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Old 11-27-2010, 01:05 PM
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670 holley gasp at idle to rev

I am running a 327 with an rv cam, weiand intake, engine is bored .40 over.
It runs around 1000rpm with the electric choke engaged, then kicks down the 800-900rpm after warm, but when I manually rev the motor from inside the bay 670 holley gasps for a second, but if u bring the rpm up a little and rev again it doesn't gasp? Is it the pump cam or 10" air cleaner or 3/8" fuel line or the jets? When I drive it I am pretty conservative and haven't floored it yet since my restoration is fairly new only driven a few times. Want to make dam sure everything is in order have to much money invested. Also my holley fuel pump has a tiny leak above the gasket when the out let to the fuel line is, the pump is a split cast and has more bolt hole pattern so every other one is used and the extra holes are only on the top and don't go throw the bottom. And the leak is on one of the top holes above the fuel out let, leak is tiny but worries me.

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Old 11-27-2010, 03:53 PM
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Please don't post the same thread twenty minutes apart, it won't get an answer any sooner.
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Old 11-27-2010, 04:38 PM
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If your engine is good and warm and it does that check the accelerator pump arm that there is no play in it. Just barely touch the throttle and see if it does a instant shot of fuel. If there is any sloppy play it will do that. Best thing I do is loosen it up then tighten it very slowly till there is no play left. They recommend to have about .015 to .020 clearance between the pump arm and pump lever at WOT so go from there.
Eric
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Old 11-27-2010, 04:57 PM
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The best way to jet is with a percy metering plate. It allows the mixture to be adjusted by screw. The number of turns out is then converted to a jet size. You remove the plate and install the corresponding jets. Worth $50 bucks , instead of 10 jetting changes.

If it needs, keep it in the accerator pump cam area, right from the start at idle.

Check timing , fuel, and anything qualifing as stupid.
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Old 11-27-2010, 07:18 PM
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Sounds like accelerator pump adjustment or different accelerator pump cam needed. Eric32 said it. whats the idle timing?

If you get the accel pump adjusted and still have a studder you can SOMETIMES turn the idle mixture screws and 1/4 turn out and see if that helps. Could also need larger shooter size on the accelerator pump. Is it the stock size in there now?
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Old 11-27-2010, 07:20 PM
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i upgraded my 670CFM to a 50CC pump shot, works great.
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Old 11-27-2010, 09:24 PM
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Thanks to all you guys,
I will check all your suggestions out and find out what is best, I will let you know. Thanks Again
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Old 11-27-2010, 10:15 PM
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670 cfm holley

What fuel line size do you guys recommend for this size carb?
Do you think this carb is to big for my 327 bored out .40 over?
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Old 11-27-2010, 10:21 PM
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No i don't think the carb is to much for your engine. JMO
I have ran the 670 avenger on some pretty light engines and done fine.
The last one was on my 68 chevelle it has a 355 in it works pretty good with alittle tuning.






Cole
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Old 11-27-2010, 10:59 PM
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carb gasp

i agree that its a little on the big side.if the pump squirters are working as others rightly suggested do this.im assuming the timing is right as that is first in order as thet will affect throttle blade opening at idle.there are transition slots in the bores where the blades close.this lets idle mixture transition through the slot when the throttle first opens to allow fuel delivery until the boosters get signal.pull the carb as it sits,flip it over and see how much of the transition slots are covered by the blades at idle.with a carb that big on a small engine id want to see thirty thousanths un covered.if it has a wide blade opening and a large section of transition slot uncovered at idle crack the secondarys open a little so the primary blades will be closed more at idle.i think this is whats happening.if this isnt your problem this has to be done to get proper idle quality and of idle response.sorry so long response.hope this helps

billy
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Old 11-28-2010, 08:56 AM
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That 670 is not to big for what you have IMHO, if you have the correct size jets and the right tune on it along with a different pump size already stated. Timing correct. Make damn sure the float levels are correct also. It will do fine on your engine,JMO You get that thing dialed in it will be fine.



Cole
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Old 11-28-2010, 09:44 AM
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Do you think I should use holley's 50cc pump conversion kit to upgrade?
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Old 11-28-2010, 01:39 PM
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Quote:
Originally Posted by chevyrally68
Do you think I should use holley's 50cc pump conversion kit to upgrade?
Swapping to this pump kit won't do anything for you if you still have the stock pump nozzle(squirter) on it. The 50cc kit is really only needed when you go above the size 35 squirter, your carb has either a 25 or 28 stock. You don't need the pump kit yet.

Sounds like you need a larger squirter and possibly a larger pump cam first(from 25 to 28, or 28 to 31). This is assuming all adjustments are currently correct, like pump arm, throttle plate opening/transfer slot exposure, idle screws.
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Old 11-28-2010, 02:44 PM
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I had to jet my holley street avenger up from 65 to 67 on the main jets and I put 72 in rear. On your squirter size it should be a .031 size but check to maker sure. If you really look close with the choke plate open you can see a number stamped on it.

As suggested above check your transfer slot. I always crack open my secondary's more then what holley has it so I can have good air flow though all four barrels.
I got one of the all aluminum 670 street avengers last year at this time and it was a piece of junk out of the box. It would lean out so bad my engine would back fire and would not stay running very good.

I sent it back and got a replacement and it worked better but for some reason if you gave it a big shot of gas it would just give a big back fire here and there. I finally went to one of there zinc original type street avenger and it works much better for me.

I am running a very mild 350 with only about 350-375 hp and cam is very small of what I have in it now and your engine should be fine with the street avenger. Double check your timing as stated above and if your running timed port on your vacuum advance try putting it to full manifold and readjust your idle and that will allow you to close it some.
Eric
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Old 11-28-2010, 07:22 PM
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carb

A lot of people think BIGGER is better but that's the cause a good street engine on a good day volumetric efficiency is about 85% and a race engine is about 95-100% natural aspirated, so it really simple the equation to use is your max rpm x your engine size then divide that number by 3456 so example. 6000rpm x 350 engine size equals. 2100000 divided by 3456. Equals 607.63 CFM. So that tells use that fairly stock 350 use would use a 600CFM carb regardless which brand (but Holley is my choice) got a customer that built a small block 350 .06 over makes it a 360 and had a new out box 650CFM elde brock and really didn't do it for him so put a 650 Holley and he loves it but just opinion on that setup.if you run a 600Cfm should be fine
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