kalli

Hi all,

so I replaced the edelbrock 650 with the holley 570 street avenger.
I changed the timing to 16 initial and advance hooked up to manifold vacuum.
I really like that, but have two issues with that

a) when driving slowly (no matter if uphill, straight or downhill) with steady throttle the car is jumpy. the throttle is only slightly tipped, like going 5-10mph. that's where it's worst
any ideas on what to try in such a situation?
I don't have any access to jets at the moment (nothing bought) and I haven't checked on my float level today (since I put it on)<-shame on me

b) low in gear WOT. it accellerates quite good, then the secondaries open and just before that there is a bog and then all hell gets loose the car runs like mad. any suggestions on what to try in that situation?
it's hard to explain. I made a graph of what it feels like. I have no tach or any measuring device so it's vague but should show the idea

boogerschnot

Why not hook it up to the timed Port? You may also want to change the spring to the lighter spring in the kit so that your secondaries open a little sooner when you floor it.. I think you would notice if the float was off.. but you may want to check it anyway.. That jumpiness is kind of weird,, what is it doing exactly..

boogerschnot

So if you go WOT the secondaries open and then it bogs and hauls butt.. Im still thinking maybe you need to get those opened a little sooner.. How is your vaccume at idle? Did you tune using a vac gauge?

Starfury

16* is too much advance at idle. Not even my Magnum 280H cam needs that much. 10-12* would be better. What's the rest of your mechanical advance curve like?

trashline

Second that however I dont do timing at idle. My curve is setup to be totally in ~3000 IIRC and at a total of 36*. and this is with the vacuum line plugged, well actually I have a mechanical advance dist so I dont need a vacuum line.


What other mods do you have? Are you at the point that a lower power valve is needed? Did you adjust your air/fuel mixture needles at all? Or just bolt it on and go?

67mustang302

The running rough could be from too much timing, try backing the idle down to like 12-14 and see if it helps any. Otherwise it COULD be jetting depending on speed, but it could also be the idle circuit, and on that carb there's nothing you can do to fix it.

As far as the bog, you either need a STIFFER secondary spring,they're opening too quickly and the engine isn't getting enough fuel so you're getting a major lean out most likely. Also you could try going bigger on the accelerator pump, bigger cam, bigger squirter etc. Try a cam first and see if it helps.

Gary H

Richer idle mix and a heavier secondary spring should fix it.

kalli

thanks for all the advise
the curve itself seems ok as I was on 34 ~3200 when I had ignition on 10 initial a few weeks ago. i'll retard to 12 and go from there. I'm with the stiffer spring theory as well. it feels like the secondaries shoot open and the engine doesn't not what to do with it

as for the idle mixture. I have the vacuum hooked to manifold, so i couldn't attach my vacuum gauge so I tried setting it with tach. I'll see if I can find something for picking up the vacuum for gauge.

powervalve: engine vacuum at idle is around 15. which powervalve would that call for?

so plan for now is retard to 12, see if I get 34 at 3000, if not recurve. richen up idle and stiffer srping. I'll let you know the results

Gary H

Wait till you get done messing with the timing and idle mix before you pick a power valve. Idle vacuum will change when you mess with them.

BTW, find your carb here to find out what jets and power valve it comes with.
http://www.holley.com/data/TechServi...%20Listing.pdf

trashline

power valve is fine for said vacuum. IIRC thats an 8.5 in that carb.