[Healeys] Cams - Was: Re: Vernier timing gears

[John Rowe]

Not sure of the advantages, by my Alfa Romeo GTV is definitely a nicer
engine than either of the Healeys or any single cam Japanese car I've driven

John Rowe

Qld Australia

 

From: Healeys [mailto:healeys-bounces at autox.team.net] On Behalf Of Bob
Spidell
Sent: Sunday, 9 July 2017 6:00 AM
To: healeys at autox.team.net
Subject: [Healeys] Cams - Was: Re: Vernier timing gears

 

I never understood the advantage of 'twin' cams (assuming two cams per bank
of cylinders, one for intake and one for exhaust).  Can't the same results
come from lobe profiles; i.e. one profile for intake and one for exhaust, on
the same cam?  All the twin cam setups I've seen have both cams driven by
the same belt, so timing will be the same for both cams.  Is this idea just
to have less 'load' for each cam?

 

What does make sense to me is variable cam timing.  My Mustang accelerates
smoothly and seamlessly, but on coasting deceleration there is a noticeable
'bump' down in RPM around 1,800-2,000 RPM as the ECU changes--advances?--the
cam timing, but it only has one cam per bank.  I know the Honda VTEC engines
have a third lobe, that only comes into play at higher speeds (thanks Edd!).

 

On 7/8/2017 12:43 PM, David Porter wrote:

I guess my point in generating some "traffic" is best expressed by Mr.
Lawrence. With a single cam acting on the valve timing, one can set it close
to factory or deviate a couple degrees advanced or retarded for low end
torque or high rpm breathing. It is still a trade off versus a twin cam head
where both can be affected and gains can be easily (?) obtained for both
instances he states. Not too sure we all have easy access to a dyno. These
old long stroke 6/4's were designed for grunt. That would be the wise
choice. They don't like to be spun up much, then the Welch crank would be
necessary. $$ dave

 

On 7/7/2017 7:16 PM, WILLIAM B LAWRENCE wrote:

According to Iskendarian You can optimize cam timing either to provide a
boost in low end torque by advancing the timing by up to 8 degrees or in
high end power by retarding it a similar amount. 

 

Since I am looking for a low end boost and will rarely exceed 3500 on the
road I set mine 4 degrees in advance.

 

Waiting to see how it works out...

 

Bill Lawrence

BN1 #554

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