Hot 454V8 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TJ2000 · 05-17-2002, 05:53 PM

Have a 71 SWB K10 stepside w/ a 454V8 and Manual 4 spd. trans., 4 core radiator, new fan clutch on fan, no thermostat at this time due to running hot. At highway speeds (60mph+) temp is fine, at slower speeds (offroad) engine tends to eventually overheat into the red zone. Also what is the purpose of the pre-formed 3/4" 90 degree bypass hose (I think people call it a bypass hose) that goes from the top of the water pump to the front of the intake manifold?? Thanks for any and all info...

Baradium · 05-17-2002, 06:30 PM

a bypass hose sends water through the block even when the thermostat is closed (recirculates in the motor) so that the engine temp is even throughout the motor. The GMC V-6 motors havea 3" bypass, I think my scout's is 2.5 (same as the rad hoses). Also, a thermostat shouldn't affect whether you run hot or not, so start changing stuff to make it run right, and if you have to, turn the heater on to save your motor.

bigjimzlll · 05-17-2002, 08:17 PM

a thermostat is supposed to allow the water to stay in the radiator longer, and restrict water flow to allow the water to cool...I have found out that the engine runs cooler with a thermostat

speeddemon · 05-17-2002, 08:45 PM

what size thermostat were you running? a thermostat will normaly open later than the temp that is marked on it. 180* - 200 degree engine temp. Do you have a fan shroud?

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69-C10 LWB

*Zkast* · 05-17-2002, 08:54 PM

Yep yep, get that thermostat back in there. Water will run through the radiator faster if un-metered (thermostat) and not allow good heat exchange.

Carefully take the radiator cap off, since you have no thermostat at this point you can do this test while the engine is cold, start the engine and watch for good coolant flow through the radiator. low flow at idle will cause overheating. This is caused from a restricted radiator core or rusted/worn pump impellers.

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Pictures and more...
Email me
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett
Olathe, Kansas

DennyB · 05-17-2002, 09:15 PM

Yep you need your thermostat.
What fan/clutch & shroud are you running?

------------------
Toms River NJ
(Transplanted Hoosier)

56 working Street Rod(under construction 71-2 coil chassis)
Give a man a fish and he will eat for a day. Teach him how to fish and he will sit in a boat & drink beer all day.

TJ2000 · 05-17-2002, 09:19 PM

Ok!! To the firs 4 replies,,,, 180, 185, 194 degree thermostat for the winter, can't remember which. Seems like no difference in temp. whether I have a thermostat or not, still runs hot. Radiator clean and not fouled. I do have a radiator shroud and pulled out the water pump and removed the back cover, the impeller is in fine shape, no corrosion and no shaft seal leaks the tell tale holes,, I don't lose any coolant, I just can't keep it cool!!

Baradium · 05-17-2002, 09:37 PM

check your mixture. running too lean can have your engine running hotter. main jets maybe too lean? Check your spark plugs to see how they look. If your cooling system was working correctly you wouldn't be overheating. You could try a different pulley on the crank or water pump to make the fan and pump spin faster. I also reccommend putting some water wetter in with your water/coolant mix.

[This message has been edited by Baradium (edited May 17, 2002).]

*Zkast* · 05-17-2002, 10:51 PM

Is your fan a direct drive or does it have a fan clutch? verify good air flow. next would be.. Does the airflow coming from the fan at idle feel VERY hot, hot, mild or cold. This will give you an idea of what temp the water is hitting the radiator.
Do you happen to have a infrared temperature gun? ok ok so maybe every doesnt have one

Verify that it is actually getting to the temp your gauge says.

------------------
Pictures and more...
Email me
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett
Olathe, Kansas

cableguy0 · 05-18-2002, 11:57 AM

i would first verify the actual temp with a temp gun and if it is actually overheating i would lookin into the lean burn condition.does ur exhaust ever glow red after a long run

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72 chevy lwb 350 lunati cam ported and polished cast 2.02 heads proform hei edelbrock performer rpm and 750 carb balanced bottom end 9.5:1 compression ps,pb th350 with a tci 2500 stall convertor full man v-body kevlar clutches and bands as well as other goodies

*Randy70C-10* · 05-18-2002, 01:13 PM

Is your timing set properly? Not enough advance could cause overheating too.

[This message has been edited by Randy70C-10 (edited May 18, 2002).]

Erl · 05-18-2002, 01:14 PM

You say the radiator is clean. The outside can be clean and the inside of the tubes covered with contamination (scale). If you have not done this remove your radiator and take it to a shop to be boiled out. It does not cost too much. Sometimes it is what you can not see that hurts you most. Post the solution when you find it.

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68 GMC 305V6 3/4 4x4 Stepside
54 Kaiser Darrin
Ducati Monster
Dallas TX

loenuf · 05-18-2002, 08:00 PM

i tell you what you need to do...i had the same prob on my truck, its strickly a mud truck only. everything is new under the hood and still had a overheating prob only in mud holes. i threw away the clutch fan and got a direct drive flex fan and it droped it 20 degreese and keeps it there! the clutch fan wont move air when your sittin in a mud hole. give it a shot, those fans are cheap, and i bet it cures your problem.

TJ2000 · 05-19-2002, 09:10 AM

THANKS everybody for your input,, I think, I found the problem. My fan clutch fan was a CCW rotation fan, its hard to tell the difference between a CW/CCW rotation fan if you don't know what you're looking for,,, I didn't!! I might try the direct drive flex fan,, maybe,, I heard they were noisy,, especially an 18" diameter one. Bought this truck last fall and have been slowly getting all the bugs out and making it road worthy,, Thanks all...

*Zkast* · 05-19-2002, 09:13 AM

Great to hear! Personaly, I would stick with a stock fan w/fan clutch.

------------------
Pictures and more...
piston@zkast.com
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett - Olathe, Kansas

05-17-2002, 05:53 PM	#1
TJ2000 Registered User Join Date: Mar 2002 Location: Page, AZ., USA Posts: 14	Hot 454V8 Have a 71 SWB K10 stepside w/ a 454V8 and Manual 4 spd. trans., 4 core radiator, new fan clutch on fan, no thermostat at this time due to running hot. At highway speeds (60mph+) temp is fine, at slower speeds (offroad) engine tends to eventually overheat into the red zone. Also what is the purpose of the pre-formed 3/4" 90 degree bypass hose (I think people call it a bypass hose) that goes from the top of the water pump to the front of the intake manifold?? Thanks for any and all info... __________________ TJ

05-17-2002, 08:17 PM	#3
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	a thermostat is supposed to allow the water to stay in the radiator longer, and restrict water flow to allow the water to cool...I have found out that the engine runs cooler with a thermostat __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

05-17-2002, 08:45 PM	#4
speeddemon Registered User Join Date: May 2002 Location: lexington,South Carolina Posts: 158	what size thermostat were you running? a thermostat will normaly open later than the temp that is marked on it. 180* - 200 degree engine temp. Do you have a fan shroud? ------------------ 69-C10 LWB __________________ 69-C10 LWB 71- fleetside shortbed It's a shame stupidity isn't painful Never play leapfrog with a unicorn

05-17-2002, 09:15 PM	#6
DennyB Led Sled! Discs R 4 ME! Join Date: Jan 2001 Location: Toms River, NJ, USA (Transplanted Hoosier) Posts: 7,327	Yep you need your thermostat. What fan/clutch & shroud are you running? ------------------ Toms River NJ (Transplanted Hoosier) 56 working Street Rod(under construction 71-2 coil chassis) Give a man a fish and he will eat for a day. Teach him how to fish and he will sit in a boat & drink beer all day. __________________ "Never ride faster than your Angel can fly" I.M.O.M,W,J&C Patriot Guard Rider

05-17-2002, 09:19 PM	#7
TJ2000 Registered User Join Date: Mar 2002 Location: Page, AZ., USA Posts: 14	Ok!! To the firs 4 replies,,,, 180, 185, 194 degree thermostat for the winter, can't remember which. Seems like no difference in temp. whether I have a thermostat or not, still runs hot. Radiator clean and not fouled. I do have a radiator shroud and pulled out the water pump and removed the back cover, the impeller is in fine shape, no corrosion and no shaft seal leaks the tell tale holes,, I don't lose any coolant, I just can't keep it cool!! __________________ TJ

05-17-2002, 06:30 PM	#2
Baradium Binder Rep Join Date: Jan 2001 Location: Salcha, AK Posts: 1,506	a bypass hose sends water through the block even when the thermostat is closed (recirculates in the motor) so that the engine temp is even throughout the motor. The GMC V-6 motors havea 3" bypass, I think my scout's is 2.5 (same as the rad hoses). Also, a thermostat shouldn't affect whether you run hot or not, so start changing stuff to make it run right, and if you have to, turn the heater on to save your motor.

05-17-2002, 08:54 PM	#5
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Yep yep, get that thermostat back in there. Water will run through the radiator faster if un-metered (thermostat) and not allow good heat exchange. Carefully take the radiator cap off, since you have no thermostat at this point you can do this test while the engine is cold, start the engine and watch for good coolant flow through the radiator. low flow at idle will cause overheating. This is caused from a restricted radiator core or rusted/worn pump impellers. ------------------ Pictures and more... Email me '71 LWB 350/350T, PS/PB Special options? Yes, RUST... Need some? Garrett Olathe, Kansas

05-17-2002, 09:37 PM	#8
Baradium Binder Rep Join Date: Jan 2001 Location: Salcha, AK Posts: 1,506	check your mixture. running too lean can have your engine running hotter. main jets maybe too lean? Check your spark plugs to see how they look. If your cooling system was working correctly you wouldn't be overheating. You could try a different pulley on the crank or water pump to make the fan and pump spin faster. I also reccommend putting some water wetter in with your water/coolant mix. [This message has been edited by Baradium (edited May 17, 2002).]

05-17-2002, 10:51 PM	#9
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Is your fan a direct drive or does it have a fan clutch? verify good air flow. next would be.. Does the airflow coming from the fan at idle feel VERY hot, hot, mild or cold. This will give you an idea of what temp the water is hitting the radiator. Do you happen to have a infrared temperature gun? ok ok so maybe every doesnt have one Verify that it is actually getting to the temp your gauge says. ------------------ Pictures and more... Email me '71 LWB 350/350T, PS/PB Special options? Yes, RUST... Need some? Garrett Olathe, Kansas

05-18-2002, 11:57 AM	#10
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	i would first verify the actual temp with a temp gun and if it is actually overheating i would lookin into the lean burn condition.does ur exhaust ever glow red after a long run ------------------ 72 chevy lwb 350 lunati cam ported and polished cast 2.02 heads proform hei edelbrock performer rpm and 750 carb balanced bottom end 9.5:1 compression ps,pb th350 with a tci 2500 stall convertor full man v-body kevlar clutches and bands as well as other goodies __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

05-18-2002, 01:13 PM	#11
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	Is your timing set properly? Not enough advance could cause overheating too. [This message has been edited by Randy70C-10 (edited May 18, 2002).]

05-18-2002, 01:14 PM	#12
Erl Registered User Join Date: Mar 2002 Location: Dallas, TX Posts: 555	You say the radiator is clean. The outside can be clean and the inside of the tubes covered with contamination (scale). If you have not done this remove your radiator and take it to a shop to be boiled out. It does not cost too much. Sometimes it is what you can not see that hurts you most. Post the solution when you find it. ------------------ 68 GMC 305V6 3/4 4x4 Stepside 54 Kaiser Darrin Ducati Monster Dallas TX __________________ 1968 GMC 305 V6 3/4 4x4 Stepside 06 Corvette Daily Driver Dallas TX

05-18-2002, 08:00 PM	#13
loenuf Registered User Join Date: May 2000 Location: trenton texas usa Posts: 232	i tell you what you need to do...i had the same prob on my truck, its strickly a mud truck only. everything is new under the hood and still had a overheating prob only in mud holes. i threw away the clutch fan and got a direct drive flex fan and it droped it 20 degreese and keeps it there! the clutch fan wont move air when your sittin in a mud hole. give it a shot, those fans are cheap, and i bet it cures your problem.

05-19-2002, 09:10 AM	#14
TJ2000 Registered User Join Date: Mar 2002 Location: Page, AZ., USA Posts: 14	THANKS everybody for your input,, I think, I found the problem. My fan clutch fan was a CCW rotation fan, its hard to tell the difference between a CW/CCW rotation fan if you don't know what you're looking for,,, I didn't!! I might try the direct drive flex fan,, maybe,, I heard they were noisy,, especially an 18" diameter one. Bought this truck last fall and have been slowly getting all the bugs out and making it road worthy,, Thanks all... __________________ TJ

05-19-2002, 09:13 AM	#15
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Great to hear! Personaly, I would stick with a stock fan w/fan clutch. ------------------ Pictures and more... piston@zkast.com '71 LWB 350/350T, PS/PB Special options? Yes, RUST... Need some? Garrett - Olathe, Kansas



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