Hesitation Problem-327ci - Team Camaro Tech
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post #1 of 15 (permalink) Old May 13th, 09, 10:59 AM Thread Starter
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Matt
 
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Hesitation Problem-327ci

Here's my problem, hoping some experts out here would be able to help me guide me in finding a solution:

Car Details:
-68 camaro, 327ci with 202 heads(supposedly rebuilt 10K ago), 750 edelbrock w/performance edelbrock alum. manifold, mild cam, headers, TH350 trans w/manual valve body. I just bought it and don't have a ton of history on it.

Problem:
-at 1800 RPM's the engine stumbles/hesitates on a consistant basis.
-when the engine is cold, the hesitation almost causes it to kill.
-currently gets what I think is 10mpg, which seems low to me, even for a car like that.

What I have tried thus far:
-I took some advice from this website on getting a vacuum guage and attempting to adjust the set screws to optimize vacuum in an attempt to eliminate the hesitation. That didn't help the hesitation at all and I think I made the overall performance worse. I need to try again I think.
-Note, when I hooked up the vac guage, the needle shook pretty violently, making it hard to guage the real vac reading. When I looked at the vac instructions, it said a shaky needle could mean several things, like: leaky manifold, stuck spring, burnt valve, etc....
-seafoam directly into the carb
-carb cleaner in carb to clean varnish/gum

Any ideas on what I can try at home before I take it to a professional? On a scale of 1-10, I would say my mech. skills are a 5, just to give you an idea of how much/little I know. Thanks!
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post #2 of 15 (permalink) Old May 13th, 09, 11:28 AM
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Re: Hesitation Problem-327ci

You failed to mention what type of ignition system you're running, is it points or electronic?....And, is the choke working properly on the Edelbrock carb, assuming you're using an electric choke?
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post #3 of 15 (permalink) Old May 14th, 09, 05:10 AM Thread Starter
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Re: Hesitation Problem-327ci

Electronic ignition and I believe the carb has a manual choke that as far as I can tell is not engaged at all.
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post #4 of 15 (permalink) Old May 14th, 09, 05:33 AM
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Re: Hesitation Problem-327ci

sounds like ignition problem
bad wires or worn cap and rotor.
if it has Taylor plug wires I would replace them ( never seen a set last too long)
also start car in the dark and look into engine bay
if you see sparks then wire are definately bad.


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post #5 of 15 (permalink) Old May 14th, 09, 05:47 AM Thread Starter
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Re: Hesitation Problem-327ci

Thanks Dawg. It does have Taylor wires, not sure how old they are. I didn't think to look for arc'ing, duh. I suppose a cap would be a cheap thing to try as well. I was just thinking for sure it was fuel related, but I am certainly no expert. Any recommendation on wires?
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post #6 of 15 (permalink) Old May 14th, 09, 05:53 AM
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Re: Hesitation Problem-327ci

Here is a link to how to read your vacuum gauge. If the needle shakes violently over 10"-14" of vacuum as the engine RPM's increase, that is an indication of a weak valve spring. Look at the 14th scenario. How far through the vacuum range does it fluctuate?
http://www.secondchancegarage.com/public/186.cfm

Another site says possible blown head gasket or incorrect valve timing. Does the needle fluctuate violently at idle, but steady out as the RPM's increas? If so, one site says that is worn valve guides.

Here is another link to a site that describes the vacuum gauge readings.
http://www.theautoist.com/vacuum_guage.htm

Charlie Knudsen 67 Camaro RS/SS 350 TKO 600, 4.10's, AFR 195 Street Heads, Comp 270H, Rhoads Lifters, Crane Ignition, Pertronix Dizzy, Performer RPM Q-Jet, Heavily Modified Q-Jet, Hooker Comp Headers, MagnaFlow 2 1/2", 144 Decibles(Alpine CDA-7998 Head Unit, RF X7 and RF 750X Amps, MB Quart Mid's & High's, Kicker L7 12" Solo Barics)

Last edited by 67CamaroRS/SS; May 14th, 09 at 05:58 AM. Reason: Added Information
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post #7 of 15 (permalink) Old May 14th, 09, 06:48 AM Thread Starter
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Matt
 
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Re: Hesitation Problem-327ci

Thanks for the links, those are great. The guage fluctuates maybe 2-3 hg's, pretty rapid at that, so it makes it hard to use the set screws to adjust the carb to get the highest vacuum because the needle is moving so quickly and visualizing progress on the guage is tough. Right now it is reading about 9-10 hg's(without adjusting for elevation changes). The book said the guage is calibrated at a sea level of zero and as you go up in 1000's of ft, you should add 1 hg to your number.

I need to try it again and see how the guage reacts as I give it gas, that might help tell the whole picture. I will post what I find tonight.
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post #8 of 15 (permalink) Old May 14th, 09, 07:51 AM
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Re: Hesitation Problem-327ci

Quote:
Originally Posted by mkoon View Post
Thanks Dawg. It does have Taylor wires, not sure how old they are. I didn't think to look for arc'ing, duh. I suppose a cap would be a cheap thing to try as well. I was just thinking for sure it was fuel related, but I am certainly no expert. Any recommendation on wires?
anything but taylor or elcheapo wires
accell 300+ is a great wire btw
but if cost is no option run the moroso super 40s those wires come with extra heat sheilding


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post #9 of 15 (permalink) Old May 14th, 09, 08:19 AM Thread Starter
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Re: Hesitation Problem-327ci

Any idea what vacuum reading I should be getting with my setup? I am hovering around 10-11 and I am in Minneapolis, which is 800-1000ft above sea level.
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post #10 of 15 (permalink) Old May 14th, 09, 08:44 AM
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Re: Hesitation Problem-327ci

vacumm is pretty much dictated by cam profile
stock cams will give you between 18 and 20"


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post #11 of 15 (permalink) Old May 15th, 09, 05:00 AM
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Re: Hesitation Problem-327ci

Too much fuel maybe? 750 carb seems big for that setup not knowing rest of the specs...

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post #12 of 15 (permalink) Old May 15th, 09, 05:36 AM
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Re: Hesitation Problem-327ci

I think the issue is laying in the valve adjustment. What type of cam are you running and what is the specs?

Charlie Knudsen 67 Camaro RS/SS 350 TKO 600, 4.10's, AFR 195 Street Heads, Comp 270H, Rhoads Lifters, Crane Ignition, Pertronix Dizzy, Performer RPM Q-Jet, Heavily Modified Q-Jet, Hooker Comp Headers, MagnaFlow 2 1/2", 144 Decibles(Alpine CDA-7998 Head Unit, RF X7 and RF 750X Amps, MB Quart Mid's & High's, Kicker L7 12" Solo Barics)
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post #13 of 15 (permalink) Old May 15th, 09, 05:39 AM
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Re: Hesitation Problem-327ci

Let's put it this way, I run a Comp 270H and I get 18" of vacuum idling at 950rpm(park/neutral) and 12" idling at 750rpm(drive). The 270H is a 224/224 @.050" and 470/470 lift. I am also running Rhoads variable duration lifters which reduce lift and duration by the amount of lash you set into them. I run .020" lash so at idle I have 204/204 @.050" and 450/450 lift. Once I hit 4000rpm, full lift and duration are restored.

Charlie Knudsen 67 Camaro RS/SS 350 TKO 600, 4.10's, AFR 195 Street Heads, Comp 270H, Rhoads Lifters, Crane Ignition, Pertronix Dizzy, Performer RPM Q-Jet, Heavily Modified Q-Jet, Hooker Comp Headers, MagnaFlow 2 1/2", 144 Decibles(Alpine CDA-7998 Head Unit, RF X7 and RF 750X Amps, MB Quart Mid's & High's, Kicker L7 12" Solo Barics)
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post #14 of 15 (permalink) Old May 15th, 09, 05:51 AM Thread Starter
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Re: Hesitation Problem-327ci

I do not know what type of cam is in the car. I just bought it two months ago and did not get much information on the car when I bought it. It has a nice lope, so I know it isn't stock.

Based on all the replies(thank you by the way), sounds like I may need to take this thing to a professional as it could be many things, which most are out of my skill set.

I think I might take Dawg's advice and buy new wires and distributor and then run some marvel through the oil as well to possibly free a sticky spring or lifter.
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post #15 of 15 (permalink) Old May 21st, 09, 10:39 AM Thread Starter
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Matt
 
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Re: Hesitation Problem-327ci

I had some time over the last week to poke around a bit more and here's what I have done:

1) Checked for arching-didn't see any
2) Tried adjusting the set points on the carb again using the vacuum gauge-was able to get vacuum around 11hg, shakes a little, maybe 1-2hg's worth.
3) Changed the oil and put some Marvel Oil in there.

I will likely try replacing the plug wires and distributor cap before I take it to a professional. At which point I will have them look at the timing and carb. I am getting a little residual oil on top of my manifold adjacent to the head, so I think I do have a manifold leak(not major-the oil is minimul, but it is reoccurring because if I clean it up-it comes back).

Anyone have advice on where to take a car like this in Minneapolis or what other things I could try?
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