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Old 10-05-2002, 08:58 PM
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the motor in my truck is running rich and is backfiring through the carb. one of the plug wires is melted to the header so im gonna replace it tomorrow. anyways it dies a lot, when you give it gas it backfires through the carb and dies. what would cause this?

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Old 10-05-2002, 09:04 PM
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bad timing, sticking valves, or burned valves maybe.
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Old 10-05-2002, 09:12 PM
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well the motor is a fresh rebuild, the guy i bought it off of, said the timing needed to be adjusted. sound reasonable to you?
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Old 10-05-2002, 09:30 PM
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another q. the guy said it came with 375 heads stock, but because he didn't want to run race gas, he put 300 heads on it. somebody care to ellaborate on what that means exactly?
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Old 10-05-2002, 09:32 PM
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Melted plug wire bad...replace. But seriously, while yer at it, check all the wires out, make sure you use looms or even wire ties to keep them away from those headers. Timing is probably off, as well.
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Old 10-05-2002, 09:41 PM
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im gonna go buy a set of hi temp wires tomorrow. probably some looms and header wrap while im at it. friend owed me 75 dollars im gonna put it to good use
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Old 10-05-2002, 10:02 PM
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Header wraps will fry your headers, dont waste the time and money.. Get 8MM plug wires, and check that timing.
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Old 10-05-2002, 10:06 PM
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thanks for the heads up on the wraps. i was asking a friend of mine about them and he said they were great(doesn't have any on his stang, bug surprise lol) anyways hate to bother you again but what do you think about the heads i asked about earlier in the thread?
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Old 10-06-2002, 08:25 PM
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got a mechanic friend of mine to come over today and he adjusted the idle on it. it runs a lot better now but still backfires through the carb. got a set of plug wires today but forgot that the motor had been upgraded to HEI, so i had to go out tonight and get a new set, was dark by the time i got home, so i didn't get to put em on. He is sposed to come back another day and help me adjust the timing. should run like a top after that. anyways anybody else have any ideas about the heads?

[ October 06, 2002: Message edited by: Lightspeed ]</p>
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Old 10-06-2002, 08:32 PM
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I'm going to assume you have a small block chevy, I didn't read every post, but if it is. He's referring to 327 cubic inch, 375 horsepower heads, which would have been 461 casting double hump heads that came on a fuel injected, solid lifter corvette engine. The 327-300 horse heads of the same era were the same basic casting with 1.94 inch intakes and 1.5 inch exhaust valves.
So hence the term "375" heads or "300" heads.
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Old 10-06-2002, 08:35 PM
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yeah, that makes a lot of sense how much would this hurt the performance of the motor?

oh and btw, its a 1970 LT1

[ October 06, 2002: Message edited by: Lightspeed ]</p>
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Old 10-06-2002, 09:00 PM
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If it has a set of old double-hump heads, it will run very well with the standard 1.94-1.5 head. Remove the valve cover off of the engine and look at the casting number on the top of the head, look at the last three digits, that will tell you what you've got.
The only thing I can say is if he put newer, open chamber style heads on the engine, which would cost you about 20-25 horsepower.
Anyway, you'll be looking for these numbers 461, 462, 186, 041, 291 or 492. These are most of the numbers for the closed chambered 1970 and earlier high performance factory heads. Smog heads will carry 441,882,993 or 624 amongst others. Let us know what you have.
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