Thought I'd share my recent experience with vapor lock. I bought an old Chevy truck that would get up to about 215 degrees, then shut down with vapor lock, every time I drove it, even on the interstate with plenty of air moving through the grill... I also noticed after coasting to the side of the road and popping the hood open, the amount of heat under the hood was unbearable, forcing you to step back... First, I replaced everything in the cooling system, new radiator, new water pump, new thermostat, new fan clutch, and it still would get too hot and shut down... Then I tried insulating the fuel lines, blocked off the heat riser passages in the intake, and added a carburetor spacer, still got too hot... Then I started to notice a pattern where I could hear the fan clutch engage and start to pull more air through the radiator right before it would shut down at 215 degrees. So, I "recalibrated" the fan clutch by adjusting the little thermostatic clock spring on the front of the fan clutch. Only had to turn it like an 1/8 of an inch (think it was counterclockwise) and now the fan pulls much more air, but it still would get too hot and shut down... Then I did a little research and decided to check my vacuum advance... Then, the only changes I made were to switch the vacuum advance from a ported vacuum source to a manifold vacuum source, and adjusted the vacuum pot one and a half turns to maximize advance... That is what finally fixed it!!! Now the temperature gauge stays around 170-180 degrees even in traffic, in the hot south-east. My gas mileage got much better as well... Anyway, great videos!!

Just to get some of youse guyz tinkin', back in the 80's Mercedes used to run the fuel line up into the engine compartment, coil it about a dozen times around the cold side A/C line, and then on the the throttle body. So, if it was hot enough outside to turn on the A/C, presto you had cold gas going into the engine. Smart dudes them Germanz.

UTG is like an encyclopedia of motoring knowledge with a historical perspective like no other.

The information basically correct but it could have been a bit clearer. When fuel boils in the carb it's called percolation not vapor lock. Vapor lock is the inability to pump fuel in the vapor state. Vapor lock causes fuel starvation. Percolation occurs in the carb and causes flooding. Both are fuel problems caused by heat but they are very different. One is too lean the other too rich. Calling both of them vapor lock is going to confuse people.

My only experience with it was on my 74 VW super beetle. My friend and I pushed that car for miles and when my dad got me back to it the car started just fine. That’s when he told me about vapor lock… proving an 18 year old kid can learn from his dad.

I used the "eight dollar" cure on my '68 Fury VIP (318 2 bbl) by getting the same Wix fuel filter that would have gone on my '80 Cordoba (318 2bbl) and adding a return line that is hooked up to a tee at the tank. Also covered all my fuel lines under the hood with that slip on insulation from the carb to the filter, the factory fuel line down to the pump and also the return line from the filter down to the frame rail. Works great, no more problems after that.

You are far more informative than my ASE teacher was 20 years ago. You really are a wealth of knowledge!

My grandfather used to keep clothes pins on his line to draw heat out

One other thing about modern fuel… they actually CHANGE the boiling point of the fuel twice a year. They lower the boiling point (raise the equilibrium vapor pressure) in winter, allegedly to lower emissions by getting the fuel to vaporize better for clean combustion. Then they raise it in summer to prevent unburned fuel emissions from gas evaporation out of car gas tanks and gas station storage tanks. The result of that is that you are now more likely to get vapor lock on a warm day in winter than on a hot day in summer… and it’s really bad on cars that are rarely driven and can get all the way into late spring early summer and still have winter gas in the tank.

Two other things, though, one commenter had touched on one. Electric cooling fans on a timer and pressure. The cooling fans do double duty. They reduce the heat soak in both the cooling system and the fuel system after the engine is off. The pressure thing is kinda touched on, but not directly addressed on Bottle Rocket. Much like pressure in a cooling system keeps the water from boiling, so too will pressure help keep fuel from boiling. Having a high pressure fuel delivery system with a return style pressure regulator is ideal to reduce vapor lock.

I always liked watching the temperature gauge go up after shutting off the engine, and then restarting it after 15-20 minutes, and watching the temp gauge drop significantly as the water from the radiator which was able to cool down, circulates through the engine, dropping the temperature.

Allied forces during WW2 behind enemy lines in Africa(Long Range Desert Group - look it up) , used to,when they stopped, turn their trucks/jeeps into the wind and lift up their bonnets (hoods) to get the latent cooling while taking a break.

I never heard of the clothes pin trick; but a trick i did learn is to crumple aluminum foil over the fuel line from pump to carb. It acts as a heat sink and cured my vapor lock issues.

15:02 I use to use a small Ford power steering cooler in line with the fuel line.

Workin on a Chevy 350, Ive been rebuilding the fuel system and that 3rd vent line caused so many headaches cause so many people just dont understand. You helped me understand way more. Love the channel. You have helped so much. Knowledge is greatest when it can be transfered

along time in the past i had a 49 ford pickup with vaporlock i found that puting 3 closepegs on the line near the fulepump fixed it

I use a plywood spacer under my quadrajet.. yes... Wood .. helped a lot with heat soak ..

The fuel injection returnless systems have this topic covered. The method is to vary fuel pump speed based on fuel rail temp. At higher fuel rail temp, fuel pump output is increased, increasing rail pressure, raising boiling point to prevent vapor lock.

I swear to the almighty, your video might have just helped me figure out an issue I've been stumped on for 6 months now. I've got this 91 Camaro that was molested the worst I've ever seen a third gen butchered. I'll try and keep it short, It was gutted of it's electronics and had a 305 someone put effort into slapped with a Edelbrock 1406 on top, ran great without issue for the first 3 weeks into owning it. Throws a rod bearing, pretty sure the external balance flywheel they put on the neutral balanced engine was the culprit. They ran an inline pump mounted on the driver rear floor pan with specs saying it pumped 5psi to a regulator by the brake master cylinder with no return. I decided to spend the last 2 years restoring it, I put a crate motor 350 mounted to a T-5 and decided to put a posi/disk 4th gen rear end in it, figured I'd replace the fuel tank/sender/in tank pump while I'm at it so I have the option to convert it back to it's factory fuel injection. So I converted it from the dead head returnless to a return system with a quality regulator. Got it together, first 4-5 test runs ran perfectly,they were only 20 mins at most. First time I drove it longer about 45 mins in it's like it's starving for fuel as I'm cruising down the highway, pull over pressure gauge say 0, can hear the pump and see fuel in the inline filter, adjust it back to 5psi runs fine for another hour. I start it the next day it's pegging 14psi blowing fuel out of everywhere on the carburetor. Just a pack pressure held same thing 45 minutes in does it and I repeat this cycle several times, trying different things they'll finally I just say screw it and put a second regulator in line, It reduced the erratic fuel pressure but it still happens enough to be a problem. All right now realize I have about 3 ft of rubber hose probably two of it wrapping around the carburetor sitting on top of a GM 350 stove basically cooking the fuel past the second regulator and probably about another foot between the two regulators and the return line that sits within 4 in of an exhaust header. I am now thinking my problem is the heat soaking into the rubber fuel line is the reason why with fixed spring rate set at the regulators the fuel pressure is All over the place without rhyme or reason. I'm going to try rerouting with Hardline avoiding the engine as much as possible and see if that fixes it running one regulator and if it does I'll have to come back with a big fat thank you for making this video.

Vapor lock is a pain.

Late 70’s and early 80’s Datsun Z’s with the inline 6 had a small fan on the side of the engine with plastic ducting that would turn on after the engine was shut off. It would kick on maybe 30 seconds after the key is shut off and would run for a few minutes. The air would come from the cooler side of the engine and blow over the fuel rail, to keep it cool for that first few minutes after the key was shut off, so that you could restart the car if you only stopped for a minute. Even some recirculating fuel systems had vapor lock issues.

My Dad was a woodworker and had a guy buying carb spacers made of oak, as he said they were the best insulators available.

Clothes pins was my father’s cure for vapor lock. I have seen tin foil wrapped around the fuel line also.

Yep, low fuel pressure and high temperature is the cause. The condition was first noticed on old gravity fed carburetors like the old Tractors, & Model A's T's and all it required to cure was the lowly clothes pin.

A few ideas that help in this issue of vapor lock: like your brake lines'coils next to the master cylinder: Coil/ spiral your steel fuel line.. this technique disperses heat (remember why the brake lines are like that by the master cylinder, & very close to the exhaust manifold/ header: to disperse heat: boiled brake lines= no brakes. Another idea: coil up/ spiral up your fuel line away from headers/ exhaust piping & have it inside a metal coffee can: if need being on certain occasions now u can fill that coffee can with ice. Another idea: use a brand new "universal trans cooler" plumb your fuel lines through that, then to fuel pressure regulator/ carb, & so forth. Header wrap exhaust stuff, & coolant hoses if need being. You'd be surprised how well a combination of these techniques work well.

Having delt with vapor lock over many times, ive went to a home made bypass fuel system using an electric fuel pump. Lots of examples to look up and copy, I route the lines away from the heat as much as possible, it works great when properly setup to keep your good ol simple carb system going on the dishwater crap fuel we have to run, I used non eth gas when I can but its just not available everywhere.

EEEEEK! A thermo- turd! Where's my wooden stakes and silver bullet's. Don't think I ever came across one that didn't have a warped body.😆

Remember the 80s action movies when the car would explode for a mile. Now a days you can barely get the gas to ignite. So our cars and movies suck now. How about chuck norris vs vapor lock..how would that play out?

This is foundational Learning, and I love it, UTG. 🥝✔️ Vapor Lock is a Whole lotta Nothing with the proper tools Chrysler and AMC devised. Love especially the Hot Engine Idle Compensators and the very rare Bleed back system used on Trip Master equiped Variable Venturi and Cop car 2150E Motor Craft 5.8 liter HO engines, 1980-85, and 85 to 91 Squad cars. Simarly, Ford Australia used the Mopar ThermoQuad in Cleveland's from 76-85, and some AMCs, Ford and GM overseas in Australia sorted the 4bbl problems out in the 80s, and won at the European Touring car races with 350 hp Q jets on 5 liter racing Holdens which took down BMW and used some really tricky parts most people no longer understand.

I had vapor lock issues in both my 351 Ford V-8's. One was in a 1976 Ford E250 van and the other was in my 26 ft. Shamrock boat. The inboard engine in the boat wouldn't start when I needed it most. In the Atlantic Ocean with a sudden drop in temps on a hot day and a BAD summer storm with really heavy winds and seas heading right for us.

There’s actually a technical service bulletin for vapor lock on the Jeep 4.0. It is mostly a problem with the 2000 and later engines that had iron exhaust manifolds and the two pre-cats up close to the manifold below the engine, rather than back under the floor. The “fix” is insulating socks over the fuel injectors (especially #3). It definerky helped on my 2000 Cherokee. My daughter’s 99 Cherokee never had the problem, since it had the older exhaust design.

I ran a external fuel pump on my jeep till a few hot days during the summer caused vapor lock. I finally got the correct stock intank pump for it.

This guy has learned me more in the last 3 hours then any asshole wanting my money when they see my old k10 come beating the earth when I pull into the shop. I'm new to the SBC game and I can tell you Everyone needs a uncle tony.

I've had Vapor lock in a fuel injected car. a 98 (catfish) Camaro. It was a very hot day. 112 Degrees in the shade. After driving 45 mins and then sitting in traffic, i then pulled into a place to get some take-out for my dinner. Came back out, and the car wouldn't start. Siting there parked after that long drive on such a hot day, it became heat-soaked and the fuel in the fuel rails boiled off. The fuel pump was making a very weird noise too. I was told that the fuel boiling in the rail, being a closed system, the increased pressure pushed fuel backward through the fuel pump and the fuel pump and the entire fuel system filled with vapor. The fuel pump failed about two weeks later. I'm guessing it became damaged in some way from this.

Living in Florida, this is a constant struggle. Recently caved in and added an electric pump to my friend’s 1939 Ford Woody. Was sick and tired of him getting stuck. Flathead pumps are right on top of the engine, in the worst spot for percolation.

My dad had an old pontiac that vapor locked frequently. He fixed it by clipping a bunch od spring type wooden cloths pins to the metal gas line between the fuel pump and carb. Every time a mechanic saw them they would always ask about the cloths pins!😂

Man I love the knowledge you share on these videos!! Thank you UTG!!!

And people told me I was wasting money with an inline pump and a return style bypass regulator on a carbureted engine..."you can just deadhead it! you don't need all that junk!" HA!

Watching your videos is always time well spent. I'm always learning something. Thanks, Uncle Tony.

Can’t tell you how much I enjoyed this video. Very new to working on a ‘78 Ford 400 and this helped me understand a lot about these two issues. Already subscribed, thanks a ton Sir.

Its interesting that your 4.0 has a non return fuel system. My 89, 94, and 95 4.0s all have a fuel return to the tank. Must be one of the many small things they changed in 97. Actually, that would make it NOT a problem with early fuel injection systems, just later ones.

Tony, your video on vapor lock reminded me of another problem we had in the 70's, IIRC was related, to heat and bad quality gas. If you need a topic to discuss for a future video, consider doing one regarding "Diesling" and what was needed to fix the issue.

Finally! Some solid tips on fixin yo ride, clothespin I knew it ,if I kept watching this channel I would finally get some real solid advice, perseverance paid off lol

Good info to know and keep in mind, Tony. Thanks

Thank you. Great teacher. I'm learning, and will pass on. To my son. Have a great summer.

These are great tips. I live in hot central Florida and get periodic vapor lock in my Paxton supercharged built 302. I will look at adding some of these ideas. THANKS TONY!!! June 29, 2023.

Ive actually seen a vapor lock issue on a Jeep 4.0 before. the technician put heat wrap on the fuel rail. seemed to do the trick

My new favorite channel. And all necause I experienced Vapor Lock for the first time this past 4th of July.

Another Great Video UTG. On the fuel pumps, one of the old tricks we used to do in this high altitude in Idaho was to use a mechanical fuel pump for a vehicle that calls for Air Conditioning. The AC cars and trucks used that 3rd nipple. If it didn't have it, then we would have to run the line back to the tank. Again, good stuff guys!

we actually just saw that return filter trick used on a 49 chevy for the first time the other day. a friend solved his vapor lock issue that way, i thought it was a good move. nice video tony look forward to more

Love ur knowledge UTG, Thanks a lot for sharing.

Tony I use header wrap on my all Jeep fuel rails. This does help with the heat..

I always wondered why some people wou have clothes pegs on the fuel lines, 😮 but haven't seen them since I started playing with engines in the 84's thanks for sharing, all the best to you and your loved ones

Yes your correct. Thank You Tony. 👍

Same problem with my slant six Volare, which would stall after running for a bit then restart when it sat for a few minutes. The heat riser was stuck open roasting the carburetor. I wired it shut while trying to find a replacement which of course makes it cold-blooded while it warms up.

At last, something in common with a UTG segment. My 1979 Ford F100 with 351M would vapor lock. Wooden clothes pins on the fuel line worked.

Had problems on my 74C10 truck with a holley not starting after running and stopping. Got a phenolic spacer and it helped out a bunch.

Great video. I have had this problem as well being a Mopar guy with older vehicles. I changed my steel fuel line with aluminum line and problem was solved. Good time to change to 3/8 line to keep big hp engines from starvation at higher rpm's. Insulating the line going into the engine compartment all the way to the carb also helps a bunch. Also changed to an electric fuel pump so as to eliminate the heat that a mechanical pump can hold. Keep up the great video's, thank you

Thanks UT. I currently use a rubber fuel line wrapped with heat foil from the fuel pump to the carb. I guess I'll convert back to steel on your advice.

I ran into the heat soak/vapor lock issue with my 4L in my jeep off roading on hot summer days. my fix was hood louvers, and it fixed the problem 100% BUT some aftermarket off road companies sell a foil back shaped insulation to go over the fuel rail to help keep the fuel cool.

Those early 4.0 jeeps with returnless fuel systems had a tsb back in the day where we would put a heat shield under the rail to protect it from exhaust heat to help with vapor lock/bucking and stalling

Great video! Just going to point out that ethonal has been around a lot longer in the corn growing states, mandated in Minnesota in the 90s. I first saw "gasohol" in the late 70s on a trip to Iowa. Most of the coop gas stations had it in farm towns because the corn lobby was pushing it heavily. Car companies were gearing up for it by the early 80s. I remember Ford issued a service bulletin for the variable venturi carburetors, you drill one hole and replaced the diafram that worked the venturi. It also boils at 160 degrees, which is hotter than other components in gasoline since they started making gasoline. I don't care for the political aspects of the stuff but having used it in all sorts of things for years and looking at it objectively, it gets blamed for more problems than it causes, like a ballast resister.

I had a 59 Chevy apache that would vapor lock and close pins on the fuel line between the pump and carb fixed it. This was back in the early 80s in Dallas

You are my go to man with any regards I have with my 73 440 roadrunner, and as I live in Australia, good advice isn’t available here. If u were my neighbor 🤔………….. ude be sick of the sight of me 😂😂😂😂. 🙌🙌🙌. Keep up the great work UT. Regards, Dave Australia.

UT - Good video - it makes me remember something from 42 years ago... My Dad bought a new 1980 Chevy Caprice wagon - I was 15 years old at the time. It had a 267 V8, which was a Chevy smog engine in those days. In '81, to prepair for a long road trip, my Dad replaced the oil and filters. (I always helped my Dad work on cars, even back then). We found that the carburator looked like a Q-Jet, but there were no secondaries in the carb - just metal over where the secondary barrels would be. It was actually just a two barrel carb. (GM probably did this to manufacture one intake manifold). They even put steel caps over the mixture adustment screws. If I am full of whooey about this, let me know - but that's the way I remember it 42 years ago. Anyway, during our road trip to Colorado, we drove up Pike's Peak. The car was acting like it was running out of gas while climbing the mountain. At the time, my Dad thought it was caused by the high altitude (which it was). But after whatching this video, I think it was vapor lock. Here is my theory : The engine was laboring to pull the car up the mountain. The air was thin so it was running lean and generating lot of heat. Since the Q-Jet style carburator didn't have secondaries, there was no air flow at the back of the fuel bowl to cool the bowl. This caused vapor lock and the car behaved like it was running out of gas. Mystery solved ? Probably. Thanks UT.

On point, UT. Ford 300 6 EFI from 87-95 some models have an electric blower that directs air flow to the rail and injectors, and they run higher fuel pressure than the 5.0/5.8 and 7.5, to combat vapor lock on those models. High altitude can factor in also.

Have a 51 Chrysler. Got vapor lock like crazy on 80-90 degree days in traffic. Replaced all steel fuel lines with Copper lines, also made a coil of it from the pump to the carb that sits near the fan for added cooling. Never had an issue again.

I just discussed this video with my ‘86 Grand Wagoneer. It got all choked up in reply…🤣

The Toyota straight six 2F engine has a the carb sitting above the interlinked intake and exhaust manifold. They added a fan to blow on the carb for 10 minutes after you turn off the engine. There is also a bakelite spacer at the base of carb that is more heat resistant than aluminum.

My 1973 Datsun 240Z was mostly stock when I got it. It had the dealer-installed vapor-lock update equipment on it: - An electric pusher pump n front of the fuel tank, to pressurize the fuel line and mechanical pump on the engine. - An upgraded mechanical fuel pump - A heat shield between the intake and exhaust manifolds - Aluminum coated fiberglass wrapping on the fuel lines from the mechanical pump to the 2 carburetors.

Ive used the 3 nipple filter suggested by UTG and also a small electric pusher pump at the fuel tank. Get rid of the mechanical pump, and reroute the fuel line to carb to the firewall. Keeps it away from exhaust maniolds altogether.

had it happen in my 90s car, during a hot day, car would start then act like it was dying/stall, had to just rev the gas a few times and it fixed it

Passing by it , Uncle Tony

Also for Jeeps there's a company or two that sell heat shields and insulation jackets for the fuel rail. They seem to help.

I've owned three carbureted cars, and *knock on wood* I only experienced vapor lock on one of them. My first car was an 81 horizon with the Volkswagen 1.7 that was given to me and that thing would vapor lock like crazy. It ran very hot and when I'd restart it on a hot day it would only make it about 50 ft before it would die and not start up again. I occasionally got to the point where I actually would remove the fuel filter and suck fuel on through to get it to be able to pump. I never experienced vapor lock with my 79 225 Volare or my 68 318 Barracuda.

Your injury videos are the best. 65 barracuda seats 45lbs each.. Sheeez

A thermoquad would still be a problem on intake systems that use exhaust crossovers that meter localized egr components, and hot air chokes. That’s why GM didn’t use them. It was still cooler leaving the bowl between the throttles, abs just isolate the whole thing with fat gaskets and tin plates.

My 54 international pickup thats stock wanted to vapor lock but seven wooden clothespins on the fuel line pre-vent it from doing such, mostly when I'm above 7000 ft

My sisters friends brother in law had a vapour lock so he ran the vapour lock to the carby on a seperate line... Long story short... He finnished up getting 250 mpg... on a long run !!! 🤔🙄😁

Blocking off the heat riser passages when possible helps big time. Completely filling them is even better.

My 81 gmc Caballero started vapor locking on me this weekend so i got a ducting tube from O'Reilly's ran it from in front of the radiator to the carburetor to feed it cool fresh air and it started running so much better and vapor lock stopped. Im running a 305 with a 2 barrel Rochester.

Carb spacer and a pint of kerosene, that worked best for me after the fuel changes from the 90s until 2015 when I had my 400 Ltd. Never had any issues.

Tony..you nailed it man and great job as a small scale carb. rebuilder I have said the same to guys that i do carbs with man as far as the heat/gas goes for the regular guy/no money here in east tn. the blame the carb. usually the quad or edelbrock are the worse,even with a insulater block,holley...not as bad....but the gas is the culprit..if you dig end why the thermoquad was designed after the quad was due to the gas and g.m. had pull back then to get the gas companys to put whatever it was in the gas to make it not to that...unlike today...beleive me doing carbs for people just dont understand what you stated and you nailed it man.....I tell people to at least run a air gap intake....the plastic/wood insulators sometimes work...but depending on the carb.....you are spot on.

You taught me how to fix my vapor lock. I drive a 62 impala that I’m restoring and restored 4 years ago. I would drive it in the summer and my car would shut off in the Wendy’s drive thru and everywhere in between. I thought I was running out of gas. Anyways you sir taught me how to fix mine. Routed a return line with a fuel filter that has 3rd nipple. I routed my return line to the filler neck. Drilled a hole into the filler neck then cleaned it out. Everyone else drills a hole into the gas tank, I’m too lazy I didn’t go that route. Well it’s worked well for me. I’ve been driving in 2 summers since. I live in south texas and drive my Lowrider every single day. It gets 110 degrees here sometimes. Anyways since you taught me how to fix it I’ve never had problems. Close to my manifold I covered my fuel lines with heat shield. Car has never ever stalled since. I’ve been driving long distance to car shows with the engine on for 4+ hours at a time. No vapor lock

Chrysler also used the 3rd nipple filters on their fwd platform cars in the late 70s and 80s because of under hood heat issues.

One thing to note is as pressure increases more energy is required to turn a liquid to a gas. Thats why a lot of older efi systems and especially carbs are susceptible to vapor lock. An old school efi such as that 4L runs somewhere around 40 psi max. Mopar tbi was around 15 psi but is a return style. Modern mopars and the like are dead headed fuel systems but are around 60 psi. Main thing to do is isolate from heat and keep fuel moving. Only times my old rides have vapor lock is if it sits for 30 min after driving it will boil and cause a longer crank. No big deal for me. Very good info as usual 👍

Great work sir Thank you

I used a fuel filter with the 3 nipples on my carbureted 83 5.0 Mustang and even on 100+ degree days driving in heavy traffic I never had a vapor lock in the 15 years I owned it.

THX Tony😊

I tried the Wix filter with the return line. 1975 Ford Fe. All it did was mess up my fuel pressure and leaned out the carb. Need to find another fix.

Uncle Tony in the 1970’s my mum sold a cleaning product here in australia called “Swipe” it was a copy of “Amway” and i swear that bottle on your left with the red cap looks like an old swipe/Amway dishwashing detergent bottle……!!! Surely not - couldn’t last that long….??!!

Good content, thanks for the video

Wood clothes pin, huh, who would have thought? Thank for the tips.

Dodge neons don't have a return in the fuel system and I've never had an issue with vapor lock but we add a return line to our circle track cars at the end of the fuel rail as a precaution.

In a trippy sort of way people 100 Years from now will watch this to see how to get an old car to run. It’s like a video encyclopedia of knowledge. Crazy to think ahead like that

I have a 62 galaxie I should un hook carburetor spacer with heater hose running through it.

The b&b line honed was 900.00 Nelson stock car racing started and tuned it for 150 bucks

Vapor lock helped to keep Auto zone (was Auto Shack) in business for years. From people not knowing what it was and just firing the old parts cannon at their engines and cars.. 😂 until someone that did know walks up and said "well there's yer problem right there Vern."

My old scooter had a air breather on the gas cap that you had to open. If you didn't shed run what's in the carb and thats it

I suspect the reason the recirculating fuel filter works so well is because the constant flow of fuel over the pump is enough to keep it cool.