|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
09-30-2020, 06:54 PM | #1 |
Member
Join Date: Jun 2020
Location: Orange Massachusetts
Posts: 75
|
Carburetor backfire
I have a 31 three window four-door with a B motor the car runs great up until 45 miles an hour anything over 45 it starts to pop through the carburetor any suggestions would be grateful. Carburetor adjustment? Timing adjustment? fuel mixture adjustment? drive the car off a cliff ?? Lol
Thanks again Daba 31 three window four-door deluxe with B motor 31 slant window four-door deluxe |
09-30-2020, 08:39 PM | #2 |
Senior Member
Join Date: Sep 2017
Location: Mint Hill, North Carolina
Posts: 386
|
Re: Carburetor backfire
I would check point gap setting to be sure that there is enough dwell angle to allow coil to build back it's field.
As point rubbing block wears, the points ride closer to the cam, holding them open too long. Then as speed increases, you get to a point where the points are not closed long enough to build up a full field in the coil. A weak spark results. |
Sponsored Links (Register now to hide all advertisements) |
|
09-30-2020, 10:34 PM | #3 |
Senior Member
Join Date: May 2010
Location: Between Seattle & Tacoma
Posts: 2,354
|
Re: Carburetor backfire
It sounds lean to me. Have you opened up the GAV when it starts popping to see if it runs a little better? Be sure to let us know what the solution is.
Have you played with the timing recently? |
10-01-2020, 12:45 AM | #4 |
Member
Join Date: Aug 2020
Location: Belmont N.C.
Posts: 85
|
Re: Carburetor backfire
I would guess lean mixture as Chuck Sea/Tac said or timing is off for that engine rpm and load.
I recently had a Porsche ( I know way different beast hear me out though) that had some surging and backfiring problems at cruising speed . I ended up finding the intake valves way too tight and a series of small vacuum leaks. Adjusting the valves cleared up a lot of issue and fixing the vacuum leaks cleared up the rest. |
10-01-2020, 03:06 AM | #5 |
Senior Member
Join Date: Jul 2010
Location: United Kingdom
Posts: 1,441
|
Re: Carburetor backfire
yep often a symptom of a weak mixture/fuel starvation, ... so easy things first ... check the flow of fuel from tank to carb and the various stariners filters etc.. then move on to other stuff.
|
10-01-2020, 06:22 AM | #6 |
Member
Join Date: Jun 2020
Location: Orange Massachusetts
Posts: 75
|
Re: Carburetor backfire
Sponsored Links (Register now to hide all advertisements)
|
10-01-2020, 06:46 AM | #7 |
Senior Member
Join Date: May 2010
Location: Richmond, VA
Posts: 189
|
Re: Carburetor backfire
It sounds like it is time to get that 'B' carburetor cleaned out.
|
10-01-2020, 06:52 AM | #8 |
Senior Member
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
|
Re: Carburetor backfire
Good info, but, loosen the fuel cap and take it for a drive. The vents are known to plug.
|
10-01-2020, 08:36 AM | #9 |
Senior Member
Join Date: Mar 2014
Location: Midland Park,N.J.
Posts: 1,108
|
Re: Carburetor backfire
Intake valve hanging up try MMO in the gas tank.
|
10-01-2020, 11:06 AM | #10 |
Senior Member
Join Date: Jul 2010
Location: United Kingdom
Posts: 1,441
|
Re: Carburetor backfire
|
10-01-2020, 11:58 AM | #11 |
Senior Member
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
|
Re: Carburetor backfire
|
10-01-2020, 03:37 PM | #12 |
Member
Join Date: Jun 2020
Location: Orange Massachusetts
Posts: 75
|
Re: Carburetor backfire
I tried the gav no difference then the timing much worse. I used the New timing wrench I got for the model a apparently the timing is slightly different. It moved about a quarter of a turn more than it was to start I think I’m going to go back to that point and try again.
|
10-01-2020, 06:08 PM | #13 |
Member
Join Date: Jun 2020
Location: Orange Massachusetts
Posts: 75
|
Re: Carburetor backfire
I opened up the points and BINGO it did the trick. Thanks again for all your suggestions.
Daba |
10-01-2020, 09:25 PM | #14 |
Senior Member
Join Date: Sep 2017
Location: Mint Hill, North Carolina
Posts: 386
|
Re: Carburetor backfire
Glad to see that fixed it for you.
George |
10-02-2020, 03:28 PM | #15 |
Senior Member
Join Date: Sep 2016
Location: Roanoke, VA USA
Posts: 1,908
|
Carburetor backfire
|
|
|
Sponsored Links (Register now to hide all advertisements) |
|