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Old 10-24-2014, 02:14 PM   #1
expavr
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Default L100 vs Potvin 3/4 ???

I found a Potvin 3/4 cam (card attached) among some old Ford parts at a garage sale. I have a 59 engine that I intend to build (254/286 CI) for street use with period correct Edmunds Custom heads, an Edmunds Custom dual intake manifold with Holley 91/99 "94" carbs and a OEM crab distributor. I had intended to use the L100 cam, but the Potvin cam would be more in keeping with the period assuming it will deliver some punch. Your thoughts?
Les Williams
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File Type: pdf cam card potvin.pdf (407.2 KB, 128 views)
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Old 10-24-2014, 05:24 PM   #2
scooder
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Default Re: L100 vs Potvin 3/4 ???

I spec it'll deliver some punch, the card don't give enough details for reasonable comparison. Jist going by the card, the Potvin has less lift and less duration than the L100. The real telling would be the lift rate.
More in keeping with the period, don't think the L100 is a new grind, it's been around for a long time, just mostly on the east coast roundy roundy boys.
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Old 10-24-2014, 05:36 PM   #3
Ol' Ron
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Default Re: L100 vs Potvin 3/4 ???

The L-100 was developed was first produced in 1952. The Edmunds heads have very small combustion chambers, so you might want to measure them before you put them on a 284ci engine. These heads have 8;1 on a 239 ci eng
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Old 10-24-2014, 07:17 PM   #4
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Default Re: L100 vs Potvin 3/4 ???

Ol' Ron will have to correct me if I've gotten this wrong, but although the L100 is an old grind I seem to remember that Cam Techniques "cleaned it up". I can't give any details, maybe Ol' Ron can add to it.
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Old 10-24-2014, 08:37 PM   #5
Tim Ayers
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Default Re: L100 vs Potvin 3/4 ???

Judging by the handwriting on the cam card, that cam was ground by Bill Jenks (RIP).

Potvin cams were very effective grinds and I would use this one (assume it is new or in good shape). I do believe they were all quick action grinds.
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Old 10-24-2014, 09:52 PM   #6
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Default Re: L100 vs Potvin 3/4 ???

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Yes, Given the fact that you want to keep the engine as It might have been back in the day, I'd go for the Potvin as well
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Old 10-24-2014, 10:37 PM   #7
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Default Re: L100 vs Potvin 3/4 ???

I've never ran that Potvin grind, but with a stroker motor (like 260+ inches), I'd rather see you run a Potvin 3/8. It is a beautiful grind, had a nice nasty sound and really runs well. The grind you showed was a bit mild in my opinion - but I like nasty cams!

If you want the real flathead sound and some great performance, go for the Potvin 3/8. If you need one, have Pete1 grind you one off of a stock billet. Pete and I go back a ways, he's part of the FlatCad Bonneville team and his work is second to none - you'll be extremely happy that you followed my advice!

FYI: The Potvin 3/8 lifts as noted - .375 . . . some of the Edmunds heads have small chambers and they've been milled too many times. Always CLAY the heads with a gasket - to understand exactly how much valve to head clearance you have (with any performance cam). Edmunds was not known for high valve reliefs or large chambers - he was much more like Eddie Meyer - small and traditional!

If you need more infor, just PM me.

B&S
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Old 10-25-2014, 05:31 AM   #8
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Default Re: L100 vs Potvin 3/4 ???

It depends on what your definition is when you say "deliver some punch". Actually the cam specs in the opening question would indicate a poor performer for delivering "punch" but would begin working reasonably well at the upper end of the Flathead RPM range. Of course the larger engine would lower the beginning power delivery RPM somewhat. So, it just depends on what you want.
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Old 10-25-2014, 09:28 AM   #9
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Default Re: L100 vs Potvin 3/4 ???

The l100 will deliver the punch from1952
So will An Isky 1007LD another old cam design
Both sound mean and pull hard
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Old 10-25-2014, 09:41 AM   #10
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Default Re: L100 vs Potvin 3/4 ???

Lots of good opinions and I agree with JWL on the fact that big cams will hurt the lower end of the power band (in any engine). So - you lose on the lower-end and gain on the top-end . . . same old story. If you chose a more mild grind, then the low-end will have more power. There is 'no replacement for displacement' when it comes to helping tame a snotty cam and return some low-end power.

I struggle with this at times . . . as I want big n' nasty cams, so I'm willing to sacrifice the low-end (and ease of stop-light drive-off driveability). I'll probably rev it more than I'd like (slipping the clutch a bit) and it maybe a bit of a dog for a bit, but then things start to take off and I'm happy.

Another consideration along this line is the overall weight of the car, gearing, tire-sizes, etc.. A big cam in a light AV8 roadster is a lot easier to drive than a big cam, with stiff gears and a 14 lb aluminum flywheel in a 40 Ford.

Just know what your goals are, let us know more about them - and also what the complete 'package' is that you're looking to put together.
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Old 10-25-2014, 10:37 AM   #11
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Default Re: L100 vs Potvin 3/4 ???

In the case of our beloved Flathead, aesthetics plays an important role in its presentation to the outside world. When dressed in it's finery, it's probably one of the most beautiful engine in the world. And the sound is different than any other engine. The plan here is to accent the sound, with out limiting the performance and economy of the engine. Properly tuned the L-100 does just that. However, there are probably many other cams that will do the same thing. IF the individual building the engine would take the time and expense to find the optimun timing and AF needs of the engine. All this has to start when putting it together. Discussing the power is a MOOoo question, or a cows opinion.
Have fun.
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Old 10-25-2014, 11:15 AM   #12
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Default Re: L100 vs Potvin 3/4 ???

I hesitate to write about this, but I must:
There is always the discussion about how a hotter cam gives up so much low end performance. I don't buy it. It's always a combination that makes the car/engine run well.
I run a Potvin "Eliminator" 425 in my 32 Tudor (Pete's grind). I don't care what anyone says, there is no stock cam (or stock flathead engine) that will outpull my engine across a stoplighted intersection. NONE.
I firmly believe that performance is the combination of the car, gearing, engine that produces the package.
Having said that, YES... If you were to compare a stock engine with a stock cam to the same stock engine with a larger/bigger/more duration cam, then maybe the stocker is better. BUT, no one does that. No one takes a stock engine and puts a dragster cam in it without a host of other modifications.
Just my firm opinion

Last edited by Kahuna; 10-25-2014 at 11:17 AM. Reason: sp
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Old 10-26-2014, 06:58 AM   #13
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Default Re: L100 vs Potvin 3/4 ???

Just what part of this is not understandable? So, if the car is cruising along at 1000 RPM in second gear and the throttle is stomped the Potvin 425 will deliver unmatched acceleration?? Maybe with 4;1 trans gear and 6:1 ring and pinion. Why have engine designers spent millions of dollars developing variable valve timing mechanisms? As I have said in my book, there is no free lunch. There are compromises when building an engine for daily transportation if the BEST overall performance is contemplated. From compression ratio, to valve timing, to carburetion. One size does not fit all.

Perhaps the most important aspect of any installation is that the owner is comfortable with his choice. If so, it does not matter whether or not HIS choice was the best option for all such vehicles. It only matters for HIS vehicle and should be confined therein. Each owner/driver has important points of interest regarding engine characteristics which should be understood before advice is dispensed. For an installation to "deliver punch", the definition of this "punch" resides in the eyes of each, individual, owner/driver. For example, I would not be happy giving up 15% of 1800 RPM torque while others, for the sake of having a radical, nasty, loping idle characteristic, and ability to rev beyond 4000 RPM would completely ignore such different performance.
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Old 10-26-2014, 11:07 AM   #14
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Default Re: L100 vs Potvin 3/4 ???

The above is why some of us ask lots of questions when asked to recommend a cam or inlet setup or ignition or heads or....... I also tend to add honest expectations and use of the engine. There are no fits all's.
Martin
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Old 10-26-2014, 01:44 PM   #15
Ol' Ron
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Default Re: L100 vs Potvin 3/4 ???

My latest project has a 280ci flathead with 8.2 cr and stock EAB cam driving a 3.73 rear through a T170 trans with 3:1 first gear. First gear punch is hard to control.
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Old 10-27-2014, 12:36 AM   #16
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Default Re: L100 vs Potvin 3/4 ???

Thanks for your thoughts. I understand that "Punch" is in the eye of the beholder and its meaning is subjective. For the final driveline I'm considering 28" tires, 4.11 diff. gears, a 49 Merc O/D trans with a 2.80 1st gear. Depending on the engine's torque curve that tire, trans and diff gear combo should be able to provide some punch off the line and still offer some economy at cruising speeds. How best to build the engine which includes displacement and cam is the missing piece. This thread has helped move that thinking along.
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