LocostUSA.com

Two things I would check,
1. You might have a high pressure area where the radiator exhausts open on top of the pontoons. Try a temporary air dam at the leading edge of the exhaust air opening.

2. Assuming that the radiators are sealed around the edges we had a discussion on another topic that the air entering the area in front of the radiator needs to expand into the area so it slows down to pass through the radiator.

Take a look at this url;
http://www.ch601.org/resources/cooling_systems2.htm

The article is concerned with aircraft but the principles are the same. I read where the P-51 aircraft actually got additional thrust from the heated air after they redesigned the original inefficient radiator ducting.

I built a rear engined car many years ago and the radiator in the nose of the car was laying down at a steeper angle than yours and I never had any overheating even with no radiator fan. I had the air outlet slot on the hood about 2/3 the way back at a low pressure point. Of course my engine wasn't as big as yours but it was the original Renault radiator that the donor car used. I did have a blower on it so it was putting out more hp than the original setup.

As a last resort you might try plumbing the two radiators in series.


[edit]I found the page where I had posted a bunch of links to streamlining etc here;

viewtopic.php?f=23&t=4406&start=75

Look at the 2nd and 5th posts on that page. Mine of course .

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"My junk is organized. At least is was when I put it wherever it is." -olrowdy
Completed building GSXR1000 CMC7, "Locouki"
Website: http://projekt.com/locouki/

A quick note before I catch a plane in Charlotte. I'll be out-of-pocket for a few days without internet access. Great suggestions so far please continue!

I can't wait to try them on for size.

Dick

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when a chevy engine is mounted in your average sedan or pick-up, it sits at an angle pointing up at the front, look at all inlet manifolds and you will see the carb flange is tilted compared to the block, on standard installations the engine is tilted by this amount, up at the front.

if, as i asked previously, the engine is level in the frame, meaning the pan rails, read on, if it points up at the front, ignor the rest.

there is an area at the rear of the cylinder heads that will trap air. this is due to the casting design enabling the head to be installed on either bank so a water gallery is cast in for the cross-over in the manifold on both ends of the head.

generally there is no air (or steam) trapped here in normal applications due to the tilt of the stock motor, however, if the engine is level or indeed tilted down at the front, air (or steam) will be trapped in this location on both heads,

prior to the thermostat opening, this air can expand, forcing water out of the system but not the air, the rear of the heads is the hotest end, so heats up first.

the standard mod is to tap the manifold on both sides where the water ports in the head are and install pipes to vent the air to the thermostat housing above the thermostat.

i have seen this occure on many performance applications.

so to my original question, is the engine level?

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Thanks to each of you on Locost Builders.UK and Locost USA.com who offered suggestions for evaluating and correcting the overheating problem on the Mabaan build.

I’m back from a long weekend trip to Iowa and ready to attack the issue armed with the suggestions made by you all. I’m sure that through one or more adjustments drawn from those offered the issue can be solved.

To help organize my plan of attack I thought I’d list the suggestions here in one place for quick review. Perhaps in the future others may run into a similar situation and find the paraphrased information/suggestions provided here helpful as well.


AIR FLOW:
KB58, carguy123, Kartracer47 and olrowdy-01 offered suggestions for analyzing and increasing the effectiveness of airflow through the ducts and radiator cores including wool-tuft studies and cautions associated with rad angle, relative intake/exit dimensions, air direction diffusers as well as concerns about the debris screens.

Olrowdy-01 listed two suggestions for information and review: http://www.ch601.org/resources/cooling_systems2.htm and viewtopic.php?f=23&t=4406&start=75

I’ll be conducting airflow circulation studies. Thanks!


ENGINE BUILD[u]:
KB58 alerted me to the fact that if the engine is built “too tight” an overheating issue may occur.

Based upon the race engine experience of the builder I don’t see this as being a factor but thanks for the alert.


[u]RADIATOR BLEED TUBES:
Kartracer47 pointed out the need for bleed tubes from the rads to the higher components of the cooling system to eliminate the possibility of trapped steam pockets forming in the lower areas of the rads.

Currently I have bleed vales on each rad but neither of them is connected back to the surge tank. I installed them to drain-off trapped air during the initial filling of the cooling system. An open valve connection will be one of the first retrofits made. Thanks!


INNATE CHARACTERISTIC OF LT1 ENGINES AND LEVEL INSTALLATION: John Hennessy identified a potential problem when this engine is mounted in a level orientation (as is the case here) causing trapped air (steam) to form in the rear portion of the heads.

John’s suggestion of tapping into the rear section of the heads with a pressure release pipe or tube connected to the thermostat housing will be done. Thanks!


COOLANT FLOW:
Oldejack suggested and MYTF seconded his suggestion of running the rads in series rather than in parallel as they are now. He also suggested in-line flow restrictors to control time and velocity of the fluid as it passes different areas in the system guarding against possible unequal usage between the two rads. Doug68 provided two interesting and extensive reference sites dealing with coolant flow, rad and pipe differences and a convenient list of basic rules for reducing heat in performance engines.

http://www.gt40s.com/forum/gt40-tech-en ... tions.html

and

http://www.arrowheadradiator.com/14_rul ... obiles.htm

Gakes pointed out possible fluid flow issues caused by different configurations of hose connectors “T-type” vs. “Y-type” connectors and seconded the series arrangement.

Fred W B simply agreed with Series over parallel plumbing.

Hughpinder agreed with the parallel plumbing and suggested running W/O a thermostat in addition to suggesting the possible need for an auxiliary water pump to increase flow.

Interestingly, I debated with myself, series over parallel plumbing, and it seems that true to my history of choosing the wrong choice in a 50/50 proposition, went with parallel. Now with the preponderance of you believing that series would be better, it will be changed to series. Thanks!


CHECKS TO BE MADE: Ivan suggested checking temp differences between the rads to determine if flow is an issue.


Thanks to all who offered critique and possible solutions. Again, I’m confident that through one, or more likely multiple corrections, drawn from your experiences this problem will be alleviated on the Mabaan.

Thanks again,

Dick Bear

when i said about tapping the back of the heads, usually, you would drill and tap the flat area on the manifold flanges through to the water jacket in the head.

just a thought, is the expansion tank of sufficient volume for the capacity of the cooling system cos with all that pipe work it looks like the volume is quite high.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

concerning parallel or series, in a parallel system, the coolant will follow the path of least resistance, so may only circulate through one rad.

i do not recommend removing the thermostat, the restriction slows down the flow and allows the water/coolant to pick up more heat from the heads before leaving the engine, usually, removing the thermostat, is more a success by allowing trapped air to vent, if you do remove it then look for a suitable restrictor, these are available.

when the engine is running at low speeds, and consiquently the car, the air flow over the rads is less and the coolant pump is also running slowly, this seems like a recipe for overheating, consider running an electric coolant pump or driving the existing pump with an electric motor and a belt, this is very common and kits are available as a bolt on for your engine.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

Dick I have just been through this with my twin radiators and air was just a pain in the ass to get all out and ended up making an extra bleed valve at a new 'highest point' in the system. This gave me 4 bleeds in total, highest point on engine, 2 high rad caps and the new point close to the rads. My rads are way more vertical than yours therefore I had much higher points than you and each rad has a normal rad cap which were the second highest points but was still painful to get all air out and I had zero water flow unless every drop of air was expelled.

Many times there was evidence to suggest there was no air but still no or very little water flow so I had to continue to chase, reroute things and yet find more air. Even the way pipe elbows sit makes a difference (elbow sticking up high etc.).

I have to ask as others have, how are you getting rid of the air from the upper edges of your rads?

With airflow, whats the square patch in the lower bodywork directly under the rad? (Green in the pic below) I would be going for some air deflectors at the top edge of the rad air exit scoops too to help with pressure differential (blue in the pic below).

I've been pondering 2 things on your cooling system. First, it seems like there are too many places that air can escape you radiators, at least from the pictures (pg 3 or 4). I can see open air around both sides, and whatever that hole on the bottom is looks like it will become a suction point once you get some speed on the car. I would think sealing the areas on both sides of the radiator, and closing off that hole would be a good start to get air moving through the radiator. Second, I don't know that a simple fan on the back of the radiator is going to promote enough air flow, you may think about making a shroud for it as well, to get airflow through the entire core and not just the center section.

As an afterthought, you are also running an LT1, which have really bad water pumps. Even brand new water pumps can leak and create lots of headaches (nothing like having to buy a $300-400 "distributor" because of a water pump leak).

It may also help to better describe the overheating issue. When does it do it, how long can the car run before it overheats, does it do ok when cruising, etc.

O' it's been so long!

Following the 7,600 mile coast to coast to coast tour in the McBearen for the Prostate Cancer Foundation driving solo from Winston to Minneapolis to Seattle to LA to San Diego to Denver to St Louis to Knoxville and home in 21-days with the McBearen not missing a beat I went into the hospital on Sept. 8th to have a total knee replacement (not associated with the PCF Tour ) and then sat around the studio for the next several weeks going to PT and not much else in an effort to regain control and full movement of my new knee.

Obviously I had a lot of time to think, draw and amuse myself with possible solutions to the over heating issue on the Mabaan. Taking into account the many suggestions provided by members on the forum and trying to incorporate as many of those ideas as I could on two different designs all to now avail and after returning from California for the holidays I bit the bullet and ripped everything out of the side pods, ordered a two core, two pass single radiator and modified it, along with the fuel cell, to allow the radiator to fit neatly behind the cockpit and directly in front of the engine.



The 6-8 feet of plumbing shrunk suddenly to less than 2' total. I fitted it with high volume fan and shroud pushing cool air through the radiator towards the engine itself. NOW IT HOLDS A CONSTANT 180 - 200 degree temp with the fan switching on and off actuated by the temp sensor!!!!

Next I will modify (baffle) air flow from the side pods to the face of the fan/shroud to accommodate the hot humid summer weather in the SE to complete the systems design.

With tech inspections next month and the first track days at VIR and elsewhere coming up in May I'm on the down hill side for some track time this Spring, Summer and Fall!

This evening I installed the 6-point harness and still have to install mirrors, refit the back body panel, finish the nose cone and finesse the car through the NCDOT inspection for a title and street driving privileges.



Thanks to all of you who offered suggestions, comments and knowledge. Going to a single radiator and moving it (them) from the pods seemed to be the only way to address everyones' thoughts. And although I wasn't sure if I'd like it from an aesthetic stand point but after doing it, I think it looks fine.

Dick Bear

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Some updated photos

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Holy Headlights Batman!

Yo, Mr. Bear!
Yeah, what he said! Holy Guacamole, those are two amazing looking cars!!! The sheet metal work on the new one is just incredible!!! Well done X 2, Sir!
JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Pretty neat. Do they have mirrors incorporated into the backs of them? More info please!

_________________
-Keith

I know the head lights are a bit on the large side but because they are there primarily to pass DOT inspection and will, in most cases, be removed while on the track I wanted an all-inclusive module (bright, dim & turn signal).

I found these unit(s) from a strange source that may cause some of you to snicker, but I'll survive the moment. They are headlight fixtures from Myers ... the snow plow manufacturer. They meet my requirements for a self contained, sealed unit that can be treated as complete bolt-off pieces.

And to answer Acreguy's question, I won't be incorporating rearview mirrors into the back of the headlight units. I made the mountings so they can be easily disconnected for the track .... That is unless I'm fortunate enough to participate in a 12-hour event sometime. 12-hour and longer events are starting to emerge around the country complete with team drivers and pit stops. Hopefully I can take part in such an event sometime soon. Pretty exciting stuff!

Dick Bear

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Yesterday I placed the rear panel on the car for the first time since making several changes during the last 6-months to the internals correcting the over heating issues I had. I knew that taking the radiators from the pods and installing a single unit at mid-ship (between the cockpit and the engine) would require some refitting of the panel so my day was spend evaluating what needed to be done and I slowly began to make those adjustments.

It's not completely corrected at this point but I have confidence that with a bit more tweaking the large rear panel will once again slide into place as it had done before. The major change needed will be to form twin blisters to accommodate the upper-outside corners of the radiator (see red circle).

I'm still waiting on the NCDMV to return the documentation for registration, title and licensing. Hopefully that will arrive by the end of this week and we will add a new member of the 'street legal' club. I won't celebrate until the Custom 2011 classification VIN number is placed onto the Mabaan's frame by the Inspector. At that time... I surly will!

Dick Bear

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