tuning a flathead?
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Senior User
Joined: Oct 2003
Posts: 278
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From: Lewisville, NC
tuning a flathead?
I've got the original repair manuals for my merc flathead in my '53 F100. It's starting and running, but roughly. I set the timing for #1 TDC right on the mark at idle (~450 rpm) with the vacuum advance disconnected. With the vacuum connected, that puts the timing about 0.5" towards the driver at idle and the same amount on the passenger side as it advances at higher rpm. Hesitates on acceleration, backfires, etc. Gonna go over the manuals again tonight, but anyone got a how to tune a V8 flathead (stock but Mercury)?
Another annoyance - the inline fuel filter I put in seemed to run mostly full last week. This week it is almost empty - plenty of gas in tank. The sediment bowl is full but pulls air bubbles at idle, at higher rpm's the bubbles slow to stop but the fuel filter doesn't fill up. Crack in the filter - checked as best I could and seems ok - air leak somewhere? I can see the vacuum being pulled on the filter by the fuel pump - the paper filters move slightly.
Advice, good web site?
-Scott
Elvis - '53 F100 with Merc 254 flathead
Another annoyance - the inline fuel filter I put in seemed to run mostly full last week. This week it is almost empty - plenty of gas in tank. The sediment bowl is full but pulls air bubbles at idle, at higher rpm's the bubbles slow to stop but the fuel filter doesn't fill up. Crack in the filter - checked as best I could and seems ok - air leak somewhere? I can see the vacuum being pulled on the filter by the fuel pump - the paper filters move slightly.
Advice, good web site?
-Scott
Elvis - '53 F100 with Merc 254 flathead
Fleet Mechanic
Joined: Jun 2004
Posts: 1,784
Likes: 45
From: Minnesota
The gas line pulling a vaccuum is a sign the pump is working but there is a restriction before the pump.
- Remove the gas cap and see if that helps. If it does where is your fuel tank vented to and where is the vent plugged?
- Working back do you have a rubber line before the pump that could be collapsing?
- Maybe the gas line is plugged or the new fuel filter is plugged. If you have the cheap plastic filter the same as I do I would start there.
- While you have the filter off drain some gas into a gallon jug and see if it flows or trickles. If it is trickling look for a kink in the gas line and blow air back through the line into the tank to try and move the obstruction.
Post Fiend
Joined: Jun 2001
Posts: 7,493
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From: Erie, pa
The Guys that write the books hang their hats here: http://www.btc-bci.com/~billben/flathead.htm
There is also a link to the 32 - 53 MSN Flathead site where they also hang out.
There is also a link to the 32 - 53 MSN Flathead site where they also hang out.
Posting Guru
Joined: Mar 2002
Posts: 2,070
Likes: 2
From: Boise, Idaho
You should probably set the timing statically. I'll assume that you still have a points ignition. I think you can set the idle mixture by turning the idle mixture screw in and then backing it out 1 1/2 turns.
You'll probably have to run a compression test to see if all the cylinders are holding compression.
You'll probably have to run a compression test to see if all the cylinders are holding compression.
Posting Guru
Joined: Apr 2004
Posts: 1,908
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From: Seattle WA.
I had the same problem when I drove my 51 home when I purchased it. When I pulled the tank I found a bunch of junk in it. Pieces of wood, a small plastic indian toy, once I cleaned out the tank its been ok sense.
Freshman User
Joined: Jul 2004
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Another thing you can do is to hook a vacuum guage on the engine and it will tell you status of timing and other things. I did that on my 38 and found that my timing was way off.
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Fleet Mechanic
Joined: Jun 2004
Posts: 1,784
Likes: 45
From: Minnesota
That is very true I like to aim for about 18" of vaccuum. You can try to get more than that but the timing is usually to advanced and causes hot starting problems.
Originally Posted by gut
Another thing you can do is to hook a vacuum guage on the engine and it will tell you status of timing and other things. I did that on my 38 and found that my timing was way off.
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