Tuning my new Holley

[DAverkamp]

Well guys and girls, I decided against EFI and put on a new Holley SA 670 Ultra spec’d for the Clev and at first we thought we had it made at start up, responsive at throttle crack, sounded crisper, went thru all timing, adjustments, no vacuum leaks, but once it got up to op temp, the hesitation at pegging it was there again. I have it mounted on a Performer and on a 1/2” fiber spacer. We can’t find anything obvious in whats going on however my only correlation to performance is that back in March here in WI the roads were salt free and I cranked her up to go to the KwikTrip across town for more premium and it was 35ish degrees and let her get up to 180 before I pulled out and she absolutely loved the cold air she was breathing. She was actually quite the handful and all I wanted from her. My next guess is fuel is getting too hot as the fuel line does run on top of this manifold to the log, and either a 3/4 or 1” spacer (I have the clearance) to attempt to keep the fuel as high and cool as possible, or is it a combo of manifold, height, and heat or? I am looking forward to learning from the experiences you all may have had. TY

 

[Cleveland Crush]

Well guys and girls, I decided against EFI and put on a new Holley SA 670 Ultra spec’d for the Clev and at first we thought we had it made at start up, responsive at throttle crack, sounded crisper, went thru all timing, adjustments, no vacuum leaks, but once it got up to op temp, the hesitation at pegging it was there again. I have it mounted on a Performer and on a 1/2” fiber spacer. We can’t find anything obvious in whats going on however my only correlation to performance is that back in March here in WI the roads were salt free and I cranked her up to go to the KwikTrip across town for more premium and it was 35ish degrees and let her get up to 180 before I pulled out and she absolutely loved the cold air she was breathing. She was actually quite the handful and all I wanted from her. My next guess is fuel is getting too hot as the fuel line does run on top of this manifold to the log, and either a 3/4 or 1” spacer (I have the clearance) to attempt to keep the fuel as high and cool as possible, or is it a combo of manifold, height, and heat or? I am looking forward to learning from the experiences you all may have had. TY

Few easy things to start DAverkamp:
#1-You mentioned timing was "checked" but consider checking it at operating temperature while revving the engine at the rpm the hesitation occurs, you are looking for erratic timing marks on the harmonic balancer/damper indicating ignition related.
#2-ohm test your plug wires to ensure they are all within manufacturer spec. (do a good visual wire inspection as well, looking for arcing).
#3-Check fuel pressure at or very near the carb when at operating temperature and at part and WOT.
You'll get it sorted out in no time!

 

[Hemikiller]

@DAverkamp - If you want, I'll split this thread into a separate discussion about getting your carburetor tuned with an appropriate title.

 

[Sheriff41]

@Cleveland Crush brings up some good steps to take. Also, read through this article for some things to try: https://www.onallcylinders.com/2019...ng-a-new-carb-to-fix-engine-stumble-try-this/

If you search through the tech articles on that site under induction, you'll find several articles addressing the stumbling issue.

 

[DAverkamp]

@DAverkamp - If you want, I'll split this thread into a separate discussion about getting your carburetor tuned with an appropriate title.

I would appreciate that!

 

[Hemikiller]

I would appreciate that!

Done!

 

[AcesArneson]

Well guys and girls, I decided against EFI and put on a new Holley SA 670 Ultra spec’d for the Clev and at first we thought we had it made at start up, responsive at throttle crack, sounded crisper, went thru all timing, adjustments, no vacuum leaks, but once it got up to op temp, the hesitation at pegging it was there again. I have it mounted on a Performer and on a 1/2” fiber spacer. We can’t find anything obvious in whats going on however my only correlation to performance is that back in March here in WI the roads were salt free and I cranked her up to go to the KwikTrip across town for more premium and it was 35ish degrees and let her get up to 180 before I pulled out and she absolutely loved the cold air she was breathing. She was actually quite the handful and all I wanted from her. My next guess is fuel is getting too hot as the fuel line does run on top of this manifold to the log, and either a 3/4 or 1” spacer (I have the clearance) to attempt to keep the fuel as high and cool as possible, or is it a combo of manifold, height, and heat or? I am looking forward to learning from the experiences you all may have had. TY

How old is your balancer?

 

[AcesArneson]

Is this the same issue you had before replacing the carb?

 

[Stanglover]

When I bought my Holley 670 a few years back, it was not spec'd for anything specific. At first I did have issues with it and some problems as you describe. The worst of which was a very over rich idle, stank the garage out!!
This was on my M code, so a slightly different engine. It took me quite a while to figure it out and some of the tweaks found to work, again on MY engine, have been called into question, but it worked.
Here's what my engine ended up with;
1) intake heat cross over passages blocked off at the heads.
2) a 1" fiber spacer with a steel insert gasket underneath. On the 71 4V intake, without a spacer, the primary butterflies could stick in the bores.
3) I took the car to a tuning specialist and he drilled a 3/32" hole in the front/center of the primary plates. That enabled the transfer slot to be set where they ought to be, square. That alone greatly improved the over rich issue, no more stink. An AFR gauge confirmed a much better ratio.
4) I tried a couple of different power valves, but ended up using the original 6.5 even though the motor runs at 17" of mercury. I also kept the stock jets.
5) To fix a bogging when I hit the loud pedal, I increased the squirter from a 31 to a 35. After final adjustments to mixture settings, no more bogging, it pulls clean and hard.
6) TIMING; I choose to use an original Autolite distributor, but curved for MY engine. This has been discussed many times on the forum so I'll not waste time going over all the details. In a nut shell, it has a 10L limit slot, so 20 degrees crank timing. The initial is set at 14 degrees for a total mechanic timing of 34 deg. The vacuum canister is adjustable and adds 4-6 deg. on top. Springs were also changed and set as needed. Timing is powered by a Pertronix Ignitor II and matching coil supplied by a full 12V.
That's basically it. It took quite a while, but I've had no more problems since.
Good luck, hope you get it set for your engine.

 

[Hemikiller]

I believe @Animal Lawyer also has a 670 Street Avenger, which he had tuned by Allstate Carb on Long Island. Hoepfully he can chime in with what they did.

 

[DAverkamp]

How old is your balancer?

Its brand new from when my previous FT cam washed out.

 

[Animal Lawyer]

I did, couldn't get it tuned right, after many attempts and changing parts took it off. Still have it in my garage, nearly new, if anyone wants one

 

[basstrix]

I did, couldn't get it tuned right, after many attempts and changing parts took it off. Still have it in my garage, nearly new, if anyone wants one

What model/list number is it? I may be interested.

 

[c9zx]

The idle channel restrictors (ICR) are too large in the "Street Avenger" series and the idle air bleeds (IAB) are too small. Making the ICR changeable is delicate and tedious work as is the IABs. Most Holleys don't have enough adjustability. QF is a much better bang for the buck. AED and Pro Systems build custom carbs at fair prices. Chuck