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Topic Review (Newest First)
01-30-2013 04:47 PM
snakebit68
carb

Yeah...I'm betting that took care of most of it. Havent heard from him since he fixed it...could be a good sign he's out tearing up the streets and has forgotten all about us...lol
01-30-2013 04:07 PM
cdminter59
New Intake Manifold/Carb now sputters

I wonder how the 650 DP runs on dub's car now that he has the temperature back to normal. Hope everything worked out without anymore problems.
01-30-2013 01:25 PM
painted jester You can disconnect the actuating arm to the secondary linkage And drive on the primary and see if the bog is still there! if it is take care of the primary bog before hooking up the secondary's! Then hook up the arm and test the secondary's! Unless your carb literate Its the easier way for a novice on carbs to start!

Jester
01-30-2013 08:37 AM
snakebit68
carb and intake

Yes, change out the thermostat first to eliminate that as a cause. I would also advise you to run a simple check for any vacuum leaks around the manifold and carb with a can of carb cleaner. Just to eliminate a vacuum leak as a possible cause. Then I would look more deeply into the adjustments on the carb, specifically the secondaries. It may be dumping way too much fuel initially causing a hiccup before the engine can catch up with the fuel flow. A recurve kit on your advance will probably help as well. Just a thought, with a stock convertor you may not be building enough RPM's directly off idle acceleration to allow a complete burn of the fuel entering the chambers. Good luck
01-30-2013 07:38 AM
cdminter59
New Intake Manifold/Carb now sputters

dub, The best way to adjust your carburetor is with a vacuum gauge. Just hook up the vacuum gauge to a manifold vacuum source. Then adjust your idle mixture screws out until you have the highest reading. With the RV cam start out with about 12* initial and 24* mechanical (distributor weights). If it is a stock GM distributor untouched it will probably add 25* that will be fine. Total will be something like 37*. Don't add no more than 10-12* vacuum advance. Crane has an adjustable vacuum advance can kit, Crane Vacuum Advance Kits 99600-1 - SummitRacing.com that will fit the GM HEI. This also includes an advance curve kit to bring the mechanical advance all in by 3000 rpms.
01-30-2013 02:05 AM
71nova355 scratch my last post then...lol
now I feel dumb
01-29-2013 11:36 PM
vinniekq2 If thats the only mistake you ever make then we will all bow down to you,,,lol. Things happen ,and the day continues on anyways
keep it fun and interesting
01-29-2013 11:16 PM
dub Ok, well.....Feel kind of dumb. But have no problem admitting my faults...
I put the thermostat in backwards....Yup....sure did. I was on such a hurry because I was on limited time. So, that problem is fixed. That's my karma for not putting a new one while I was doing the swap.
As far as the sputtering, I adjusted the ratio screws. The process i used was basically set them all the way lean, then turning them 1-1/2 turns to rich. I test drove it and it much better. However I need to see what the total timing is and adjust more from there.
Ill update the page when I am able tomorrow.
Oh yea and by the way I still feel dumb about the thermostat. But whatever.


Thanks for all the replies.

Mike
01-29-2013 03:20 PM
71nova355 I would say since you just changed the intake and carb the problem lies there not the thermo stat. I bet you need to check your accelerator pump linkage and make sure that gas starts squirting the instant the throttle blades open. sounds like its getting air from the blades opening and then following an instant late with fuel. make sure both promary and secondary blades are set equally and keep them that way. only ajusting both equaly if need be. the transistion slots should only just barely show under the carb below the throttle blades. your pump linkage should have a small amount left in it at full throttle so you dont prematurely wear out the plunger or pump. but it should also be set like .020 from actually squirting gas out. lol like the linkage should be just barely touching the pump arm and you can look down the carb when you apply throttle by hand and make sure that gas and air comes on together. also start with the fuel air screws 1-11/2 turns out and adjust from there with a vacuum guage getting the highest vacuum reading you can and the fuell mixture screws equally turned. what power valve do you have compared to vacuum reading? hang in there bud you got this. also are you running a fuel pressure regulator? and your floats are set right? Ive read double pumpers prefer single planes but ive seen all kinds of combos work and work good so that shouldnt be the problem. Have you tried a spacer? I just swapped from a open spacer to a 4 hole and I can definitely feel the better low end response. Although I have a single plane so maybe an open would give you more plenum area? idk oh you can also buy a set of colored pump cams and that will change the amount of pump shot sent to the squirters. maybe larger squirters would get fuel there faster too. you have plenty of room to grow before needing a bigger 50 cc pump shot too. Even new out of the box tho the carb should be checked thoroughly and set to spec.
01-29-2013 02:26 PM
dub the carb is brand new. out the box
01-29-2013 01:04 PM
painted jester Is the carb new out of the box or used? If out of the box no tuning except basic. it should work very well and be pretty snappy on your combo! If its used it may have been tampered with! to match a different engines demands!!!

Jester
01-29-2013 11:40 AM
ap72
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...
01-29-2013 11:31 AM
vinniekq2 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?
01-29-2013 11:29 AM
ap72
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.
01-29-2013 11:18 AM
F-BIRD'88 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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