[Healeys] Valve clearances
Kees Oudesluijs
coudesluijs at chello.nl
Mon Jan 14 00:41:48 MST 2019
Extra wear on camshaft, tappets, followers and valve stems because of
the higher impact loads.
KKees Oudesluijs
Op 13-1-2019 om 23:42 schreef i erbs:
> What issues with too wide a gap?
>
> Ira Erbs
> Portland, OR
> typos and artifacts are the fault of my phone
>
> On Sun, Jan 13, 2019, 11:10 AM David P <frogeye at porterscustom.com
> <mailto:frogeye at porterscustom.com> wrote:
>
> Absolutely correct......
>
>
> On 1/12/2019 11:26 PM, WILLIAM B LAWRENCE 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/ <http://WWW.PORTERBIKES.COM/>
>
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