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#1 |
OurLadyofBlessedAccelerat ion
Join Date: Aug 2007
Location: Denver, CO
Posts: 148
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I've had my '68 now for over a year, and the guy I purchased it from "had the motor rebuilt" but then it sat parked in his shop for 5 years before I purchased it. It's never run great, but for the past 6 months or so is been SUPER rough, too sketchy to even rip around the block.
It'll turn over okay (after a jump..... alternator maybe?) and even idles OK for a few minutes. Once it warms up it begins to spit and sputter a bit, sometimes sounding like it's on the verge of dying. The left side (driver's side) seems to be the worse as it blows black smoke (not TONS) out of the pipe. Also, when I dump the throttle and throw open the carb, it is VERY late to respond and near dies. First, the thought was carbs because the Quadrajunk that was on there wasn't even opening up with the throttle. Replaced it with a brand new Holley Street Avenger. That didn't fix it, but the motor gets more gas now. The thought now is that the issue is something internal: compression, valves, gasket, piston (rings), etc etc. My major dilemma is that my network of 'gearhead' buddies are all in Colorado and I now live in Charlotte where no one in my network fiddles with or knows much about old cars. Oh, and I know very little about the diagnosis and repair of internal components. ![]() So here's what I'm asking the forum for help on: 1) What novice level tests can I do to further diagnose the issues I am having. 2) Does anyone know anybody or is anyone in the great Charlotte area willing to help me learn the ropes. It's a very clean truck and motor, so I'd hate to just scrap it and replace it with a rebuilt 350.... but am willing to if that seems like the best case scenario. Anyways, you all have been very helpful in the past so I have no doubt that someone, somewhere will have some ideas. Much appreciated, Jordan
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_______________________________________________ 1968 Chevy C-20 w/ 396 ![]() 1997 HD Sportster 1200 street tracker 1994 Chevy 1500 Silverado ![]() Last edited by Rippin-J; 07-17-2008 at 11:02 PM. Reason: to make description of problem more thorough.... |
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#2 |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,553
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Re: Help Needed - '68 c20 w/ 396
I'd go after a valve adjustment first, followed by a compression test.
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#3 |
Saving 1 truck at a time!
Join Date: Aug 2001
Location: Kent, WA
Posts: 6,465
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Re: Help Needed - '68 c20 w/ 396
I agree with KW but would do the compression check first since it will be much easier with your level of experience. All you have to do is purchase a compression gauge from your local auto parts store and follow the instructions. Some of your problems could be timing as well as compression due to valves or poor break-in on the cam.
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'68 C20 Longhorn 50th Anniversary 400/TH400 '68 C20 Longhorn 50th Anniversary 468/TH400w/buckets '72 C20 Halfhorn (Longhorn w/o cab and front clip) '69 Flxible Cruiser (look up ugly in the dictionary) |
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#4 | |
Senior Member
![]() Join Date: Mar 2003
Location: Colfax-California
Posts: 8,553
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Re: Help Needed - '68 c20 w/ 396
Quote:
Hence the reason for the valve adj first----if the valves are too tight then the compression is gonna be a false reading |
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#5 | |
Size Matters
Join Date: Aug 2007
Location: Lyman, SC
Posts: 9,189
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Re: Help Needed - '68 c20 w/ 396
Quote:
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"Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ![]() ![]() |
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#6 |
RIP BigDaddyDave ~7-23-09~ You will be missed~
Join Date: Aug 2007
Location: Concord NC
Posts: 1,361
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Re: Help Needed - '68 c20 w/ 396
Have you tuned it up? I can tell when mine starts running rough that it is time. I spent a lot of money on my junk,then replaced the distributor and it made a world of difference.
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BigDaddyDave's Truck: http://www.flickr.com/photos/daves71chevy/ | See it in Action! |
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#7 |
OurLadyofBlessedAccelerat ion
Join Date: Aug 2007
Location: Denver, CO
Posts: 148
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Re: Help Needed - '68 c20 w/ 396
You know, I hate to admit, but I've heard the term 'tune up' used my whole life and I can't say that I know exactly what that entails.
When you say tune up, what all does that include? timing, distributor, wires, oil, ? Any chance you feel like making a trip down I-85 to help out? ![]() I think the tune up sounds like a good first step, followed up by compression test and then valve adjustments. My assumption is that tune would eliminate a bunch of other possibilities, then the compression would confirm others, and finally a valve adjustment would be the last case scenario.
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_______________________________________________ 1968 Chevy C-20 w/ 396 ![]() 1997 HD Sportster 1200 street tracker 1994 Chevy 1500 Silverado ![]() |
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#8 |
OurLadyofBlessedAccelerat ion
Join Date: Aug 2007
Location: Denver, CO
Posts: 148
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Re: Help Needed - '68 c20 w/ 396
Gas is another good point to check... the gas that's in there is at least 3 months old now.
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_______________________________________________ 1968 Chevy C-20 w/ 396 ![]() 1997 HD Sportster 1200 street tracker 1994 Chevy 1500 Silverado ![]() |
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#9 |
Size Matters
Join Date: Aug 2007
Location: Lyman, SC
Posts: 9,189
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Re: Help Needed - '68 c20 w/ 396
Have you tried a new set of plugs? I would start there if you haven't tried that already and then look at the timing, compression and cylinder leakage, and then the valve adjustment as stated above. The timing and valve adjustment would be more suspect to me due to the fact that you said the motor had been rebuilt and had not run great since you have had it...who knows if the PO knew what he was doing.
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"Reading the owners manual is only for quitters." Jason Harper, Bloomberg News. ![]() ![]() Last edited by Longhorn321; 07-18-2008 at 02:54 PM. |
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#10 |
OurLadyofBlessedAccelerat ion
Join Date: Aug 2007
Location: Denver, CO
Posts: 148
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Re: Help Needed - '68 c20 w/ 396
yep, new plugs for sure. replaced those with the carb in April.
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_______________________________________________ 1968 Chevy C-20 w/ 396 ![]() 1997 HD Sportster 1200 street tracker 1994 Chevy 1500 Silverado ![]() Last edited by Rippin-J; 07-18-2008 at 02:59 PM. |
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#11 |
Registered User
Join Date: Jan 2007
Location: Mississippi
Posts: 2,121
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Re: Help Needed - '68 c20 w/ 396
?bad gas? Drain lines, tank & all. Just a thought if it's been sitting with same gas for over a month or so, especially as crappy as gas is now. I spent $100+ on mine one time, when it was acting like that, & it was just the gas.
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'72 C to K20 "Cannibalizer" http://67-72chevytrucks.com/vboard/s...32#post8653432 '85 K30 "Big Nassy" '01 2500 Suburban ...party wagon & tow truck '06 Silverado SS...DD '06 C1500 WT...DD '07 Classic C1500 WT...DD Built & sold cause can't keep 'em all: '72 Blazer "The Bucket" http://67-72chevytrucks.com/vboard/s...d.php?t=433190 '55 Chevy straight axle gasser https://www.trifive.com/forums/showthread.php?t=173938 '69 Pro Street Chevelle http://www.chevelles.com/forums/showthread.php?t=332541 '86 M1031 CUCV http://67-72chevytrucks.com/vboard/s...d.php?t=553619 |
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