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#1 |
Psalm 23
Join Date: Apr 2005
Location: Utah
Posts: 360
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V8 350 question
I've brought my 350 small block a long ways since when I got it a year ago. When I got it, it ran horribly but after a good bit of work it seems to be running really good now however I have a question. It wasn't until about, mmm 1-2 weeks ago that my truck saw road time since I got it. I took it to get exhaust and to get emissions tested. Anyways I decided to pull the plugs and found something kinda weird. I started taking them with the right one ad working my way back. The first 3 were all tan and looked good but the last spark plug on the right side was a little blacker. I made a mental note then proceeded to take out the left side spark plugs. The first plug was one that was older than the others because I broke the previous one. It was a little blacker than I wanted it but not horrible. The middle two again were tan, but the last one was noticably blacker than the previous ones on the left side. I started wondering what might have cause this. Any ideas? Could the timing be off?..., I'm thinking it's something either with the timing or its something electrical.
Any help would be awesome, thanks!
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy Last edited by R@nger; 04-25-2005 at 09:52 PM. |
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#2 |
got boost?
Join Date: Mar 2005
Posts: 123
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you using the stock intake manifold?
some manifolds, especially stock ones are notorious for improper A/F distribution to the cylinders. check your plug wires.is it dry black & smell like fuel or wet black & smell like oil? if your plug gaps aren't right or the heat range is off it can cause similar reads. could also be valve problems. i suggest a leakdown test & an upgrade to a performer rpm airgap. it has better A/F distribution to the cylinders. best would be mpfi if you can afford at least $2k
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'70 chevy lwb w/'67 hood. 357 s.b.c. built, 4l60 w/vigilante lockup high stall converter, edelbrock pro-flo,brodix heads,comp cams rollerized w/ belt drive, one piece d-shaft, yada, yada, yada..... '82 honda v45 sabre"the black" ![]() |
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#3 |
Psalm 23
Join Date: Apr 2005
Location: Utah
Posts: 360
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It's the stock manifold.
The plugs..well the two end one I mentioned are a dry black..like carbon buildup. I know all the gaps are fine because I cleaned and gapped the plugs about a month ago. Whats a "leakdown test"?
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy |
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#4 |
Registered User
Join Date: Dec 1999
Location: Old Mission, MI, USA
Posts: 2,510
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If it has a Q-Jet, it could be starting to drip fuel out the plugs in the bottom of the fuel bowl. When this happens, un-atomized fuel drips into the intake and it runs to the back cylinders since that is the way the engine leans. This causes a rich condition at the rear cylinders and fuel fouled plugs like you describe.
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Tim |
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#5 |
Its Magically Delicious
Join Date: Jan 2003
Location: oregon
Posts: 2,398
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interesting ...
i never understood why a larger gap would yield better economy but less power ...
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71 C10 LWB 350sbc -TH350 12 bolt 3.42 Posi Of all my favorite things to do, The utmost is to have a brew. My love grows for my foamy friend, with each thirst-quenching elbow bend. Beer so frosty, smooth, and cold it's paradise pure liquid gold. Yes beer means many things to me that's all for now cus I gotta pee. |
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#6 |
Registered User
Join Date: Apr 2003
Location: NB
Posts: 3,367
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start new so you know what you got.
plugs wire cap rotor intake manifold, carb rebuild. 0.02
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1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD |
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#7 |
Psalm 23
Join Date: Apr 2005
Location: Utah
Posts: 360
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I rebuilt the carb not long ago at all...and yep it has a qjet.
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy |
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#8 |
Psalm 23
Join Date: Apr 2005
Location: Utah
Posts: 360
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ttt
Any more idea?
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy |
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#9 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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I believe that Blazer1970 has come up with the most likely cause. The plugs on the Q-Jets do leak. Did you epoxie the plugs when the carb was rebuilt?
Jim |
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#10 |
Psalm 23
Join Date: Apr 2005
Location: Utah
Posts: 360
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Nope I didn't epoxy the plugs. I was unaware I had to.
What plugs are we talking about here..I'm a bit confused. I know ya said the plugs at the bottom of the fuel bowl but I thought the fuel bowl was the little black bucket looking thing...I don't seem to remember plugs being in it. I rebuilt it last summer so again I don't exactly remember.
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy Last edited by R@nger; 04-28-2005 at 03:36 PM. |
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#11 |
Working on a Nova.
Join Date: Nov 2002
Location: ##
Posts: 506
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The first question I have to ask is how old are the plugs. If they are older plugs get new. Same thing with the wires, cap, and rotor. Are you running points, these can get a little tricky to set just right and need fairly constant attention. Then we can go from there into more costly and time consuming problems.
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#12 |
Psalm 23
Join Date: Apr 2005
Location: Utah
Posts: 360
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Ok the plugs are...maybe 6 months old, the wires are brand spanking new(Accel 8.8 spiral wound), I have HEI ignition and I'm not exactly sure how old the cap or rotor is.
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD. "Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy |
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#13 | |
Registered User
Join Date: Dec 1999
Location: Old Mission, MI, USA
Posts: 2,510
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Quote:
The bowl plugs are in the bottom of the fuel bowl in the carb. They look like little aluminum freeze plugs. They are in the bottom of the main body (center section, between the air horn and the throttle plate) of the carb. To access them, you have to remove the throttle plate from the bottom of the carb (remove the two long back screws from the top of the carb, and two phillips head screws from the bottom). Then clean up the area around the plugs with a file and coat them over with some JB weld. They are VERY prone to leaking, and will cause the EXACT symptom that you are describing.
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Tim Last edited by Blazer1970; 04-28-2005 at 05:20 PM. |
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#14 |
Registered User
Join Date: Nov 2004
Location: Central Ohio
Posts: 215
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71 K20 350/350/205, dealer air, 4" lift, Flowtech,Edel 1406 on 2101, procomp HEI,4.10's, 33x12.50x16.5 BFG MT's on slots. 4 wheel disc brakes. My lame K20 page My lame Eaton disc brake page ![]() |
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