try breaking it down , 4 screws if I remember on the front which are horizontal. Will find the two jets in there and a power valve. Unscrew power valve and check, check jets and take note of size... Then obtain gasket set and new power valve. Forgotten what the spray setup was but I am sure it is pretty simple also... Had same problem years ago on an old Nissan 4WD.... Cheers nev

thanks nev, i might have to try and pull it apart in the end  to save the $ but will be trying another method first and see how that goes

I had a flat spot in my car years ago and slightly larger jets fixed it. It's been a long time but if my memory serves me right they are pretty simple as nev said.

GO BLUES.

It has been a while since i was in the parts game but the jets, powervalves and gaskets are all available seperatley or else you can get a kit quite easily (part no HY- 353). They arent a difficult carby to service, One thing though is to check for play in the main shaft holding the butterflys as they can wear and suck air and cause problems. If this is the case it will need rebushing.

Hi Russ first off Holley carbs are very simple in design with few moving parts so there is minimal chance off dropping things down into the bilge, the only thing to watch out for is maybe a check ball under the pump squirter depending on model but thats about it. Obviously eaiser if you take it off and do it on the bench....

If you do pull it apart yourself I would stongly suggest you get the better quality gaskets { not the "Fuel Miser" brand /style of rebuild kits } they are coloured blue and are non stick so you get a few goes at tuning the carb before the gasket tears, I know them as BG gaskets but Peter at Holley carbs in Bassendean will know what you are talking about if you ask him...

Now onto the tech, the problem is there is two kinds of flat spots or "bogs" and the carb can be either rich or lean to cause either of the two....

Generally these can be cured by playing with the accelerator pump circiut/squirters unless there are other problems involved..

I'll add to this that the engine be in good condition and state of tune such as plugs , timing, vacuum leaks, float level,idle mixture etc etc are all ok as any of these will also cause your flat spot thus giving you false symtoms and causing you to chase your tail and looking in the wrong area...

I'll give you a basic description of the accelerator pump circuit so you can follow in your mind whats happening. The pump circuit is basically a band aid where it dumps raw fuel into the engine to cover the fuel needed until the carb circuits start flowing,a carb is a vacuum device and there is a slight delay from when the throttle is opened to when fuel starts flowing hence the extra fuel needed to cover that "hole"..

I'll try and describe the two types of bogs and give you a cause and cure for each..

The first  { 1 } is where the engine will go flat the instant the throttle is opened and then recover and take off. Whats happening here is the engine is consuming all the available fuel supplied by the squirters and then basically stalling until the carb circuits start flowing, this is a lean condition and is cured by using a pump squirter with a bigger hole { ie go from a 28 squirter to a 35 }. This allows the same amount of fuel the circuit supplys but quicker. If its still not enough fuel you can go bigger again and also change the pump cam which can give you more fuel and also at a different rate { shape of the cam}...

Ok description two ,if the engine accelerates for say a second ?? and then bogs and then recovers again whats happening is its too rich. The engine is responding and then cant handle the extra fuel supplied so stumbles until it clears and then takes off again. This description will also be more noticable down low with low engine revs where as if the throttle is rolled on from higher up in the revs ie passing or powering up a wave the engine more able to handle the extra fuel .The cure here is to go to a smaller squirter allowing the same amount of fuel to be supplied over a longer period ,again if this is still too much smaller cams with flater profiles can be used...

What I have described here are noticable flat spots which require large changes to the carb sometimes its just simple matter of a slightly rich idle mixture or bigger/smaller jets etc or even a slight idle change { butterflies maybe too far open or closed }...But from what you desribe its sounds noticable so hence Ive given you a few more involved tuning tips...

Hope this helps and any more info you can supply or describe will help out ..

Cheers fishfish..

the powervalve is not the carb a powervalve is in a 2 stroke exhaust system

first get a service manuel and go from there, you need to get torque settings and the like, also if you follow the manuel youlle be fine

thanks for all the info. i will see what happens

Wideopen there is a power valve located in a Holley carb { and some times two},granted same name but different function but anyhow please try and give correct info on forums as this is how internet rumours start...

Cheers fishfish..