M loss of power

FarmallFred · Jun 30, 2009

Recently rebuilt my M with 4" domed pistons. Since this was bigger than stock, I drilled main jet slightly bigger to make sure it was getting enough fuel, governor is rebuilt, electronic ignition in dist., head machined, etc... Ran good, but now it seems to fall on it's face when I lug it down. I pulled a plug and it looks pretty black. Will this allow it to run great until under load, or could I have more going on than that?

scott mcintosh · Jun 30, 2009

Drilling out the main jet is a no.no. with out putting in bigger venturi.To much fuel for that size venturi,turn main jet down,clean plugs,check dist. timing also check dist advance springs.Scott

Allan in NE · Jul 1, 2009

You really drilled out the main jet?

Allan

CLIFF S · Jul 1, 2009

Fred, Did you Retime the Distubitor after you installed the Pertronix in the Distubitor?
What i have found is that it Advances the Timing and it wont Loug!

Cliff S

FarmallFred · Jul 1, 2009

I installed it the same time that all the other work was done. I will re-check it today. What do you recommend the timing set at? Thanks to all.

rustyfarmall · Jul 1, 2009

(quoted from post at 18:08:56 06/30/09) Recently rebuilt my M with 4" domed pistons. Since this was bigger than stock, I drilled main jet slightly bigger to make sure it was getting enough fuel, governor is rebuilt, electronic ignition in dist., head machined, etc... Ran good, but now it seems to fall on it's face when I lug it down. I pulled a plug and it looks pretty black. Will this allow it to run great until under load, or could I have more going on than that?

You ruined a perfectly good carburetor. That main jet is no longer available as a replacement part.

Janicholson · Jul 1, 2009

I agree with the posts below put a stock jet in it. Put in new plugs, check the timing. Starts at TDC static timing, ang goes up from there (uses the IH advance mechanism in the dist).
The high speed needle will adjust all the richness you will need to account for the engine (usually none) JimN

teddy52food · Jul 1, 2009

If you know the oridginal size, just solder it shut and redrill it.

KAC · Jul 1, 2009

The needle still seats in the jet. Why can't it still be adjusted? I only went slightly oversize. Nothing too drastic.

Janicholson · Jul 1, 2009

The needle is not "in the jet" it is a separate deal that adds to or "adjusts" the total fuel.
The jet enlargement can change total flow just from changing the contours of the passage. It can even reduce the flow, in some cases, by changing the fluidic nature of the passage. The main thing is to get it back to a known flow, then the load screw will adjust any extra needed. I would guess that the load screw can be screwed in all the way (gently) and it will still run well at High speed. Which it should get leanish. JimN

D Slater · Jul 1, 2009

IH used a .061 main seat with there fire crator package. They also changed the air bleed size and a few other things along with that. Also the distributor advance was changed. Original M gas main seat was .0545. Don't know what you are calling a little. I would check the distributor advance parts and the timing before blaming the carburetor though. What heat range are the spark plugs? Its not unheard of to get a bad electronic ignition or the wrong unit. Also make sure the governor and linkage it moving the butterfly in carburetor to wide open when it starts lugging down. Also is the air cleaner clean.

D Slater · Jul 1, 2009

If you ever need one order 355003 R1 for less than $10. Its .051 orfice size and can be opened a little if needed.
Also think you can still get a 376440 R1 = .054, but for some reason they think its gold.

M loss of power

FarmallFred

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scott mcintosh

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Allan in NE

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CLIFF S

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FarmallFred

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rustyfarmall

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Janicholson

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teddy52food

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KAC

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Janicholson

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D Slater

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D Slater

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