Thread: Hp drops when warmed up

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is there a perfect temp to run 350/carborated/hei/auto at? my motor seems to lose about 40/50 HP when warmed up.any ideas?

Engine compartment getting hot. Need to pull cooler air into the intake. Cold air box.

Originally Posted by plumpurpleplym

is there a perfect temp to run 350/carborated/hei/auto at? my motor seems to lose about 40/50 HP when warmed up.any ideas?

How are you coming up with your estimated loss of 40/50HP? Seat of the pants? Just asking, as that's a lot of power to be dropping if you're tuned right and everything is functioning right. Are you sure your HEI distributor is not breakingdown with heat?

Thermodynamically the hotter you run without detonation the better your efficiency and power. I would say a nominal 195F thermostat is right for most modern engines and your 350, and some OEM's run 205F to 210F to help get their CAFE numbers up.

What kind of car, and what are the temps before and after the horsepower loss?
As Mikej mentioned, underhood heat and nothing but hot air making it into the air cleaner doesn't do anything positive for the power output.....

aba-so-looootly on the seat of pants ? might be 15 0r 20.when I start cold she brakes the tires a little and barkes when she hits 2nd.when she runs for 2 min. wont burn out at all.

36 plymouth 5 window coupe,temp is fresh start not showing any temp on gauge runs stronger.2/3 min. running 150* seems to loose some power from line.does not seem to chang at all from 150-190

Originally Posted by plumpurpleplym

aba-so-looootly on the seat of pants ? might be 15 0r 20.when I start cold she brakes the tires a little and barkes when she hits 2nd.when she runs for 2 min. wont burn out at all.

I agree that underhood temps can cause all sorts of problems, but two minutes of warming time shouldn't be getting that hot, seems to me, and it sounds like it's pretty consistent. Could it be as simple as your carb jetting? Cold start, choke plate closed, rich mixture and good power; and two minutes later power loss, maybe as your choke plate opens and you lean out with unrestricted air flow? Just a thought - how do your plugs look?

plugs look fine.had carb jetted and set up by pro. I use the term loosly but he's supose to be the best in town.he also recurved dist. and removed vac. advance,timed to 13* with total of 38.not sure where he comes up with all the #'s but like I said he's highly rec.around here.

No vacuum advance? That seems strange for a street driven car.

You say it looses power, dose it stumble?? or just take right off???

Originally Posted by robot

No vacuum advance? That seems strange for a street driven car.

Good possibility that's where his problem lies

no stumble,just not as much power

Originally Posted by robot

No vacuum advance? That seems strange for a street driven car.

Originally Posted by NTFDAY

Good possibility that's where his problem lies

Help me understand why that would be temperature related? I'm leaning to mixture since it runs great immediately on cold start, but within one to two minutes and temps up to 150F it falls off. The only thing changing during that time is the choke unless the HEI is breaking down. What am I missing?

are you sure that your fuel lines are not getting heated as your car warms. that would cause your car to start vapor locking.