WOT Miss or hesitation - Team Camaro Tech
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post #1 of 24 (permalink) Old Mar 10th, 06, 07:30 PM Thread Starter
 
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Exclamation WOT Miss or hesitation

I have a 68 Camaro with 327/210. I have recently installed an Edelbrock Performer intake (2101) and Carb (1406). I am running 10 degrees BTDC at idle and around 40 degrees at 4000RPM. At WOT and around 3500 to 4000RPM the engine misses or stumbles. Not really sure how to describe the symptom. This issue isn't as bad after you have been driving it for 20 to 30minutes, but it is still present. Any ideas what could be causing it? I understand an engine can and does perform different when cold but this missing or hesitating doesn't seem normal to me. Before the intake and card swap I was running the original intake and 2barrel carb with the current distributor I am running now (Jegs HEI). I didn't have this issue then. Thanks for any help and direction
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post #2 of 24 (permalink) Old Mar 10th, 06, 08:19 PM
 
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Re: WOT Miss or hesitation

You always want to tune an engine when its up to full operating temperature. If it runs better when its hot, then its just running to lean when its cold, and may cause the symptoms you describe. Is the choke on the new carb hooked up and functioning? If it still stumbles when its hot, you have some more work to do. Are you SURE you set the timing correctly? With the vacuum advance disconnected? It should run fine with 40 deg.s total. Maybe you need to jet up the carb a little bit.
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post #3 of 24 (permalink) Old Mar 11th, 06, 06:30 AM Thread Starter
 
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Re: WOT Miss or hesitation

I thought it was a choke issue and took the choke completely off. I have went 2 stages rich in both the power and cruise mode by changing the metering rod. I also changed the push up spring for 8" of vacuum at RPM. None of these have fixed the problem. I have been running 87 octane gas, I may try higher octane just to see what that does. Honestly when I checked the timing the vacuum advace was connected but at 4000RPM's the dominant force is the mechanical advace, right? I'll check it with vacuum off and see if there is a difference.
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post #4 of 24 (permalink) Old Mar 11th, 06, 07:14 AM
 
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Re: WOT Miss or hesitation

I dont think there is one person here that hasent made that mistake once. Yes at 4000 rpm with NO LOAD the throttle blades will still be nearly closed and it will produce a boat load of vaccum. Under a load the blades will open up and vaccum will drop to nearly zero. So, depending on how much advance your vaccum canister gives you, you very well may be running 15 degrees advance. Unplug the vaccum, plug the vaccum port on the carb, set the timing( I would start with 36*) and enjoy a stumble/miss free engine!(as well as about 100 more HP!) Have fun!

Randy
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post #5 of 24 (permalink) Old Mar 11th, 06, 08:44 AM
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Re: WOT Miss or hesitation

check your dist. cap and rotor for cracks etc.
reason im saying this is after I did my motor and installed the original distributor the car ran fine at idle but wot it would miss .
found a crack in the dist cap.
and carbon tracking.
change cap and rotor and problem went away


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post #6 of 24 (permalink) Old Mar 12th, 06, 02:17 PM Thread Starter
 
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Re: WOT Miss or hesitation

What is strange to me is that the problem I described before isn't as bad if you ease into the throttle. It just happens if you floor it. It's as if its rev limiting. I can determine if its spark or fuel mixture.
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post #7 of 24 (permalink) Old Mar 12th, 06, 02:48 PM
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Re: WOT Miss or hesitation

how old are your wires and plugs?
I still believe its ignition problem.
yeah easing into it will work as in my problem.
you just gotta go through a process of elimination.


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post #8 of 24 (permalink) Old Mar 12th, 06, 02:54 PM
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Re: WOT Miss or hesitation

I think Randy hit the nail on the head. You have to check initial and total timing with the vac disconnected. If I were to check my timing at 4000 rpm with the vac connected, it would read over 60 degrees!!





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post #9 of 24 (permalink) Old Mar 13th, 06, 06:26 AM Thread Starter
 
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Re: WOT Miss or hesitation

The plugs/wires/HEI distributor are brand new. I will double check the timing again with the vacuum advance disconnected. I am running a stock 327/210 with Edelbrock intake and carb (Performer series). I'm thinking my idle should be around 6 degrees BTDC and around 36 degrees BTDC at 4000. Does this seem right? I know it can vary per engine but that should be a good starting point, right? Thanks for everyone's help.
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post #10 of 24 (permalink) Old Mar 13th, 06, 07:34 AM
 
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Re: WOT Miss or hesitation

With 6 degrees at idle and 36 total your mechanical advance needs to be 30. Although it can be modified to do so, thats asking alot and really is not necissary. Most distributors will give around 15-20 mechanical. If the starter cranks the motor with 18 initial, that will be fine. Also, you should have ALL your mechanical advance in by 3000 rpm. This is easily changed by swapping the springs.Now... go reset the timing with the vacuum advance unhooked and report back!

Randy
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post #11 of 24 (permalink) Old Mar 14th, 06, 12:01 AM
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Re: WOT Miss or hesitation

the easyest thing to do is set the total timing (with the vacuum disconnected) to 36 degrees and see what it reads at idle
and as long as it easily starts you should be ok
and like rlovell said you need some lighter springs to get the mechanical advance in sooner
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post #12 of 24 (permalink) Old Mar 14th, 06, 02:55 PM Thread Starter
 
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Re: WOT Miss or hesitation

OK, I checked the timing with the vacuum advance disconnected and plugged. I am seeing 25 degrees at 3000 and sort of flattens out any higher. I'll look at getting some different springs and report back.
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post #13 of 24 (permalink) Old Mar 14th, 06, 03:18 PM
 
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Re: WOT Miss or hesitation

If the advance curve flattens out at 3000 RPM no need to change springs. Just crank in another 11-12 degs of timing and your good to go.

Randy
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post #14 of 24 (permalink) Old Mar 14th, 06, 03:33 PM
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Re: WOT Miss or hesitation

I am not familar with the Carb (1406). If it was a holley I would be looking at in order.
1/pump gap setting at WOT around 18/1000 not critcal but there HAS to be a gap about that.
2/secondary idle butterfly setting...a little screw under the base plate accessable with a bent rivet stem, with a flatebed end
3/Power valve is within range
4/ Correct setting and throttle cam
5/ WOT CO level and jets.

There is an old saying "there is many a carb problem/tune fixed by changing spark plugs"
"Spark plugs" basically refers to sparking system...make sure all is right there before going into the carb.

My Spelling is not incorrect...it is creative

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post #15 of 24 (permalink) Old Mar 14th, 06, 03:40 PM
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Re: WOT Miss or hesitation

geez id say take it to a shop and let them hook it up to an analyzier.


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