Although my new fans keep the engine temp very steady, I do note that my amp gauge is jumpy at highway speeds, which tells me the fans are turning on and off...this troubles me as I don't think they should have to do that.

My working theory is that the thermostat in the top hose sees regular mini-surges of 200 deg coolant at highway speeds. While the system keeps a steady temperature overall, this makes the fans cut on and off.

The shroud doesn't have flaps that can open during highway speeds, so I think it's not getting quite enough airflow to keep the coolant coming out of the block below 200 deg. I could add some openings and flaps...or, I think switching to the 190 on/170 off thermstat in the bottom hose would likely stop this, because a thermostat in the bottom hose wouldn't be exposed to coolant coming straight out of the block, but rather coolant coming out of the radiator which is probably of more uniform temperature at highway speeds - i.e. the fans wouldn't turn on at all at highway speeds, but at stop lights or in traffic the fans would still do their job because the coolant coming out of the radiator would have larger temp fluxes.

Anyway, since the fans only turn on occasionally in traffic, I'm seeing more heat soak; so I'm going to have to (finally) fabricate that carb heat shield I've been thinking about...I got less heat soak with the belt drive fan since it was going all the time. Ugh. Makes me want to go back to the belt fan and add that shroud I never built.... but I worked so hard on the electric fans...I'll tweak the system a bit more before I give up....I still owe you guys a picture.

bg

Never heard of that type of a problem........
My fans never come on at hi-way speeds. The air dam shoves so much air through the radiator they don't have to. I also have the temp switch screwed in to the top tank which are standard tank bosses in 1974.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Yes, I think it's not getting enough airflow; that's why some of the fan shrouds have extra apertures above and below the fans, with rubber flaps over them. At highway speeds air can flow through, but when the fans are sucking, the flaps pull shut so the fans get proper suction...

Here is a pic of the final install.

http://s785.photobucket.com/user/67dart ... e.jpg.html

I've been designing a heat shield for the dual Webers for some time, but my buddies' CNC has been down for the past 8 months. I'll ping him again now that my heat soak is back with a vengence. I may install something crude for now, just to see if it helps. The DD and factory rear-half exhaust manifolds are a lot of cast iron and build up a lot of heat sitting in traffic. I suppose it didn't help that I jet hotted them black - the most emmissive color possible (but I really love the chrysler red/black motif).

I'm sure if I go back to the mechanical fan and add a badly needed shroud that would help a ton. I was seeing some heat soak issues when stuck in traffic on hot summer days anyway (without a shroud or air dam).

I think a heat shield is inevitably a good idea.

BG

What part of the country do you live?
Chrysler was on to something when they designed them. It sure helped stop the heat soak of the carb along with the electric fans for cool down stops heat soak cold! The fans usually kick on for a few minutes after I shut the engine off on hot days. I would make a prototype heat shield out of light gauge aluminum and use it for a template for your machinist.

Your installation looks very neat. After running the lower temp switches, I really prefer the GM 205/210 switch. It keeps the fans off 95% of the time and allows the air flow to control the temps very nicely. In the summer months the air dam under the radiator is very nice.......I take it off in the winter as it is too efficient. To make the bracket bend up some aluminum at a 120 degree angle and attach with 4 bolts. Then attach a sacrificial air dam that can be removed or replaced. I have made the dam out of 3/8 plywood as a test, then another out of the plastic found in the bottom of dog kennel then recently out of the plastic snow plow blade. You can whack a curb and it bends and does not break.

You can see the angle and the four mounting points by clicking on the red link below my name.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

BG, Your car is beautiful. I looked at all the photos you have posted, and anticipate great progress in every area as you get to it. I would love to see a photo or two of the entire car.

I would focus on the type of fan control you have, and its placement rather than change your fans or shrouds. Where is the sensor for the fan control currently placed? Your radiator looks large and efficient, so I suspect it cools the incoming hot water very quickly. I think the system would work better if the on and off settings for your fan control were further apart. I think hysteresis is the correct term. Also if you put it on the lower tank, the temp of the tank will be more stable. My fan is controlled by the ECU, which gets its signal from the temp sensor in the head, and is set to come on at 200 and off at 185. It seems to run at normal times without cycling too much. I put a 180 thermostat in the engine last year, but think I will go back to a 195.

I think your engine will run better at the higher tempts. I know the heat soak is a problem regardless of what temp the engine operates at. The carb shield is a terrific addition, as well as shielding the fuel lines in some way. Yours are laying right against the thermostat housing. There are some who think heating the fuel makes for higher efficiency, but I think it also contributes to the heat soak problem these engines are "blessed" with.

Another consideration is getting the hot air out of the engine compartment. The design of the body and inner fenders on these Mopars creates a very cramped engine compartment, with little room for air flow around the engine. There should be some way to get that hot exhaust system heat out of there. I wrapped my exhaust with heat wrap tape and then painted that black with high heat silicone paint. My heat shield is not pretty, but wraps all the way down around the exhaust pipes to keep the heat moving down and away from the fuel system.

I am not recommending that you cut your hood, but the Shelby Daytona back in the early 60's had the radiator in its own compartment that exhausted out through the hood in front of the engine. It looks kind of ugly, I would never go that far. But before you get too far into the body work on this car, maybe you will be clever enough to think up a way to get air go to flow out through the side of the inner fenders and out of the engine bay. I think an electric fan to assist this might be a reasonable addition as well. The later Shelby Cobra exhausted heat through large, direct from the engine compartment vents in the sides of the fenders, behind the wheels. I went with the BMW vents when designing mine, and they are just too small to do much, and the upper, inner fenders have too much junk on them which gets in the way of air flow.

In order to make this work you would have to cut the inner fender and fabricate a duct between the inner and out fender and a large vent of some kind. I looked at every available commercial OEM fixture, and aftermarket fixture I could find. Looking back, I would do something larger. Any opening out of the engine compartment will also allow road grime and junk in, so you must consider that. Those wheel throw up an enormous amount of stuff trying to get in and dirty up your beautiful engine compartment. Even the existing holes for the shocks let in a lot of road grime. As an added aside I do have plastic inner fenders in my car, taken from a 1979 Chrysler New Yorker parts car, which helps in this regard.

Some street rod guys run the heater hoses outside the inner fenders, mostly for aesthetics, but that would keep some of the heat out from under the hood.

I would like to hear what your thoughts are on this.

Sam

PS, What does BG stand for. Are you Barry Gibb? Barry Grant?

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Thanks for the kudos on my car, the engine compartment looks better than the rest of the car, but I'm focusing on the engine/drive train/suspension before I get to the interior and body work.

I live in SF Bay area, it's been like 65-70 degrees lately...we need rain!!!

OK, so I built a heat shield out of light aluminum and it seems to help the carbs ward off the heat...

See: http://s785.photobucket.com/user/67dart ... d.jpg.html

BUT now, the engine compartment gets really hot! I guess I didn't appreciate how little the electric fans circulate air for the engine compartment; they're very efficient, perhaps too much so given the Dart engine compartment's poor air flow. My downpipes are also wrapped with header wrap and siliconed, but it's way too hot in there with the electric fans; the heat shield is reflecting the heat back to the manifolds etc and it's literally baking in there. Also, my TEMP gauge is the same (cool level) at highway speeds, but in traffic it goes up higher than it was doing before (not overheating, the fans are too efficient), the engine is still cooling fine, but the engine compartment is frickin on fire.

I pulled the electric fans for now and put the belt fan back on for comparision; I'll do that test when I drive her to work tomorrow. I started it up and I didn't realize how much the old fan circulates air, it really sucks (in a good way). The old fan was this one: http://www.summitracing.com/parts/der-19118/overview/ It really pulls a ton of air through the engine compartment, even at idle. I didn't appreciate how bad the airflow is in the Dart engine compartment, and how much my old fan was doing to push massive amounts of air through there. The electric fans are nice, but I believe my old fan was better in my application. Anyway, I'll know this week when I'm stuck in traffic.

Hopefully the mechanical fan and the heat shield will solve my heat soak issue, if not, I may well go for the air dam and possibly the extra ventilation you were suggesting. With the old fan, I was fine without the heat shield except when stuck in traffic for more than say 10 minutes. So, now with the heat shield, I'm hoping that's enough. If I stay with the old fan, I will have to fabricate a shroud, those SS fan blades are thin and very sharp.

It took me like 10 hours of hard work (mostly cause I had to straighten/reweld my power steering bracket) to get that electric setup in there so nice and cleanly....but it only took me 20 minutes to pull it out and swap back the old fan. There's something to be said for simplicity.

Thanks everyone for all your input. Good stuff.

BG

These fuel lines aren't the issue. I realize they're next to the thermostat housing, but they're SS and insulated rubber. When I first installed the rebuild I had plain old steel lines and those were a problem. Also, the Webers can't handle (despite what people say) 8-9 psi that a mechanical fuel pump puts out, they tend to flood. I had to put a Holley pressure regulator to get the pressure down to 3-4 psi - no more flooding issues and even at full throttle the carbs have all the fuel they need. I love these Webers, when I nail it on the on ramp, and it kicks down into second gear, they sound like a quadrajet or a thermoquad kicking in...

BTW, I don't run a mechanical fuel pump any longer, electric and it works great. I think it's a Mr. Gasket, $25. The trick is the mounts are really like jello so it's whisper quiet, and using an emergency inertia cutoff switch (Ford type, see: http://www.summitracing.com/parts/sum-890145/overview/, very easy to wire up).

BG

of the make shift heat shield...

http://s785.photobucket.com/user/67dart ... a.jpg.html

For what it is worth, My BMW 328 has a mechanical, clutched fan, and an electric fan which comes on when the AC is on, and when the engine goes beyond a preset temp. Overheating kills the aluminum head of a BMW so you would think they feel this is the best system. The temp gauge stays pegged right dead in the middle at all times. The manual says if the gauge goes above the middle, shut the engine off and have the car towed. Well, it's not a Dart is it.

I think you are on to something with your conclusion that the engine bay gets too hot because of the electric fan. I have a 16" electric fan, and my engine bay has been too hot for quite some time. I never connected those two ideas, thinking the cause was the turbo. I am thinking a small electric fan on the driver's side fender might move air out of the engine bay effectively. Something to think about. Keep the thoughts coming.

Sam

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Thanks so much, yes, I was considering an auxilliary electric fan to blow on the carbs; any info on these? I've not seen any. I can't fit electric and standard fan - the slant is too long. My SS blade fan is 18" diameter, so it spans the entire radiator's height and most of it's width (23 3/4 inches). When I was considering radiators, I wanted to make sure I had plenty of cooling power for the slant, but I never considered the engine compartment and how much airflow it gets...do you have any pics of fender cut outs and various airflow augmentations? I don't like cutting the hood, but I'd consider an intake if my carbs needed the extra cooling.

If the old fan plus heat shield ends up being enough (I won't really know until one of those 90 degree days in San Jose where I'm stuck in traffic) then I'm pretty much done, but might still add the air dam like Ted has for extra air.

I'll post my results with the old fan and heat shield next weekend; I'm sure to be stuck in traffic with the new year getting in full swing this week. Supposedly the economy is going to really pick up this year as well; although a good thing, that means more traffic!

BG

Here is a pic of my Dart on the flatbed when the engine blew...

http://s785.photobucket.com/user/67dart ... f.jpg.html

It came with 13" rims, but I upgraded to 14" rims/ '67 hubcaps until I eventually go to 15" wider rims, Cragars or Ralleye's.

This car was made in CA and lived it's life in CA, so the underneath is nearly like new, and the sheet metal is very straight. Only one front fender has some rust through on the lower portion, 'cause pine needles and gunk built up and were never taken out. The interior was pretty good considering it's age and it's black (aborbs more heat). I have it torn out currently pending fixing windshield and rear window leaks, etc. That all comes after the suspension work. Give me at least a few years.

The guy who owned it before me primed it gray, but not a good job, it'll all have to be stripped off before doing it correctly. It was originally that forest green color. I plan on painting it some sort of metallic teal so its still metallic green as the paint code indicates, but not the ugly original metallic green.

BG

OK, the votes are in, my SL6 really likes the belt driven fan way better than the electric fans.

This was essentially because, although the electric fan setup did a great job of cooling the engine, it did not do much of anything to keep the engine bay temperature down. It was cooking in there. The SS blade aftermarket fan, pulls an amazing amount of air through the engine compartment even at idle. Now with the heat shield, my car seems way happier. I haven't been stuck in traffic yet, but I'm not seeing any heat soak issues at all, like I did with the electric setup (even with the heat shield it was bad).

So, I'll have to fabricate some kind of shroud so I don't cut my fingers off on those sharp SS blades...again, this is the fan I'm using, really pulls air well. http://www.summitracing.com/parts/der-19118/overview/

Here are a few more pics of my makeshift heatshield process.

http://s785.photobucket.com/user/67dart ... 9.jpg.html

http://s785.photobucket.com/user/67dart ... 9.jpg.html

http://s785.photobucket.com/user/67dart ... c.jpg.html

http://s785.photobucket.com/user/67dart ... d.jpg.html

I used really thin aluminum sheet from the hardware store, screwed it to a piece of plywood (flat head screws in the areas to be cut out) after transferring the pattern and then used a jigsaw to cut it out. Took a few hours or so to fabricate. I made some of the holes too big in my original plans so "back filled" with some pieces of the sheet, you can see e.g. in the front of the carb where only a little slot was needed for an arm, and I had a big rectangle previously cut out...I'll someday make another one, but this is a great way to figure out exactly what apertures one needs, that is, bolt in place and cover the extra hole space with pieces, rivet them on, once removed you have exactly how much space and where figured out. Just reproduce on a new sheet... If anyone else is planning to try the dual 32/34 DFT Weber setup, I'll send them the final plans for the heat shield pattern when I have them (or the rough ones I have now), just PM me.

Again, here's with some extra pieces pop riveted on:
http://s785.photobucket.com/user/67dart ... a.jpg.html

http://s785.photobucket.com/user/67dart ... d.jpg.html

The heat shield isn't as shiny as the stock sheet, I ran the vibrating sander over it with 220 grit to remove all the scratches from when I ran the jigsaw over it. I could have masking taped the whole thing, drew the pattern on that, cut it out, then removed the tape, I may do that next time. Or, if my buddy's CNC is ever up, make a more solid one out of that sheet of 1/4" thick aluminum I gave him a year ago...still setting next to his CNC. I was planning on having him CNC the shield to about 1/8" thick and leave a beveled ridge of the 1/4" thickness around the perimeter and with ridges running inside the perimeter where theres room for strength (like a valve body of a tranny or whatever, so it's strong but thin where possible). I still think we'll get to it, but at least now I'll have better dimensions for it. Not sure how I'd do the vertical part, likely a bolt (or rivet) on section.

BG

Anyone need two 10" electric fans, the relay and circuit breaker? I just got them new for Christmas, but I'm motivated to sell...cheap.

Now that I'm back to my belt driven fan, I got some 2.5" wide aluminum stock (1/8" thick) and fabricated a fan shroud. Took about a half hour, as I already had holes/bolts for mounting to the radiator, just had to make four bends and cut it once (I had six feet, only needed part of that).

http://s785.photobucket.com/user/67dart ... 2.jpg.html

http://s785.photobucket.com/user/67dart ... a.jpg.html


BG