Camshaft ideas?

Ken Henry

Ken Henry

Senior Member
I hesitate to start another camshaft thread but am really not sure how to proceed. I’m building a 276 ci 8BA engine to go in my 51 tudor sedan and find myself waffling about the camshaft. I’ll use a dual carb intake, EAB heads milled for a tight squish area over the piston, stock valves, and zephyr-type springs. The block will have some mild porting done. The car has an overdrive, 3.73 rear gears, and fully programmable fuel injection and ignition systems currently operating on a stock 239 ci engine.


My goal is to make the most power possible from the new 276 ci engine without degrading idle quality. I had originally planned to use a stock EAB camshaft, and have access to an NOS one, but am starting to wonder whether I’m leaving too much on the table with the stock cam? I’ve read ‘Flathead Facts’ and understand that any non-stock cam will sacrifice torque at typical ‘cruising-around’ RPMs, but it might be worth it for the added power at 3000 RPM and above. Plus low-end torque will still be way up compared to my current smaller engine with lower compression ratio, which seems to sign off pretty early with increasing RPM.


[FONT=&quot]Any recommendations would be very welcome! Ken[/FONT]


51142579268_7c5346208e_b.jpg81E4F735-C76B-400B-B889-208BFE47883C by kenhenry_06268, on Flickr
 
Reach out to CharlieNY here on the barn. He recently built a similar engine for his 32 pickup & loves his choice of cam. Cheers
Tony
 
Regardless of what cam you decide on, you are NOT going to have enough power to use the gear combination you have with the most efficiency and best drivability. You are geared too tall.
Look up typical dyno sheets on hp and torque curves for that engine combination and compare them to street driving speeds and engine rpm.
Look up several information sources. Don't rely on just one.
 
I've got a Winfield SU-1A in my 39 with a 276 and 3.70 rear gears and OD. The SU-1A is very similar to the 100. My car cruises at 70 mph at about 2400 rpm. I just got back from a trip to Back to the 50's ( about a 600 mi round trip). Averaged right at 19 mpg without vacuum advance(crab distributor). Driveability is great. Still lots of low end torque. 25 years and 70,000 miles of experience.
 
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Pete said:
Regardless of what cam you decide on, you are NOT going to have enough power to use the gear combination you have with the most efficiency and best drivability. You are geared too tall.
Look up typical dyno sheets on hp and torque curves for that engine combination and compare them to street driving speeds and engine rpm.
Look up several information sources. Don't rely on just one.
Click to expand...

I, for one, will want to hear how his setup runs out. The standard, 100 HP cars have a 4.11 with the overdrive option, so I would expect his choice of gears (3.73) to be just about perfect with his upgraded engine. Of course rear tire size comes into play as well. The reason I am interested is that I am currently running a warmed over 255 Merc in my '51 with no OD, 3.55 gears, and 2.25/75R15 tires. At the present time, the car will cruise at 65 quite easily (2700 RPM), but after that, the engine gets a little "busy". When on the highway, I am always trying to "grab another gear" at 45 or 50. I am going to try to run the OD with the 3.55 gears at first, but realize that they may be a bit much (but maybe not). After that, it's a choice of 3.73's or 4.11's depending on how the 3.55's work out.

Keep us informed.
 
I think the 3.73 gears are original, as this car was not built with overdrive. Tires are 6.70-15 and the engine turns ~2000RPM at 65 mph. I would say it feels a little underpowered, probably because the original 239 IS, but I rarely need to kick it down out of overdrive for climbing hills.


Back to cams: while I done enjoy the choppy idle of a tall cam in a flathead, that's not what I'm looking for in this car. Something pretty smooth that gives a good vacuum signal would be best.


50212091747_6517af460c_b.jpg0A123251-307B-42A6-BCB7-1AFA70AF1D46 by kenhenry_06268, on Flickr
 
The original SU1A is a 280 degree cam that was designed strictly for Bonneville racing.
It had low lift, low acceleration and low velocity numbers.
The SU1A is probably one of the most prostituted grinds in history. There are probably very few cam grinders offering the original grind these days.
It is a poor choice for efficient street use.
 
Are you sure about the 3.73 rear end gears? My '51 runs 2700 rpm at 65 with 225/75 R15 tires; I would be very happy with 2000 rpm. 2000 rpm @65 sounds inconsistent with 3.73's to me.

As to cams, after a bunch of research and discussion on here, I decided that the stock Merc cam was the best choice for a relatively heavy car like mine.
 
Tubman, that is with the overdrive engaged. I added the overdrive a few years ago and it totally transformed highway driving. The stock Merc cam is pretty similar to to the EAB, correct? I have an NOS EAB cam on hand with ~0.328" lift...
 
Ooops, missed the overdrive part. The "Tllden Cam Technology" flathead cam chart lists the 8CM (Mercury) camshaft as having a .338 lift (I don't know how to make that neat little squiggle thingy).
 
tubman said:
ooops, missed the overdrive part. The "tllden cam technology" flathead cam chart lists the 8cm (mercury) camshaft as having a .338 lift (i don't know how to make that neat little squiggle thingy).
Click to expand...





~ ............This thingie ?








.
 
That's the one. I see it now; it's on the upper left hand side of the keyboard (which is so dirty I can't make out half the characters).

OK ~.338".:D
 
It's proper name is, "Tilde".

Origin.
It was originally written over an omitted letter or several letters as a scribal abbreviation, or "mark of suspension" and "mark of contraction",[2] shown as a straight line when used with capitals. Thus, the commonly used words Anno Domini were frequently abbreviated to Ao Dñi, with an elevated terminal with a suspension mark placed over the "n". Such a mark could denote the omission of one letter or several letters. This saved on the expense of the scribe's labour and the cost of vellum and ink. Medieval European charters written in Latin are largely made up of such abbreviated words with suspension marks and other abbreviations; only uncommon words were given in full.

The tilde has since been applied to a number of other uses as a diacritic mark or a character in its own right. These are encoded in Unicode with many precomposed characters as well as individually at U+0303 ◌̃ COMBINING TILDE and U+007E ~ TILDE (as a spacing character), and there are additional similar characters for different roles. In lexicography, the latter kind of tilde and the swung dash, ⁓, are used in dictionaries to indicate the omission of the entry word.

You can delete this if you aleady knew it from writing your doctorate thesis on computer language.....LOL
 
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The L 100 has a LOPEY idle at 700 rpm and you'd swear it would take up to 1800 to clear, but that is not the case at all. Off idle the truck pulls fiercely when my foot tells it to. The LOPE seems to go away by 1000/1200. Intown/traffic/freeway drivability is

a pleasure. The Max 1 cam in my '41 has no lope with good pull to 5000.
Not that you asked but think about sourcing your lifters...adjustables ....from VanPelt.
his are European manufacture and are a no issue product.
Charlie ny
 
In all my years I have met only one person who thought he made a bad choice with his cam. And, the truth is, very few understand what performance they are giving away or where their cam excels. Actually it makes no difference since they are happy with it. I have mentioned previously the famous SU1A is a poor cam for the street and not much better anywhere else. But many owners have been happy with it, so there you go. The torque curves of our Flathead engines are very "flat" leading to sophisticated measuring being necessary to highlight differences from cam to cam unless there are very significant differences. With good compression, adequate airflow, and reasonably large displacement it is seldom a problem to "over-cam". Even the Potvin 425 can be considered OK for some street use. If good power in the 2000 to 3000 RPM range is important milder will be better than wilder.
 
I am very pleased with Schneider 248f in my medium weight '41 coupe with 284 inches and Offy 425 heads. Great low and medium rpm torque gets me going easily with 3.25 rear end gears and larger tires. Cruises peacefully at 65 on the Interstate at about 2300 rpm. I would describe the 650 rpm idle as an irregular burble. You know it has a cam in it, but without the "is it going to keep running?" drama.
 
The Schneider 248 looks like a good option based on what I'm looking for, thanks. Did you get a new core or regrind?


JWL, these are some good points. I have been dissatisfied with a camshaft before (non flathead) but it was because the duration and overlap did not match the advertised cam specs by which I had selected it. I guess that given the relatively subtle changes produced by most camshaft changes these difference would not be noticeable on the road (and this was pointed out by the supplier), but still frustrating!!
 
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