[Healeys] Valve clearances

[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 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>
> <healeys-bounces at autox.team.net> on behalf of Bob Spidell
> <bspidell at comcast.net> <bspidell at comcast.net>
> *Sent:* Saturday, January 12, 2019 11:10 PM
> *To:* Michael MacLean; 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> <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
> <healeys-bounces at autox.team.net>] *On Behalf Of *
> 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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