Vacuum Secondary Issues

[69 Post Sedan]

I just installed a brand new Holley 80531 850 vacuum secondary on the car. The issue I'm having is that the secondary's aren't opening soon enough (5500rpm) and I have the lightest spring installed (Yellow/Short). It's not a smooth transition either. [img]<<GRAEMLIN_URL>>/mad.gif[/img]

I do have the check ball installed which is highly recommended by Holley. I am using a thin 4 hole aluminum spacer plate under the carb with my Edelbrock TM2R intake.

Thanks, Kurt

P.S......the initial feeling is that the motor REALLY likes the 850 vs. 780. Only the track will tell! [img]<<GRAEMLIN_URL>>/naughty.gif[/img]

[Hemicolt]

If the secondaries are opening to quickly it will also not have a smooth transition. Have you played around with all types of springs? Is there a reason for the spacer?

[69 Post Sedan]

Tracy, after running the 850 with the pink spring it came with, I switched it to the yellow short which is what I was using on my 780. They both felt the same although I didn't wasn't watching the tach with the pink spring. [img]<<GRAEMLIN_URL>>/stupid.gif[/img] but they both felt the same.

I use the thin 4 hole (1/16&quot plus a couple other thin ones to get the carb off the intake....keeps it cooler. [img]<<GRAEMLIN_URL>>/dunno.gif[/img]

[69 Post Sedan]

Here is a quick video of me jumping on it in first then shifting to second.....watch the tach when it hits 5500-5700rpms.

Kurt

https://www.youtube.com/watch?v=UNZ2a0cvHxg

[Hemicolt]

Did you do a before and after test to check intake vac. signal?

The reason I ask this is because if you had, let's say 13&quot; of vac. with the smaller carb., and now you have a lot lower vac. signal.....you may need to start at the beginning of the carb. tune and work your way up to the secondary circuit.

[69 Post Sedan]

Both carbs have about 11&quot;-12&quot; of vacuum at idle.

[Postsedan]

When is the next track day?

Dan

[69 Post Sedan]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Postsedan</div><div class="ubbcode-body">When is the next track day?

Dan </div></div>

I would like to get this carb thing fixed first. If this keeps up I'm going to sell a bunch of parts and buy a new Holley HP for the strip only and keep the 4346 for the street!

Kurt

[Hemicolt]

Instead of posting back and forth with 20 questions, here is a great tech article that covers all the basics.

http://www.nastyz28.com/~ericf/tech/htune.pdf

[69 Post Sedan]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hemicolt</div><div class="ubbcode-body">Instead of posting back and forth with 20 questions, here is a great tech article that covers all the basics.

http://www.nastyz28.com/~ericf/tech/htune.pdf </div></div>

Thanks Tracy.....I'll check it out.

Kurt