any ideas as to why i would have flat spots between 3000 and 4000 RPM??

it was the head gasket but still doesn't explain over heating,

cheers to ernie (bige) on this 1 for hooking me up so fast with the parts i needed

i replaced everything, flushed the radiator and now its running better then ever and not overheating , i have no idea why it overheated in the first place

cheers

We don,t have a result yet but i,m with bige 100% no brainer head gasket

Quote:

I stand corrected =)

Datsun started fitting thermostats with the small hole in them in 1969, and by 1979 were in every Datsun. A-series will not overheat if you take the thermostat out. Also, running plain water with no coolant/antifreeze mix will not cause overheating either.

maddatter1, I think you're on to something with the thermostat, but replace it, don't remove it from the equation too quickly! Smaller motors rely on the thermostat, especially with higher anti-freeze mixes. Next time you replace your thermostat, drill a small hole in the outer housing. For some odd reason this improves the thermostat life and prevents 'sticking'.

I know these are silly things to mention, but I noticed how quickly they can cause your temp. to shoot up, and even if they don't help you, they might count for advice...

1 - Check if your overflow hose is properly connected.
.
2 - Electric fan's wire polarity.
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3 - Fan belt loose. This is an easy one to miss!
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4 - Antifreeze/water ratio weak (especially in conjuction with a disconnected overflow!)
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5 - I've also noted that a bigger radiator mounted to an unmodfied body also heats up a LOT quicker.

Something you could check into is a product to clean out the corrosion in your water system. Usually a small bottle added to your coolent. This helped me quite a bit by making 2 (almost unnoticible) leaks evident.

Link for some advice/direction if it is the head gasket:
http://datsun1200.com/modules/mediawi ... tle=Changing_Head_Gasket.

i'll make the call,blown head gasket, 100% sure.no mucking around.

lol brendon,cheers

Overheating does not cause burnt valves -- not in the A-series engines -- so no worries.

Burnt valves usually are caused by overtight valves, or by carboned valves -- the engine starts running rough and rather than fix it the owner continues to drive it, burning the valves.

On the other hand, when my radiator cracked on the freeway (100 kph) last September it overheated and within about 90 seconds warped the cylinder head. It wouldn't start and when I removed the plugs, water came out.

Im just worried I may have burnt the valves , ill try it after work, I know I can fix it myself, the problem is getting the ute home, my mate is good with cares and he has said he will be able to start it to drive home, I don't Evan want to entertain what he had said?