we are on our way to putting my merc crank into my flatmotor. we'll be using my EAB heads. as i understand it, the ford/merc rods are the same, the pistons are diff. i can seem to find info on whether the cams are different for a ford vs. merc. can anyone help??

 

The attached hard-to-read chart shows the '49 Merc cam vs stock Ford. Interestingly, the late-model Ford cams were more conservative than early 59-series engine. Anyway, The late-Merc (EAC era) cams are supposed to be the hot ticket for a stock cam. Pretty sure 55 F350/Kevin is using one in his flathead build.

 

yep ross was going to use one of the two i got , but the one i was planning on using is a regrind with .364 degrees of lift ! so i'm not inclined to put the mint one i got in it and got the other hanging around , looking at different cams from howards , camcraft , and a custom grind from comp , when i get rich , to replace it thaat are comparable to the 8cm merc cams . reed check out the site for tilden technologies , click on cam design , the flathead cams , it's full of info on oe cams and aftermarket , cam design , etc. and gives you links to harvey cranes site for his thoughts on cam design . the 8cm holds up well against all the so called street cams offered by the aftermarket , and actually has more lift than most of them . larry young the man behind the site , designed an 8cm plus cam that a custom cam grinder was supposed to be making but have not heard as too whether or not they have . it has the same timing card as the 8cm but features more lift , .350 i believe over the 8cm's .338 . i too am using a set of eab heads i had milled .010 to clean them up , but will be running the stock 3 3/4 ford crank , a merc 4 bolt intake and a 350 cfm rochester 2 jet and aftermarket electronic ignition .

 

thanks, guys, that gives me much to look into. i'll look into this and report to my good friend and engine builder neil. he did many flatheads back in the day, just trying to update our information. as always, it's all here on FTE. dick r

 

Would the cam be stamped 8CM on the 'nose' or cast between the lobes.
Thanks
Chris

 

between the lobes chris ....... also if you have an 8cm it would pay to measure the lobes for wear , or in the case of the one i was intending to use , a regrind on it . measure the base of the lobe side to side , the measure the lobe top to bottom and subtract the base of the lobe from it it will give you the lift . the 8cm has .338 lift oe . it pays to check . i got one that measures within .336 too .338 on all lobes , and one that measure .364 , which means the base has been ground to acheive these numbers , and adjustable lifters are required . also oe heads , the eab's reed and i both have as well as the 8ba's and the 8rt's i have can only handle . 350 lift before you run into the valve hitting the chamber . so getting crazy on lift will mean machine work on the chamber if your gonna run a high lift cam , i.e mine thats a regrind . or many of the popular aftermarket cams for race , or aftermarket heads , which come in .400 and .425 . confused yet ?????

 

Does that chart really say 0 degrees (TDC) for intake valve open on a late stock? A pushmower from WalMart has more aggressive valve timing

 

It's hard to tell, but judging from the rest of the late Ford cams' specs, it wouldn't surprise me. You can see why aftermarket cams were so popular for flatheads...

 

Here is another chart (Thanks Ross for the conversion)

 

This website has more information on flathead cams and cam design in general than can be found this side of a graduate engineering class: Flathead Performance Cams

There were two different 49-53 Ford cams and 2 different 49-53 Mercury cams. Most folks agree that the 49-50 Mercury cam is the best stock cam.

 

Would John Lawson's book talk about this? I've had his book on my list of wants for quite awhile, but always ends up playing second fiddle.

 

Dick sent me this website today.

Flathead Performance Cams

There is discussion on the techniques used to measure these old flatty cams. They didn't follow a standardized set of rules like they do today. (i.e. .006 and .050 advertised and effective duration specs. I will certainly do some research before I arbitrarily pick a cam based on specs published decades ago.

 

IMO, it doesn't pay to pick ANY cam based on ANY specs. Best to talk to people who have tried them on the street and put 10,000+ miles on them, in all kinds of weather, not just running them on a dyno. The Merc cam is a proven piece and works well in heavier vehicles. Mamy of the high-lift cams offered are great in a light 32 roadster but pigs in a heavy truck, especially with taller gears for lower RPM.

 

Agree, I've become spoiled running custom cams in my last few street/strip 306 and 347 combos. It is crazy how accurately a knowledgeable cam grinder can predict performance if you give him good numbers to put into the equation. If they are any good, you can tell them what rpm you want max power, peak power, idle rpm etc., and get exactly what you ask for.

For the flatty I may be forced to copy a known sucessfull combo exactly. Not my style at all, but better than a motor than doesn't run the way I want it to at lower rpms.

 

The big adjustment IMO for a flatty vs "regular" OHV engines is the RPM band you're tuning for. 1,500 - 3,500 is where you want to look, which for an OHV engine (or OHC) is where they are just getting up on the cam. It's all about the breathing (lack thereof).