Cj7 w/ sb350 and cooling....and carbureting...

Cody

Random Quote Generator
Supporting Member
Location
East Stabbington
So I have this CJ7 that has some running issues. I feel like it's just a few things away from being a decent little weekend trail rig slash cruise around town rig. The first problem I need to address is keeping it running.

Going up AF canyon, the hill leading up before the Forest Lake trail caused it to overheat. It also can't run during the summer in stop and go traffic without overheating/vapor locking. It clearly needs better cooling. After some poking around for fans, it looks like this is the exact product the previous owner put in it...


Now, is it possible to just add a bigger fan, or am I better just replacing the radiator with a radiator/fan combo larger and with more CFM's? Or would a larger overflow bottle holding more coolant in the system make a difference (typing this, I'm not 100% sure it even has an overflow bottle now...I assume it does but I don't recall seeing it specifically...will check after work).

The second problem to address is TBI. Part of the problem I have is that the carb doesn't want to run at any angle, and elevation really ****s with it. I also think the fuel is getting too hot and the fuel lines might need to be re-routed and/or shielded where they are running close to the block and above the dual exhaust. (I kind of want to just get rid of the dual exhaust in favor of a single so that it isn't even an issue, but that might be more dollars than just shielding). So, in which order do I attack this? I was thinking of jumping to TBI and just seeing if that eliminates the issue all together, but maybe both of those problems need to be addressed at the same time?

After I can keep it running, I want to improve ride quality/offroad quality most likely by going to YJ springs and pushing the wheelbase 2" in both directions. But that's probably for a later discussion.
 
Last edited:

Hickey

Burn-barrel enthusiast
Supporting Member
It seems like a decent fan/radiator combo. Could be a stuck thermostat or even a bad water pump. Is it leaking any coolant? There's a weep hole on the bottom of the water pump. If it's leaking out of that spot, it needs replacement.
 

Cody

Random Quote Generator
Supporting Member
Location
East Stabbington
The water pump and t-stat were all replaced at the same time, but I suppose that doesn't mean that neither of them are faulty.

No coolant leak.

Another thing I really haven't done yet (which should have been first), is open the radiator once cooled to see if it's full. I wonder if he got a bubble in there when he drained and refilled the system.
 

mbryson

.......a few dollars more
Supporting Member
I've had fantastic results with the Taurus fan on my Mepco era (just rebuilt) brass YJ radiator. I believe the Mark VIII fan and some of the other fans are even more cooler than the Taurus.

I have a Ford Escape setup on my 455 Buick. The Buick 400-430-455 are NOTORIOUS for overheating (even worse than a Big Block Chev in a CJ) and mine never skipped a beat this summer (that I drove it a lot but I did drive it on some hot days just to figure out if that was going to be something I needed to account for as I complete it).

Brett Davis has like 5-6 heat exchangers on his TBI 454 CJ8. He had some "off brand" fans on all of those. Solved his overheating issues with a Taurus fan. I don't know if the enginerd in him let him take all the heat exchangers out or not?

These experiences make me think the OEM fans are more awesomer than most/any aftermarket units?

I'd fix the cooling issue before attacking the carb issue. Holley Sniper ($1000-2000) are a great way to go there in my opinion. (my opinion just bought an Edelbrock AVS2 though instead of putting my $ where my mouth is. My reasoning was vacuum related. I don't have much at all and the Holley seems to really like the vacuum for some reason)
 

DaveB

Long Jeep Fan
Location
Holladay, Utah
My old jeeps (CJ8 and Commando) have large aluminum Chevy conversion radiators with stock mechanical fans. Never any overheating issues.
 

Cody

Random Quote Generator
Supporting Member
Location
East Stabbington
I've had fantastic results with the Taurus fan on my Mepco era (just rebuilt) brass YJ radiator. I believe the Mark VIII fan and some of the other fans are even more cooler than the Taurus.

I have a Ford Escape setup on my 455 Buick. The Buick 400-430-455 are NOTORIOUS for overheating (even worse than a Big Block Chev in a CJ) and mine never skipped a beat this summer (that I drove it a lot but I did drive it on some hot days just to figure out if that was going to be something I needed to account for as I complete it).

Brett Davis has like 5-6 heat exchangers on his TBI 454 CJ8. He had some "off brand" fans on all of those. Solved his overheating issues with a Taurus fan. I don't know if the enginerd in him let him take all the heat exchangers out or not?

These experiences make me think the OEM fans are more awesomer than most/any aftermarket units?

I'd fix the cooling issue before attacking the carb issue. Holley Sniper ($1000-2000) are a great way to go there in my opinion. (my opinion just bought an Edelbrock AVS2 though instead of putting my $ where my mouth is. My reasoning was vacuum related. I don't have much at all and the Holley seems to really like the vacuum for some reason)
Is a taurus fan electric or mechanical? I'm not worried about the power loss of a mechanical fan, but I'm not sure what it would take to fit it where one isn't currently.
 

mbryson

.......a few dollars more
Supporting Member
Is a taurus fan electric or mechanical? I'm not worried about the power loss of a mechanical fan, but I'm not sure what it would take to fit it where one isn't currently.


Taurus, Mark VIII, Volvo, etc are all electric fans. Pretty massive electrical hit to get them going. You'll want a good relay to get them going.
 

Hickey

Burn-barrel enthusiast
Supporting Member
That sounds promising! Do they all have similar mounting points, or is a little fabbin in order?
It would take some fabbing. Carl would need to cut you a new shroud that fits your radiator, but I would think the wiring you have in place for the current fans could be recycled.

It looks like you can unbolt that current shroud and take it to Carl for replicating purposes.
 

Greg

Make RME Rockcrawling Again!
Admin
If that is a big enough radiator and it flows enough air, it should stay decently cool. Do the fans only come on when the engine gets hot or do they run all the time? You might be able to lower the temp the fans come on, to get ahead of the overheating. Should just be a sensor at the engine.

I'd highly recommend swapping out the current thermostat for a low temp thermostat... it probably has a 185* thermostat, I'd try a 165-175* thermostat.

Also, add a bottle of WaterWetter to your cooling system... it breaks the surface tension of coolant and allows better heat transfer. - https://www.redlineoil.com/waterwetter

Do you know what carb is on it now, 2 or 4 barrel? Most carbs are terrible offroad. I'd honestly try a Holley Truck Avenger carb, they're build for offroading. You can get factory refurb carbs from Holley for "cheap" .... but they're not in stock at the moment. - https://www.holley.com/products/fue...actory_refurbished_carburetors/parts/FR-90670

New, they're like $700... :oops: At that point, I'd work on adding TBI.

To deal with vaporlock and if you keep the carb, I'd suggest adding an inline electric fuel pump. Put it close to the gas tank and as low as possible, 7-12 PSI should be plenty. You'll need a pressure regulator as well, to lower it to 4-5 PSI. I'd put the regulator as close to the carb as possible, so the fuel pressure
 

Cody

Random Quote Generator
Supporting Member
Location
East Stabbington
I guess I don't know enough about carbs to know if that one would make it run reasonably well at different altitudes and going up hills... If so, that's a cheaper solution, but I don't want to throw 250 at it only to find out it's still finicky everywhere but my driveway
 

Greg

Make RME Rockcrawling Again!
Admin
I guess I don't know enough about carbs to know if that one would make it run reasonably well at different altitudes and going up hills... If so, that's a cheaper solution, but I don't want to throw 250 at it only to find out it's still finicky everywhere but my driveway

It would run better on rough offroad trails, but EFI is the only way your engine will compensate for big elevation changes.
 
Hated the edelbrock on my CJ, Holley truck avenger was worth every penny. It ran better out of the box than the Edelbrock ever did with hours of tuning, jet swapping, Fidelf**kery and witch craft.
 

spaggyroe

Man Flu Survivor
Location
Lehi
I've got a mark viii fan I can make you a deal on. Carl made that slick shroud for nates bronco
Can confirm... The mark VIII fan is a beefcake and is superior to the taurus fan. It's the largest electric fan that would fit in my Bronco (and it barely fits, and that's only because of the custom shroud). I've had 2 instances now where the taurus fan wasn't enough but the mark VIII fan was. YMMV

There are a million ways to control an electric fan. I used an HF-125 controller from autocoolguy.com

Also, check your timing. Retarded timing can cause things to heat up.
 

xjtony

Well-Known Member
Location
Grantsville, Ut
100% on the timing. Quadrajets are know to be decent carbs for off-road due to the center float bowl. They are spreadbore though and would require an adapter.
 

lhracing

Well-Known Member
Location
Layton, UT
I have a friend that struggled with overheating issues with a V8 powered YJ, typically at higher speeds. He tried several different radiators and fans but nothing fixed the problem. The problem ended up being a simple fix, the lower radiator hose did not have a spring in it and would collapse restricting the water flow. He put a spring in the hose and no more overheating.
 
Top