engine dead spot - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sbc10guy · 09-30-2011, 10:20 PM

Hi guys, ive been messing with my 327 lately and it has a dead spot as soon as you hit the throttle.It runs great at higher rpm when you hit the gas but the throttle response is terrible and it hesitates and spits and sputters when you hit the gas hard at a dead stop. If i drive it normal it runs fine but as soon as you hammer on it it hesitates and runs bad. The motor is a 327 thats bored .30, has a .464/.480 crane cam, 202 camel hump heads 487 casting, hydraulic lifters harland sharp roller rockers, victor jr. edelbrock intake, and holley 650 double pumper carb. I dont know if its the mix of parts thats wrong, ive messed with the timing and made it better but i cant get it right. Any advice is greatly appreciated. Thanks.

68streetrod · 09-30-2011, 10:45 PM

the victor jr is made for best preformance in the upper rpm range but it should Not be totally flat. Does it rev up nice from a idle with no load (in park) or stumble till it builds rpms?

What kind of ignition are you running? and are you running a good premuim octane gas ?

sbc10guy · 09-30-2011, 11:04 PM

When its in park it has a small dead spot right away and the rest of the rpm range is awesome. I run premium gas with a mix of turbo blue 110 octane every once in a while. It has an hei distributer too.

landsurvey1 · 09-30-2011, 11:26 PM

I had a similar problem and it turned out to be a bad carburetor gasket.

edhtrd71 · 10-01-2011, 12:02 AM

make sure the accelerator pump is squirting as soon as the linkage moves

into69z · 10-01-2011, 12:55 AM

Quote:

Originally Posted by edhtrd71

make sure the accelerator pump is squirting as soon as the linkage moves

that's important and there are accelerator "cams" that have an adjustment as well. You may need to change the size of the accelerator nozzels as well-if you go to holley.com they have a tech section on how to adjust those as well as the rest of the carb-good luck-it just wants more fuel I think.....Steve

hotrod farm truck · 10-01-2011, 01:43 AM

Quote:

Originally Posted by 68streetrod

the victor jr is made for best preformance in the upper rpm range but it should Not be totally flat. Does it rev up nice from a idle with no load (in park) or stumble till it builds rpms?

What kind of ignition are you running? and are you running a good premuim octane gas ?

x2 try a dual plane intake.

OJ1988 · 10-01-2011, 09:04 AM

Dual plane would be a better choice, but IMO it is not what is causing his problem. Its the carb, and maybe even a little bit of a timing issue. Do you have vacume advance?

It needs 'dialed in'

long69 · 10-01-2011, 01:37 PM

fairly sure it needs some carb adjustments. changing the cam thing on mine made a big difference. mine had a nice stumble off the line. now i can go as slow as i want to, and i dont have to power thru the flat spot.

GASoline71 · 10-01-2011, 03:31 PM

That thing needs MORE PUMP SHOT!

Step up about 3 or 4 sizes in the primary squirter.

Even though the Victor Jr. manifolds look sick on a street rig... they suck as far as driveability goes. RPM range is somewhere around 3,500 to 8,000. So unless you're seein' above 6 grand on a consistent basis... you're losing a lot of low end torque. Which could also help increase the big stumble you have now.

Change over to an Edelbrock Performer RPM Air-gap intake. You'll be glad you did.

Gary

Gary

CC69Rat · 10-01-2011, 05:27 PM

Quote:

Originally Posted by landsurvey1

I had a similar problem and it turned out to be a bad carburetor gasket.

I agree.. I fought with a stumble like this for months. I had an old 307 in a 69 Camaro I bought. When I got it, it was a 2brl just a stock setup and the carb was in need of a rebuild. I had an extra 650 and an Edelbrock Performer intake. .. so, I put it on. It was acting very similar to what you describe above. I changed the dist, fuel pump, plugs, everything I could think of until I finally got tired of messing with it. I ordered a 350/290hp crate engine thinking 'Ah! This is going to fix it for sure'

When I got the new crate engine, I just moved the intake and carb, new dist, etc. from the 307 over to the new 350. Guess what !! The stumble is still there.

All that trouble, $1800 engine and the time it took to swap it for a bad carb gasket. As soon as we replaced it, the stumble was gone.

Hope you get it figured out

09-30-2011, 10:20 PM	#1
sbc10guy Registered User Join Date: Sep 2011 Location: Eau Claire, Wisconsin Posts: 415	engine dead spot Hi guys, ive been messing with my 327 lately and it has a dead spot as soon as you hit the throttle.It runs great at higher rpm when you hit the gas but the throttle response is terrible and it hesitates and spits and sputters when you hit the gas hard at a dead stop. If i drive it normal it runs fine but as soon as you hammer on it it hesitates and runs bad. The motor is a 327 thats bored .30, has a .464/.480 crane cam, 202 camel hump heads 487 casting, hydraulic lifters harland sharp roller rockers, victor jr. edelbrock intake, and holley 650 double pumper carb. I dont know if its the mix of parts thats wrong, ive messed with the timing and made it better but i cant get it right. Any advice is greatly appreciated. Thanks. __________________ 1969 shortbed c/10 1998 GMC sierra

09-30-2011, 10:45 PM	#2
68streetrod Registered User Join Date: Jan 2010 Location: Liberty In Posts: 46	Re: engine dead spot the victor jr is made for best preformance in the upper rpm range but it should Not be totally flat. Does it rev up nice from a idle with no load (in park) or stumble till it builds rpms? What kind of ignition are you running? and are you running a good premuim octane gas ? Last edited by 68streetrod; 09-30-2011 at 10:46 PM. Reason: left word out

09-30-2011, 11:04 PM	#3
sbc10guy Registered User Join Date: Sep 2011 Location: Eau Claire, Wisconsin Posts: 415	Re: engine dead spot When its in park it has a small dead spot right away and the rest of the rpm range is awesome. I run premium gas with a mix of turbo blue 110 octane every once in a while. It has an hei distributer too. __________________ 1969 shortbed c/10 1998 GMC sierra

09-30-2011, 11:26 PM	#4
landsurvey1 Registered User Join Date: Jan 2009 Location: Arizona Posts: 404	Re: engine dead spot I had a similar problem and it turned out to be a bad carburetor gasket.

10-01-2011, 12:02 AM	#5
edhtrd71 Registered User Join Date: Jan 2011 Location: Edinburg, Texas. Posts: 194	Re: engine dead spot make sure the accelerator pump is squirting as soon as the linkage moves

10-01-2011, 09:04 AM	#8
OJ1988 Just a car guy Join Date: Feb 2006 Location: New Washington, IN Posts: 991	Re: engine dead spot Dual plane would be a better choice, but IMO it is not what is causing his problem. Its the carb, and maybe even a little bit of a timing issue. Do you have vacume advance? It needs 'dialed in' __________________ 1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig

10-01-2011, 01:37 PM	#9
long69 Registered User Join Date: Oct 2006 Location: lost angeles Posts: 159	Re: engine dead spot fairly sure it needs some carb adjustments. changing the cam thing on mine made a big difference. mine had a nice stumble off the line. now i can go as slow as i want to, and i dont have to power thru the flat spot.



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