355 V8 Cooling options (yes I searched)

[Guy From Nowhere]

Morning all,

EQUIPMENT:
I have a Brocky black 308 V8 bored/stroked to 355. I run twin thermos on an HX V8 radiator. The engine runs on straight gas (VN heads). The thermos are mounted behind the radiator; i.e. they pull the air through the radiator, rather than push.

SITUATION:
1. During the winter months it has been perfect; this is obviously due to a lower ambient temperature. As soon as the heat got to 30 degrees plus I started to have overheating problems. According to the bloke who built the engine, it is designed to run at about 90 dgrees as this is the best temp for gas efficiency.

2. The radiator simply has a pressure cap and is designed to run up to temperatures of 120 degrees without boiling.

3. The engine runs coolant and the temp gauage is an electronic sender conected into the engine itself.

4. I found that the temp was fine if I were only doing 80 km/h and not pushing it up a hill. This pointed towards a flow restriction in my mind, but the radiator has recently been sweated apart, recored and reassembled (less than 1500 km ago). The engine was rebuilt approximately the same number of kms ago, and the impella was assessed as operating perfectly.

5. Wanting to get home, I took the rubber seal from the back of the bonnet off (this would allow a draft and therefore increase suction through the radiator). I also removed the spotlights on the front of the bullbar; these sat in front of the radiator. I then found that the temp dropped down about 15 to 20 degrees. I find it interesting that the lights would have this effect, as the bottom half of the radiator was unrestricted to air flow and the lights only took up approximately half of the surface area of the top (i.e. approximately 1/4 of the radiator).

6. Recently, we had high 30s (approx 38 degrees) and the temp still climbed to just under 100 degrees at 11 km/h.

7. The thermos were working at all times (I tested with paper on the opposite side of the radiator - they were definitely sucking and sucking hard).

QUESTIONS

1. Is this a normal issue, or should I be looking into this further; i.e. upgrading thermos etc? I ideally want to put my lights back on the bar.

2. In a similar thread, Chimboy mentioned that a shroud was required for rear mounted thermos, why is this? Is it still required with twin thermos?

3. Are there other options to keep the egnine cool; i.e. bonnet scoop to increase airflow, quarter panel gills to increase airflow?
(a) If a bonnet scoop would help, should it face front or rear - what are the pros and cons of each?

Cheers in advance dudes,
GFN

[Struth]

What car is this in?

Many a time refitting the cars standard radiator after adding an extra core will fix the problem, becuase that radiatir was designed to get good airflow in that car.

I had a Kingswood V8 radiator and when I measured it against my Hilux V6 radiator the hilux unit had more surface area.

Without a shroud the fans will draw air from the top, bottom and sides of the radiator, reducing the amount of air drawn through the actual radiator.

Also if the coolant is flowing too fast through the engine and hence too fast through the radiator it will have two effects, it will not draw as much heat from the engine and it will not dissipate enough heat through the radiator.

[stitch_all4x4]

id sugest you try some 40 below my friend i've run it in my own 333ci and in a previous 383ci helps drop temp
http://cgi.ebay.com/ebaymotors/PRO-BLEN ... 0392235534" onclick="window.open(this.href);return false;

[gingerbreadman]

you are not far off being at a reasonable temp. the fact that its sufficient in winter but not quite good enough in summer is telling me your close.

now if its heating up at idle or very slow speeds when your using your fan than your fan is not sufficient and a shroud is 99% of the time required ..sometimes a big 16 inch spal fan on a big 4 core radiator will be fine without a shroud but its rare. even the spals have a shroud although its about as small as shrouds get. here is a picture to illustrate...



now adversely if your having problems at cruise speed than it can be either timing too advanced or retarded , or that your radiator seals are not in good shape and air is finding a path of less resistance around your radiator rather than through it.

of course it can also be in both cases that your radiator is just not up to the task. in most v8 powered cars i find 3 core is the minimum and 4 core preferable. dont know if you have ever seen corvette, camaro etc radiators but they are BIg and WIDE . be sure to cross check your gauge is accurate as well with another gauge or infa red heat gun.

in all my v8,s they will run 160f in winter if i choose that thermostat and even cooler if i allowed it . in summer 180 f is about there best in the brissy heat so the difference between summer and winter is quite a difference i find running a 160 stat in summer and a 180 stat in winter works best for me.



like you said going up a hill will always produce a rise in temp. 2 reasons and thats your generally loosing speed and airflow and secondly your engine is working twice as hard producing more heat so there is no ways around that.

if i was you i would go through all those things from size of your fan, shrouds, seals, timing, fan off on highway, fan on at low speeds only ( fan on at cruise speed actually restricts airflow) , be sure to drill a 1/8 hole in the flat part of your thermostat to allow air to pass when filling ,timing and advance curve if you have an adjustable distributor ....another left field thing that can happen is if your lower radiator hose is in bad shape it can collapse at cruise speed so some come with a spring inside.if its old might be worth a look but to be honest i think yours is an airflow/radiator issue.

[Guy From Nowhere]

STRUTH:
1. sadly the engine is in my 1982 WB and not my 4x4.

GINGERBREADMAN:
1. I have removed the thermostat from it for the moment to eliminate it as variable. I also tested this in water with a laboratory grade thermometer, and the result is a perfectly functioning thermostat designed to open at 70 degrees C.

2. I can leave it idling all day and it will not overheat. It does not lose water, so there is no pressure moving from the cyclinders into the water (i.e. bad juju crack).

3. Hoses are brand new.

4. Radiator has the right amount of cores, 4 I am lead to believe (the radiator was supplied by the bloke who built the engine, as were the thermos).

5. I reckon the timing would be in order considering it was just rebuilt and tested. Nothing feels out of whack.

6. Gauge has been check with a second gauge by me and an infra red heat thingo by the dudes who intalled the engine for me.

I am a little stumped - perhaps the radiator still has issues even though it was recored and rebuilt (i.e. I might benefit from a new one...thoughts?).

[hulsty]

Whats the engine tune and timing like?

[gingerbreadman]

STRUTH:
1. sadly the engine is in my 1982 WB and not my 4x4.

GINGERBREADMAN:
1. I have removed the thermostat from it for the moment to eliminate it as variable. I also tested this in water with a laboratory grade thermometer, and the result is a perfectly functioning thermostat designed to open at 70 degrees C.

2. I can leave it idling all day and it will not overheat. It does not lose water, so there is no pressure moving from the cyclinders into the water (i.e. bad juju crack).

3. Hoses are brand new.

4. Radiator has the right amount of cores, 4 I am lead to believe (the radiator was supplied by the bloke who built the engine, as were the thermos).

5. I reckon the timing would be in order considering it was just rebuilt and tested. Nothing feels out of whack.

6. Gauge has been check with a second gauge by me and an infra red heat thingo by the dudes who intalled the engine for me.

I am a little stumped - perhaps the radiator still has issues even though it was recored and rebuilt (i.e. I might benefit from a new one...thoughts?).

sounds like your covering all bases . the fact that it does not overheat in the driveway is a good sign and takes your fan right out of the equation as the fan only has benefits at low or dead stop.... so lets look at your seals around your radiator. I would make sure every part including the top and both sides, even the bottom to the radiator support are all sealed with foam .The more air you can get going through that radiator the better.And at cruise speed leave that fan OFF ...other than that look for a lean mixture and a badly set up advance curve.

its a shame the big dollar item is the radiator but you might have to bite the bullet in the end. unless it had a full re-core and your positive it actually got it then there might be blanked tubes or tubes half blocked .

[brad 93hilux]

id sugest you try some 40 below my friend i've run it in my own 333ci and in a previous 383ci helps drop temp
http://cgi.ebay.com/ebaymotors/PRO-BLEN ... 0392235534" onclick="window.open(this.href);return false;

They can't ship that to Australia any way, not sure why... I've tried

[Guy From Nowhere]

Whats the engine tune and timing like?

The engine tune and timing was done with the rebuld about 1500 km ago. I can't say I have noticed any difference since then.

GINGERBREADMAN:
You may have just struck the answer to the question. The HX radiator was not modified for the WB, the mounts were. In doing this they used some box steel lengths. This means there is a gap! I will getin in there with some plastic, foam and no more-gaps and shape me up a shroud of sorts!

Given everything else is so close, I bet this is the reason. So simple. I guess it pays to nut these things out here on outers.

Cheers all, I will let you know how I go this weekend,
GFN

[turbo gu]

STRUTH:
1. sadly the engine is in my 1982 WB and not my 4x4.

GINGERBREADMAN:
1. I have removed the thermostat from it for the moment to eliminate it as variable. I also tested this in water with a laboratory grade thermometer, and the result is a perfectly functioning thermostat designed to open at 70 degrees C.

2. I can leave it idling all day and it will not overheat. It does not lose water, so there is no pressure moving from the cyclinders into the water (i.e. bad juju crack).

3. Hoses are brand new.

4. Radiator has the right amount of cores, 4 I am lead to believe (the radiator was supplied by the bloke who built the engine, as were the thermos).

5. I reckon the timing would be in order considering it was just rebuilt and tested. Nothing feels out of whack.

6. Gauge has been check with a second gauge by me and an infra red heat thingo by the dudes who intalled the engine for me.

I am a little stumped - perhaps the radiator still has issues even though it was recored and rebuilt (i.e. I might benefit from a new one...thoughts?).

1st thing put the thermostat back in. 308 will actually run hotter if its removed.

2nd from memory a WB radiator is a bit wider than a HX one. Might be worth trying a WB one in it. Also try putting an original fan and shroud back on.

[MightyMouse]

Yep - removing the thermostat can actually be a problem in itself.

The rate at which coolant flows through the engine needs to be controlled to allow it to pick up the engines heat - too fast a flow and issues can occur.

Cavitation / circulation issues can also be an issue - fitting a transparent tube section to the block discharge is sometimes done so you can see if its bubble free flow or not.

Just background info........

[Guy From Nowhere]

I just spoke to the mechanic that built it and the head conversion does not allow for the original style fan to be run; only themos are to be used according to him.

I will chuck the thermostat back in though.

Cheers,
GFN

[gingerbreadman]

if you go to bunnings they sell this foam thats used in aircon and other aplications. i think you find it in the insulation aisle. its about 50mm wide and comes in a square shape about 1metre long.... much like a suare snake. Not sure if that would work for you but i have used it before to seal down the side of radiators. Its squishy so forms to almost any shape.

[Guy From Nowhere]

Cheers Gingerbreadman,
I will investigate Bunnings on Saturday morning.

[Vman]

I cannot see why a normal clutch fan or flex fan cannot be used because of the heads?? I mean even the efi 304's run clutch fans.

Anyway. If you remove the thermostat completely that could be causing the water to flow too fast and not cool down. You should at least put the housing back in with the thermostat function removed to restrict flow - just while trying to trouble shoot.

My old 308 which had a some work done to it always ran hot. We tried everything we could to fix it. In the end everyone put it down to thin water jackets. Mind you while it appeared to run hotter than normal it was about the same as yours and never really caused any dramas except on the extreme days where it would creap past the point of recovery.

I know it sounds stupid but it may pay to check the inlet manifold gaskets that join the heads. They can be put on backwards which restricts water flow and can cause over heating. The comment your mechanic makes about the head v fan is concerning and it may be worth checking if you cant find a simple solution.

[Guy From Nowhere]

I cannot see why a normal clutch fan or flex fan cannot be used because of the heads?? I mean even the efi 304's run clutch fans.

Anyway. If you remove the thermostat completely that could be causing the water to flow too fast and not cool down. You should at least put the housing back in with the thermostat function removed to restrict flow - just while trying to trouble shoot.

My old 308 which had a some work done to it always ran hot. We tried everything we could to fix it. In the end everyone put it down to thin water jackets. Mind you while it appeared to run hotter than normal it was about the same as yours and never really caused any dramas except on the extreme days where it would creap past the point of recovery.

I know it sounds stupid but it may pay to check the inlet manifold gaskets that join the heads. They can be put on backwards which restricts water flow and can cause over heating. The comment your mechanic makes about the head v fan is concerning and it may be worth checking if you cant find a simple solution.

The reason a fan cannot be mounted is due to the way that the gas inlet was manufactured. It was done out of necessity to fit everything under the bonnet. I don't know if it was on oversight, or done on purpose, but it is a tad annoying. I can't really complain though, as I got it secondhand.