Iroc Z28

i got iroc z28 5.7l. it have LT4 cam. when i drive it for a bit the water start boiling. passenger side fan is working but the other one is not. im gonna change fan soon. so will it be fixed after than or there is something else to change too? im gonna change Temp sensor too. the guage is not accurate. its too slow. so i dont know it show me correct temperature or not. anyone know perfect aftermarket gauge? i want one. the main thing is about water boiling.

Your gage is not too slow. Your engine is overheating.

So, you gots one of these in it.

Who installed it?
What else have you done to the engine? The total list, please.
So, the main cooling fan isn’t working and you’re still driving it? Do you really expect that monster to be dissipating all the necessary heat with no air passing through the radiator?

First fix the cooling system.
Test the temp senor and the fan, and change whichever is bad.
Replace the stock radiator with one big enough to cool that monster you’ve made. You may want to consult a radiator manufacturer. They’ll be happy to help you.
Replace the T-stat. I wouldn’t trust that one anymore.
While you’re working on the car, check for any evidence of hydrocarbons in the coolant. Repeated overheating can cause failure of the head gasket(s) and/or warping of the head(s).

You might even consider an upgraded water pump.

Performance cams operate by allowing the cylinders to draw in more air/fuel mix, creating higher cylinder pressures and bigger bangs. Higher pressures and bigger bangs can be much hotter. Just the added pressures alone make the cylinders much hotter. You change one part of the engine, you need to be prepared to change more. Engine parts don’t operate in isolation from one another. They all need to be sufficient to support the others.

IIRC, the LT4 cam was for primarily for LT1 engines, which were on the 93-97 Camaro’s. If you have an IROC then you have 3rd gen Camaro and if you have a 3rd gen Camaro with 5.7L, you have the L98, which is not an LT1. I wouldn’t have chosen that cam for a TPI 350.

You might want to consider electric fans and an electric water pump.

If the engine overheats very quickly from a cold start you may have a bad thermostat.

Only one fan will run when the engine temp exceeds a certain temperature. WIth the A/C compressor running both fans should operate.

There’s a lot of missing detail which could affect any advice offered.

Temp sensor? Which one are you changing; the one for the gauge, the one for the engine management system, or the one for the cooling fan? You need to be sure of which sensor you’re buying and the purpose behind it.

There are so many things that could be causing this… The cam isn’t all that big and should’t cause overheating even in a 305 V8 BUT is it timed correctly? Retarded cam timing can stress the cooling system as can over-advanced ignition timing.

Is the radiator clean? - dirty or clogged rads will overheat. Is there oil gunk in the overflow bottle? - blown head gasket. Bad fan sensor, bad fan relay, bad water pump, clogged water passages in the block. What ELSE has been done to the engine? Does it still have factory fuel injection? Stock chip or aftermarket? Have you swapped the FI for a carb? Different heads? What? More info, please.

i think timeing is correct maybe water pump is bad. never change water pump its almost 135000 km on it. i just change cam. everything else almost factory original

i order new temp gauge sending unit nd fan too. so ill try those both if not than maybe ill put new water pump too

The lift and duration of the LT4 cam is not that radical to effect the engine’s running temperature much, if any.

The gauge and it’s sending unit have nothing to do with causing the overheating. Fix that first, which is most likely thermostat, or a clogged radiator, or weak water pump.

Could you have installed the thermostat upside down.

With the radiator cap off is there good flow, showing that the coolant if getting circulated properly.

What year is this Z28.


You say “the water starts boiling”. What exactly do you mean? A bad head gasket can make the coolant bubble in the overflow tank.

From your posts it comes across that your mechanical skills are not very deep. Maybe you need to just pay a pro to diagnose and fix the problem rather than throw parts at it.

+1 to ok4450’s post.
You’re just guessing at parts. You’ll more than likely spend a fortune and never get the problem resolved. You need someone with the knowledge and equipment to diagnose the problem. You’ll save a ton of money in the long run, and perhaps even prevent destruction of the motor from repeated overheating.

I agree with ok4450 and the same mountainbike. But if it makes you feel better that you figured it out, have at it, keep throwing parts and money at it. You might, even hit the right part eventually.