Farmal 450 Cam Timing

LarryM · Dec 30, 2012

My Dad overhauled his 450 about 8 years ago and it has never had the horsepower it should. We have recently gone through the carb, governor and ignition but the one thing I do not have the knowledge of is the cam specs. What we have is a cam that on the number 1 cylinder starts to open the intake at about 8-10 deg past TDC. It reaches peak lift at about 98 deg past TDC and stays at peak lift for about 30 deg or until 128 deg past TDC and then starts to close. I did not check to see at what point the intake valve is fully closed. We placed a dial indicator on the top of the #1 intake valve rocker right on the adjustment screw to check this and the total lift was .234". I am hoping that is enough information for someone to be able to tell us if the cam is worn down or not timed properly. What are the specs on an original c-281 cam? One last thing; with the manifold off it has exactly 150 psi compression on all four cylinders running it over with the starter.

El Toro · Dec 30, 2012

You should bring No1 piston to TDC on the compression stroke and then remove the distributor cap and see where your rotor is pointing. Should be at the No1 plug tower. Hal
PS: If that carburetor has a main jet adjusting sc/ew you may need to open it as this will enrich the fuel mixture.Hal

CNKS · Dec 30, 2012

I agree with El Toro. Your cam may be worn, but you first need to check the static timing. Then use a timing light and check the advance -- it could be a distributer problem. All 4 cylinder IH distributers are interchangeable, but they do not all have the same advance curve, you might have the wrong advance curve. I don't have the advance numbers handy.

D Slater · Dec 30, 2012

Timing gears and keyway placement, plus wear may change the readings, but sounds like a M or SM cam maybe installed. They open the intake 5, ATDC. 400 and 450 cam should open the intake 5, BTDC. Lobe lift I think for all the cams was .2725. .020 less than that is about all you want for performance. Intake closes 41 ABDC. Exhaust opens 42 BBDC. Closes 10 ATDC.
Hope I didn't get my numbers mixed up.
If you end up removing the cam, look for a number on it to determine the one it is, if IH.

rhtx55 · Dec 30, 2012

Per IHC ISS-1039-1 page 11
281 ci
Intake opens 5 degrees before TDC
Intake closes 41 degrees after BDC

Exhaust opens 42 degrees before BDC
Exhaust closes 10 degrees after TDC

Push rod length 17 11/64 in.

The book does not list the lift or duration...sorry.

Sorry Mr. Slater, looks like you posted while I was looking it up, ....sorry.

Fritz Maurer · Dec 30, 2012

If it's supposed to open 5 deg. BTC as per the other posts, and it's opening 8-10 deg. after, that's about the right amount of delay for the timing to be one tooth off at the gear train.

LarryM · Dec 30, 2012

I sincerely appreciate those number. I am going to copy and past that into my "Farmall" document I keep adding to. The cam has left hand threads so it has to be the later one. It appears that he may have gotten it in one tooth off and it definitely appears to have lost some lift over the years. Again much appreciated.

Farmal 450 Cam Timing

LarryM

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El Toro

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CNKS

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D Slater

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rhtx55

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Fritz Maurer

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LarryM

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