tuning a big block - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 2 (permalink) Old Oct 29th, 00, 09:35 AM Thread Starter
Join Date: Sep 1999
Posts: 108

i have a 402 that is basically stock internally that i have added a new holley 750 (vacuum secondaries), headers, HEI ignition, and edelbrock intake to. the problem is this: the car bogs like crazy when its at idle and you romp on the gas. when you unplug the vacuum advance line to adjust the timing with a light, the line on the balancer jumps around from like 4 to 10 and back again. I have replaced the advance springs with a looser set from Mr. Gasket, if this helps any in the analysis. No matter what jetting i use (now at 69's), i cant get any good response or performance from the thing. please help! better yet, if there is anyone who lives close by (im in carrollton, tx), this could be a good opportunity to meet someone if i brought it over to their house for some power tuning lessons. thanks.

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penguinjohn is offline  
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post #2 of 2 (permalink) Old Oct 29th, 00, 11:16 AM
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Join Date: Sep 2000
Location: LaHabra, Calif. US
Posts: 65

Hey there John, I am not in Texas, Orange County Calif is home but I will try to help. The reason fo the timing moving around at idle is that the mechanincal advanse is begining to come in. At first is just searching as you are at it beging point. Slow the idle to just under that. You may want it coming in later depending on what your idle speed is. On my 67 it start at 1400 ( idles at 1200) and the 79 it starts at 1000 ( idles at 800) Both are all in at 2600 though. What intake did you install, single or dual plane? Is the HEI running to a full 12 volts plus? You need to wire it with a new wire from the IGN conector at your fuse block. The stock wire is resisted and will not let the full 12 to the distributer. The reponse thing id dependaant on the timing, type of intake also. The squirter, cam on the pump arm,need to be in tune. May need more or less, not being there I don't know. Have the distributer done by a reputable ignition place. The aftermarket spring sets are not reliable. You will get a different timing advance rate, but unless you know what to look for on the light you will need it on a machine. That is the best way. Jetting is not the culprit for the response (very little anyway) The stock power valve is a 6.5 (opens at 6 1/2" vacuem.) You may need a higher value if the cam is stock or close enough to not allow the vacuem below that point at partial throttle. I have used 10.5 on stockers and it has helped. I hope that gets you started anyway, It can be a good learning experience, frustrating at times, but an engine in good tune will be much more pleasant. Galen

S/B Chevy Lover
67 Camaro street car
10:50's @ 128 on motor w/383 cid
79 Z28 w/383 9.1:1 3.73:1 Restoring stock apearance
13:40's @ 101 stock exh.& intake& Qjet
smog legal
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Galen W. Rouse is offline  
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