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Old 01-28-2013, 11:12 PM
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New Intake Manifold/Carb now sputters

Hey guys,
I have a 72 Chevelle with a 383 Stroker. I just put on a new Holly Double Pumper, 650 CFM with a Air gap dual plane edelbrock intake manifold.
Runs great, but when I punch the throttle, it sputters and then kicks in, if Im at a stop, I punch the gas and sputters and nearly dies. But then catches and takes off. Any Ideas? Did I not tune it properly?
Timing is set at 12 degrees advance.

Next issue is that the motor under heats. Before the swap, it ran at around 190 degrees. Now it runs at 100-120. If I stop, it heats up to around 190, but then when I get going again, the temp rapidly drops back to 100-120...

Bad thermostat?

Any suggestions/troubleshooting is helpful.

Thanks,
Mike

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Old 01-28-2013, 11:17 PM
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post the stats of before and after. What was the carb and intake before,how did it run,why did you change it? The 650 is way too small but should work great for idle to 5k
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Old 01-28-2013, 11:20 PM
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Carb before was a 600 CFM edelbrock. 1405 manual choke.
Intake manifold was holly street dominator, single plane, post 82 with EGR valve spot.
And how is the 650 way to small?
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Old 01-28-2013, 11:30 PM
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I would use a 750 on a moderate 350 cube engine.Most 383s are higher out put and you did indicate it was in a chevelle,I was guessing it made some power.
If you used a street master before then you must have been looking for gas mileage?
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Old 01-28-2013, 11:33 PM
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correction street dominator,low rpm intake too,not as low as street master. I had a street dominator on my corvette when I bought it. The car mad 205 horse power with that intake,measured on a dyno-jet dyno
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Old 01-28-2013, 11:45 PM
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I primarily changed it out because I didnt like the way that the carb was running. Wasnt happy with the product, and it was borrowed. (had to give it back)
As for the manifold, It had two spots for a EGR valve, so it needed two blocker plates. I could also tell that it was restricting the hell out of the motor.
And I did specify that it was in a chevelle. (i double checked)

Once I put everything on, it ran great. I reused the thermostat, prolly a bad idea, but it didnt give me any issues prior to the swap.....
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Old 01-28-2013, 11:51 PM
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What is your total timing(@3,000),cam specs/CR,exhaust, even a meek 383 should be at least fun to drive.
The biggest issue is matching the parts,,,combination,combination

then tuning
you need to provide more information please
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Old 01-29-2013, 12:02 AM
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Ok Ill start from the top just so I dont forget anything:

-1972 Chevelle Malibu
-350 block, bored .80 over with a stroker kit.
-Stock heads
-Long tube headers
-Flow master exhaust
-Cam is a mild RV cam. Im not sure of the duration. Very mild though, just above stock.
-Air Gap Edelbrock Intake Manifold
-Holly 650 DP Carb
-Turbo 400
-Stock Differential
-Floor Shifter
-HEI Ignition

If I remember correctly, the total advance is between 32-36. Ill have to double check tomorrow.

I think thats it as far as performance mods are concerned.

Let me know if you need any additional info.

Mike

Last edited by dub; 01-29-2013 at 12:19 AM.
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Old 01-29-2013, 12:06 AM
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New Intake Manifold/Carb now sputters

I would change thermostat first to eliminate that as a problem. I have read a lot of post with the same problem of hesitation when using the Edelbrock RPM AIR GAP. It is not a good intake to use in cold weather so with the temperature running so cold that is probably the problem. If you can get the temperature up to 190-195 it will probably run better. Experiment with the timing try setting the initial at 16-18 degrees. You will have to limit the mechanical advance to 18-20 degees. What are your camshaft specs? What distributor are you using? Read this Wiki article on setting your HEI and timing. Also there is a section in the article on adjusting the transfer slot on Holley carburetors. Increase the initial timing and close the front throttle plates. http://www.crankshaftcoalition.com/w...EI_distributor. BTW you will need a timing light with advance.
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Old 01-29-2013, 12:22 AM
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As far as the cam specs, Im not sure....I dont remember.
Total advance is betweem 32-36, Ill have to double check.
Ill change out the themostat tomorrow and see if that helps..

Thanks for the help guys.

Mike
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Old 01-29-2013, 12:33 AM
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Quote:
Originally Posted by cdminter59 View Post
I would change thermostat first to eliminate that as a problem. I have read a lot of post with the same problem of hesitation when using the Edelbrock RPM AIR GAP. It is not a good intake to use in cold weather so with the temperature running so cold that is probably the problem. If you can get the temperature up to 190-195 it will probably run better. Experiment with the timing try setting the initial at 16-18 degrees. You will have to limit the mechanical advance to 18-20 degees. What are your camshaft specs? What distributor are you using? Read this Wiki article on setting your HEI and timing. Also there is a section in the article on adjusting the transfer slot on Holley carburetors. Increase the initial timing and close the front throttle plates. http://www.crankshaftcoalition.com/w...EI_distributor. BTW you will need a timing light with advance.
Your right the air gaps start to frost in the plenum and carb venturies about 40 degrees! In Michigan it even freezes the throttle shafts on cold days stuck at speed !!!! Not a good thing Its a warm weather intake there should be a warning on the box when a person goes to buy one LOL


Jester
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Old 01-29-2013, 11:18 AM
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The stock gears and stock low stall torque converter is not going to be very friendly to getting crisp throttle response with a double pumper carb. Just too much throttle, too fast.
Recurving the distributor advance curve will help. More initial at idle always helps throttle responce.

16-18 base inital. 34-36 at max advance. a 18deg advance curve for a mild cam.

the carb will need extensive retuneing of the accelerator pump systems. ( shooters/pump cam)
The temprature of the intake manifold plenum definatly is a factor, especially in the winter.
Cold manifold on a cold day ='s trouble with throttle respose from a very low rpm, especially compounded
by a stock low stall converter and stock sluggish gears.
A afr fuel ratio meter/gauge is great for getting the carb dialed in.
They are never right,, out of the box. A the cold manifold is going to compound that.
The performer rpm is a great manifold but the AIR GAP non heated design is not the best for WINTER driving.
The RPM manifold with the full divided plenum and under plenum heat path is a lot more winter friendly.
The Mid rise style "EPS" Performer is not bad too.

The cold plenum air gap style manifold may have been a bad choice for this near stock motor and winter driving.
Again, the stock gears and stock low stall is not helping.
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Old 01-29-2013, 11:29 AM
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Quote:
Originally Posted by dub View Post
Ok Ill start from the top just so I dont forget anything:

-1972 Chevelle Malibu
-350 block, bored .80 over with a stroker kit.
-Stock heads
-Long tube headers
-Flow master exhaust
-Cam is a mild RV cam. Im not sure of the duration. Very mild though, just above stock.
-Air Gap Edelbrock Intake Manifold
-Holly 650 DP Carb
-Turbo 400
-Stock Differential
-Floor Shifter
-HEI Ignition

If I remember correctly, the total advance is between 32-36. Ill have to double check tomorrow.

I think thats it as far as performance mods are concerned.

Let me know if you need any additional info.

Mike

".080" over"?! are you sure? That's going to lead to a LOT of problems.

The timing has already been mentioned.

And for that mild combo that 600 edelbrock is a MUCH better match, though it may have needed tuning and/or cleaning.
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Old 01-29-2013, 11:31 AM
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RE:
(The stock gears and stock low stall torque converter is not going to be very friendly to getting crisp throttle response with a double pumper carb. Just too much throttle, too fast.
Recurving the distributor advance curve will help. More initial at idle always helps throttle responce.)

please explain this? a 650 DP is extremely responsive,even on a 283 with 3.08 gears?
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Old 01-29-2013, 11:40 AM
How fast is fast enough?
 
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Quote:
Originally Posted by vinniekq2 View Post
RE:
(The stock gears and stock low stall torque converter is not going to be very friendly to getting crisp throttle response with a double pumper carb. Just too much throttle, too fast.
Recurving the distributor advance curve will help. More initial at idle always helps throttle responce.)

please explain this? a 650 DP is extremely responsive,even on a 283 with 3.08 gears?
That depends on how it is tuned. He may have way too much coming in from the accelerator pumps, or too early, or not enough, or too late, or too long/short duration. The joys of running that much pump on a heavy car with stock stall and mild gears...
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