442olds

Ok here's the situation. My temp gage (senders in the head) reads high, real high 230~250F. So I bought a new sender, same problem. So I get out he infrared temp gun and start poking around. The end of the cylinder heads read around 190~220 depending on the status of the fans (on/off), water pump casting the same way along with the radiator hoses and the cylinder block. But when I check the area between the exhaust ports on the heads its sure enough exactly the temps the temp gage is reading.

The motor is a fresh rebuild of a stock engine (maybe 20,000 miles since installed) with k&n cold air intake, 1.6 roller rockers, coated headers, no cat, hypertech chip, 180F thermostat, and a flowmaster muffler. I have 202,000 miles or thereabouts on pretty much everything else. I have replaced the water pump recently with a rebuilt one but the problem didn't exist till recently and the pump has been on there since the rebuild. This problem started about 5000 miles ago. The raditor is newer but not as fresh. The previous 383 ran consistantly at 195F with the same radiator. The radiator doesn't appear to be the issue as it shows a good temp drop across the radiator.

I don't believe there to be any air pockets in the heads as the bleed line from teh back of the head has good flow and the temp issue occurs on both heads in the areas between the exhaust ports.

This is driving me nuts, the engine really doesn't seem to be overheated, the water isn't boiling, its just hot in 4 localized spots in the heads.

Any thoughts, ideas, things to trouble shoot would be greatly appreciated....I'm running out of ideas.

maverickmk

small blocks will always have higher temps in the middle of the heads because there a two exhaust ports next to one another - this may be what you are experiencing

442olds

I'm talking in the gaps between 1/3 5/7 2/4 6/8, not 3/5 and 4/6. The same area where the temp sender goes in. I've never experienced this much of a temp difference on any of my previous small blocks.

shoebox

IMHO, it's more likely you have some air in the system.

442olds

I'm open to the air in the system explanation, but on both heads at the lowest part of the head's water jacket, and this started recently. The system has been filled with water for sometime now. So where might the air have come from? There's no head gasket leaks, the system isn't filling with air or losing water to the oil.....air pockets just don't devolpe without something else causing it.

Injuneer

Is the radiator cap holding the pressure up where its supposed to be? Without adequate pressure on the coolant, its possible to get localized boiling on the hot spots in the head. Vapor will reduce heat transfer just as effectively as an air pocket. You also indicate the system has been "filled with water for some time now".... if you are not running an ethylene glycol mix, the boiling point will be even lower.

442olds

Caps good and the "water" is good to -20F. I always refer to it as water, bad habit I picked up from my mechanic father i guess. Any other suggestions.....

What about dirty injectors....like say they aren't spitting out the proper amount of fuel and its running lean? the fuel pump has 202000 miles on it, I haven't checked the fuel pressure yet?