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2000xj running hot

Not sure why you had such issues with heat boiling the gas in a 69 Camaro. I've run 800hp in a big block stroker duster, 500hp in a Sbc Chevelle. 450hp in a 454 in my 70 elcamino that ran a Holley 850 with 1 7/8 hooker headers with a 3 core copper/brass, no shroud and road and drag raced it and never had issues like that. I could sit in 100 degree dead stopped traffic and might break 200, maybe. I best on that thing hard. Redlined first and second 50% of the time it shifted. I daily drove that over 30 miles to work with 3.73 gears and a th400. If your Camaro is running that hot either it has some serious hp or a serious problem.

On the hood venting. I'm on the fence. The science is sound for not proping the hood, think a cowl hood off said Camaro or Chevelle, they pull in cold low pressure air from the bottom of the windshield. You would think with the airflow coming through the radiator would offset the possible air coming back into the engine compartment due to this low pressure zone, I don't know. What I do know, is, in my 70 Chevelle I went from a flat hood to a fiberglass cowl hood that was just open at the windshield and my front end was no longer "getting light" at over 120 mph. I assume because air was flowing through the cowl over the roof giving some down force. Odd as it also cut about 40lbs off the front of the car.
 
Boiling the fuel , or more correctly, vapor lock, is usually from exhaust/header heat....not engine/radiator heat....

And if you are using an engine mounted pump you are just asking for it.....as the suction side of the pump will flash to vapor very easily since it is at a lower pressure.

I had the same problem on my 76 firebird 69 428 HO combo......solution for the vapor lock was moving the fuel pump to an electric in the trunk. so it pushed fuel and kept it under pressure instead of sucking it forr the tank.
 
I've never ran anything but mechanical pumps, never had these issues in dozens of muscle cars I've built over the years. Some running deep into the 9's. A 76 firebird probably had 5/16 fuel line too, not 3/8 or larger like it needs to be. All of my muscle cars had headers and holleys. No problems restarting after hot laps at the strip or hard runs on the road course. The biggest issue I've seen is people lack the skills in properly tuning a carb. It's more than an idle screw and idle air mix screws. Anything with a big cam can benefit from 4 corner idle or drilled primary butterflies. Then tuning high/low speed bleeds, power valves, pump cams and nozzles, the list goes on.
 
Cherokeefan,

With all due respect. Cars that generate high HP within small engine compartments can generate high temperatures/heat that needs to be removed when driving in traffic. Cases in point; Ferrarri large fender vents, Herb Adams large fender vents on new big block sport car Contessa Coupe, etc. Large engines with reduced timing typically run cool. Also, small engines operating at 13,000+RPM develop high HP and high heat. Likewise, short runtime (9 second) drag racing cars do not induce long-term sustained heating problems. Matter of fact, on some high HP engines the cooling passages in the heads are filled or blocked. Because after shutdown, all kinds of cooling devices are used to remove the heat that would damage the engine as it thermally expands. High HP engines develop high heat.

For the record, I too love cars and have experience in racing; circle track & sportscar hill climbs. My BS in Mechanical Engineering, with a Minor in Internal Combustion Engines, has given me the knowledge to design engines from scratch and improve performance in racing/street applications.

Finally, I do respect your experience with your cars. However, for the record, your experience does not mirror my experience with many high HP cars; mine or clients.

Best regards,

CJR
 
A suggestion so the truck is drivable until you determine the main problem:

1. hookup your electric fan to a relay and rocker switch for manual on/off
2. turn on your electric fan after you start your engine to help cool the xj well before it gets too hot
 
Do not throw money at "snake oil" fixes, gadgets, or mods. Find and fix the issue(something's wrong), you guy's don't even live where it get's that hot. Were on a record setting year of the most days above *110 and I own 2 2000's that neither have a over-heating problem. My 325+HP stroker runs at *205 but can get to *210-215 when towing on a grade which isn't a issue or last's very long. My stock XJ only has a single core radiator in it and still does not have any sings of over-heating.

OP, you haven't mentioned anything about your transmission, but that's a major contributor of heat to the cooling system.
 
I also don't see one mention of using a IR meter to check inlet/outlet temps of everything along with reading the head/intake/exhaust temps ???
 
I've never ran anything but mechanical pumps, never had these issues in dozens of muscle cars I've built over the years. Some running deep into the 9's. A 76 firebird probably had 5/16 fuel line too, not 3/8 or larger like it needs to be. All of my muscle cars had headers and holleys. No problems restarting after hot laps at the strip or hard runs on the road course. The biggest issue I've seen is people lack the skills in properly tuning a carb. It's more than an idle screw and idle air mix screws. Anything with a big cam can benefit from 4 corner idle or drilled primary butterflies. Then tuning high/low speed bleeds, power valves, pump cams and nozzles, the list goes on.


Funny how simply putting the fuel pump in the back so it pushes fuel from the tank and keeps it pressurized vice sucking it from the tank 10 or more feet away......solved my problem...no carb or tuning issues before or after.

Science and real life agree....
 
Do not throw money at "snake oil" fixes, gadgets, or mods. Find and fix the issue(something's wrong), you guy's don't even live where it get's that hot. Were on a record setting year of the most days above *110 and I own 2 2000's that neither have a over-heating problem. My 325+HP stroker runs at *205 but can get to *210-215 when towing on a grade which isn't a issue or last's very long. My stock XJ only has a single core radiator in it and still does not have any sings of over-heating.

OP, you haven't mentioned anything about your transmission, but that's a major contributor of heat to the cooling system.

RCP I agree 100%. Troubleshoot and diagnose before spending a dime on replacing anything.

Don't know about you RCP but my XJ is my daily driver/only vehicle and I cannot afford, the time or money, to have it offline for one day. Just like adding a donut if a tire goes flat on the highway or a quick fix on the trail with a ratchet strap, I'm going to do what i need to do to get where I need to go timely and safely. That is why I suggested the manual fan switch which is a nice feature to have even if you don't have an overheating issue.

Speaking of the transmission causing excess heat, what is the best way you recommend to diagnose this as a possible problem?
 
RCP I agree 100%. Troubleshoot and diagnose before spending a dime on replacing anything.

Don't know about you RCP but my XJ is my daily driver/only vehicle and I cannot afford, the time or money, to have it offline for one day. Just like adding a donut if a tire goes flat on the highway or a quick fix on the trail with a ratchet strap, I'm going to do what i need to do to get where I need to go timely and safely. That is why I suggested the manual fan switch which is a nice feature to have even if you don't have an overheating issue.

Speaking of the transmission causing excess heat, what is the best way you recommend to diagnose this as a possible problem?

That's were the IR gauge really comes into play. You can check all the inlet/outlet points at every location to see how they are performing.
 
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