GP cam specs

1940 - 1941 BRC, MA, GP, Preproduction Prototypes. Knowledge Base NO EBAY or COMMERCIAL SALES.

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Adam
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GP cam specs

Post by Adam » Sat Mar 19, 2022 8:31 am

Does anybody have the cam specs on a gp cam, duration at .050", lift, overlap?

Adam


rjbeamer
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Re: GP cam specs

Post by rjbeamer » Sat Mar 19, 2022 12:45 pm

Adam I have looked for these spec's in the past to no avail. There is a good chance that it was the same grind as the N series pickup and car 4 cyl motors from 1940-1942. One of the difficulty's that i found is that the way that the cam spec's were listed and measured prior to about 1965 is very different than today. For one thing they didn't start measuring the lift at .050" like now. I gave up after talking with a lot of Ford experts and cam grinders from the past and present.

Roger

Adam
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Re: GP cam specs

Post by Adam » Sat Mar 19, 2022 5:12 pm

I think the old specs were at .004 or .011. I have some crane cam cards with specs at .006.
i have some gp marked cams from the old truck engine and from gp marked engines, wanted to compare the actual between the 2 different engine types to see if they are the same. 1 cam does have gp on the shaft, but no gp by the dist drive, wonder what that is.

What are people doing when they need a cam for a gp? 9n cam? might be able to find the specs for one of them. I don't think anybody is repoping any of the early truck 4cyl cams or on1 or 2's. If i needed to get one resurfaced or reground,, wonder what specs they would use?

I have a truck engine on the stand now, will get the numbers myself before i pull that cam out. never thought i would need that magnetic degree wheel again.

Now on another note, rods in the truck engine are marked 9n, I c the rods in the series 2 engine say 9n too. for sure anybody could of replaced them, were gp rods marked gp? a pic? How about the crankshaft? I c no marks on them.

Adam

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rjbeamer
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Re: GP cam specs

Post by rjbeamer » Sat Mar 19, 2022 6:38 pm

Adam in my neck of the woods i never saw anyone regrinding 9n cams. New ones from TISCO were to cheap and a lot of farm 9n rebuilds reused the old cams.

I am not for certain but I think when Ford first started with the GP it was the first to have a fuel pump lobe on the cam so all of the other engines that used or had a need for a fuel pump used the GP cast cam shaft blank. I am just unsure if all of the fuel pump cams were ground the same but there is a good chance that they were. Tractors needed a profile for constant rpm and trucks and GP's needed a profile for variable rpm's and load condition.

But that's just my thoughts as I have no written spec's. Just observations.

Roger

Brad Gates
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Re: GP cam specs

Post by Brad Gates » Tue Mar 22, 2022 12:53 pm

Adam,
A long time ago when I got into this GP business I had the opportunity to place an NOS GP cam in "V" blocks and measure lobe lift. Not duration, nor degree. I compared those numbers to a truck 4 cylinder cam. Definitely a diff on lift, but just on the intake lobe if I remember correctly. I can go thru my records and check if you're interested.
The fuel pump lobe has been on cams for a few years before the GP I believe. And the fuel pump lobe measures the same on all cams.
Later years I think all the cams interchanged, truck and tractor and as the GP cams became unavailable the replacement was the tractor/truck cam.
I have seen GP cams just etched on the end but believe the correct marking is the forged 'GP'.
The rods in all the 4 cyl engines are forged 9N. Tractor, truck and GP.
If you need a cam I would use the truck version as available.
Let me know if I can help.
BRAD

Adam
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Re: GP cam specs

Post by Adam » Wed Mar 23, 2022 9:31 am

I have GP camshafts, will sell them shortly if their specs match. So trying to find if Old henry ford used the gp blank and cut different grinds on them.

As found in a genset engine, Cam is embossed with GP and front is stamped GP.

Non adjustable valves so lift may be a little different than actual measurement. Timing marks were aligned. seems very mild, no real overlap for scavaging.

Intake .293" exhaust .289" measured at valve 1:1 cam to lift since no rocker arms.

intake at .006"
opens 1* BTDC
closes 39* ABDC

220* duration

exhaust at .006"
opens 26* BBDC
closes 4* ATDC

duration 210*
overlap 5*

Will c what the others measure shortly. 2 are in gp marked engines, but who knows what has been done in the last 80 years.

Adam


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