239 flathead v8 timing issues

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Aug 29, 2012 | 10:29 PM

cosmaar1

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239 flathead v8 timing issues

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I have a 1951 ford f1 with a flathead v8. I have installed new plugs, wires, ignition coil, and condenser on the distributor.

I am having some issues with my timing. When I set the time to 2 degrees before top dead center, I have the distributor hose taken off of the carb and blocked off so no vacuum is present. The motor has slight hesitation when I stomp on the gas, but sounds very good with no issues after. It is very smooth and isn’t missing a beat.

When I hook the vacuum line back up and check the timing again, it seems like the timing has went from 2 degrees BTC to probably 35-40 degrees. When I hit the gas, there is minimal hesitation (not nearly as before), but going up in RPMs the motor struggles and sounds like its drowning out. It sounds like there is a governor on it holding the motor back.
Lastly, with the vacuum line still hooked up, I put the motor at 2 degrees BTC to see what that would do. There was NO hesitation, but again it sounded like the motor was drowning.

Can someone please try to help me explain why this is happening? From what I have read and talked to friends of mine, the vacuum line needs to be blocked and not hooked up. When I did that, everything was good. Why would it change that much when hooking it back up?

One note I would like to make is that when I dump fuel down the carb (it’s hard to start because my battery is going bad) fuel leaks out of one of the gaskets. There are 3 sections of the carb. It doesn’t leak where the top section and middle section come together, it leaks from the middle section and bottom section meet. Could this be the reason why it isn’t running right when the vacuum line is hooked back up?

thanks guys

Aug 29, 2012 | 11:08 PM

ALBUQ F-1

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From: NM

It sounds like your power valve is shot. Here's a link to a manual for the carb: Ford F1 Carburetor Rebuilding Instructions

When a power valve is leaking, it dumps gas continuously.

It's normal for advance to jump when you hook the vacuum up.

Aug 29, 2012 | 11:20 PM

52 Merc

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From: Burbank, WA

It sounds like you're hooking your distributor vacuum line to full manifold vacuum instead of ported vacuum from the carb like it's supposed to be. Your timing shouldn't change by more than a few degrees when hooking up the vacuum to the dist.

Aug 30, 2012 | 08:05 AM

cosmaar1

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Quote:

Originally Posted by ALBUQ F-1

i have rebuilt this carb. i replaced all gaskets, o rings, and jets inside. like i said with the vacuum off, it runs soooooooooo smooth. a friend of mine told me last night that it could be sucking more vacuum that necessary (i said the one gasket leaks when i dump fuel straight down the carb) therefore giving it the bogging feeling. do you think that may be the case?

Quote:

Originally Posted by 52 Merc

my vacuum line runs from the distributor to the backside of the carb. it is the only hole on the carb that isnt used. this line IS NOT connected to the intake manifold. am i right?

thanks guys for your help!

Aug 30, 2012 | 09:23 AM

1952henry

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From: Mandan, ND

Some power valve gaskets don't seal well, and some power valves, like the modern Holleys are tought to seal due to the stepped mounting flange.

Aug 30, 2012 | 09:23 AM

oldmerc

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From: Edmonton,Alberta

Sounds right dist. vacuum should be ported (line should connect above throttle body) . If you installed a carb kit it may have contained the wrong power valve .

Aug 30, 2012 | 09:57 AM

52 Merc

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From: Burbank, WA

Quote:

Originally Posted by cosmaar1

Put a vacuum gauge on the port and see what it says.

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Aug 31, 2012 | 10:30 AM

petemcl

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From: Northville, MI

First you need to fix the carb leak.

Then, while you did the right thing disconnecting the vacuum from the vacuum advance you didn't say anything about using a tachometer. You need to make sure that your RPMs are below 500 when checking the timing. Otherwise the centrifugal advance kicks in giving you erratic readings. Also make sure that your breaker plate is moving freely. It should rotate as smooth as silk else it will also contribute to erratic readings. If it doesn't you will need to disassemble and clean your distributor. Not a bad job as long as you remember to take a picture of the distributor with the cap off before you remove it. I soaked mine in my solvent vat overnight and that cleaned out a lot of 62 year old gunk.

On reassembly make sure that you oil the shaft well and then check to see if there is any side to side play in the shaft indicating a worn bushing. Usually they are OK but it doesn't hurt to check.

Also consider investing in a Pertronix ignitor that replaces the points and condenser. It is easy to install and eliminates all the dwell setting (point gap) guess work and questions regarding whether the condenser is working properly or not. Amazon.com had the cheapest price that I found (around $75).

My engine ran a lot smoother and the hesitation was gone after installing it.

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Aug 31, 2012 | 10:59 AM

#10

ALBUQ F-1

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From: NM

No mechanical advance with the Load-A-Crapic distributor. All vacuum.

Aug 31, 2012 | 11:27 AM

#11

petemcl

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From: Northville, MI

Quote:

Originally Posted by ALBUQ F-1

No mechanical advance with the Load-A-Crapic distributor. All vacuum.

Uh . . . OK Ross . . . I believe you but then what are those little springs for in the picture?

Since my truck is a late '50 and since he has a '51 shouldn't it be the same? My RPM definitely needed to be below 500 when setting initial timing.

I did find this article on line that may be of interest to cosmaar1
http://classicinlines.com/Loadomatic.asp

Aug 31, 2012 | 11:55 AM

#12

ALBUQ F-1

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From: NM

That's a good article, to sum it up:

"Unfortunately the "Load-O-Matic" distributors were designed for simplicity and economy, rather than performance. The primary reason for this, is that the "Load-O-Matic" distributors have no provisions for mechanical advance. Instead they rely solely on relatively weak vacuum signals to sense changes in load and speed (rpm). "

I'm running the MSD Ready-to-Run dizzy, which has the GM style mechanical advance and vacuum advance with what seems to be a Ford or Chrysler pickup. For a long time I was running the vacuum advance from the Loadamatic port on the carb, and then realized that was wrong. The loadamatic vacuum port simulates mechanical advance needs (RPM) as well as load (venturi vacuum). So I had two "Mechanical" advance curves plus a load curve. I'm in the process of hooking the vac advance up to manifold vacuum, which should give better economy and be a pure "load" signal.

To answer your question, the two springs in the Loadamatic calibrate the amount of advance a vacuum signal produces. And there is no signifcant change in the Loadamatics from '48 thru the '60's.

That's the big catch IMO with the Pertronix; you get a consistent spark, but none of the benefits of a true mechanical advance, i.e., you still have a LoadaMatic curve. If I were doing it over, I'd probably get one of Bubba Linden's converted Chevy distributors.

Aug 31, 2012 | 12:05 PM

#13

cosmaar1

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Quote:

Originally Posted by ALBUQ F-1

no i do not have a manual, but i am looking online to buy one as we speak.

Quote:

Originally Posted by petemcl

i have already rebuilt the carb and figured i wouldnt have any leaks, but i guess i was wrong. i have been told that it is possible that where the two plates meet on the carb, they might be warped because of the cheap metal the carbs are made out of. i am going to try to install a new gasket and if that doesnt work i will be buying a rebuilt carb.

you are right. i did not use a tachometer. the one inside the truck doesnt work so i just ran the truck at a slow idle speed and figured i was good. i guess i should invest in one and make sure i am getting the timing correct.

i only have one problem. i want to spend as little as possible to get this thing going. its not that im trying to put together a junker, its just i do not want this motor or this DREADFUL 6V electrical system. i hate to spend hundreds of dollars on fixing it because come spring time, im taking it all out anyways. that is why i came on here for some tips and advice to see what all of you experienced guys think.

again i appreciate all of your help! this site is great!

Aug 31, 2012 | 12:15 PM

#14

ALBUQ F-1

Fleet Owner

Joined: Jul 2004

Posts: 27,294

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From: NM

When you pull the carb apart, try assembling the lowest section of the carb (with throttle plates) to the body without any gasket. See if the power valve is too tall, preventing the two from mating. Pretty common problem.