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Old 10-12-2019, 05:39 PM   #1
cadillac512
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Default 8CM or EAB cam for 260" Merc?

I'm putting together a .030" over Merc ( with a stock Merc 4" crank) for my '41 Town Sedan. I'll mill a set of stock iron heads to get proper piston to head clearance of approx .040" and have converted a Chevy distributor to Flathead specs for centrifugal advance and added an adjustable vacuum can for light throttle cruise. I have a four bolt Merc intake and both a small pattern Rochester 2G carb and an Autolite 2100 two barrel with 1.02 venturii. (and an adapter to fit the Autolite). I'll see which carb I like best. I have the required bell and starter plate to bolt the later engine up, and have the belt routing handled.

My main question: I have both an 8CM and an EAB cam, and can't decide which to use. Both are in perfect condition and the reviews are good on here for both...so what to do?? Opinions please,especially if you've experienced these two cams.

Thanks in advance to all who share knowledge here-it's such a great resource!


Terry
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Old 10-12-2019, 06:31 PM   #2
KiWinUS
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Default Re: 8CM or EAB cam for 260" Merc?

EAB is my vote. But honestly you probably would not notice the difference from one to the other.
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Old 10-12-2019, 06:52 PM   #3
51 MERC-CT
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Default Re: 8CM or EAB cam for 260" Merc?

As stated you most likely won't notice any difference.
For reference the 8CM specs. (.338) lift.
You could measure the EAB just to see how they compare in that feature.
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Old 10-12-2019, 07:07 PM   #4
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Default Re: 8CM or EAB cam for 260" Merc?

Perusing some of the old threads on here shows the 8CM to have .010 (.338 vs. .328) more lift than the EAB. Of course, there's more to it than that, but I think it would be enough for me to pick the 8CM.
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Old 10-12-2019, 10:09 PM   #5
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Default Re: 8CM or EAB cam for 260" Merc?

I have an EAB cam in my 280 and love it. I don;t think the 8CM cam is the same as the EAC 52/3 cam
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Old 10-12-2019, 10:54 PM   #6
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Default Re: 8CM or EAB cam for 260" Merc?

Like others have said, you probably won't be able to tell the difference. I would think the condition of the respective cams (new or used) and what you have for lifters would be the determining factor.
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Old 10-12-2019, 11:11 PM   #7
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Default Re: 8CM or EAB cam for 260" Merc?

Thanks,guys. I plan to mock up both cams in an extra block with crank and a piston/rod assembly and use my degree wheel to plot the lobes as best I can. I'm curious how they compare. It'll be interesting as well to see if one or the other are advanced/retarded any as well. I might even be tempted to advance the cam timing a touch (for better low end in a heavy car) if the numbers suggest it might help.



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Old 10-13-2019, 12:29 AM   #8
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Default Re: 8CM or EAB cam for 260" Merc?

I will mention that I have a '51 Merc with a stock cam, massaged Edmunds heads, a 2GC, and Mallory dual point distributor in my '51 club coupe. This is also a heavy car. I had an Isky MAX-1 I was going to use, but after some discussion here and elsewhere, I decided to stick with the stock cam for this car. When I got it all installed and dialed in, I was completely satisfied with performance improvement over the rather tired stocker it replaced. This fall, when I was adjusting the automatic choke for better cold weather performance, I discovered that the throttle linkage was not opening the carburetor all the way. A modification to the linkage to allow the carburetor to open all the way made a surprising difference in performance. I went from being satisfied with the performance to actually being impressed with it.

The one thing about it is that revving much beyond 4000 RPM produces more noise, but not much more performance, The engine has a lot of torque, so much so that I can negotiate the "roundabouts" that are becoming more common around here without downshifting. BTW, the car has 3.55 rear-end gears, which are OK with the standard transmission. I am planning on installing an overdrive, and perhaps going to a 4.11 rear. With that combination, I would expect the performance to be even more impressive. The way it is now, the car will cruise all day at 65 with the revs at 2700. It will easily turn a lot more than that, but doesn't seem to be happy at those higher revs.

Last edited by tubman; 10-13-2019 at 12:39 AM.
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Old 10-13-2019, 07:39 AM   #9
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Default Re: 8CM or EAB cam for 260" Merc?

Quote:
Originally Posted by tubman View Post
I will mention that I have a '51 Merc with a stock cam, massaged Edmunds heads, a 2GC, and Mallory dual point distributor in my '51 club coupe. This is also a heavy car. I had an Isky MAX-1 I was going to use, but after some discussion here and elsewhere, I decided to stick with the stock cam for this car. When I got it all installed and dialed in, I was completely satisfied with performance improvement over the rather tired stocker it replaced. This fall, when I was adjusting the automatic choke for better cold weather performance, I discovered that the throttle linkage was not opening the carburetor all the way. A modification to the linkage to allow the carburetor to open all the way made a surprising difference in performance. I went from being satisfied with the performance to actually being impressed with it.

The one thing about it is that revving much beyond 4000 RPM produces more noise, but not much more performance, The engine has a lot of torque, so much so that I can negotiate the "roundabouts" that are becoming more common around here without downshifting. BTW, the car has 3.55 rear-end gears, which are OK with the standard transmission. I am planning on installing an overdrive, and perhaps going to a 4.11 rear. With that combination, I would expect the performance to be even more impressive. The way it is now, the car will cruise all day at 65 with the revs at 2700. It will easily turn a lot more than that, but doesn't seem to be happy at those higher revs.
I run 3.78 gears with an overdrive on a bone stock 49 convertible and I have been everywhere except Pike's peak.
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Old 10-13-2019, 08:37 AM   #10
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Default Re: 8CM or EAB cam for 260" Merc?

Frank, I would not install the 4.11's until I had driven the car for a while and was sure they would be beneficial. From what you are saying, the 3.55's might be just fine with the modified engine.
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Old 10-13-2019, 08:45 AM   #11
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Default Re: 8CM or EAB cam for 260" Merc?

Tubman-
Thanks for the info on your car. I'm also planning to use lower rpm for 99% of the driving in this car,and am sure the stock cams are a good choice. I do have 3.54 gears now,and with 29" tires the rpm isn't bad a cruise speeds. I'm hoping to have a similar experience to yours when this engine is installed-a nice power improvement that makes the car more able to keep up with modern traffic.

I do have an overdrive trans in the shed, and maybe later on if I deem it necessary (and can work up the ambition!) to change to open drive and install it, I'll do that. For now at least, I'll keep things as-is and see how it works out. I REALLY like driving this old Merc... and I really like building engines.



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Old 10-13-2019, 09:39 AM   #12
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Default Re: 8CM or EAB cam for 260" Merc?

Ford was looking for more torque for the Mercury and later for the Ford too. There is likely not much of a noticeable difference. The EAB cam was the replacement for both Ford 239 and Mercury 255 engines. It's a good torque cam for both engines.
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Old 10-13-2019, 09:46 AM   #13
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Default Re: 8CM or EAB cam for 260" Merc?

None of the stock flathead cams are performance oriented.
Why not install a 3/4 cam and gain a few horsepower and a little more torque
Since your engine is apart anyway?
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Old 10-13-2019, 10:05 AM   #14
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Default Re: 8CM or EAB cam for 260" Merc?

Quote:
Originally Posted by Init1 View Post
None of the stock flathead cams are performance oriented.
Why not install a 3/4 cam and gain a few horsepower and a little more torque
Since your engine is apart anyway?
The OPs goal is "99 percent low rpm driving" in a '41 town sedan. The word from Ol'Ron has claimed that low end torque is never improved with a reground cam.
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Old 10-13-2019, 10:11 AM   #15
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Default Re: 8CM or EAB cam for 260" Merc?

Listen to Ol Ron.
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Old 10-13-2019, 11:33 AM   #16
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Default Re: 8CM or EAB cam for 260" Merc?

I've checked a number of EA and 8CM cams. Generally the 8CM has .335 lift and the EA .325. Lobe centers are 110 on the 8CM and 112 on the EA. The EA has 2 deg advance. Keep in mind these measurements are all on used cams.
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Old 10-13-2019, 01:07 PM   #17
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Default Re: 8CM or EAB cam for 260" Merc?

Quote:
Originally Posted by flatjack9 View Post
I've checked a number of EA and 8CM cams. Generally the 8CM has .335 lift and the EA .325. Lobe centers are 110 on the 8CM and 112 on the EA. The EA has 2 deg advance. Keep in mind these measurements are all on used cams.



Thanks flatjack9-I'll compare those figures to what I find. The 110 lsa on the 8CM should make for a nice early tq peak and the 112 advanced 2 deg on the EA should be very similar if lobe designs are close to same. Interesting!


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Old 10-13-2019, 03:28 PM   #18
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Default Re: 8CM or EAB cam for 260" Merc?

I think the 8CM cam your measuring is the EAC cam. Both the EAC and EAC cams came out in mid 51 thru 53. I have always thought the 8CM can was the same as the 49 thru early 51 engines.. i've never run an EAC Nerc cam, so I wouldn't have ant thoughts about it, The EAB cam in the 28 and 3.73 reak pulled the 14% grade of the Weston/andover hill at 43 MPH in OD engine was turning 1300 rpm's I didn't believe it myself
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Old 10-13-2019, 04:54 PM   #19
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Default Re: 8CM or EAB cam for 260" Merc?

have you seen this? https://www.tildentechnologies.com/C...rformance.html
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Old 10-13-2019, 07:37 PM   #20
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Default Re: 8CM or EAB cam for 260" Merc?

My measurements mirror the Tilden site's measurements.
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