help with 425hp stroker carb
Thread Starter
Instructor
Joined: Sep 2010
Posts: 157
Likes: 0
From: Rockwood TN
help with 425hp stroker carb
Hi Guys,If anyone can please tell me or point me in the right direction on the proper set-up for my 76 stingray with a 425hp 388 stroker.I have a 670 street avenger and the factory set-up for a L-48 as far as the super T10 4 speed and the rear gear ratio.I use the car about every day and would like to know what would be the best carb,rear gear ratio for street racing if the need be.I was told the carb was to small for my 425hp stroker and the 308 rear gear ratio was wrong for what I had in mind.As you can see I have no clue and any help would be very appriciated.
Tech Contributor
Joined: Jun 2004
Posts: 20,868
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Hi Guys,If anyone can please tell me or point me in the right direction on the proper set-up for my 76 stingray with a 425hp 388 stroker.I have a 670 street avenger and the factory set-up for a L-48 as far as the super T10 4 speed and the rear gear ratio.I use the car about every day and would like to know what would be the best carb,rear gear ratio for street racing if the need be.I was told the carb was to small for my 425hp stroker and the 308 rear gear ratio was wrong for what I had in mind.As you can see I have no clue and any help would be very appriciated.
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
If by illegal street racing you mean going to the drag strip then a 750 holley double pumper or speed demon would probably be fine however a good tuner can make the 670 work just as well. Depending on how much air the engine is sucking through the 670 it might not even using all that the 670 can deliver. Fuel can be changed with jets.
Thread Starter
Instructor
Joined: Sep 2010
Posts: 157
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From: Rockwood TN
I was going to go up a couple of jet sizes on the primary and secondaries to try to get rid of the stumble when I pull out.I was also thinking of going from the 6.5 power valve to a 3.5 as the Holley techs recommended.I just put an Edelbrock Air-gap on the engine and can tell a great difference now,But still have the stumble,What do you think?
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
I was going to go up a couple of jet sizes on the primary and secondaries to try to get rid of the stumble when I pull out.I was also thinking of going from the 6.5 power valve to a 3.5 as the Holley techs recommended.I just put an Edelbrock Air-gap on the engine and can tell a great difference now,But still have the stumble,What do you think?
Thread Starter
Instructor
Joined: Sep 2010
Posts: 157
Likes: 0
From: Rockwood TN
You are right,Im was running 10 vacume at idle with the Edelbrock RPM intake that I had on the car.Since I changed the intake to the Air-Gap afew days ago,Ive only test drove the car for about 50-60 miles or so,mostly interstate driving.I havent checked the vacume since the intake switch.I have great response with accelration at 50 plus MPH.Im getting the stumble only when I pull out now.With the first intake it was every time I would push the accelarator,pulling out or at speed.I know Im getting more air with the Air-Gap intake,and it has helped,just need some advise on the off line stumble.Im running a 510 lift intake,exhaust cam,109 center line with 246 duration.I dont know the A/F ratio,but can find out in afew days,I will get back at you when I get these specs.Thank-you for thed help.
Last edited by bobs76stingray; Nov 21, 2010 at 08:09 AM. Reason: more info
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Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Could you please post your cam specs from the cam card?
246 I duration is over cammed for only 388 ci. You also need to read up on how to tune Holley carbs. Changing power valves should only be don't with some kind of A/F ratio sensor.
Bigger carbs don't fix problems. 500 - 670 work really well on smaller motors from 350 - 388 ci
246 I duration is over cammed for only 388 ci. You also need to read up on how to tune Holley carbs. Changing power valves should only be don't with some kind of A/F ratio sensor.
Bigger carbs don't fix problems. 500 - 670 work really well on smaller motors from 350 - 388 ci
Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
Put the old jets back in thats not how you fix a stumble and put the 6.5 PV back in also. the 1/2 vacuum rule is bs and if youre pulling 10 in vacuum theres no reason for a 3.5. Toss the 308s in the trash
Street racing is for kids get it to a track and see what it really runs.
750DP would (as said above) work nice, bet right out of the box you shouldnt have to touch it or if you did it would be minimal.
Street racing is for kids get it to a track and see what it really runs.
750DP would (as said above) work nice, bet right out of the box you shouldnt have to touch it or if you did it would be minimal.
Thread Starter
Instructor
Joined: Sep 2010
Posts: 157
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From: Rockwood TN
havent changed anything in carb yet,Im only relaying what the Holley techs told me I need to do to get rid of the stumble.I have a set of Procomp aluminum heads,64cc/190cc.2.02 intake and1.600 exhaust.The cam is a howards,109 centerline,246 duration intake and exhaust.510 lift on intake and exhaust.I cant find the cam card as of yet,Im going through a divorce a its been misplaced.when I refered to street racing I am refering to drag strip.
Thread Starter
Instructor
Joined: Sep 2010
Posts: 157
Likes: 0
From: Rockwood TN
The street Im refering to is a privately owned stretch of straight road that was left from a highway change.It is alittle over 1/2 mile and is not on the main road.We set up our own light to race by.Nothing illegal.I dont break the law in my car or any other time.Im only asking for alittle help.
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Holley 750 DP #4779 is the best bang for the buck out there, ran one on my 355ci with no problems, then ran the same carb on a 406ci and no problems 
