Before removing the head I would put a laser temp gauge on the head and check several points to see if there are any hot points and compare the 2 heads. I found the laser temp gauge such a handy tool and they are not expensive anymore. I found that the temp gauge and thermostat where buggered on an old fairlane was reading 105c on the gauge in the car and with the laser on the thermostat and the temp sender it was actually 73c, new gauge and thermostat no more overheating problems.

Hi Treeve,

Hmm perhaps I should have continued on the path to pulling the heads off. I had the inlet and exhaust manifolds off and started thinking about rocker value clearances did some research and thought if I get this wrong things could go from bad to worse. When I had the inlet manifold off I could see the tell tale rusty color in the water jacket this also made me think the head gasket was ok.

I know the radiator was badly blocked so maybe that was the problem and they just used a different type of gasket when the engine was built. To my knowledge from speaking to the previous owner and the original builder the heads haven't been off since the engine was built (gasket tags are the same color as the block). The original owner had no problems with over heating.

You make a very valid point regarding the location of the temp sender, it is located on the passenger side of the block at the front of the inlet manifold (Edelbrock Performer RPM). The suspected reversed gasket is on the drivers side bank. Therefore if I am getting water flow past the temp gauge I am getting a false reading. I ran this theory past both mechanics and they said it wouldn't matter if i had a flow problem in the block it would over heat regardless.

So in summary still a bit confused, but you are right the only way to be sure is pull the heads off which I reckon is probably a job for a mechanic. The theory is easy but practice is often very different particularly when getting clearances right.

Thanks for your thoughts Treeve

Oh yeah thats a really good point never thought of that. Thanks

A little different tack - your temperatures don't sound like anything to worry about based on your description so far. But, it may pay to check your timing and make sure it's where it needs to be and is not retarded. Also, if you have vacuum advance on your distributor (probably not) be sure it's hooked up to a manifold source of vacuum. You don't want ported vacuum advance - that's a 60's era pollution control device.

Insufficient timing advance is a major contributor to engine overheating - especially around town and at low speeds.

I do need to check the timing just need to find the timing gun but that was something that has been suggested. On the vac advance front the dizzy does have vacuum advance and it is feed from the carby which is a holley. I recently replaced the tube for this as it was old and didn't fit tightly.

Thanks

OK - Holleys have different vacuum sources depending on the model. You want to hook it up to a vacuum source that comes from below the throttle blades and not above. Basically just make sure it's pulling a strong vacuum signal when idling by pulling the hose off the carb and making sure there is good suction.

A ported vacuum source is from above the throttle blade and has a low vacuum signal at idle but it will increase at steady throttle as the throttle is opened and airflow increases. OK for the highway but doesn't do much at idle or low speed.

I have an old Corvette and factory was ported vacuum advance - switching it to manifold vacuum outlet off the Holley dropped it's water temperature when running around town by probably 15 - 20 degrees. It was a startling difference. Good luck.

Ok thats very interesting see the picture below. You will notice there is a small black pipe coming off the carby on the right hand side this is the vacuum advance pipe does this look right to you.

Thanks Andrew

That larger black hose coming off of the right side, rear area of the carb is usually for a PVC setup or valve cover brearther - something like that. The full time vacuum source you should hook to your distributor is under the front bowl, coming out at an angle and currently capped.

Not completely sure but I think the upper port on the right front side of the carburetor and fuel bowl is a ported vacuum source. You can check it with the engine at hot idle and see if it reads the same as your manifold vacuum. I doubt that it does and I would not use that for the distributor.

Hope this helps a little

Agreed - in the photo you can see the end of the black cap sticking out a bit from under the primary fuel bowl - that's a manifold vacuum port. Just remove that black cap and connect the vacuum line which is currently connected to the timed / ported vacuum fitting on the side of the metering block. Don't forget to cap the timed / ported vacuum fitting on the carb that the vacuum hose is currently connected to. I believe both ports take 3/16" hose.

You'll find the idle speed will go up and the idle will most likely be a bit smoother after switching from ported / timed vacuum to manifold vacuum.

I used manifold vacuum for my connection and had to adjust the idle speed screws to drop the idle by about 200 RPM after I made the switch. Make sure the engine is fully warmed up and off fast idle before you make any idle speed and/or mixture adjustments.

I checked a Holley diagram and confirmed the upper port on the primary metering block is a timed / ported vacuum source.

Dan and Brian thanks guys for you input looks like I have some testing to do on the weekend. Will be interesting to see what I find out.

Thanks again Andrew

Good luck. No promises, but since you have vacuum advance there's a good chance changing it over to manifold vacuum could make a noticeable difference in engine temps in traffic, at idle and slow to moderate speeds. It's an easy to do change also. If your engine is a bit weak and lumpy at idle, as Cycleguy55 mentioned it will also smooth that out a little due to the greater timing advance and make normal starts from a stop a bit easier.

[IMG]http://s24.postimg.org/9jp75fc5t/IMG_0519.jpg[/IMG]

This is a photo of a Windsor head (buggered), plus two head gaskets. One gasket is upside down so you can see the difference.

Hope this helps you a bit.


Cheers
Dave

[IMG]http://s24.postimg.org/xxbzwphsh/IMG_0517.jpg[/IMG]

hello Andrew i had a similliar problem on my big block cobra tried everything,
shrouds/ fans/ e waterpump/oil cooler each time cost money car never boiled
but i new something was not right took me 5 years to figure out .
dont drive the car very often and yep engine builder put head gasket on backwards,
i bought new set of gaskets then sat them on top of rocker covers and looked where
the tags were proud around outside of the head compared to the new ones sitting on top and you could tell without pulling the heads that passenger side was wrong now it never gets hot at all . so try and see before pulling heads it was really easy to spot in the end on the bib block anyway.
chris

hello Andrew i had a similliar problem on my big block cobra tried everything,
shrouds/ fans/ e waterpump/oil cooler each time cost money car never boiled
but i new something was not right took me 5 years to figure out .
dont drive the car very often and yep engine builder put head gasket on backwards,
i bought new set of gaskets then sat them on top of rocker covers and looked where
the tags were proud around outside of the head compared to the new ones sitting on top and you could tell without pulling the heads that passenger side was wrong now it never gets hot at all . so try and see before pulling heads it was really easy to spot in the end on the bib block anyway.
chris

Well the temp test was interesting found about 30 degrees difference on the drivers side head at the back of the heads (this is the side I suspect the gasket is the wrong way around) but not much difference at the front of the heads. %/

So decent road test time drove it to work in the morning cool light traffic. So the temp gauge barely moved off the "0" of 180 F, crept up a smidge at the lights but not much. Next was the real test the drive home in the traffic outside temp was about 20 ish degress again not very hot. I did how ever sit in heavy traffic doing about 20-40 km/h for about 20 mins. Thermo fan on the temp got up to just shade before the "2" of the 210 F mark and stayed there (thankgod). Once I cleared the traffic and started moving again temp came back down to just above 180 F. So all good so far drove around in it most odf the weekend with no problems still no a particularly hot day. next big test is wait for a hot day and go for a drive and cross my fingers.

snakesaway

I put the gauge temp sender at the rear of the intake manifold at some stage and found the gauge read low. Very little heat regardless of driving. Moved the sender back to the usual place (front right) and temp was all back to normal.

Geof

The main problem with the temperature sender is it needs to be submerged in water. I have seen many overheating problems where the water was so low that it didn't register on the gauge. Or the customer has driven the car, it's overheated, they saw it on the gauge, pressed on, it's then lost all it's water and the gauge reading went back down. So they think it's alright. Then 5 to 10 minutes later, the engine starts to seize and the paint is melting of the block. The worst scenario, is that all the fluid leaks overnight, you then drive away with no water in the engine, the gauge doesn't register until it's to late. So what I've done is fit a airplane head temp gauge. It is a washer that has 2 bimetallic wires about 5 inches long and you screw the washer under the spark plug or a head bolt. As it heat up it sends a weak voltage signal to the gauge. No 12 volts needed. So if there is no water, it will still show the head temp. It's very accurate. It's a VDO gauge. It's really designed for air cooled engines. On my VW powered gyrocopter, I had one on either side cylinders.
JD

Andrew good to put a face to the name at the club meeting last night.

Trolling the forum for some info I spied this thread and thought I'd add some detail.

On the advice of my engine builder, Don Stafford, I've used a 90C water temp sender to trigger thermo fan on. Don's theory is these cars are generally under gunned for cooling so better the thermo comes on sooner rather than later.

I also had a thermo over-ride switch installed when the car was first wired to turn the fan on whenever I want. This may become somewhat redundant as I did previously have a high temp switch trigger but you never know.

I too plan on shrouding the radiator to maximise cooling air effect but currently the system has worked well for me.

Just some food for thought.

So how had you head gasket exploration gone?

Cheers

Hi Steve,

Yes it is good to put a face to your name as well. I currently have the termo switch for my Davies Craig fan set to about 85 C because that to was my theory better to have it run a bit more than not enough. The car was originally built with just a manual on/off switch for the fan so I have kept this in circuit just a precaution.

Getting the shroud back into the front of the nose around the radiator too I think has also helped. The temp comes back down quicker once I start moving after sitting at the lights.

After lots of research on the net and looking at gaskets, heads and blocks. I feel almost certain the gasket on the drivers side bank is backwards. As Rob has suggested he spoke to Don Stafford about this.

The car hasn't overheated since the new radiator core, water pump and fan. Its just the nagging thought I really should pull the heads and double check the head gasket to be 100% sure. So I spoke to Rob last night and he is busy for the next few weeks, once he has sorted out his current list of jobs He is going to help me pull the heads and check the gasket. we will do both sides and send the heads off to be crack tested being the car has overheated twice just to be sure.

Cheers