I need a flathead experts advice on bogging

It's been two years of a bogging issue that has got me pulling my hair out.

The Issue: When engine reaches a temperature of approximately 180º, under load, there is a definitive bogging in the engine. When throttle is pushed down, there is no more acceleration once the bogging begins; The only solution is to switch to a lower gear. The bogging occurs around 25-30 mph in 1st gear, 35-40 in 2nd gear, and as low of a speed of 45 mph in third but can be upwards of 70 mph, depending on how long and hot the engine has been performing. When engine is cold (sits over night) the issue does not occur until temperature reaches 180º again.

Numerous shops and ASC certified mechanics have been under the hood along side myself who are dumb founded on what is making this occur. Even old timers who've been running Flatheads are scratching their heads on this one.

*Note* much of what is below in the back story simply can't be the issue, but I thought it was fair to share all information about what has been done just incase.

The Back Story/Upgrades:
This bogging first began to be noticeable with a major overhaul to the car in Oct. of 2007. When I purchased the car in 2006 it was 6 volt and ran with a 4 barrel carburetor on an original factory rebuilt flathead in 1953 with several hop up parts including aluminum heads, and 4 barrel aluminum Offy intake. Outside of what I mentioned, the car for the most part was mechanically and electrically stock. The car was having problems restarting when hot and a leaking gas tank at the time. I took it on simple trips and drove it with some care to take it easy on the old girl, but certainly had ideas that I could get it running much better.

Upgrades made in Oct of 2007 converting to 12 volt:

-Fuses
-fuel pressure regulator
-starter solenoid
-positive and neg. bat. cables
-Battery
-Headlight and all bulbs
-replaced w Pertronix Coil
-Mallory duel point Distributor
-Offy duel intake manifold
-Stromberg 97 rebuilt carbs (x2)
-12 volt electric wiper
-fuel tank and relay
-GM style single wire Alternator
-spark plugs

Not much road testing was done until the following Spring of 08 (May) season which proved to show significant problems that was believed to be due to misjetted carburetors and bad points in the Mallory distributor. After the carbs were rejetted and needles were adjusted at idle speeds and the points were replaced and spun up to spec at a Engine shop. The performance didn’t show significant increases but ran better at idle speeds without stalling.

Summer of 08 it was suggested that a engine compression test occur which showed a significant loss of power after a dry and wet tests occurred. It was then recommended that the problem was due to tired rings. At this point in time the engine was completely torn down by me then taken to a machine shop and rebuilt professionally including the following upgrades:


-Stroke: 4” Merc Crank
-Bore: 3 5/16”
-Isky Max 1 Cam.
-Mech Fuel pump removed
-Oil Pump rebuilt
-Electric Fuel Pump installed
-Oil Filter Removed
-Spark Plug Wires replaced
-Spark Plugs Replaced
-Mallory Electric Distributor
-Transmission Rebuilt
-New drive shaft
-Thermostats replaces to 180º
-Radiator neck replaced for more for higher pressure cap Water Temp gauges replaced
-Oil Pressure gauge
-Fenton Headers
-Gear Shift Pin
-All new gaskets/motor mounts
-Trans Bearing


The bogging still continued after the break in point, under load.

Summer of 09: Knowing now that nearly everything mechanical has been replaced, the only mystery point that could be turned to was wiring. A 9+3 kit from Rebel Wire was just installed 9-19-09 by a certified mechanic with my help. After hours of work everything electrically seems to work perfectly, but the bogging still continues. All wires throughout the car have been replaced from front to back, leaving no existing original wires anywhere. Beyond the wiring, the following was also replaced/deleted:

-Starter Solenoid
-Keyed Ignition
-radio guts removed
-heater electronics removed
-Horn ring button removed
-Starter button is now horn

After the bogging issue remained after all connections were double checked, a few other attempts were made to see if they were the problem:

-Ignition coil was swapped out for a known working one
-Mechanical Fuel Pump was bypassed
-Duel point Mallory distributor was reattempted to be used
-Second set of Stromberg 97’s were swapped out and installed
-Additional body to frame ground wire was installed
-Fuel pressure regulator was increased to 5 lb.

After none of the following changed the bogging issue, these attempts were returned to their previous states.

As of yesterday I took it to a highly recommended shop to have them diagnose the issue and they ruled out everything electrically related and from the fuel tank up to the intake manifold. They have some thoughts about the fact that the heat risers haven't been blocked off causing vapor lock or that the intake manifold may be poorly casted or have a crack somewhere along the line.

Any thoughts or ideas here?

 

Condenser? The newer Mallory stuff has been problematic for the past decade ... from what I hear.

 

Your post is interesting to me because I have some nagging problems as well with high rpm breaking up, but I wouldn't describe it as "bogging". My car runs great until I rev it out and then it bobbles and spits. It's driving me crazy.


My thoughts on your situation:
Fuel pressure @ 5 lbs is high for Strombergs. Should be half that.
Have you read your spark plugs?
You didn't mention a valve job in your overhaul. Did you recheck compression after the overhaul? You may have cracks through the valve seats or burned valves causing a loss of compression. You might have cracks causing coolant leaks into the combustion chambers which would be worse at higher temps/pressures.

Any liquids or water vapor in the exhaust? Any exhaust in the coolant ? (you can test this with a kit).

I don't think heat risers are a problem with dual Strombergs, at least I never heard of that before (on the contrary I've heard about cold running problems if they are blocked off).

I assume when you went to 12 volts that you also swapped polarity, so be sure the coil is also swapped with the negative terminal going to the distributor. Also verify whether your coil needs a ballast resistor because the original 6v probably didn't.

What spark plugs are you running? I like the NGK B6L over the Champ H10 over the Autolite 216.

Good luck finding the problem.

 

Two different Mallory Distributors were used/tested. The one duel point had a problem burning up points and the second it the Mallory electronic distributor which is working fine.

 

Runs fine until it reach's 180? If this is true sounds like vapor lock problem.

 

I'm using the term "Bogging" for lack of a better one. It as if the car is shifted into neutral at that point and the exhaust sound significantly changes. There is no more power coming from the engine going to the tires until shifting happens then it all better until the next magical speed/rpm is hit, then it "bogs down" again. This only occurs under load and can't be mimicked idling where it revs up high without back firing or sputtering of any kind.

-Valves: The original valves were cleaned up and returned to the car after inspection showed they were fine as were the lifters. All new springs, seats, guides, clips, keepers, etc.

The important factoid on the valves is that when this car was 6v, it didn't have this problem.

-Fuel pressure is set at 3.5 lb per. It was increased just to see if that would help. It's is running now back at 3.5 but I can try to run it lower.

-The block was magnafluxed showing no cracks anywhere... rare!

-Coolant is perfect after draining it the other day. Not chemically tested though.

-Coil: using a 12v 1.5 ohm which doesn't require a ballast resistor (a second one was tried to double check that.

-Spark plugs: Champion RC12YC

The thing I've noticed about some of the different manifolds out there is some allow for heat risers and some do not. Edelbrock Super duel and triple intakes come pre blocked off for instance. Another note is that the Offy 4 barrel used to run the vacuum off the heat risers for my old vacuum windshield wipers. Could that help with the heat dissipation some more than spitting it back into the exhaust?

 

Not only runs fine, it runs GREAT! I can push the hammer to the floor when it's cold and run cars into the dirt off the light... once it gets near 180º I am worse than grandma's moped.

How does one fix vapor lock on a flathead outside of blocking heat risers?

 

Basics...
Study your actual advance curve. Disconnect vac if you have it to look at centrifugal, then study things with a vac pump to sure that works.
Rebuild the Mallory with all NAPA parts. Look for its grounding places, carefully studying all the places the points and connecting straps are toodamnclose to the case....it needs COMPREHENSIVE debugging. I have posted lists of things to look for.
At very least on the advance be sure you have a reasonable amount of advance and all of it comes in by 2,000. It is unlikely to be right out of the box.
Easiest way to debug Mallory is to replace it with a good crab.
Be sure accel pumps are working. You can yank Stromberg jets and emulsion tubes without removing carbs, clean parts, spray clean the holes.
Air cleaners...most hotrod air cleaners are crap. Takemoff and see what happens.

Fuel delivery...can be crudely tested by getting to your bog point, then test 2 ways: First pull out choke slowly and see if that helps, second test fan gaspedal rapidly to dump in gas from accel pumps. If leaning out, these types of actions will crudely patch the problem momentarily.

 

This is probably not the cause of your problem but I do think a 1.5 ohm coil should have a ballast resistor.
Problem is ignition or gas, Bruce's suggestion re gas sounds like a nice test of the gas.

 

Do you have an anti-leak rollover valve in your tank. It sounds a lot like a problem I ran across with a car that seem to run out gas about 3 or 4 miles down the road, maybe about 180 degrees about then.
The anti spill valve was stuck, and it was not pulling the proper amount of fuel at that RPM.
My 2 cents.
Scot

 

Not to discredit your ideas, but many of these have already been comprehensively tested.

Again:

-two different distributors were used. The mallory Duel point was spun up at a performance engine shop twice before being ruled out. Then an Electric mallory was used and has no problems plus has operated fine in a similar Ford running flathead. The grounding has been checked to show proper levels too.

-A second set of Strombergs were used as a replacement from a known running car that didn't have issues.

-Air cleaners have been removed for some time now during all testing.

-Fuel delievery has been ruled out. Flow tests from the pump to the regulator show proper flow. Regulator shows proper lbs of pressure at the gauge at the fuel log, and as mentioned both sets of carbs perform identical in this situation.

My original list seems haphazard because I've listed many other changes to the car. Some were upgrades some where disconnects along the way. I wanted to make mention of everything just to be on the safe side.

 

what bruce said. except one additional comment on the fuel, if it's running out of fuel badly the choke and quick pumps may not help.....

 

if you didn't already know, bruce knows more about flatheads than every shop you've taken that car to combined.

the "performance shop" you took your dizzy to probably didn't realize how quick the advance has to come in on a flathead. Most mallory units come with a SBC advance curve that would look perfectly normal to your guy.


I still wouldn't rule out fuel.

 

Too much timing!!!

 

Flathead curve is quick and short. Mallory curve can somethimes be too long and too slow as delivered. The internal shorts I referred to I guess are irrelevant on electronic ones...points ones have serious issues there. Fid out what your curve is YOURSELF with a light...disconnect vac for now if you have it.
Static timing is low...they tend to like around 4 degrees. Curve come in fast (stock early spec was for idle at 400, curve underway at 500!) and needs to have it allin fast, by 2,000. For a conservative starting point try 4 static and 20 total by 2,000...if it is going beyond this area with one of the random curves supplied, worry. A late Mallory is a pig in a poke and needs careful study.
If all remains mysterious after lots of study and testing, my first thought would be to punt on some of the compexities and start over from simple.
Toss the whole manifold for now...that is quick and easy...and pop on a single Stromberg and stock manifold. Easy to debug and be sure all is right, then complicate things. I would also start with a a better distributor, the REAL Mallory designed Crab, assuming early engine, and debug the Mallory AFTER getting engine running with a proper distributor so you know where you are looking for the probs.
Other stuff...what jets, PV's? Is trouble on only at full throttle or at higher speeds while still at partial throttle opening? What is actual, measured fuel pressure throughout, NOT the number indicated by pump maker or regulator dial??
On the Mallory...check its phasing. Turn engine to its static firing point. Mark where wire terminal for #1 is in relation to distrib body. Is rotor there? Next grab rotor and twist to full advance...whereinhell is it pointing now?? Bad phasing can lead to rotor getting closer to wrong terminal than right as advance happens...crab has no possible phasing issues. Older Mallories have phasing adjust...cannot remember if new ones do.

 

I'm going to chime in... My Model A 4 cyl (half of a V8) has done something similar the last few long drives (starts after about 25 minutes) I've taken.

My distributor is a stock body with pertronix in it. I originally thought it was the old distrib cap I was running, so I changed out the cap to a new one and it ran great.

Well, I thought, but it then started bogging again after a 30 minute drive on a 98 degree day.

I'm not running a fuel pump, just gravity, two rebuilt back to stock stromberg 81s. It seems like the engine just shuts off and I'm coasting. If I take my foot off the accelerator for a few seconds, it catches up starts accelerating for a few moments and boggs again. It's definitely related to heat, so I would see if you have a fuel starvation issue.

I'm hoping to add a fuel pump to the car and have that fix it.

 

After just posting that, I had another thought...


ICING.


My intake hangs way out to the side and if I'm running for an extended period of time, there is a big chance for icing since there is no heat riser.

Have you considered that your carbs might be icing? I just re-read that your heat riser was blocked off. I bet your carbs are icing.

 

What year car are we dealing with here?
(I read the initial post and skimmed it twice and didn't see a reference to car or engine year.)


RE: the fuel problem, got an electric pump you could plumb in temporarily?

They'll work fine in the engine comp't.
Not as good as they do near the tank, but they'll get you home that way.

If the car is a late model flathead, does it have an overdrive transmission?

 

Elrod's comment about icing is interesting.

Look for NealinCa's recent thread about icing with his dual carb flatmotor.

He did cure the problem.

 

Here is NealinCa's post about icing...

http://www.jalopyjournal.com/forum/showthread.php?t=400406&highlight=flathead+icing&showall=1

 

oops! my bad! This is a 1949 Ford. 8BA.

I should have made mention of that first. I kept reading "crab" thinking it was a misspelling of "carb". Not a crab style distributor.

I am employing an electric fuel pump. The Fuel still passes through the old mechanical fuel pump but the rod has been removed so there is no pumping happening from the cam. Its a Mallory 4070M. rated at 6 psi but regulated down to 3-3.5

no overdrive. Just 3 speed manual.

 

Heat riser is NOT blocked off, but I'm considering doing so because I feel I'm getting Vapor Lock.

Carbs are HOT. No ice here, ever.

 

If you had a mechanical pump diaphragm leak would the elec pump push gas into the crankcase?
Doesn't apply to your bog, but can be a problem.

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This probably wouldn't enter into your problem since it happens at a particular temperature, but, since a relay is involved underhood temps could affect it.

An overdrive trans kicks down by cutting the ignition momentarily.
You can duplicate the kickdown switch operation by a quick off-on of the ignition switch.

I'm wondering if your kickdown switch or relay can be dropping out and staying out until the throttle is lifted.

Assuming you have an OD.

 

This exactly describes the same issue. Not that the engine actually shuts off. It still runs, just doesn't have any power at all and you coast. Wait a few seconds and then push the throttle down and get a few more seconds of power before happening again. While "bogging" happens the sound of the engine changes to a grown.. sort of empty sounding. It still revs up, but no more power comes out.

 

GMC Bubba is THE MAN for checking and validating distributors.

 

As mentioned near the end of the original post, the mechanical fuel pump was bypassed to test that theory as well. I also thought that oil pressure could cause the diaphragm to balloon outward, choking the fuel supply.

even with the bypass, the bogging still happened.

I'm running a electric fuel pump.

Again, no Overdrive. Never was an overdrive.

 

The "catching up" statement does sound like fuel delivery is inadequate. Try those caveman enrichment techniques as a diagnostic--you can use either of them to yank in some more fuesl from a nearly empty carb for a second or two.

 

Did you drive it with the gas cap off to ck for venting of fuel tank?

 

I had a very similar problem with my 47 Merc. BTW, I ran the Mallory Unilite dizzy for years, worked flawlessly. The car ran fine until reaching around 2500 rpm with my foot in it whereupon it would bog and act like it was simply out of gas. If I feathered the throttle way back I could get more rpm but no power. This was with Offy 4bbl and Holley 390. Took me weeks to figure out. Deposits had formed inside the fuel pickup in the tank. These deposits were cone shaped with the small end towards the engine. This cone would allow enough fuel to pass to run the car at lighter throttle/ low rpm and fill the carb bowls but created anough restriction to starve out under load. I could punch it and it would respond nicely until the bowl ran out of gas, back off it would catch up then do it all over again. Drove me nuts. found it by cutting the fuel line near the tank, removing sending unit, then pushing a stiff piece of wire down the fuel line toward the tank. Out popped this little cone about 1/2 inch long, hard as a rock. Damnedest thing I ever saw. Fished it out and never had another problem.
Have you found the cause of your problem? This is kind of an old thread, hope you can post back with some good news.

 

I did find the problem. The issue was with the distributor shaft being too long after the drive gear. There were no signs of wear on the shaft so I assume it was an electrical problem in the end with it grounding out on the timing gear cover.

This all came to light when I had to give the second Mallory distributor back to its owner and ordered yet another one and found a xeroxed half sheet of paper stuck in the box that mentioned that the shaft needs to be cut unless it is going into a flathead truck engine application. Taking a quick look at the other two distributors that I had tried I noticed that neither of them had been cut down after the drive gear. So out came the cut off wheel and dropped it back in the car and away I went without any problems!

Now I found a new issue with the car: When I drive super effin' fast my kingpins are too loose and scare the Bajebus out of me. haha.