[Healeys] Valve clearances
Kees Oudesluijs
coudesluijs at chello.nl
Sat Feb 16 07:21:12 MST 2019
Check the valve clearances at least every 10.000km/6000mls. Easy job. Do
it yourself and do not trust a mechanic doing it properly, he might or
he might not. To many cars suffer a burned valve after a major service!!!
Kees Oudesluijs
Op 16-2-2019 om 14:09 schreef BJ8Healeys:
>
> Jim, I had my engine rebuilt in 1999 with hardened valves seats and
> stellite exhaust valves. When installed, the engine ran just fine. I
> never bothered to check or adjust the valve clearances. In 2001, I
> ended up with a burned exhaust valve. Since then, I have
> checked/adjusted the clearances once a year and no further valve problems.
>
> Is that an "old wives tale", or did I have a bad valve out of the box?
>
> Steve Byers
>
> HBJ8L/36666
>
> BJ8 Registry
>
> AHCA Delegate at Large
>
> Havelock, NC
>
> *From:*Healeys [mailto:healeys-bounces at autox.team.net] *On Behalf Of
> *rjhco at att.net
> *Sent:* Tuesday, February 12, 2019 10:30 AM
> *To:* michaelsalter at gmail.com; 'WILLIAM B LAWRENCE'
> *Cc:* healeys at autox.team.net
> *Subject:* Re: [Healeys] Valve clearances
>
> Mike,
>
> You are correct that the valve train components change very, very
> little. Expansion of components causing valves to not close is an old
> wives tale that gets repeated many times until shade tree mechanics
> turn it into gospel…… Burned valves are caused by other design,
> assembly or materials factors.
>
> Best regards,
>
> Jim
>
> *From:* Healeys <healeys-bounces at autox.team.net> *On Behalf Of
> *Michael Salter
> *Sent:* Sunday, January 13, 2019 5:23 PM
> *To:* WILLIAM B LAWRENCE <ynotink at msn.com>
> *Cc:* healeys at autox.team.net
> *Subject:* Re: [Healeys] Valve clearances
>
> 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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