Noise at kickdown

[PapaBird]

So recently I replaced the old Holley that previous owner had with a new Brawler one. I also took off the old adapter that had the pvc port and the coolant line (neither were hooked up). Car runs good but ever since I did this When I am driving and I go to hit kickdown the car sounds like it has a blow off valve on it for a few seconds and then goes away. Checked around carb and new spacer for vacuum leaks and found nothing. Just looking see if someone has had the same issue.

[dgalietti]

Nothing? Maybe send a pic of your setup with you air cleaner and off setup .

[PapaBird]

Here a couple of pics that I have. Will try and grab a better one later if it helps.
A local car guy suggested changing the transmission modulator valve.

[dgalietti]

I can't really see in the Pics, but is there still a PCV in place? I was thinking that with only a breather on it, maybe you are hearing some noise at higher pressures.

[PapaBird]

I can't really see in the Pics, but is there still a PCV in place? I was thinking that with only a breather on it, maybe you are hearing some noise at higher pressures.

Stock PCV is in place and attached to the rear of the carb. I have seen a few around that have updated carbs and intake and use a port in the manifold, not sure if that would make a difference.

[dgalietti]

well, it could very well be a bad trans. modulator. Have you taken the vacuum line off to see if there is any ATF in it?

I would think there would be some other symptoms like harsh shifting and smoking to go along with the noise. Possibly idle issues.. but that may not be noticeable with the new carb.

[dgalietti]

sorry.. about the pcv... Is it just a hose going to the intake with the PCV inline and then to the carb? If it is, check for the hose collapsing or blockage.

[PapaBird]

sorry.. about the pcv... Is it just a hose going to the intake with the PCV inline and then to the carb? If it is, check for the hose collapsing or blockage.

When I get home monday I'll double check. It's the stock PCV so has the hose from back of block to PCV then hose to back of carb.

[PapaBird]

So had a guy from a local car club came over to look at the car. He gave me a reason for the vacuum noise and want to see if you guys can agree and then will figure how to fix. My car was originally an A/C car but when I bought it the only A/C parts left were the hoses hanging in the engine bay. Needles to say I cut the hoses off at the fire wall when I did the carb swap but didn't think A/C lines had anything to do with the noise.

[dgalietti]

It's hard to say how exactly the vacuum hose setup is on there right now. You should have one vacuum hose still going into the passenger side of the firewall to supply vacuum to the parking brake, trunk switch, rear vents, and door locks if you have them.

If you still have that one line going in.. I would cap it off temporarily and see if the noise stops.

[PapaBird]

It's hard to say how exactly the vacuum hose setup is on there right now. You should have one vacuum hose still going into the passenger side of the firewall to supply vacuum to the parking brake, trunk switch, rear vents, and door locks if you have them.

If you still have that one line going in.. I would cap it off temporarily and see if the noise stops.

What fun it was to redo all my vacuum lines and cap the AC stuff off. The now runs completely different, delays in shifting and hard when catches that gear, sitting idle almost sounds like it has a skip now and the noise is still there but not as noticable.

I appreciate all the help

[dgalietti]

No problem! Did you try just eliminate all of the vacuum lines except the vacuum modulator and brake booster temporarily? None of the other ones have anything to do with the engine, so there is no need to redo anything. Just cap it off at the carb or intake and take it for a drive.

Also.. Where did you plug in your vacuum advance?

[PapaBird]

Tried it capped at the manifold and the just running vacuum to the brake booster and no change. My vacuum advance comes off from the carb where Holley recommends to the distributor.

[dgalietti]

Have you tried capping off the modulator and booster lines to see what kind of change that brings? Obviously you can't drive it that way, but you should be able to see the idle smooth out if either one is leaking.