Hi,
I suggest to have about 0.05" clearance.
It is not only deflection of the crank, also a bearing failure you should take
in account.
Cheers
Chris
------- Original Message -------
From : Charly[mailto:charly@mitchelplumbing.com]
Sent : 5/25/2016 6:52:35 PM
To : tr4@wi.rr.com; toodamnfunky@comcast.net
Cc : fot@autox.team.net
Subject : RE: Re: [Fot] TR6 Piston / Head Clearance
I tried b u idling a TR6 motor with a pop-up on the piston on c e. Instead of
having the pistons cut down to zero clearance I left them about .005" high.
It eventually bent the rod and broken it. The pistons had an imprint of the
combustion chamber on them. I learned that at 6000 rpm's, there is enough
deflection in the crank to let them hit the head.
I believe most head gaskets are .0035" aren't they?
Charly Mitchel
TR6 #44
On Wed 25/05/16 11:31 AM , toodamnfunky@comcast.net sent:
> The rattling is likely piston slap on cold forged
pistons. Did it go
> away when it warmed up and came back on the next
cold start ?jim
>
> -------------------------
> FROM: "Steve Yott"
> TO: "Robert Lang" , "FOT List"
> SENT: Wednesday, May 25, 2016 11:27:27 AM
> SUBJECT: Re: [Fot] TR6 Piston / Head Clearance I doubt that your .030
> squish would cause the
rattling as you
> describe. The deflection caused by the crank, rod
and piston in order
> to hit the head at .030 would be way up in the
rpmâ??s like 8000!
> Did the rattling go away after all the parts warmed
up and oil was
> well disbursed or is it still rattling? My first
guess would be
> either the engine was not pre-oiled or you have
loose piston pin
> bushingsâ?¦. Were the rods rebuilt with new bushings
fitted to about
> .0003?
> Steve Yott
> FROM: Fot [ mailto:fot-bounces@autox.team.net ] ON
BEHALF OF Robert
> Lang
> SENT: Wednesday, May 25, 2016 11:29 AM
> TO: FOT List
> SUBJECT: Re: [Fot] TR6 Piston / Head Clearance Hi, Where I was going
> with the query was this: I had a
late block
> "decked" with the intent of making the deck flat.
The machinist took
> of .032 to accomplish the goal. With a head gasket
installed and the
> head torqued, the clearance in the squish area is .030.
>
> I had initially wanted only about .025 removed, but
we had to shave
> an extra .007 to get rid of the fire ring cuts.
>
> On initial startup, the motor sounded like it might
be "rattling" and
> I'm trying to figure out why.
>
> When I used a stethescope on the block, everything
sounds okay - no
> rapping and the valve train sounds "normal" and
there were no weird
> sounds coming from the crank.
>
> I guess where I'm going with this is: if piston /
head clearance is
> too tight, I'll see some sort of indication on the
piston, right?
>
> TIA for any sage advice.
>
> This is my first experience "decking" a block. I'd
like to get it
> right, I don't have the resources to start a new
block from scratch.
>
> Regards,
>
> Bob Lang
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