Engine Misfiring? - Team Camaro Tech
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post #1 of 5 (permalink) Old Jul 28th, 09, 07:07 PM Thread Starter
Senior Tech
Dario
 
Join Date: Jan 2007
Location: Las Vegas, NV
Posts: 230
Engine Misfiring?

I recently did a cam swap to something much milder.

Cam Style Hydraulic flat tappet
Basic Operating RPM Range 1,500-4,000
Intake Duration at 050 inch Lift 204
Exhaust Duration at 050 inch Lift 214
Duration at 050 inch Lift 204 int./214 exh.
Advertised Intake Duration 262
Advertised Exhaust Duration 272
Advertised Duration 262 int./272 exh.
Lobe Separation (degrees)112

I put on a 4 bbl edelbrock 1407 with electric choke (that I rebuilt myself... so that can be an issue) and intake. Reattached everything but now I seem to have issues. The car sounds as though it's skipping a beat randomly. I just rechecked the plugs with a plug light attachment and they all seem to be firing normally. I've also pulled out each plug and found them fouled (blackened with soot- I think this is because too much fuel in mix?). I cleaned them and regapped them to .045. I've used the dizzy (Pertronix flamethrower and coil) before with my old 2 barrel and it ran fine (didn't have this problem). I checked the timing... 12* initial, 36* total, 44* total+vacuum. The light shows timing steady but drops (retards) 10* randomly every few seconds for just a split second. I idle beautifully at 750 RPM in gear and 950 RPM in park. It takes off from a stop just fine but the engine stalls (almost dies) at higher RPM about (3500-4000) when driving only and there is a vibration like a missfiring cylinder and there is a severe lack of power. I have the dizzy vac set at manifold vac. A vacuum gauge attached in line reads 17-17.5 in Hg. What the heck is up? Anyone have a clue? Should I switch back to timed vacuum for the dizzy? I haven't adjusted my valves but I hear no tapping through a stethescope. Might the hydraulic lifters be too tight? Can that cause it? What gets me is that the stuttering in the timing is coompletely random. What could do that? Do I have both a carb and electrical issue here? That's about as much info as I can think of that might be of help. Can anyone suggest a possible cause for the problem and a solution?

Thanks for taking the time.

67 RS Camaro
Originally: Stock 327/210 w/AC, 2 Speed Powerglide & Deluxe Interior
Now: Hotchkis SB TVS, Cross-Drilled/Slotted Disc Brake Conversion, 327/330, Headers w/ Pypes Dual Street Pros & more to come.

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Last edited by jet-tech1; Jul 28th, 09 at 07:33 PM.
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post #2 of 5 (permalink) Old Jul 28th, 09, 08:07 PM
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CHRIS
 
Join Date: Oct 2007
Location: VA
Posts: 89
Re: Engine Misfiring?

sell the carb.
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post #3 of 5 (permalink) Old Jul 29th, 09, 01:02 PM Thread Starter
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Dario
 
Join Date: Jan 2007
Location: Las Vegas, NV
Posts: 230
Re: Engine Misfiring?

No ideas other than sell my carb?

I had a thought last night. Since I stepped down my cam from a very radical cam to a mild street cam and the carb was tuned for the radical cam... might that be why I'm having fouled plugs from too rich a mix and lose power at higher RPMs? Might the carb be too rich? could that be part of my problem? Does too rich a mix cause power loss when you gun it? Should I decrease the size of the jets and the metering rods?

Anyone...anyone...Bueler... Bueler?

67 RS Camaro
Originally: Stock 327/210 w/AC, 2 Speed Powerglide & Deluxe Interior
Now: Hotchkis SB TVS, Cross-Drilled/Slotted Disc Brake Conversion, 327/330, Headers w/ Pypes Dual Street Pros & more to come.

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post #4 of 5 (permalink) Old Jul 29th, 09, 03:55 PM
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Tom
 
Join Date: Jun 2001
Location: Rochester Mn
Posts: 7,749
Smile Re: Engine Misfiring?

A 750 cfm carb is too big for a 327. A 650 is the max you would want. If you want a 750 then use a Quadrajet. A 750cfm carb has too big of primaries, except for a Quadrajet. I am running a 600 CFM Edelbrock on my 327, after I was unable to get a 750 Holley to work.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #5 of 5 (permalink) Old Jul 30th, 09, 06:17 PM Thread Starter
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Dario
 
Join Date: Jan 2007
Location: Las Vegas, NV
Posts: 230
Re: Engine Misfiring?

You know I've heard both sides of that carb being too big issue. Since it has vacuum secondaries it shouldn't make a difference should it. At least that's what some say. Since they will only open up as much as the engine demands... odds are that I'll never see 750cfm going in unless the engine can demand it. It makes sense to me but I might have misunderstood that part. But I think I have an idea as to why it's running rich. I used to have a huge cam and when the carb was set up it was set up for that particular setup. I've stepped down my jets... taking what used to be in my secondaries and putting them in my primary position and then stepping down my secondaries by 2 levels. All that's left now is to test it out. It doesn't explain my timing mark randomly bouncing around though. Or does it. Can a rich mix cause it or should I go looking for an electrical problem too?

67 RS Camaro
Originally: Stock 327/210 w/AC, 2 Speed Powerglide & Deluxe Interior
Now: Hotchkis SB TVS, Cross-Drilled/Slotted Disc Brake Conversion, 327/330, Headers w/ Pypes Dual Street Pros & more to come.

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