that block as well from not running distilled and or antifreeze in it.
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Re: SBC 350 with overheating issues

Post by Afflicted » Thu Nov 05, 2015 11:34 am

Say if the overheating is fixed and it runs for a bit then dies it sound like you R sucking the bowls dry??

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Re: SBC 350 with overheating issues

Post by SthrnStyle3 » Thu Nov 05, 2015 2:06 pm

May need to clean or rebuild the carb. Especially if you thought you had bad gas, it could be gummed up. Sounds like a fuel issue to me, imo.
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