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i am having a little problem with my holley 650 double pumper. what i have is a 69 mustang and at the dragstrip the car seems to bog down for a few seconds after launching. it is a 302 with a comp 280 magnum cam roller rockers, performer rpm intake, 1 inch carb spacer 2500 stall and 3.80 gears. the car takes off slow, but once it hits 3000 rpms it really takes off. i think the carb may be too big. any suggestions like down jetting it or?

Maybe This Site Can Help

http://www.mortec.com/carbtip1.htm

Sounds Possible That It May Be Something In The Timing As Well.

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i think it may have too much cam for the gearing. can you give some more cam specs?

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"but its that gut feeling of you're drawn to what feels right for yourself and what you're passionate about..."

Yeah That Is Possible Aswell I Didn't Think Of That. Could Be Due To Converter Aswell You May Need To Go With A Larger One, You Said It Picked Up At 3000 Maybe A 3000's Stall Would Be Nice Eh?


But A 650 Should Be No Where Near To Being To Big For A 302.

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yeah i dont think its over carbed, but it might still be runnin piggy at the bottom end. but thats neither here nor there. it sound like to me that the motor needs to leave the line at a higher rpm. so id say go with somethin like a 4.30 gear or something if its just a track car and occasional street machine.

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"but its that gut feeling of you're drawn to what feels right for yourself and what you're passionate about..."

Yeah Either or Bigger Stall Converter or Lower Gear Ratio, Maybe Both.

The Engine Should Hold A 750, SHOULD...No Promise....But It Should. I Have Seen and Done It Before W/ A 750 on Stock 302's.

Hard To Tell Without The Specs of The Engine/Valve Train. But If The Cam Isn't Building Power To 3000 Then I Would Suggest Having A Converter That Stall To The Point That Your Lunching Right In Your Power Band That Way You Eliminate The Hesetation or Bogging, Yes A Lower Gear Would Give You A Little More Lee Way As Far As Climbing RPM's Faster But It Sounds Like Its More To Do With The Stall As Far As Coming Out Of The Hole. Plus You Would Still Have The Drive Ability of Your 3.80 Gears, If It's A Street Car.

If Its A Track Only Car You Would Want To Set It Up Where You Would Be Running Out Of Gear Just Slightly Past The 1320 FT. Mark.

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the cam has a 512 lift and a 231 duation @ .050 lift. im thinking more converter, but i was going to try down jetting the carb 2 sizes.

Is it on the launch? Have you tried adjusting the pump nozzles is it 30cc or a 50cc. Have you checked you timing lately? Timing is critical maysure it is where it needs to be.

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Money can't buy happiness, but it can buy horsepower...and that's kind of the same thing...

It could be the cam for the rear squirters needs to be changed for one that's quicker.

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If you think no one cares, try missing a couple of payments...



FIAA!

SFPP!

What jets are in it? I got 70s in front and 76 inrear of a 650 demon . 355 is still a little rich . I don't think it gear or stall . Make sure your accelerator pump is set right , starts squirting as soon as the linkage even starts to move. Also check your float levels and fuel pressure , the car will run different with 4 #s of fuel pressure than it will with 7#s . The cam is on the large side , but if you have the heads to move the air it'll be ok . probably need more info on your set up.

it has stock 302 heads. i know that the carb has been up jetted one size all around than what the carb origionally had. i am not sure of the #s. i tried reversing the accelerator pump cam and it made the car stumble. The problem that im having is not immediately when i hit the gas like a stumble, it is more like a lack of power until bout 3000 rpms.

Sounds like that's just where your power band kicks in for that camshaft and your engine size.

The 289/302/351 w Ford motors have way smaller exhaust ports than intake ports . they need a split duration cam to compensate for exhaust short comings . The valva size is small too . Holding the valve open longer is the only way to compensate , besides heavy porting . IMHO you need less cam or more cylinder head. For your current combo I would make a pass , read the plug , and jet down accordingly . Your mph should go up until you get to lean . I keep changing jets untill my mph is highest . Also A pic of the car wouldn't hurt

what do the plugs look like? to get a accurate reading the vehicle should be ran through all gears at wide open throttle and then immediate shut down, find a side road and check your plugs

Check your timing curve as you have a pretty big cam and you will need more timing to make it and the fuel work right. Your power curve is going to be high so don't expect allot off idle and remember that you more timing to burn the fuel from the acc. pumps."Again it si the timing curve"

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

Hey , grudd I have a 650 on my 355 . So far I have 70's in front and 72's in the rear jet wise .

Call Holley. They deal with every combination under the Sun, and can tell you pretty quickly what you need to do. Everyone on here has given you good information, and a means to solve your problem, but they can cut down on the trial and error especially with the carb.

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I want to be different like everybody else.

Another clue: try borrowing some ones vac.secondary carb and try it,with the d/p carbs you are dumping alot of fuel at low RPM's the vac. carb will let the engine start revving before the fuel comes in. Try lower gears or about a 3600 stall converter.The point is that normally a d/p carb is not the best carb for a heavy street car at lower RPM's

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

Go to the Mortec site. It covers the problem.

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I want to be different like everybody else.

Thank u for the help. I ran a rubber hose from one vent tube to the other. I also went from a open spacer to a four hole. I gained a lot more low end. I raced it today and while the 60 foots are at 2.0, more stall converter should wake it up.

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'78 Luv 1.8, soon to be 350
'69 mustang 302
'68 lemans 455