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#3956 06/09/04 10:17 PM
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i have a 250 inline 6 with a 1b carb with a 2speed powerglide.
Sometimes when im pulling away from a stop sign if i dont ease on the throtle and let the car slowly crawl from a halt it will pop and stall out sometimes poping the pcv hose off.

what might be causing this?

#3957 06/09/04 11:27 PM
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First thing to check is your timing. Poping off the pvc hose is because of the back fire/poping back into the intake system. How many miles are on this motor?? }[oooooo]


Larry/Twisted6
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#3958 06/10/04 04:33 AM
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timing sounds like its quite a bit off, although i have never had that bad of issues with backfiring when the timing was off....have u recently done anything to the distributer or timing chain? did it just all of a sudden happen? worst case is that the timing chain skiped a tooth or is really loose...really loose sounds like the most likely of the two though..but check everything else that u can before u go checking the timing chain..unless u dont mind the extra work just so u know for sure.


got my 78 merc with a 250 I6 and i love it.
#3959 06/10/04 07:25 AM
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 Quote:
Originally posted by Malicer:
i have a 250 inline 6 with a 1b carb with a 2speed powerglide.
Sometimes when im pulling away from a stop sign if i dont ease on the throtle and let the car slowly crawl from a halt it will pop and stall out sometimes poping the pcv hose off.

what might be causing this?
Sounds like the accelerator pump is going bad.
You step on gas and get a lean pop.
If you're quick enough you can let off gas and car will keep running.
Sound familiar?
Has the carb been rebuilt recently?
If not might need freshening up.
Be sure to check the well that plunger fits into for corrosion.
Seems to be suseptible to water damage.
You can try polishing it up to smooth it.
If it's real bad you might have to find another carb body.
This assumes carb is set right, no vacuum leaks, etc.
BTW: The PCV hose should have the little spring clamps on it, or maybe it's hard and loose fitting?


Pete
64 Chevelle
61 C30 Panel truck
#3960 06/10/04 05:20 PM
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Malicer Offline OP
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im not sure when the last time the carb was cleaned but the good thing is the car came with an extra. i think the original rochester(one in the trunk) was replaced with a holly monojet. . . does that sound right?
i will have to get my uncle to tear the carb down and maybee do a full rebuild. or just clean it out


and i do belive there is 66 thousand miles on it

#3961 06/10/04 09:46 PM
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would a bad accelerator pump cause backfireing through the carb though? i thought it just caused more of a dead spot...my pump is going or is not setup but when i accelerate anything other that slow it has a dead spot..it doesnt die but it feels like it will..then it catches and keeps going...but i dont have any backfiring issues. although i am running a hydrogen/pcv system so that might be whats keeping it from the lean pop.


got my 78 merc with a 250 I6 and i love it.
#3962 06/11/04 01:42 AM
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ok first off their is NO chain in our chevyL6s they are gear drive. A burnt Valve will also make for a back pop in the intake system. The accelerate will make for a Dead/flat spot It will ALSO Be Very hard to start the motor Seening That It can Not Preprime the intake. when the motor has sat for a long time period.(like over nite)
Other quetsion I have Does the motor pop Even If not under a load?? Or only under a load. Does It still have points in it. A Weak condenser will also cause for back popping the intake/carb. hope this helps }[oooooo]


Larry/Twisted6
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#3963 06/11/04 05:40 AM
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Hi Malicer,

get a vacuum gauge and hook it to your carb. Tha vacuum gauge is a wonderfull instrument that tells you about:
1. Sticking Valves
2. Incorrect Valve Timing
3. Carb Adjustment Needed
4. Blown Head Gasket
5. Burnt or Leaking Valves
6. Clogged Exhaust
7. Worn Valve Guides
8. Timing

Here is a guide to "vacuum gauge tuning"
http://www.centuryperformance.com/vacuum.asp


Frank


To old to die young.
#3964 06/13/04 01:07 PM
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it only pops under load and yes there are still points in it i do have a spare set of points and a condenser also.
and it is more of a pop than a backfire
and i don't belive there are any spring clamps on the pcv hose were it connects to the pcv valve

#3965 06/13/04 02:00 PM
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I would still have to say go and change the points and condenser seeing that you have them. If It don't fix the prolem Then just hang onto the set you took out. Only thing lost there is a little bit of your time. and still hook up the vacum gage and see what that may tell you.And go from there. Hope this helps }[oooooo]


Larry/Twisted6
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Adding CFM adds boost smile
shocked God doesn't like ugly.

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