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Old 01-15-2015, 01:25 PM   #1
rodderbilly
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Default Flathead 8ba hesitate!!?

Hi all..was searching info for solve my engine issues...i have a Mallory dual point with mechanical advance ,those of late prodution not the early mallory....my 8ba flathead has 2 97s on navarro racing intake....carb are one new and one rebuild..i have a race cam on it from hnh flatheads....my problem is that that engine hesitate in acceleration and that's a problem that i have before i made that modifies ...(engine was stock).....today i check for generator issue but is good....engine is running rich and this is another problem that i have before i put 2 carbs on....i change power valves and jets but always is running rich!i know mallory distributors have some advance problems,....now i have a pertronix kit on but i'm not happy cause engine always hesitate....,coil and wires are new ,what you think about?
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Old 01-15-2015, 01:33 PM   #2
Bruce Lancaster
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Default Re: Flathead 8ba hesitate!!?

A common Mallory problem is advance starting late and moving slowly. First easy test can be done even without more than the single timing mark on an 8BA...with a timing light on that slowly open the throttle by hand. Advance should begin to move just a little bit above idle and keep moving rapidly from there as you speed up engine. If advance isn't early and rapid, you will have hesitation.
On richness, test with air cleaners off. MANY multi carb air cleaners are VERY restrictive. Note also that late timing gives some of the same symptoms as richness...
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Old 01-15-2015, 01:38 PM   #3
51 MERC-CT
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Default Re: Flathead 8ba hesitate!!?

Have the accelerator pumps been checked for correct operation?
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Old 01-15-2015, 01:45 PM   #4
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Default Re: Flathead 8ba hesitate!!?

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Originally Posted by 51 MERC-CT View Post
Have the accelerator pumps been checked for correct operation?
yes ...time ago when i rebuild the old 97 i try that the base of accel. pump was worn and i put a new one on....the other carb is new...
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Old 01-15-2015, 02:02 PM   #5
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Default Re: Flathead 8ba hesitate!!?

It may or may not be the problem but one of the requirements when using an electronic ignition such as Pertronix is to use Spiro-wound plug wires or there is the possibility of misfire due to radio frequency interference.
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Old 01-15-2015, 02:30 PM   #6
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Default Re: Flathead 8ba hesitate!!?

As Bruce stated, test the advance of that red cap of broken promise.
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Old 01-15-2015, 02:37 PM   #7
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Default Re: Flathead 8ba hesitate!!?

It has been my experience that hesitation can result if the two carburetors are not properly synchronized.

Bruce is right about restrictive air cleaners, I found out from personal experience.
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Old 01-15-2015, 03:01 PM   #8
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Default Re: Flathead 8ba hesitate!!?

He had the problem before he fitted two carbs.
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Old 01-15-2015, 03:33 PM   #9
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Default Re: Flathead 8ba hesitate!!?

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It has been my experience that hesitation can result if the two carburetors are not properly synchronized.

Bruce is right about restrictive air cleaners, I found out from personal experience.
in the top of carbs i have screens and scoops,,,,screens... no filters ,i don't think they can be restrictive...i can test without that screens but in this way in the carbs can enter a lot of dirt.....is air free. Talking about sinchro carbs...just this morning i do another test with the uni-syn and they suck the same amount of air.....
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Old 01-15-2015, 03:37 PM   #10
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Default Re: Flathead 8ba hesitate!!?

Test without the things. Unless you're on a dirt road nothing should happen on a short run...you can run it right after a rainfall, to be extra careful...
I know for sure that a simple window screen can substantially reduce wind blowing into the house, testing by simply opening it. I am suspicious of all things atop a carburetor until they are proven to be non-restrictive.
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Old 01-15-2015, 03:47 PM   #11
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Default Re: Flathead 8ba hesitate!!?

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Test without the things. Unless you're on a dirt road nothing should happen on a short run...you can run it right after a rainfall, to be extra careful...
I know for sure that a simple window screen can substantially reduce wind blowing into the house, testing by simply opening it. I am suspicious of all things atop a carburetor until they are proven to be non-restrictive.
I will do this tomorrow Bruce...i appreciate your help!and if i have a good response? i can't drive the car Always without screen!...what i need to change in this case?
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Old 01-15-2015, 03:53 PM   #12
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Default Re: Flathead 8ba hesitate!!?

Lets get a timing light on this engine . Start at idle and watch the advance move upward with engine rpm.
Most of the mallorys i do have too much advance and seem to work ok on the bottom end. Very seldom do i see a slow one.......

My bet is on fuel issues.....
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Old 01-15-2015, 04:33 PM   #13
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Default Re: Flathead 8ba hesitate!!?

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Originally Posted by BUBBAS IGNITION View Post
Lets get a timing light on this engine . Start at idle and watch the advance move upward with engine rpm.
Most of the mallorys i do have too much advance and seem to work ok on the bottom end. Very seldom do i see a slow one.......

My bet is on fuel issues.....
Hope Tomorrow to have a good response without air filter screens....if no....i need to register that Mallory mech advance....i was thinking to solve the problem when i buy from you the pertronix, new coil and plug wires....put new plugs too ..but after a short trip the car restart to hesitate and i see fouled plugs....changed plugs from ngk b6l to ngk b4l that are more hot...color in plugs is better but sure engine became more hot....they are not the summer plugs for sure.....Today i checked volts in the system....at battery 12,4volts ...with engine running i have the 14,2volts from alternator....so i think is working...at the coil from battery i have 13,2 volts.....no ballast in line...

Last edited by rodderbilly; 01-15-2015 at 04:41 PM.
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Old 01-15-2015, 04:57 PM   #14
Bruce Lancaster
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Default Re: Flathead 8ba hesitate!!?

If the screens are the problem, you need air cleaners with more flow capacity. I do know that many of the small dome/paper filter types most commonly used are completely inadequate, working as chokes, and I suspect that the good ones are probably marginal. With 2 cars over the ports, you have some room and might be able to adapt a pair of the smaller four barrel sort and be able to find name-brand paper filters with enough area.
Also, has car been driven in warm weather and run long enough to fully warm the engine? A distant possibility is the racing manifold with no heat crossover.
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Old 01-16-2015, 02:51 AM   #15
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Default Re: Flathead 8ba hesitate!!?

Quote:
Originally Posted by Bruce Lancaster View Post
If the screens are the problem, you need air cleaners with more flow capacity. I do know that many of the small dome/paper filter types most commonly used are completely inadequate, working as chokes, and I suspect that the good ones are probably marginal. With 2 cars over the ports, you have some room and might be able to adapt a pair of the smaller four barrel sort and be able to find name-brand paper filters with enough area.
Also, has car been driven in warm weather and run long enough to fully warm the engine? A distant possibility is the racing manifold with no heat crossover.
Yes..i know about the heat risers using a Navarro racing...i learn that i need to run the engine about 10 minutes to warm it,,when i rebuild the old 97 i try the brass float with fuel inside...i was happy thinking that probably the problem was solved..so i put the new dual Navarro intake ..learn about warm the engine etc etc...but ...that fastidious problem come back after run the new plugs for a short trip....another thing that i have is the fuse of electric fan that jumps frequently...
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Old 01-16-2015, 12:44 PM   #16
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Default Re: Flathead 8ba hesitate!!?

Quote:
Originally Posted by Bruce Lancaster View Post
If the screens are the problem, you need air cleaners with more flow capacity. I do know that many of the small dome/paper filter types most commonly used are completely inadequate, working as chokes, and I suspect that the good ones are probably marginal. With 2 cars over the ports, you have some room and might be able to adapt a pair of the smaller four barrel sort and be able to find name-brand paper filters with enough area.
Also, has car been driven in warm weather and run long enough to fully warm the engine? A distant possibility is the racing manifold with no heat crossover.
Hi Bruce..that's the first time i do this thing...i'm searching to set the internal advance on a Mallory dual point in my 8ba.....i use a allen head wrench...is 0,144 wide in the flats,,,looking on this page.......http://www.flatheadv8.org/rumblest/ignition.pdf
in this way i get 16 degrees of advance...what i ask to you is to see where i use the key to have that gap...i have do it right?i need to place the allen wrench in that side of the bent tab or in the other side?take a look on my pictures please.....


Last edited by rodderbilly; 01-16-2015 at 01:18 PM.
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Old 01-16-2015, 01:19 PM   #17
Bruce Lancaster
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Default Re: Flathead 8ba hesitate!!?

Before you mess with curve...make some degree marks and TDC mark on pulley and find out what it is doing!! You want to see how much advance is happening when, and see that it comes in fast and ends not much beyond 2,000 RPM.
You can CRUDELY ascertain existing total by putting on rotor, marking where it points on the aluminum rim, then twisting it hard in direction of advance and marking again. Measure with a protractor and DOUBLE those degrees.

Next, to get good TDC on an assembled engine, closer to perfection than the stock '49 bump:

Start HERE: http://www.jalopyjournal.com/?p=10940

There's a bit more discussion in comments link, but this method allows using simple drawing tools and cardboard after you find TDC and mark off degrees for your rngines timing range.

NOW...with pulley degreed, your engine is your distributor machine. Check initial timing using your marks and a timing light, then slowly rev up engine while someone watches a tachometer and note how much centrifugal advance at what RPM. THEN we can know whether your Mallory needs to visit the re-education camp!
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Old 01-21-2015, 12:57 PM   #18
rodderbilly
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Default Re: Flathead 8ba hesitate!!?

Quote:
Originally Posted by Bruce Lancaster View Post
Test without the things. Unless you're on a dirt road nothing should happen on a short run...you can run it right after a rainfall, to be extra careful...
I know for sure that a simple window screen can substantially reduce wind blowing into the house, testing by simply opening it. I am suspicious of all things atop a carburetor until they are proven to be non-restrictive.
Hi Bruce ..i test the car without screens for a short ride ,just to warm up the engine and i have a positive response....seems to run better ...hope the weather is good in this days so i can drive the car for more time, Bubba suggest me the give 22 degrees of mechanical advance too...all this things make me think that i'm in right way....
that's a picture of the screen
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Old 01-21-2015, 05:05 PM   #19
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Default Re: Flathead 8ba hesitate!!?

I had the same problem with a Mallory dual point distributor in an 8BA. I installed a Chrysler pickup in it and used it on a Mallory electronic ignition module. Had a lot of problems, one of them like yours. The advance springs were too heavy. Sent it to Bubba's to get the correct springs installed and the advance curve adjusted. Runs perfect now!! I realize you are in Italy and sending it would be a major problem - but it is a cure.
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