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Author Topic:   Hesitation on starts
mark akins
Dirt Maniac

Total posts: 131
posted October 02, 2005 03:47 PM  
I have a 80 comaro street stock with a 350 double hump heads, victor jr. intake, 750 double pump holly carb., 1.6 rockers on intake, 1.5 on exhaust. When I hit the gas it hesitates then it revs right up. It kills me coming out of the corner and on restarts.
The spark plugs look good. Any ideas on what the problem would be?

Thanks Mark

[This message has been edited by mark akins (edited October 02, 2005).]

beachracing
Dirt Forum Racer

Total posts: 94
posted October 02, 2005 07:15 PM  
Does it do it early in a race. I have always had this type of thing sting me. Our last race was on saturday for a 3 day show, and car ran fine all three nights....,until the last restart for our main. It vapor locked on a restart, lost a position, but at least it gives me something to focus on for the winter, amongst other things. Check you fuel lines, get them away from heat sources like radiator hoses, exhaust, or insulate the lines so there isn't direct heat hitting them. Float might also be off a little, or something sticking perhaps.

mark akins
Dirt Maniac

Total posts: 131
posted October 03, 2005 12:44 AM  
it does it all the time. it almost seems like it is getting gas to fast ,like it floods out for a second . but i am not sure

Steve Dupree
Dirt Freak

Total posts: 316
posted October 03, 2005 04:09 AM  
I would simply put a kit in it being that it a holley they have that problem alot. It is probally the economy valve ask and see what one would work best for your application.

mike9
Dirt Full Roller

Total posts: 72
posted October 03, 2005 06:43 AM  
sounds like an accelerater pump problem either shooting too much or not enough gas could have too large or small squirter nozles or wrong cams or improper adjustment of the pump or you could have a pump not working at all

Speedway65
Dirt Freak

Total posts: 344
posted October 03, 2005 01:35 PM  
Not sure whether the doublepumpers use them but it sounds like your power valve is blown out.They are about 6 bucks each so its worth a check.We run a 2bbl holley and had 2 go this year,it loads up on restarts and then goes like a bat out of **** .IMO

tin cup
Dirt Full Roller

Total posts: 40
posted October 03, 2005 01:35 PM  
I would go with acc. pump, too.

STREET16
Dirt Maniac

Total posts: 158
posted October 03, 2005 02:31 PM  
Are you running in the RPM band of your camshaft? I had a similar problem and went to a taller gear to fix it.

mark akins
Dirt Maniac

Total posts: 131
posted October 03, 2005 05:00 PM  
I already changed the accelerator pump and put smaller squirters in the carb. But the thought on the gear not being right has me thinking. I only get 5200 rpm's at the end of the straight. I should be getting 6200+. I knew my gearing was off and it sounds as if that might be the problem. I didn't think the gears would make that big of a difference with relation to the hesitating. Maybe I am wrong.

Mark

dirtyboy58
Dirt Full Roller

Total posts: 40
posted October 03, 2005 05:18 PM  
first check timing set by ear and try it if your chain has stretched or balancer slipped alight will not work had same problem balancer slipped set timing by ear and won that nite

mark akins
Dirt Maniac

Total posts: 131
posted October 03, 2005 06:16 PM  
i just remembered i also have an advance spring kit in , i have the weakest spring installed

oceanridge motorsports
Dirt Full Roller

Total posts: 27
posted October 03, 2005 06:26 PM  
your secondarys are coming in to quick and flooding the motor for a split second , slow up there opening just a tick and the car will shoot off the corners like a rocket. won't take you 2 minutes to fix and will cost 0$ .

mark akins
Dirt Maniac

Total posts: 131
posted October 03, 2005 11:36 PM  
how do you do that ? with your foot?

tin cup
Dirt Full Roller

Total posts: 40
posted October 04, 2005 01:32 PM  
I would go ahead and change them gear's, too. 5200 is way to low, i'm pulling atleast6800 rpm's with the same thing, but but we run a stock intake.

hotrodenford
Dirt Full Roller

Total posts: 60
posted October 04, 2005 03:55 PM  
Your problem is both the carb and the gear ratio. With a 750dp and that low of rpm's you can't "hit" the gas. Your carb is too big for the rpm's your pulling out of the corner. Basicly a mismatch of parts. Do one of the following items and your hesitation will go away:
*Smaller carb(700 or 650),
*more gear/more rpm's,
*vacume secondary carb(more low end tq with same WOT flow),
*roll onto the gas(never "hit" anything! be smooth!)

------------------
If it has wheels or a skirt, you can't afford it! But they shure are fun...

mark akins
Dirt Maniac

Total posts: 131
posted October 04, 2005 05:28 PM  
thanks for the info . one more question, i am running a 3 speed in second gear with 3.42 gear ,am i losing perfomance ? and should i look fo a 5.57 and run 3 gear or just get a 4.10 and continue running in second gear ?

tin cup
Dirt Full Roller

Total posts: 40
posted October 05, 2005 01:31 PM  
What size track are you racing on? I'm pulling a 6.20 final on a 3/8ths. Thinkin of going to a lower gear. If you are running a 9" rearend, i'd go with 3rd and use your rear gear for a final.

mark akins
Dirt Maniac

Total posts: 131
posted October 05, 2005 02:04 PM  
it is 3/8 mile track . i have a gm 8.5 rear end


thanks mark

oceanridge motorsports
Dirt Full Roller

Total posts: 27
posted October 05, 2005 02:46 PM  
hotrodnford is on the right path , I would run an 1850 or a 3310, and poke some more gear to it . BUT , to answer your ? , and if you don't have the extra $ for a new carb , check to see which hole your acc. cam is in 1 or 2 , it should be in one , and check what color it is , the colors from biggest to smallest are , brown,pink,green,black,orange,red,blue,white. Oh ya , the pump cam is located on the backside of the throttle lever.If it is white, in hole one , and the acc. pump is lever is properly adj.You are s.o.l. ,till you put more gear to it , you should be at LEAST 3200 before you get on the gas for the restart , can you shift it on the restarts ?

mark akins
Dirt Maniac

Total posts: 131
posted October 05, 2005 05:44 PM  
i tried that ,it did not work very well . i am going to change the gear and check into the carb over winter . thank for all of the advise

mark

    

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