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Old 06-08-2004, 01:04 AM
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68 GTO 400 motor problems

OK guys...I know its hard to tell without hearing and seeing, but buddy is having problems with his new motor. Engine is in his 64 Lemans. When car runs... it idles bad....but runs like striped ape, dies at stops. When the idle is good...it runs like crap. He has fuel pressure set at 7psi. Compression tested all cylinders...range from 160-170. Changed carbs and does same thing.

Here is what I know about engine:

Pontiac 400 bored .60 over
Machine Work: Block Thermal Cleaned; Turn, champher, and polish crank; Crank and rods shot peen; Blocked Decked; Honed lifter bores.
Parts: Stock crank, and rods; TRW Forged piston; Moroso High Pressure Oil pump; Moroso Deep 7 QT. oil pan; Crane Cam 282 lift, 236 duration solid lift; Harland Sharp Roller Rockers; Edelbrock Alum. Performer Edelbrock dual plane intake; 850cfm speed demon carb.; Mallory Unilite distributor; MSD Helicore Ignition wires; Holley fuel pump; MSD 6al Ignition; Flowkooler aluminum water pump; Powermaster XS starter; MSD blaster 2 coil; Fram fuel filter; Summit roller timing chain. Hedman headers into flowmaster dual h pipe kit with Delta 50s

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Old 06-08-2004, 01:16 AM
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First off I`ll ask was the Demon set up properly by the book? I had many idle problems out of my demon, I read the book over 3 times and got it right, these are real precise carbs and must be set up correctly for them to perform correctly. have you checked it for vacuum leaks? another area I`ll ask on is fuel pressure, while it`s true most Holley`s and Demons can handle fuel pressure to be around 8-9 psi, mine can`t handle over 6 before it overcomes the needle and starts flooding and this is with a stock mechanical pump. does the car load up at idle? if so this is one clue.
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Old 06-08-2004, 01:49 AM
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sucking air

sounds like your getting to much air some where intake leak carb base gasket
power brake booster even a modulator valve

use carb cleaner while its running and if the rpm s change then you got a leak

some people use either but if you get a puddle of it in a wire zaps well...
good luck
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Old 06-08-2004, 12:02 PM
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Ok....he will check for vacuum leaks. He wants to know what is best spark plug for this motor and what gap? He has solid lifters...roller rockers...he wants to know what exhaust & intake gaps should be set at? Thanks
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Old 06-08-2004, 12:28 PM
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went boatiing on lake eufaula once when i went to tech. gorgeous! cant help ya tho.
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Old 06-08-2004, 04:04 PM
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any thing but champion

if you bust the porcelain on a champion resistor plug you'll see a spring sometimes they fry
i like A/C myself you might also try a platinum plug never used the splitfire
not sure on the intake & stuff try calling NPD
national parts depot or go online npd .com i think they got almost everything u could want
good luck
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Old 06-08-2004, 05:22 PM
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platnum sucks too. trust me just more money. guess what gm 100,000 mile tune up engines(laugh) use? A/C delco. they generally last about 5500 miles on my beater camaro. it doesnt burn alot of oil though, yet.... plugs can last a lot longer than that. on a carburated engine, chances are, they will be fouled by then. just because is not missing doesnt mean it doesnt need new plugs
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Old 06-09-2004, 09:14 PM
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bosh

i know they pretty much suck and not to get off the subject
for too long when i worked @ a tune up joint i put bosh platinum in my 79 ford f-259 460 4bl and my mileage went from 9 to 11 running sunoco 94 octane if i did my math right and all that jazz
i did notice she was a little more peppyer off the line bla bla bla yakkity shmackity now adays she gets 5 down hill with the wind
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Old 06-09-2004, 09:47 PM
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UPDATE:

Ok...he got her going....seems wire from coil to dist had bad spot...replaced....regapped plugs....runs like a dream.
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Old 06-09-2004, 10:48 PM
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kool

excellent keep er sunny side up
rob
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