52 Mercury Flathead runs rough.

L

ling102

Member
I have a 52 Mercury Flathead V8 in my 48 Ford Coupe.
The car in new to me.
It has an Offenhouser intake.
It has a Holley four barrell carburator.
It has Reds headers.
The motor runs rough.
I have 100lbs compression.
No overheating.
Good oil pressure.
No vacuum leaks.
The plugs look ok.
However, I have one backfire
when I start the car.
Could this be timing?
Any help would be greatly appreciated.
Thanks guys.
 
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Could be timing, but we need to know what distributor you have. 12 or 6 volt ? Plug wires in the proper firing order etc. Others here much smarter than me will jump in and you'll get it sorted.
 
i had a leak somewhere that drew enough oxygen into the exhaust system to combust unburnt fuel passing through it. lots of pops and occasional bangs once the engine and exhaust system warmed to a critical temp.

it was very difficult to diagnose as there can be many causes, include fueling, electrical and mechanical that produce the same symptoms. it was exacerbated by a rich mixture and timing issues.
 
All the flathead Fords of the 8BA era (1948 - 1953), had Holly integral fuel delivery/ignition systems. The carburetors had vacuum systems that controled the spark timing of the distributor. If the carburetor is replaced with a unit that is not set up for Holly Load-O-Matic ignition, then some other design distributor must be used. Mallory all centrifugal distributors or modified early GM vacuum advance distributors are the easier ones to use. The GM would use manifold vacuum with an adjustable vacuum advance can installed. The flyweight springs and advance unit can be taylored to work well with any flathead. There are still a few folks that do GM distributor conversions. The old Mallory types for flatheads are harder to source now days but they are out there.
 
I truly appreciate the response.
My car is still a 6 volt.
Question: If I have a sticking or stuck valve would that show up on a compression check?
Also, how and where do I check the vacuum, and what should it be?
 
What Holley 4bbl is on it? Too big can be an issue. Also using the Load-o-matic distributor with it as mentioned.
 
Until we know exactly what he is running for an ignition, we can't be of much help. As above, the exact model of Holley carburetor would also be helpful. A "Load-A-Matic" will run with a mismatched carb, but not well.

"rotorwrench" mentioned the old Mallory distributor being an option, but said they are "harder to source". Charlie Schwendler can convert SBC Mallory's for flathead use, and they're a lot easier to find. Plus, they come in both mechanical advance and vacuum over mechanical versions, plus a few have tachometer drives built in.
 
The car is new purchase for me.
How can I tell if the distriubutor is a Loadomatic?
Does anyone make an aftermarket ready to run distributor?
I will get the information off of the carburator, but I have to remove it first, as the carburator was installed backwards.
Thanks again guys.
 
ling102 said:
The car is new purchase for me.
How can I tell if the distriubutor is a Loadomatic?
Does anyone make an aftermarket ready to run distributor?
I will get the information off of the carburator, but I have to remove it first, as the carburator was installed backwards.
Thanks again guys.
Click to expand...

You can take a cell photo of the carb. Should be a list number on the horn. A photo of the distributor would also help. There are converted SB Chevy distributors that will work with a flathead as mentioned above. These have vacuum advance not the Load-o-matic system.
 
I will try to get a photo of the carburator asap.
Unfortunatley, the carburator was mounted in reverse, and trying to take a picture with the way it was mounted was fruitless.
I will also take a photo of the distributor.
Thanks again for the replies.
 
If it is anything like he 2G Rochester I have on my car, mounting the carburetor backwards is the way to go; the throttle linkage and fuel inlet end up on the proper side so they're easier to hook up.

At this point in time, I think we're more interested in the distributor; it's more important than the exact model of carburetor.
 
The load-o-matic distributor is fully vacuum controlled (no centrifugal weights). It only has a breaker plate that rotates a little against the two coil springs in there by the pull of the vacuum can. The 8BA and 885 holley carbs used direct venturi vacuum to pull the breaker plate to advanced positions after engine start up. Under low vacuum load conditions, the spark would retard enough for load spark control. It was a basic system that just got the job done for basic operation. It wasn't designed for high performance use.
 
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