NOS 8RT camshaft

[petehoovie]

Originally Posted by GB SISSON

Thanks Vincent. Sounds like a good plan. I peeled the coating and checked them all on the lathe. So far that very first one is the only one that's out much. The two pics with the dial indicator show the first and secnd lobe differences. Throughout there are some slight varaitions in lift, and the center bearing isn't all that true, maybe .005 out, but all these cams I have are about like that. I'm guessing Kiwi's thoughts involve the center bearing coming into play to stabilize the readings. And lastly you will see it is marked 8RT, and when rotated 90 degrees it reads EA. Any tricks to inserting the cam without damaging things?I also have some stripped blocks with their cam bearings still in. Would that be a smarter place to test this?

[vincent]

Test it in a block with a cam follower - this will give the exact motion the valve will get. The cams that I got are all soft so you could regrind the wrong base circle very easily. I just reground all 16 lobes for my supercharged engine to get a bit more valve acceleration and more lift.

[GB SISSON]

Originally Posted by vincent

Test it in a block with a cam follower - this will give the exact motion the valve will get. The cams that I got are all soft so you could regrind the wrong base circle very easily. I just reground all 16 lobes for my supercharged engine to get a bit more valve acceleration and more lift.

I don't think I will be grinding this cam. I do think I have enough tools and machinery here to make a fixture to touch up the bottom of that one lobe if I had some instructions , but it would be quite scary. Out of curiosity, should all the cam lobes measure the same if they were mic'd across the long dimension? I understand that intake and exhaust could differ. First I will test the lift in a block. And what is a cam follower? I'm picturing a lifter with a slot in it for a small wheel. If so, what keeps it from turning sideways?

[flatjack9]

In this case the follower is the lifter. i use an adjustable lifter and set it so the valve is off the seat.

[GB SISSON]

Well, I just finished a full test of all 16 valves using an exhaust valve, a light spring with guide, an adjustable lifter, and my dial indicator. The forward two exhaust valves are better and all valves have a lift of .306-.307 with the exception of that one forward exhaust valve #5 cyl, which is so darn close now at .304, that the case is closed as far as I'm concerned. Had an enjoyable late evening down in my new shop space with some residual heat from today's fire in the wood stove, measuring valve lift in my bathrobe and slippers. I guess I'm just easily amused, but thanks all of you for helping me through this.

[vincent]

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Forgive me the cam follower. I am working mostly on old british bikes and being german, lifter is not the first word that comes to my mind when talking about the part that rides on the cam ;-)

[51504bat]

Originally Posted by GB SISSON

Well, I just finished a full test of all 16 valves using an exhaust valve, a light spring with guide, an adjustable lifter, and my dial indicator. The forward two exhaust valves are better and all valves have a lift of .306-.307 with the exception of that one forward exhaust valve #5 cyl, which is so darn close now at .304, that the case is closed as far as I'm concerned. Had an enjoyable late evening down in my new shop space with some residual heat from today's fire in the wood stove, measuring valve lift in my bathrobe and slippers. I guess I'm just easily amused, but thanks all of you for helping me through this.

Sounds like a perfect setting for a Norman Rockwell painting. Just need to add a corn cob pipe

[flatford8]

“ I guess I'm just easily amused, but thanks all of you for helping me through this.”
Imagining you in your robe and slippers, working in the shop …
Amuses the sh!t outta me!!……now my wife is asking what the hell am I laughing at!!….Mark

[flatjack9]

So was the "dip" noticeable?

[GB SISSON]

Originally Posted by flatjack9

So was the "dip" noticeable?

Only noticeable because I was watching for it. A very small deflection on the needle and it's just before it ramps up to where there would be any heavy spring pressure. That is if one considered 40 lbs to be 'heavy spring pressure'. The valve assemblies I have sorted through and chosen are a good set of rotator style assemblies from a friend's merc that he harvested a crank out of.
I have a feeling that this 276" stroker, with it's 4.03 first geared T5 will pull the old wooden wagon up my gravel mountain road with relative ease.

[rotorwrench]

The last new flathead cam I bought was an EAB cam. It was likely the replacement cam toward and after the end of flathead production. That purchase was back in the early 80s when there was more NOS stuff available. The local Ford garage where I grew up in Kansas, couldn't give away all the 8RT parts they had. A friend of mine, that worked there, took most of it to his Dad's shop since he was the only one around that worked on flatheads. He had new heads, cams, and all sorts of chassis stuff for trucks. He used some of it but likely scrapped a lot of it after all the old Ford trucks started to disappear. He had a 1953 1-ton that he made into a wrecker but he converted it to a later Y-block to get more power out of it.

[flatjack9]

The EAB cam was introduced in 1952

[GB SISSON]

So is this cam I bought, that says EA on one side and 8rt on the other side, more similar to an EAB cam or an 8BA cam? I have tried to find charts online that list the valve lift of various flatheads. There is a lot of conflicting info out there. I know this camshaft is no high performance cam, but I'm hopeful that it will give me the smooth Idle I like some low end pulling power for climbing Orcas Island's steep grades at 35-40 mph.

[tubman]

Looks to me to be the same as an 8BA cam (.307 lift). However, we can't be sure without the duration numbers. Have you checked out the chart on "Tilden Cam Technologies"?

[Ol' Ron]

I don't think there is any noticable difference between any stock model camshaft.
Gramps

[GB SISSON]

Originally Posted by tubman

Looks to me to be the same as an 8BA cam (.307 lift). However, we can't be sure without the duration numbers. Have you checked out the chart on "Tilden Cam Technologies"?

Denny, seems I have come across that, but I will look again. And Ron, I'm thinking the .125 over bore and the 4" stroke will be the noticable parts in this build. From 221 up to 276. No doubt I'll feel that 55 cubic inches, even with an army surplus cam from an old Canadian duece and a half.

[tubman]

That's a 25% increase in displacement. That oughta help!

[cadillac512]

If it helps, my "EA" cam in the 260" Merc will go 'round a corner at 10 mph in high gear and pull right back up to road speed no problem.This is with 3.54 gears and 29" tires. Idles smooth. You're not going to have any problem at all.

[GB SISSON]

I'm getting pretty excited about this new powerplant. I bolted up my adapter plate and hogshead, put new seals in the T5 and set it aside. Next I dug out a few old ford truck driveshafts and the 2 piece driveshaft that came from the S-10 and crawled under the wagon and took some rough measurements and it looks like I have everything I need. I will continue to collect needed parts and materials for a crossmember etc. I still need to get the transfer case I rebuilt last month installed in the Foyota and I have a list of jobs stacked up in a holding pattern for countless soon to return 'summerfolk' who continue to bug me with questions about their new entry door, or pair of rocking chairs, or whatever I said I's do over the winter. Sheesh, give a guy a break for cryin' out loud.

[38 coupe]

Now we need to figure out what valve lash this cam is designed for.
The earliest 8BA cams used the same lobe design as the 38-48 cam.
The later (late 1949 and on) cams had a new design lobe with different "ramps"

The lash is different between the two cam designs:
early intake: 0.010-0.012
early exhaust: 0.014-0.016
later intake: 0.013-0.015
later exhaust: 0.017-0.019

Looking through the 49-51 Ford F-Series Truck Shop Manual it shows 8RT part number camshafts use the later lash settings. Anyone have any other information?