[Healeys] Valve clearances

Thu Feb 14 09:32:33 MST 2019

Utube video most will find instructive..  Offset Woodruff keys are 
generally available or veneer cam gears are.. 
https://www.youtube.com/watch?v=n_9rUXYxAY0 (part 1)

On 2/14/2019 5:53 AM, David Porter wrote:
>
> Given that the timing of the cam opening and closing the valves is 
> critical to the engine performance, where as little as four degrees 
> variation of cam position relative to the piston at TDC and BTDC can 
> rob a lot of performance. Books h ave been written on this.  Best 
> advice is to always follow the cam manufacturers spec. sheet regarding 
> lash adjustments. It's ALL about timing.
> Unfortunately, I've never seen factory cam specs, aside from 
> opening/closing timing. A degree wheel is really an essential part of 
> engine assembly. DP
>
>
>
> On February 13, 2019, at 11:47 PM, Chris Dimmock 
> <austin.healey at gmail.com> wrote:
>
>
> Isn't part of the reason that the valve dissipates heat into the head 
> when it is seated, so part of the reason for valve clearance is to 
> allow the valve to cool?
> Maybe try a 4 thou valve clearance and see how it goes?
> I probably won't!!
> :-)
> Chris
>
> Sent from my iPhone
>
> On 14 Jan 2019, at 10:23 am, Michael Salter <michael.salter at gmail.com 
> <mailto:michael.salter at gmail.com>> wrote:
>
>> This is another subject that I often wonder about.
>> If the valve clearance is there to ensure that the valves are fully 
>> closed when the engine is hot then why, when I check the clearances 
>> on a hot engine after a dyno run,  are they hardly any less than they 
>> were cold?
>> I can appreciate that the valve train components grow because of the 
>> heat but surely the block and head and rocker shaft pedistals also 
>> grow and thus there is little if any net change.
>> I also appreciate that the exhaust valve stem get really hot but ????
>> Just wondering....
>>
>> M
>>
>> On Sun, Jan 13, 2019, 6:42 AM WILLIAM B LAWRENCE <ynotink at msn.com 
>> <mailto:ynotink at msn.com> wrote:
>>
>>     I disagree that valve clearances are not critical. As the engine
>>     comes up to temperature the metal parts of the valve train
>>     (valves, lifters, push rods, the head itself and the rocker shaft
>>     towers) increase in length and the valve clearances are
>>     calculated to assure that this expansion isn't allowed to affect
>>     the sealing of the valves on their seats. If the valves are set
>>     too tight they reach a point where they won't touch the seats and
>>     therefore won't seal. Hot gases rushing through the gaps will
>>     quickly erode the valves. Also increasing the duration and/or
>>     lift of the cam has the effect of the  decreasing the length of
>>     the opening and closing ramps on the back side of the cam This
>>     reduces the length of time (dwell) the valve remains on the seat.
>>     Increasing the valve clearance restores the dwell time the valve
>>     needs to transfer its heat load to the cooling system through the
>>     valve seat and the cylinder head. Too little dwell time or the
>>     lack of proper valve sealing are two causes of burned valves.
>>
>>     In my own experience I installed an Isky cam with a grind a
>>     little more aggressive than the 100M cam and set the clearances
>>     to 0.012" per the manual. Within about 2,000 miles the exhaust
>>     valves were trashed. I then took the time to read the Isky
>>     installation instructions which specifically state the valve
>>     clearance needs to be set to 0.018". I re-installed the head with
>>     new valves and set them to Isky's spec and never had another
>>     problem with burned valves.
>>
>>     Follow the cam grinder's recommendations and you will avoid trouble.
>>
>>     Bill Lawrence
>>     BN1 #554
>>     ------------------------------------------------------------------------
>>     *From:* Healeys <healeys-bounces at autox.team.net
>>     <mailto:healeys-bounces at autox.team.net>> on behalf of Bob Spidell
>>     <bspidell at comcast.net <mailto:bspidell at comcast.net>>
>>     *Sent:* Saturday, January 12, 2019 11:10 PM
>>     *To:* Michael MacLean; healeys at autox.team.net
>>     <mailto:healeys at autox.team.net>
>>     *Subject:* Re: [Healeys] Valve clearances
>>
>>     I should note the rockers are pretty noisy at 0.015; IIRC I
>>     tightened them up just a bit.
>>
>>     On 1/12/2019 2:39 PM, Michael MacLean wrote:
>>>     I'd go with .016.  You can always tighten it.  Better loose than
>>>     tight.
>>>     Mike MacLean
>>>
>>>     On Saturday, January 12, 2019, 11:01:32 AM PST, Bob Spidell
>>>     <bspidell at comcast.net> <mailto:bspidell at comcast.net> wrote:
>>>
>>>
>>>     Makes sense (for some reason).  I put a DWR1 cam in my BJ8
>>>     which, according to DWR, 'is a little better than the BJ8 cam
>>>     and so works well in any standard or mildly tuned car' but I
>>>     think the 0.015" applies to all profiles on the spec sheet.
>>>
>>>     Bob
>>>
>>>     On 1/11/2019 8:48 PM, John Rowe wrote:
>>>
>>>     Simon,
>>>
>>>     Modified cams require the large clearance (don’t ask me why?) So
>>>     go for .015 that is what mine is.
>>>
>>>     John Rowe
>>>
>>>     Qld
>>>
>>>     Australia
>>>
>>>     *From:*Healeys [mailto:healeys-bounces at autox.team.net] *On
>>>     Behalf Of *simon.lachlan at alexarevel.plus.com
>>>     <mailto:simon.lachlan at alexarevel.plus.com>
>>>     *Sent:* Saturday, 12 January 2019 9:14 AM
>>>     *To:* Healeys
>>>     *Subject:* [Healeys] Valve clearances
>>>
>>>     The car is a MkII BT7.
>>>
>>>     The BMC manual says adjust the clearances, cold, to 0.012”.
>>>
>>>     Denis Welch said I should go 0.015”, cold, after fitting their
>>>     “Fast Road” cam.
>>>
>>>     The rolling road guy said 0.016”, warm.
>>>
>>>     I have the radiator out right now so I can get a nice socket
>>>     onto that nut and have a go at the clearances.
>>>
>>>     Stick with 0.015”, cold?
>>>
>>>     Thanks,
>>>
>>>     Simon
>>>
>>>
>>>
>>>     	
>>>
>
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-- 
Porter Custom Bicycles 2909 Arno St. NE Albuquerque, NM. 505-352-1378 My World go here: WWW.PORTERBIKES.COM/

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