Holley Carb Help

[1972BlueC20]

I just talked to summit racing tech help and they said my idle is dropping too much from park to drive.

my idle at park is 850
in drive its around 650 ish

He said my timing is wrong or I have a vacuum leak.


Does this sound right?

[1972BlueC20]

UPDATE :

So I replaced all the fuel line from the tank to the pump and from the pump to carb.....no improvement.

I checked the sending unit even though it was fairly new....the sock isn't collapsed.

Bypassed my fuel pressure regulator just to rule that out.....no improvement.

So there are only a few more possibilities left in my mind :

1) timing issue (i've tried 12-16 BTDC, haven't tried less than 12 yet)
2) vacuum leak that I just can't seem to find.
3) fuel pump isn't providing the correct volume, pressure is good @ 6 PSI.
4) actual carb issue


I just ordered a .035 squirter (tube style), and a hollow high flow squirter screw along with an accelerator pump cam assortment pack.

we shall see after I try the bigger squirter ect.


Anyone have any other suggestions?

[EricS76]

Did you ever find the fix to this problem? I am having the exact same issues.

[HotWheelsFan]

Hah, old post...

Kinda lame hijacking an old thread for us to read through.


Bob

[YellowK5]

Which carb do you have? I just went through all of the same issues with my 71 350..Edlebrock carb..I installed a new exhaust and welded in O2 bungs so I could use sensors to set it up. The main issue was I had to swap out the metering rods. they were too lean for high vacuum I tried just the springs first but it just made it run real bad..Then i had to install slightly larger main jets..now it is the best running 350 I have driven..which is pretty good for a crate motor installed in 1988

[EricS76]

Holley 670cfm street avenger. I’ve changed the vac secondary spring softer & stiffer, bigger & smaller squirters and it still has a horrible bog when I go quickly to WOT.

[geezer#99]

Looky here.



https://www.hotrodders.com/threads/h...on-fix.507033/

[tdangle]

If you look up the HEI part number that came with your engine (probably 8917052) you'll find that it has roughly 22 degrees of mechanical advance and 20 degrees of vacuum advance. Setting initial timing much above 12 will cause total timing to be on the high side. You will need to somehow limit the total mechanical advance as to not go higher than ~32 degrees total. Vacuum advance is only in play at idle/cruise conditions. If you hook up a vac gauge inside the cab and watch it you'll see what I mean. Timing will not normally affect part throttle driving, only reduce total power or cause detonation if to high. Cars from the 70's had very low initial timing and ran well.

You may have a ignition misfire if you get shocked touching the dist. I'd look at that.

Speaking from experience: (i bought the SP350/357 deluxe) the Holley street avenger 670 is a horrible carb. I never could really get it to run will except at full throttle. I even took my truck to Westech (as on engine masters) and they didn't do much with with. Ran pig rich all the time. Now have a Edelbrock AVS2 which I've tuned with the help of a AFR meter.

[Richard2112]

Originally Posted by geezer#99

Looky here.



https://www.hotrodders.com/threads/h...on-fix.507033/

that's a good read

[EricS76]

Thanks for the help guys & great article Geezer! I’ll give that a try & see how it goes. I did have to turn my vacuum advance down at the distributor as to not have too much total advance.

[garyd1961]

Sounds like to me it needs more advance on the timing, idle the carb down, put a lighter spring in the secondary. Don't worry about the degrees just unhook the vacuum advance and turn your distributor until the motor runs the fastest and then back it back until the rpms drop off a little, hook the vacuum advance back up. With the motor at operating temp shut it off and start it back up. If it starts ok drive it and make sure it doesn't spark knock, if it does back off on the timing a couple more degrees and drive it again.
Forgot to say after you up the timing and idle it down readjust the air mixture screws. Start with both screws 1 1/2 to 2 turns out and adjust 1/4 turns on each side until it idles the fastest.

[EricS76]

My problem is fixed! Here’s what I did in case this can help anyone else. After reading the link that Geezer sent, I started looking to see what the difference was between the Holley 670 street avenger & quick fuel slayer 600cfm carbs and the obvious difference is jetting. The Holley is 65 primary & 68 secondary. The quick fuel is 68 primary & 74 secondary. I rejetted the Holley to 68 primary & 74 secondary and it runs great now. It has the stock 31 squirter and I went with the blue accelerator pump cam in the #2 position. This is on a gm 195 hp crate motor stock with edelbrock dual plane intake, ram horn exhaust manifolds and a 3 speed manual trans.

[Richard2112]

Originally Posted by EricS76

My problem is fixed! Here’s what I did in case this can help anyone else. After reading the link that Geezer sent, I started looking to see what the difference was between the Holley 670 street avenger & quick fuel slayer 600cfm carbs and the obvious difference is jetting. The Holley is 65 primary & 68 secondary. The quick fuel is 68 primary & 74 secondary. I rejetted the Holley to 68 primary & 74 secondary and it runs great now. It has the stock 31 squirter and I went with the blue accelerator pump cam in the #2 position. This is on a gm 195 hp crate motor stock with edelbrock dual plane intake, ram horn exhaust manifolds and a 3 speed manual trans.

That's good news as I too read that article and I do have a slayer 600 to go on a new engine build. The site has an article on the slayer 600 which details adding a metering block and 4 corner idle. I don't know if I'll do that as the information isn't updated and the metering block/jets they recommend are out of stock in many places.