So how major is this going to be??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hemihead · 03-07-2010, 09:42 PM

Just started up a fresh rebuild on a 454 on Fri night. Engine has been sitting for about 3 yrs. New main bearings pistons, cam, oil pump, timing set intake, carb, HEI, Etc.

Started and ran well, really responsive the whole time.

Had trouble keeping the engine temp down at anything above idle, tried running it at about 2000rpm for break in but in about 3 min the temp gauge would creep up to the high mark. First time we thought we had air locked the cooling system (bottom hose was cool). Pulled rad cap and way we went, saw lots of air coming through so ran motor with out cap for a while. seemed to be okay, replaced rad cap and increased rpm, temp increased again. let cool down and tried again with rad cap off, again more air bubbles, reved motor seemed to get worse, finally ended up with a hot cooling system and steam puff through rad cap hole. FYI using a aluminum rad.

Our thoughts were possibly a bad thermostat but top hose was hot, pulled thermostat and is in correect position.

Other suggestions thoughts were exhaust gases getting into water jacket via blown intake gasket or head gasket or cracked head.

Oil stayed clean and no moisture out the tail pipes during the run.

Before i begin ripping doeas any one else have a diagnoses??

**passthebuck** · 03-07-2010, 09:50 PM

I've had the same thing happen with my motor when i broke it in back in the mid 90's. I figured that the cooling system was not designed to cool a motor spinning that RPM while standing still. Had a new 3 core rad in it too. The motor was not hurt & it is still running well today.

67vetteal · 03-07-2010, 10:02 PM

Check your Timing. You can also run without the Therm. as a test. Perform all the usual Diagnostics before you start a tear down. Pressure test the cooling system, Compression test, air flo thru Rad. etc. Al W.

j_cst_10 · 03-07-2010, 10:28 PM

like 67vetteal said, check the timing and make sure it's not going lean.

Jayss109 · 03-07-2010, 11:09 PM

Also, make sure and get a big a$$ fan when doing a break in. I would also get a cheapo gauge (not the L-H) so you know exactly how hot it is. Leave the cap off until you are sure all the air is out of the system.

my 2 cents

J

hemihead · 03-07-2010, 11:57 PM

Anyone knowif there is a passage on the intake gasket that could get exhaust pressure/gases to the cooling side?

67vetteal · 03-08-2010, 08:32 PM

Not by design. Cylinder to cooling is possible via blown or improperly installed Head Gasket. Who installed the Heads and were they Torqued properly and after first running cycle of engine? Why did you ask this question? Do you have a Cooling system pressure tester. If so install it and pump up the system and see if it bleeds down. Al W.

hemihead · 03-09-2010, 02:51 PM

Did a cooling system pressure check all is good there. Check cylinders for moisture...nope. Tmin is at aboyut 18 d advanced..what shoulkd a big blck typically be set at or what range should the timing be in??

One other thought, I have the same size inlet/outlet hose on my water pump, could this be a problem? Pump cavitation, reduced flow, etc

roadracer9 · 03-09-2010, 04:03 PM

Remove thermostat and housing, remove all belts, on water pump as not to spin later. Fill engine with water at thermostat hole, in the intake to the top, let settle, re-fill if needed to top. Start engine, water pump not turning! Look at water you just added in the thermostst seat, if you have bubbles coming up constantly while running, you have head, or gasket problems! Period ! No bubbling, no problems!

If ok,...drain all water, fill again, same way, through the thermostat seat, remove a heater hose, or a plug in the intake and fill until coolant, runs out the hose/plug. Replace hose/plug, install therm. & housing, hose, etc. Re-fill at radiator, start eng. run at idle, fill as needed, watch coolant in rad. it will stand still for 5 to 10 minutes or so, you will see water level drop instantly in rad. when thermostat opens, add coolant until full, I constantly squeeze top radiator hose to help the air out, install cap. That should have all air out of system, and should cure your issue. If not, I have more things to look at, before you tear down. 31 yrs. exp.

monte0185 · 03-09-2010, 05:17 PM

Trick i leaned years ago is to drill 2 1/4" holes on either side of the thermostat in the flat area. That way when you fill it the air can still pass through aleviating the air pocket problem. Just a tidbit to help.

hemihead · 03-10-2010, 06:01 PM

Took therm out and she runs like a charm, I will likely change the thermostat out for a 160. I have the timing set at 8 degress advanced, is this about the right range?

Seems to start well and I don't have the vac advance set up yet.

j_cst_10 · 03-10-2010, 10:57 PM

Your total timing is the key factor, but typically you should be around 8-12 degrees initial with around 32-34 degrees total for a big block. This and carb tuning will play a big factor in what temp your engine runs at when it is at steady state.

03-07-2010, 09:42 PM	#1
hemihead Registered User Join Date: Mar 2007 Location: Estevan, Sask, Canada Posts: 185	So how major is this going to be??? Just started up a fresh rebuild on a 454 on Fri night. Engine has been sitting for about 3 yrs. New main bearings pistons, cam, oil pump, timing set intake, carb, HEI, Etc. Started and ran well, really responsive the whole time. Had trouble keeping the engine temp down at anything above idle, tried running it at about 2000rpm for break in but in about 3 min the temp gauge would creep up to the high mark. First time we thought we had air locked the cooling system (bottom hose was cool). Pulled rad cap and way we went, saw lots of air coming through so ran motor with out cap for a while. seemed to be okay, replaced rad cap and increased rpm, temp increased again. let cool down and tried again with rad cap off, again more air bubbles, reved motor seemed to get worse, finally ended up with a hot cooling system and steam puff through rad cap hole. FYI using a aluminum rad. Our thoughts were possibly a bad thermostat but top hose was hot, pulled thermostat and is in correect position. Other suggestions thoughts were exhaust gases getting into water jacket via blown intake gasket or head gasket or cracked head. Oil stayed clean and no moisture out the tail pipes during the run. Before i begin ripping doeas any one else have a diagnoses?? __________________ 1967 SWB C-10, BBC 454, T400, 3.73 posi, 20" Coys 1972 K5 Blazer, SBC 400, 4 spd, 3.73, 6" lift, 35" mud grapplers 2011 Sierra Denali HD, 6.6 L Duramax, RBP 96R rims, leveled and Nitto trail grapplers, 2009 Acura MDX

03-07-2010, 09:50 PM	#2
passthebuck Sisyphus was my mentor! Join Date: Sep 2002 Location: Carleton Place, Ontario CANADA Posts: 984	Re: So how major is this going to be??? I've had the same thing happen with my motor when i broke it in back in the mid 90's. I figured that the cooling system was not designed to cool a motor spinning that RPM while standing still. Had a new 3 core rad in it too. The motor was not hurt & it is still running well today. __________________ passthebuck #5642 -TWO 1967 GMC 910's. One with L6/3-on-the tree and the other with 355 w/435hp & a 700r4. -a 2013 Honda Civic as my "sensible" car

03-07-2010, 10:02 PM	#3
67vetteal Registered User Join Date: Apr 2008 Location: riverhead,new york Posts: 160	Re: So how major is this going to be??? Check your Timing. You can also run without the Therm. as a test. Perform all the usual Diagnostics before you start a tear down. Pressure test the cooling system, Compression test, air flo thru Rad. etc. Al W.

03-07-2010, 10:28 PM	#4
j_cst_10 Registered User Join Date: Nov 2008 Location: Cleveland, OH Posts: 592	Re: So how major is this going to be??? like 67vetteal said, check the timing and make sure it's not going lean.

03-07-2010, 11:09 PM	#5
Jayss109 Active Member Join Date: May 2005 Location: San Jose, CA Posts: 235	Re: So how major is this going to be??? Also, make sure and get a big a$$ fan when doing a break in. I would also get a cheapo gauge (not the L-H) so you know exactly how hot it is. Leave the cap off until you are sure all the air is out of the system. my 2 cents J __________________ Cadillac Powered

03-07-2010, 11:57 PM	#6
hemihead Registered User Join Date: Mar 2007 Location: Estevan, Sask, Canada Posts: 185	Re: So how major is this going to be??? Anyone knowif there is a passage on the intake gasket that could get exhaust pressure/gases to the cooling side? __________________ 1967 SWB C-10, BBC 454, T400, 3.73 posi, 20" Coys 1972 K5 Blazer, SBC 400, 4 spd, 3.73, 6" lift, 35" mud grapplers 2011 Sierra Denali HD, 6.6 L Duramax, RBP 96R rims, leveled and Nitto trail grapplers, 2009 Acura MDX Last edited by hemihead; 03-07-2010 at 11:57 PM.

03-08-2010, 08:32 PM	#7
67vetteal Registered User Join Date: Apr 2008 Location: riverhead,new york Posts: 160	Re: So how major is this going to be??? Not by design. Cylinder to cooling is possible via blown or improperly installed Head Gasket. Who installed the Heads and were they Torqued properly and after first running cycle of engine? Why did you ask this question? Do you have a Cooling system pressure tester. If so install it and pump up the system and see if it bleeds down. Al W.

03-09-2010, 02:51 PM	#8
hemihead Registered User Join Date: Mar 2007 Location: Estevan, Sask, Canada Posts: 185	Re: So how major is this going to be??? Did a cooling system pressure check all is good there. Check cylinders for moisture...nope. Tmin is at aboyut 18 d advanced..what shoulkd a big blck typically be set at or what range should the timing be in?? One other thought, I have the same size inlet/outlet hose on my water pump, could this be a problem? Pump cavitation, reduced flow, etc __________________ 1967 SWB C-10, BBC 454, T400, 3.73 posi, 20" Coys 1972 K5 Blazer, SBC 400, 4 spd, 3.73, 6" lift, 35" mud grapplers 2011 Sierra Denali HD, 6.6 L Duramax, RBP 96R rims, leveled and Nitto trail grapplers, 2009 Acura MDX

03-09-2010, 04:03 PM	#9
roadracer9 Retired from a track near you! Join Date: Feb 2010 Location: Mid-Tn Posts: 216	Re: So how major is this going to be??? Remove thermostat and housing, remove all belts, on water pump as not to spin later. Fill engine with water at thermostat hole, in the intake to the top, let settle, re-fill if needed to top. Start engine, water pump not turning! Look at water you just added in the thermostst seat, if you have bubbles coming up constantly while running, you have head, or gasket problems! Period ! No bubbling, no problems! If ok,...drain all water, fill again, same way, through the thermostat seat, remove a heater hose, or a plug in the intake and fill until coolant, runs out the hose/plug. Replace hose/plug, install therm. & housing, hose, etc. Re-fill at radiator, start eng. run at idle, fill as needed, watch coolant in rad. it will stand still for 5 to 10 minutes or so, you will see water level drop instantly in rad. when thermostat opens, add coolant until full, I constantly squeeze top radiator hose to help the air out, install cap. That should have all air out of system, and should cure your issue. If not, I have more things to look at, before you tear down. 31 yrs. exp.

03-09-2010, 05:17 PM	#10
monte0185 Registered User Join Date: Oct 2008 Location: Brighton, TN Posts: 1,267	Re: So how major is this going to be??? Trick i leaned years ago is to drill 2 1/4" holes on either side of the thermostat in the flat area. That way when you fill it the air can still pass through aleviating the air pocket problem. Just a tidbit to help. __________________ A computer once beat me at chess, but it was no match for me at kick boxing. Duct tape is like the force. It has a light side, a dark side, and it holds the world together.

03-10-2010, 06:01 PM	#11
hemihead Registered User Join Date: Mar 2007 Location: Estevan, Sask, Canada Posts: 185	Re: So how major is this going to be??? Took therm out and she runs like a charm, I will likely change the thermostat out for a 160. I have the timing set at 8 degress advanced, is this about the right range? Seems to start well and I don't have the vac advance set up yet. __________________ 1967 SWB C-10, BBC 454, T400, 3.73 posi, 20" Coys 1972 K5 Blazer, SBC 400, 4 spd, 3.73, 6" lift, 35" mud grapplers 2011 Sierra Denali HD, 6.6 L Duramax, RBP 96R rims, leveled and Nitto trail grapplers, 2009 Acura MDX

03-10-2010, 10:57 PM	#12
j_cst_10 Registered User Join Date: Nov 2008 Location: Cleveland, OH Posts: 592	Re: So how major is this going to be??? Your total timing is the key factor, but typically you should be around 8-12 degrees initial with around 32-34 degrees total for a big block. This and carb tuning will play a big factor in what temp your engine runs at when it is at steady state.



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