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

[Bob Spidell]

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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