73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Hutch998 on April 18, 2016, 12:01:10 am
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I've got a 86' k20 with a 355, and I've been noticing for a good while that it gets crazy hot, relatively fast. I'm doing a compression test tomorrow, but what would the cut off be for 87 (regular grade) gas? My friend who builds 350's regularly said that if I'm using pump gas with a high compression (supposedly above 10:1) and cast iron heads, would make my engine grenade in no time. The engine has an offroad oriented cam, with flat top notched pistons, and its bored .30 over. Is that a bad combo? I know for super high compression, you need the better gas, but at 4.4 mpg I need to make sure it needs it before paying $2.30+ a gallon.. I can't tell you the temp because there's no gauge, which is also not good.
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If you have no temperature gauge, how do you know it is getting "crazy hot?"
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Do you know the combustion chamber size? head gasket thickness compression height of the pistons? lot of things affect compression ratio, if you have a set of rebuilder pistons in it with 64cc chambers and the block wasn't decked you might wind up with only 8 to 1 cr.
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I can tell its getting really hot because in 0 degree weather, I let it idle for about 30 minutes, and when I came out, the outer fender was almost untouchable, and the inner one burnt me. I may not be a world class mechanic, but that to me is way too hot. I have had other trucks that get no where near as hot and they did have temp gauges. I'll get back to you guys later today with definitive compression ratio.
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The cooling fan should circulate air into and through the engine compartment and flush it out the bottom. Is the fan working?
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Yes, the fan works fine. The coolant circulates in the radiator as well. Could 87 grade gas really make my engine overheat?
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Does the engine ping? If so, under what conditions? Is there any low power complaint?
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Just idling that thing shouldn't get remotely hot.
Have you checked your timing?
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It doesn't ping or make any weird noises, however when the choke is all the way open, it won't idle. I cant start it at all unless its fully closed too. I planned on doing my timing and cr test sometime this week. Maybe today if I get time. I'm not sure what the problem could be at this point. I'm not sure if this is related to timing or what, but whenever I go from park or neutral, it slams into gear, really hard. The guy before me said he put a shift kit in it, but should that do that from a stop? Could the timing solve the trans issue and my heating issue?
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So the carburetor may have float level or idle circuit problems. Slamming into gear can be caused by excessive idle RPM and/or an excessively oversized boost valve and/or accumulators that are worn out or defeated. Go ahead and perform the checks you proposed. Any idea what the engine vacuum is? From your last response, I take it, there is no complaint of low power.
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I honestly don't know what the power should be? It's a fast truck, but for 4.4 mpg, I guess I would expect a little more. It runs extremely rich too, which is part of my mpg problem, but tuning the carb does nothing. I'm not sure if theres a vacuum leak, or if the carb is shot. If the timing were off, would it run badly? It idles perfectly at 1200 rpm. If I try to adjust the idle screw any more, it just tries to die.
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first couple things i would do is get a temp gauge on it. check for vacuum leaks and it might not be a bad ideal to rebuild the carb