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Steve nailed it, both on the ##s, & the importance of it.It depends on wha=
t rods & crank, piston to wall clearance & what RPM, but for most applicati=
ons that's right in the ballpark.
I've run as little as oops not enough ie .025 or less, .028 minimum (you wo=
n't get any carbon deposit on the squish area), but to play it safe nowaday=
s I use .030-.032Also on these engines it's not only a CR related issue, th=
e squish is very critical, you want to minimize the clearance between pisto=
n top & head to maximize the squish effect, which creates turbulence, which=
assists in good combustion...
Glen Efinger.
On Thursday, January 11, 2024 at 01:00:50 PM EST, Steven Belfer via Fot=
<fot@autox.team.net> wrote: =20
=20
You want as little as necessary because this is where your high CR comes f=
rom.=C2=A0 The thickness of the head gasket is the major part of P to H cle=
arance.=C2=A0 I ran .026 P to H clearance at Cal Speedway and the piston ki=
ssed the head and I spun a bearing.=C2=A0 My machine shop guy likes .040 fo=
r safety but I=E2=80=99ve been running .032 and it=E2=80=99s working out gr=
eat
~Steve
> On Jan 11, 2024, at 9:13=E2=80=AFAM, Lorne Fritz via Fot <fot@autox.team.=
net> wrote:
>=20
> =EF=BB=BF
> Hi.=C2=A0 In the past I have had pistons hit the head and leave a mark(TR=
3/4).=C2=A0 What piston to head clearance are most of you running? Thanks i=
n advance,=C2=A0 Lorne
> _______________________________________________
> fot@autox.team.net
>=20
> http://www.fot-racing.com
>=20
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>=20
>=20
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m
=20
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<html><head></head><body><div class=3D"ydp3738bd7byahoo-style-wrap" style=
=3D"font-family:Arial, Helvetica, sans-serif;font-size:16px;"><div></div>
<div dir=3D"ltr" data-setdir=3D"false"><span><span>Steve nailed it,=
both on the ##s, & the importance of it.</span></span></div><div dir=
=3D"ltr" data-setdir=3D"false">It depends on what rods & crank, piston =
to wall clearance & what RPM, but for most applications that's right in=
the ballpark.<br></div><div dir=3D"ltr" data-setdir=3D"false">I've run as =
little as oops not enough ie .025 or less, .028 minimum (you won't get any =
carbon deposit on the squish area), but to play it safe nowadays I use .030=
-.032</div><div dir=3D"ltr" data-setdir=3D"false"><div><span><div dir=3D"lt=
r" data-setdir=3D"false">Also on these engines it's not only a CR related i=
ssue, the squish is very critical, you want to minimize the clearance betwe=
en piston top & head to maximize the squish effect, which creates turbu=
lence, which assists in good combustion...<br></div></span><div><span><div =
dir=3D"ltr" data-setdir=3D"false"><br></div></span><div><span><div dir=3D"l=
tr" data-setdir=3D"false">Glen Efinger.</div></span></div></div></div><div>=
<br></div></div><div><br></div>
=20
</div><div id=3D"ydpeb00682yahoo_quoted_5223032547" class=3D"ydpeb0=
0682yahoo_quoted">
<div style=3D"font-family:'Helvetica Neue', Helvetica, Arial, s=
ans-serif;font-size:13px;color:#26282a;">
=20
<div>
On Thursday, January 11, 2024 at 01:00:50 PM EST, Steve=
n Belfer via Fot <fot@autox.team.net> wrote:
</div>
<div><br></div>
<div><br></div>
<div><div dir=3D"ltr">You want as little as necessary becau=
se this is where your high CR comes from. The thickness of the head g=
asket is the major part of P to H clearance. I ran .026 P to H clear=
ance at Cal Speedway and the piston kissed the head and I spun a bearing.&n=
bsp; My machine shop guy likes .040 for safety but I=E2=80=99ve been runni=
ng .032 and it=E2=80=99s working out great<br clear=3D"none">~Steve<br clea=
r=3D"none"><br clear=3D"none"><br clear=3D"none">> On Jan 11, 2024, at 9=
:13=E2=80=AFAM, Lorne Fritz via Fot <<a shape=3D"rect" href=3D"mailto:fo=
t@autox.team.net" rel=3D"nofollow" target=3D"_blank">fot@autox.team.net</a>=
> wrote:<br clear=3D"none">> <br clear=3D"none">> =EF=BB=BF<br cle=
ar=3D"none">> Hi. In the past I have had pistons hit the head and =
leave a mark(TR3/4). What piston to head clearance are most of you ru=
nning? Thanks in advance, Lorne<br clear=3D"none">> _____________=
__________________________________<br clear=3D"none">> <a shape=3D"rect"=
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