[Healeys] over heat + misfire

[Reinhart Rosner]

Sam,
did your car have these problems all the time or is it new? My mechanic
always advised me to have some extra cooling installed (oil cooler, bigger
fan, additional electrical cooler) when I had overheating problems in my
100. As these occurred after some years of driving without any problems I
insisted on finding the new cause and not fight the symptom. 

Some search in the archives should bring up a lot of entries about
overheating. For instance our list member Tadek from Poland some time ago
compiled a list of possible causes on the 100:

1. Check the temperature gauge - is it functioning properly and reading
correct temperature?
2. Check the thermostat - is it operating properly, opening at the
designated temperature?
3. Try using a 180 or 160 deg thermostat, these cars originally did not use
190+ thermostats.
4. Is the coolant level proper?
5. Is the coolant a proper mix of antifreeze concentrate & water? Too much
antifreeze reduces the cooling efficiency of the coolant.
6. Is the Radiator cap a 4-7PSI cap?
7. Is the engine block/head clean? If not, redistrip/ chemistrip the block.
8. Is the radiator clean? Even if new, it could be blocked by debris from a
dirty block. A full stock radiator should empty in about 12 seconds.
9. If you changed to aluminum radiator, check it's capacity - is it not less
than the stock one?
10. If you have placed a fan in front of the radiator it may be blocking air
- try removing it
11. Are all air deflectors fitted?
12. Are the heat shields in place?
13. Check the exhaust manifold for cracks.
14. Check if the manifold is not loose.
15. It's a good idea to have your manifold ceramic coated - it prevents high
temperature radiating from the manifold.
16. Is the fan belt properly tight?
17. Is the water pump not defective?
18. Is the head gasket not cracked?
19. Is the head not cracked (the 100 heads are prone to cracking between
cylinder 2 & 3) You can check it by checking the compression on cylinders.
20. Has the head not been over shaved? If so, the water channels coming from
the block will not match the channels in the head - they run at an angle.
21. The distributor should be set to ~6-10 deg @600 RPM; 35-38 deg max @
~3000 rpm; Gap 0.015"
22. Are the carbs tuned properly?
23. The carbs are not set too lean?
24. Brake system checked? No brakes binding?
25. Is the oil pressure correct?

In an answer to his list I added the observations which I had in my 100:
When I had overheating problems with my 100 I additionally changed the
exhaust system to make sure nothing blocks gas flow.

Other suggestions I heard but did not check were too much sealant might
block passages and that the fuel pump getting too hot might cause problems
as well.

The real cause in my 100 was a combination of a faulty crankshaft bearing
and the rocker arms not moving as they should, which made the engine work
extra hard.

But begin with the easy things. Good luck

Reinhart


Reinhart Rosner
55 AH 10 BN1
Vienna - Austria