The Stovebolt.com Forums Home | FAQ | Gallery | Tech Tips | Events | Features | Search
What's going on?
What's happening?

Find out in
THE SHOPS !

Genearl Truck Talk
20,267 threads; 177,521 posts
The Engine Shop
32,460 threads; 255,065 post
Driveline
8,796 threads; 65,970 posts
The Electrical Bay
9,505 threads; 74,285 posts
Sub: The Radio Bench
The HiPo Shop
5,040 threads; 46,029 posts
Paint & Body Shop
12,505 threads; 81,120 posts
Sub: The Doors
Interiors
4,059 threads; 26,817 posts
The Tool Chest
1,762 threads; 26,817 posts
Making a Stovebolt Bed
1,052 threads; 6,659 posts
Searching the Site

Get info about how to search the entire Stovebolt site here. To do a search for just the forums, get those details in the IT Shortbus fourm.
Old Truck Calendars
Months of truck photos!
Nothing like an old truck calendar

Stovebolt Calendars

Check for details!


Who's Online Now
1 members (1 invisible), 94 guests, and 3 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums59
Topics128,612
Posts1,041,915
Members46,061
Most Online1,229
Jan 21st, 2020
Step-by-step instructions for pictures in the forums
Previous Thread
Next Thread
Print Thread
Page 1 of 2 1 2
#1451253 Tue May 10 2022 07:30 PM
Joined: Jun 2021
Posts: 38
F
flx261 Offline OP
'Bolter
Good Afternoon,

Our 261, with a 235 head, which is mounted aft in our 1945 Flxible Clipper, takes very little time to warm up and runs warmer than we anticipated it would.

We have flushed the engine, having found much 'muck' behind number 6, thoroughly. Removed the water pump up front, as well as all core plugs, blasting and running water until no more muck or discoloration of the water was observed.

We have a new radiator, with two (2) 16" electric fans sucking through said radiator, switched - but nearly always on. While driving, road air is jammed down from a scoop on the roof, across the radiator, in the same direction as the fans suck air.

It warms to @180 in short order and seems to run @200 when going down the road. It climbs above that, though does not/has not boil(ed) over when at idle.

There is no thermostat in the system, as the shutterstat system opens/closes the shutters based on coolant temperature. As such, coolant is always flowing wide-open through the engine and radiator.

We have 2" lines running to/from the radiator/engine.

What is the optimal operating temperature for the 261? Is 200 too warm?

Thanks,

Joshua L. Coder

flx261 #1451256 Tue May 10 2022 07:53 PM
Joined: Feb 2004
Posts: 24,758
H
Kettle Custodian (pot stirrer)
What pressure rating does the radiator cap have? Every pound of pressure on the cooling system raises the boiling point 3 degrees at sea level. A 15 pound cap keeps the coolant from boiling all the way to 257 degrees, and as long as the coolant is liquid, it's still moving heat from the engine to the radiator. If the engine doesn't go above 200 on a hard uphill pull, it sounds like you're OK. If you want to run a lower coolant temperature consistently, you're going to need a bigger radiator or move more air volume over the one you've got. You could also install a restrictor washer in the thermostat housing to slow down the coolant flow- - - -it might not be spending enough time in the radiator to get cooled adequately before going back to the engine to pick up more heat. Use a laser temp gun to evaluate the efficiency of the radiator- - - -aim the gun at the inlet and outlet nipples of the radiator to see how much heat is actually getting transferred to the cooling air. The results might surprise you.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

WAG MORE- - - - - -BARK LESS!
Joined: Jun 2021
Posts: 38
F
flx261 Offline OP
'Bolter
Thank you, Jerry.

I will have to check the cap. It is a bugger to access and take off.

We are getting +/-20F drop across the radiator, with the electric fans on, sitting at idle. It varies, but it always pretty close to 20F drop. If the numbers matter, 178F up top and 158F on the bottom. That is read on the tanks, as the nipples are covered by the radiator hose(s).

The hottest point in the whole system seems to be the thermostat housing. It is a pretty solid 220-230F there. Moving over inches (as in 3-4") to the radiator line, it drops 40-50F, which seems odd, but I checked it a number of times to confirm.

The radiator is coolest, right between the fans, dead center in both directions. It reads 120F there, rather steady.

Attached is an older photograph of the setup we are running. Fabricated here on the farm, not the least bit stock. The stock radiator, while thicker from front to back, by about 1.5 times, is nearly the same size in all other dimensions. That radiator is beyond repair, or so we have been told, but we have it in case we run into someone that wants to rework it on the cheap. The stock setup did NOT have electric fans and relied entirely on air from the roof scoop, which is why we are puzzled with it running hot, WITH the fans.

Thanks,

Joshua L. Coder

Attached Images
20210606_132336.jpg (445.88 KB, 203 downloads)
flx261 #1451267 Tue May 10 2022 10:50 PM
Joined: Feb 2004
Posts: 24,758
H
Kettle Custodian (pot stirrer)
I think I'd try restricting the flow rate a little, to give the coolant more time in the radiator. Don't overdo it- - - -mabe reduce the diameter of the hole in the thermostat housing by 3/8" or so, maybe 1/2" at most. Online racers' supply places like JEGS of Summit will have the reducer washers in whatever size fits the housing. I've made a little more durable ones from a piece of 1/8" thick aluminum with the edge thinned down to fit the counterbore in the housing.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

WAG MORE- - - - - -BARK LESS!
flx261 #1451292 Wed May 11 2022 03:30 AM
Joined: Jun 2011
Posts: 4,522
E
'Bolter
Have you checked your temp. gauge, it might be reading high which might explain your situation!

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
flx261 #1451305 Wed May 11 2022 05:43 AM
Joined: Apr 2005
Posts: 3,055
C
'Bolter
Heat produces power so the more heat you can generate the more power you can get. My wife had a Buick station wagon that the first fan didn't come on till 238* and the second came on at 256*. Of course a lot of this was to meet emission standards. If your cooling system components can take the pressure run a <> 10# cap and throw the worries out the window. The qualifier here is you have oil that won't break down or clearances that won't seize.


Evan
flx261 #1451312 Wed May 11 2022 06:39 AM
Joined: Jan 2003
Posts: 337
H
'Bolter
If you reduce the flow through a heat exchanger the heat transfer rate will be reduced (q=UAdT). Less heat transferred in the radiator means the engine temperature should rise.


Harold Wilson
41 Chevy 3/4 Ton
flx261 #1451313 Wed May 11 2022 06:49 AM
Joined: Jan 2003
Posts: 337
H
'Bolter
First troubleshooting process question, what changed? The radiator? The radiator is smaller ("stock radiator, while thicker from front to back, by about 1.5 times") and the picture appears to show fans that move air across 60-70% of the radiator.

Last edited by Harold41; Wed May 11 2022 07:27 AM.

Harold Wilson
41 Chevy 3/4 Ton
Joined: Jun 2021
Posts: 38
F
flx261 Offline OP
'Bolter
Originally Posted by Harold41
First troubleshooting process question, what changed? The radiator? The radiator is smaller ("stock radiator, while thicker from front to back, by about 1.5 times") and the picture appears to show fans that move air across 60-70% of the radiator.

Harold,

Correct, the radiator changed. That said, we never ran it with the factory radiator as it was unable to hold coolant long enough to try it. I would say your estimate of fan to radiator is correct, however the factory setup did NOT have any fans other than the standard engine fan - which we still have, but it does nothing to push/pull air across the radiator as it is 3' below and 3' behind the radiator.

It's tough to get a feel for how this is setup from the photograph. The radiator is about 5' off the ground, sitting at about a 15 degree angle, such that air gets jammed across it from the roof air scoop. The engine sits backwards, when compared to a 'normal' engine orientation. The engine has the stock fan, but as noted it above, it does little else besides blowing air and presenting an in-your-face body part remover if you are not mindful of said body parts.

Take Care,

Joshua L. Coder

flx261 #1451337 Wed May 11 2022 02:01 PM
Joined: Feb 2004
Posts: 24,758
H
Kettle Custodian (pot stirrer)
Restricting the flow rate through our racing radiators always resulted in the engine running cooler. Of course, at extreme RPM, it's possible the water pump impeller was cavitating and reducing its ability to move the coolant. I'm still thinking the most likely culprit is reduced radiator capacity. An aluminum radiator sinply can't transfer heat as efficiently as a copper core OEM style. If you have enough room, which it seems like you do, put a bigger radiator in there and solve the problem.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
Ernest Hemingway

WAG MORE- - - - - -BARK LESS!
Page 1 of 2 1 2

Moderated by  Phak1, Woogeroo 

Link Copied to Clipboard
Home | FAQ | Gallery | Tech Tips | Events | Features | Search | Hoo-Ya Shop
Powered by UBB.threads™ PHP Forum Software 7.7.5