holley help

[mr.318]

After talking to a couple carb people long distance,They both recomended a 670 avenger for my k.b. 360 headed 318 xe262-h compcam,My new one come in the mail today,it ideles good i've adjusted the mixture screws to highest vacume triplechecked checked floats tried changing springs but it has a low speedsurge like a bad vacume advance,But i disconnocted dist.vacume no change,Thinking about just selling it i'll take a loss because i'd have to pay holley double shipping, 200.00 dollars plus shipping if anybody wants it,I should have know i don't have anyluck with holleys it's only been run mabey 40 mins.

 

[furz4]

It is probably running lean. I would make sure the timing was correct and check for any kind of a vacume leak. You might need to go up a couple of jet sizes. Check the plugs and see if they indicate a lean condition. Holleys are usaually pretty close out of the box but every engine is different and it's not uncommon for to need bigger jets when the motor is built up to allow more airflow though the engine.

 

[KP]

If you adjust one on the primary mixture screws the entire way in does the engine try to stall out? If not then you either have a bad vacuum leak or need to open up the top 4 outer holes (Air Bleeds). Then can be opened up to .080” (the larger the hole the leaner the mixture).

 

[JackDW]

My experience is that I have had to go with smaller jets. As suggested check the plugs and go from there. I have had a lot of luck with this Carb and in most cases it is very close right out of the box for that size of an engine.

 

[HemiPar]

I am no expert on carbs by no means. But, (there is always a but). As stated about most holly are great right out of the box. You said that you adjusted the mixture screw. Maybe you should try to set them back where they were. Also, why would you set the vacuum at its highest point? I would think set vacuum where you need it, like for brakes or whatever.
What type of driving is the car used for? If it were me and some day it will i would not change the jets just yet but try to figure out what I needed then go from there (maybe just wrong adjustments).
But all this is just my $.02

 

[dgc333]

I am using a 670 Street Avenger on my magnum headed 360 and it has to be the closest to a drop on and go carb I have ever used. I fiddled with the idle mixture screws but wound up with them back where I started. Tweaked the choke adjustment so the choke would stay closed a little longer and went from the plain to purple spring in the secondaries. That's it no other adjustments, and the bowls have never been off.

If you read any tuning guide you have to get the timing dialed in before you enven try to touch the carb.

With magnum heads you will need less total advance, on the order of 32-33 degrees and with the XE262 cam you will need more initial timing than stock, on the order of 15 degrees BTDC. Get that stuff sorted out then work on the carb. Will likely only take a main jet change of a couple of sizes to dial it in.

 

[crackedback]

If you read any tuning guide you have to get the timing dialed in before you enven try to touch the carb.

DING DING DING... we have a winner!!!

Lots of carb issues are really timing related. Timing first, then carb.
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Did you take it apart to clean out the passages?

Seen far too many new carbs have junk in them over the past few years.

If it's surging at cruise, it's likely lean and need some more main jet.

I would take it apart and reverse blow all the passages to make sure no foreign matter is blocking anything.

Good luck

 

[fishy68]

Actually when you are cruising low speed the carb may still be operating in the idle circuit. Depends on how much pedal you have to give it to cruise. That being said check the idle adjustments once again. Make sure their adjusted close to the same on both sides too.

And as was mentioned make sure the ignition is sorted out before trying to "fix" the carb.

I have only installed one of the Avengers. Put it on a buddy's 454 pickup and it was real close out of the box. Just had to adjust the floats slightly and put in a heavier spring in the secondaries and adjust the choke a little. Runs like a champ.

 

[mguner]

Check your vacuum at cruise VS the power valve rating. It may not be sufficient to keep it closed or you may be jetted too lean, or both. Sure you don't have a vacuum leak or PCV problem? How do your plugs look? Air filter on or off make a difference? Have you checked your fuel pressure at the speed of the problem? Fuel sock in the tank, mechanical pump issues etc..