Camshaft for 86mm Big Bore engine

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Gary Campbell
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Camshaft for 86mm Big Bore engine

#1 Post by Gary Campbell » Sun Feb 26, 2017 11:24 pm

I am building an engine using 86mm cylinders/pistons.
Good street drivability and reliability is of paramount importance.
What is a good camshaft to use? Is there an aftermarket cam available that is better than the stock 912 grind?
I prefer to not have to do a lot of other mods to make this work.

AA Automotive Products is the big bore kit manufacturer - is this a quality product?
It came with the engine cases that I am planning to use. It is at least 10 years old, maybe more.

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C J Murray
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Re: Camshaft for 86mm Big Bore engine

#2 Post by C J Murray » Mon Feb 27, 2017 8:33 am

AA had some very weak wrist pins at times so do a search here for the details or call them and ask for details. AA is otherwise ok but not super high quality. The stock 912 cam is very good and combined with the larger displacement will make it better. Don't be sucked in by a hotter cam unless you want to always drive the car higher in the rev range.
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Re: Camshaft for 86mm Big Bore engine

#3 Post by C J Murray » Mon Feb 27, 2017 8:37 am

By the way the stock 912 cam is 233* duration at .050" lift but many of our suppliers incorrectly sell a 240*+ cam as a stock 912 cam. Don't be fooled.
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Re: Camshaft for 86mm Big Bore engine

#4 Post by Roger Shapiro » Mon Feb 27, 2017 11:37 am

Talk to John (Willhoit) about his WR58 cam.
I love mine.
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Re: Camshaft for 86mm Big Bore engine

#5 Post by Jeffrey Leeds » Mon Feb 27, 2017 12:08 pm

FWIW Gary, you will get a lot of advice (or should I say opinions?) on camshaft selection here. But much of the advice is anecdotal, while Cliff's has been derived from extensive dyno testing.
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Re: Camshaft for 86mm Big Bore engine

#6 Post by Jacques Lefriant » Mon Feb 27, 2017 12:45 pm

Hi Gary
the present AA 86mm set in my opinion is better quality than the NPR sets of old. The piston top is machined not as cast and they come coated now. As far as cams go the increased duration cam is the favorite of i would say 90% of the engine builders out there. if you want a new 912 stock grind go to one of my vendors i have them in stock and only Cj has expressed a desire for them.
j
 

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Re: Camshaft for 86mm Big Bore engine

#7 Post by Dan Epperly » Mon Feb 27, 2017 5:40 pm

Jacques Lefriant wrote:Hi Gary
the present AA 86mm set in my opinion is better quality than the NPR sets of old. The piston top is machined not as cast and they come coated now. As far as cams go the increased duration cam is the favorite of i would say 90% of the engine builders out there. if you want a new 912 stock grind go to one of my vendors i have them in stock and only Cj has expressed a desire for them.
j
I used one ground by Schneider, yes they of the Iron cross logo, in my recent build with big Solexes and big bore with 912 heads and It idles great and is responsive across the power band.

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Re: Camshaft for 86mm Big Bore engine

#8 Post by C J Murray » Mon Feb 27, 2017 6:37 pm

Dan, which cam specs exactly? The stock stock or the 10*+ more duration "stock"?
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Re: Camshaft for 86mm Big Bore engine

#9 Post by C J Murray » Mon Feb 27, 2017 6:47 pm

Jacques Lefriant wrote:if you want a new 912 stock grind go to one of my vendors i have them in stock and only Cj has expressed a desire for them.
Jacques also provides a stock C cam which is around 221* duration as well as lower lift. I am building an engine using the stock C cam right now for a car that I want to have big low rpm torque and 5000rpm redline.
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Re: Camshaft for 86mm Big Bore engine

#10 Post by Dan Macdonald » Mon Feb 27, 2017 9:04 pm

Here's the guy to talk to about camshafts: http://www.elgincams.com
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Re: Camshaft for 86mm Big Bore engine

#11 Post by Dan Epperly » Mon Feb 27, 2017 11:36 pm

C J Murray wrote:Dan, which cam specs exactly? The stock stock or the 10*+ more duration "stock"?
Cliff, I don't speak cam, but the call the grind a Porsche 912 specific grind and they call it the 282-F
The spec sheet says camlift .330 with duration at .050 cam lift is 246
There's a bunch of other numbers I can relay if this doesn't make sense.

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Re: Camshaft for 86mm Big Bore engine

#12 Post by C J Murray » Tue Feb 28, 2017 8:49 am

Thanks Dan. Somehow many many years ago the parts suppliers got confused and started selling a cam with 240*+ of duration as "stock". The Elgin 7008 has 240*+. The difference is not gigantic but there is a difference. So, if I understand you correctly you are very happy so more duration works for you. More than stock duration is fine but it should be by your choice and not because of a supplier mistake.

My Dad Jacques mocks me for my obsession for stock replacement cams and he is very smart and very helpful in the 356 community so he deserves to express his opinion. I don't always use stock cams but I am pretty sure that most owners are driving their cars in a way where a stock cam works best. There are many companies that provide multiple levels of high performance cam grinds but every time peak power is increased the low end power is reduced. There is no way around that.
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Re: Camshaft for 86mm Big Bore engine

#13 Post by Gary Campbell » Tue Feb 28, 2017 5:56 pm

Thanks for the feedback, I will explore my options here. I sounds like the stock 912 cam with 912 heads to match. I will probably run with the Webers that are on my current engine as they are working well.

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Re: Camshaft for 86mm Big Bore engine

#14 Post by Jacques Lefriant » Tue Feb 28, 2017 6:38 pm

my apologies to junior but the 912 stock cam profile was developed for the early super engine. Porsche was lazy and never developed an alternative to address all the changes.
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Re: Camshaft for 86mm Big Bore engine

#15 Post by C J Murray » Tue Feb 28, 2017 8:46 pm

Jacques Lefriant wrote:my apologies to junior but the 912 stock cam profile was developed for the early super engine. Porsche was lazy and never developed an alternative to address all the changes.
j
But Dad, Porsche took the engineer that designed many famous Porsche racing engines and had him do development to the 616 pushrod engine in 1963. Why? Because they knew they would be using the engine for 6 more years and because customers were expecting more. There were quite a few changes made that cost Porsche money and there was a brand new cam developed for the C engine. I am willing to bet that different cam grinds were tried for the Solex equipped engines also at that time. After all that cam was to be used in the new 912 until 1969 while the C cam was only used 2 years until 1965.

I will admit that some of the very most recent cam lobe designs offer advantages over older designs however the people that produce those lobes are not producing cams for our cars. Those lobes use very advanced technology, very complicated math, to open and close the valve more abruptly without causing unstable movements that are not easily controlled buy other valvetrain components.
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