05-28-2019, 06:44 PM | #1 |
Senior Member
Join Date: Feb 2011
Location: SUNSHINE MD.
Posts: 318
|
Carb problem
How can I tell if a pwr. Valve is Bad ., other than a bad idle . Is ther a way to test them . Also is it true if you get a backfire thru the carb .your pwr. Valve is automatically shot . Thank You Sunshine.
|
05-28-2019, 07:10 PM | #2 |
Senior Member
Join Date: Sep 2016
Location: sydney australia
Posts: 1,029
|
Re: Carb problem
first of all what carb im assuming its a holley yes the power valve is fairly robust but they do fail with age generally power valve failure will show up as super excessive fuel consumption
|
Sponsored Links (Register now to hide all advertisements) |
|
05-28-2019, 07:20 PM | #3 |
Senior Member
Join Date: May 2010
Location: Gerrardstown, WV
Posts: 2,265
|
Re: Carb problem
Usually, they will leak gas if they are bad.⁰
|
05-28-2019, 08:27 PM | #4 |
Senior Member
Join Date: Feb 2011
Location: SUNSHINE MD.
Posts: 318
|
Re: Carb problem
Thanks Cecil and Aussie . For the help , but I need to know if there is away to test them out of the carb. I am having a problem getting the 39 to ldle and run . I stated with an expert rebuilt carb. It backfired thru the carb.I have tried 3 other carbs. I need to check there pwr. Valves. Thanks Sunshine.
|
05-28-2019, 08:44 PM | #5 |
Senior Member
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 10,302
|
Re: Carb problem
Take it out of the carb, Clean t off, put it in your mouth and suck. After you have created a vacuum in the unit, close it off with your tongue. If it sticks, it's good; if it doesn't, it's bad.
|
05-28-2019, 08:59 PM | #6 |
Senior Member
Join Date: May 2010
Location: Near Rising Sun, Maryland
Posts: 10,858
|
Re: Carb problem
Sponsored Links (Register now to hide all advertisements)
__________________
John "Never give up on what you really want to do. The person with big dreams is more powerful than one with all the facts". Albert Einstein Last edited by JM 35 Sedan; 05-28-2019 at 09:25 PM. |
05-29-2019, 01:11 AM | #7 |
Senior Member
Join Date: Jul 2011
Location: SF Bay Area
Posts: 6,633
|
Re: Carb problem
What he said.
__________________
Alan |
05-29-2019, 11:11 AM | #8 |
Senior Member
Join Date: Jul 2014
Location: Iowa
Posts: 1,634
|
Re: Carb problem
Usually, a problem with the power valve is due to a backfire that damages the diaphragm. The easiest way to diagnose the problem is to replace the valve with a new or known good one.
|
05-29-2019, 02:43 PM | #9 |
Senior Member
Join Date: Feb 2011
Location: SUNSHINE MD.
Posts: 318
|
Re: Carb problem
Thanks everyone for your help,After using a vaciuum gauge it's showing a vacuum leak , after checking all of the obvious places I believe it is the valve guides , On a recent overhauled engine Thanks All. BOb.
|
05-29-2019, 04:50 PM | #10 | |
Senior Member
Join Date: Jun 2014
Location: New Jersey
Posts: 1,772
|
Re: Carb problem
Quote:
DITTO
__________________
Thanks Andy 1952 F1 |
|
05-29-2019, 06:18 PM | #11 |
Senior Member
Join Date: Apr 2018
Location: Chelmsford, ON Canada
Posts: 528
|
Re: Carb problem
Can you explain the "vacuum leak" a bit more? Not sure that valve guides are likely to be the problem. Loss/low vacuum can be caused by a number of things such as leaking or missing gaskets (don't ask), disconnected, loose or split vacuum hose, incorrect timing and other causes. Have a look at this chart, and it may give you an idea for where to look.
Sorry, the chart is not readable on this post, but google engine vacuum readings, and you should find a chart |
05-30-2019, 06:18 AM | #12 |
Senior Member
Join Date: Feb 2011
Location: SUNSHINE MD.
Posts: 318
|
Re: Carb problem
The vacuum needle quivers between 10 and 15 at idle I have checked all gaskets and the only two vacuum connections the one I am using for the gauge usally wiper by spraying starter fluid on them . The only change I get is when squirt MMO down the throat of the carb.the engine smooths out temporarily . Thank You. BOB
|
05-30-2019, 07:08 AM | #13 |
BANNED
Join Date: May 2010
Posts: 3,019
|
Re: Carb problem
sun,
If it is one my builds send it back of course. Here is where I would address the issues you are having....the MMO in the carb throat performing a temporary fix tells me that the throttle shaft / base may be excessively worn. I build a fair number of 94's and came to realize the neg- ative effect wear in the throttle shaft area can have on these carbs....especially idle characteristics. OMHO. Charlie ny |
05-30-2019, 07:09 AM | #14 | |
Senior Member
Join Date: May 2010
Location: Schooley's Mountain
Posts: 530
|
Re: Carb problem
Quote:
Check out the "Second Chance Garage" http://www.secondchancegarage.com/public/186.cfm Look at the vacuum gauge readings that are displayed there. The depictions there show the actual movement of the needle and what it means. This is the best that I've seen to figure out the problem. |
|
05-31-2019, 07:19 AM | #15 |
Senior Member
Join Date: Jun 2013
Location: Marana Arizona
Posts: 1,776
|
Re: Carb problem
Contact CharlieNY as suggested. He also had pv's that he has "massaged" the seats on for a better fit. Great guy, always helpful and will walk you through the problem. Chap
|
05-31-2019, 08:15 AM | #16 |
BANNED
Join Date: May 2010
Posts: 3,019
|
Re: Carb problem
Guys,
'sunshine' and I had a nice visit. The carb is one of mine but the issue seems to be else where. Great guy to talk to, he will update us accordingly. Charlie ny |
Thread Tools | |
Display Modes | |
|
|
Sponsored Links (Register now to hide all advertisements) |
|