[Fot] piston/head clearance

Thu Aug 24 16:35:29 MDT 2017

That's a significant difference in CR.
I'm still trying to wrap my mind around how extra piston/head clearance is a power gain, but I can't argue with real world dyno tests, all being equal, CR included.
Glen

-----Original Message-----
From: Chris Marx via Fot <fot at autox.team.net>
To: 'Jim Gray' <toodamnfunky at comcast.net>; tr4racing <tr4racing at googlemail.com>
Cc: fot <fot at autox.team.net>
Sent: Thu, Aug 24, 2017 4:29 pm
Subject: Re: [Fot] piston/head clearance

Hi Jim,

the change in compression ratio is not that big.
My compression ratio is around 11.3:1.
So with the thicker gasket you get 10.9, with the thinnest 11.5….so just about these values.
It doesn’t hurt so much the power output, more the torque.

With European 102 octane fuel I run about 28 degree of advance. More didn’t give more power.

Cheers
Chris

Von: Jim Gray [mailto:toodamnfunky at comcast.net] 
Gesendet: Donnerstag, 24. August 2017 20:50
An: tr4racing at googlemail.com
Cc: fot at autox.team.net
Betreff: Re: [Fot] piston/head clearance

Chris,  

I finding it interesting you saw best power at .472. How much change in compression ratio did you get from

.023 to .047. Im assuming you tried different ignition timing and at what

Compression ratio did you start with?

Jim g

Sent from my iPhone

On Aug 23, 2017, at 4:07 PM, Chris Marx via Fot <fot at autox.team.net> wrote:

On dyno test we found a disturbing issue that lowers the power if the piston to head clearance is less than 0.039“.
We didn’t find a cause for this but tested thoroughly clearances from 0.0236” upwards.
Best power reading was with 0.0472”.

Cheers
Chris

Von: Fot [mailto:fot-bounces at autox.team.net] Im Auftrag von fubog1 via Fot
Gesendet: Mittwoch, 23. August 2017 23:52
An: timmmurphh at gmail.com; fot at autox.team.net
Betreff: Re: [Fot] FW: Grattan VSCDA next weekend? piston/head clearance

With the good rods and reasonable rpm you have plenty of clearance.
You don't want too much clearance either cuz then it lessens the "squish" effect.
The idea is to have enough clearance for all running conditions, plus a few thou safety margin, and no more.
Glen

-----Original Message-----
From: timmmurphh <timmmurphh at gmail.com>
To: 'fubog1' <fubog1 at aol.com>; fot <fot at autox.team.net>
Sent: Wed, Aug 23, 2017 3:38 pm
Subject: RE: [Fot] FW: Grattan VSCDA next weekend? piston/head clearance

The Payen head gasket last used was compressed to 0.055 at the fire ring.  So, with the 0.010 pop-up that I have from the all efforts to deck the block, I will have 0.045 clearance.  I have Carrillo rods and we try to stay to under 6000 RPM for engine “longevity”.  (Not sure “longevity” is a term that can be used with a race engine!)  At the most we’ll hit 6200 or 6300 RPM briefly before upshifting.  Therefore, I should be within the 0.030 clearance that you recommended.  It will be interesting to see what the top of the pistons looks like on the next rebuild with regard to carbon build up in the squish area.

Thanks for the advice and all the other comments on this subject.  All much appreciated.  Still a lot to learn😊

Tim

P.S. Finally got everything together on the engine and about ready to mate up to the transmission and put back in the car.  Looking forward to ELVF next month.  That will be the test.

From: fubog1 [mailto:fubog1 at aol.com] 
Sent: Wednesday, August 16, 2017 5:27 PM
To: timmmurphh at gmail.com; fot at autox.team.net
Subject: Re: [Fot] FW: Grattan VSCDA next weekend?

Check the gasket thickness, it depends on what piston/wall clearance, rods, and RPM you use.
You generally need around .030 piston/head with stock rods, so add that to your pop-up of .010 for minimum gasket thickness.
If you run good rods you can run a little less before the pistons smack the head.
It's perfect when there isn't any carbon build up on the piston tops under the squish area.
When it's not right, it goes BRRRRRRRRRRRRR...
HTH
Glen

After all the machining to get the stick out
right I now have the pistons sticking up about 0.010 above the tops of the
liners. No problem with the composite Payen head gasket.

-----Original Message-----
From: timmmurphh--- via Fot <fot at autox.team.net>
To: fot <fot at autox.team.net>
Sent: Wed, Aug 16, 2017 5:48 pm
Subject: [Fot] FW: Grattan VSCDA next weekend?

-----Original Message-----
From: timmmurphh at gmail.com [mailto:timmmurphh at gmail.com] 
Sent: Monday, August 14, 2017 12:20 PM
To: 'Tony Drews' <tony at tonydrews.com>
Cc: ryan.murphy at fdlco.wi.gov; Steve Yott <tr4 at wi.rr.com>
Subject: RE: [Fot] Grattan VSCDA next weekend?

Sadly, we won't be able to make it.

I just got the block back from the machine shop last Tuesday. Not enough
time to get everything together and in the car and ready to go by Thursday.
The good news is the liner stick out is the 0.004 the machine shop said they
machined the liner seats and deck to. It's still a bitch to measure, as the
liners "wobble" on the seats and when you're looking for 0.004 it's a
problem. I finally have a decent dial indicator gage setup to at least give
repeatable readings. The figure 8's used was a set of copper ones I had
that measured 0.016. The machining was done on a single setup on a Rottler
floor type vertical 4-inch spindle milling/boring machine. These are
special purpose machine tools built specifically to machine engine parts,
such as blocks and heads. After all the machining to get the stick out
right I now have the pistons sticking up about 0.010 above the tops of the
liners. No problem with the composite Payen head gasket.

Thanks for all the responses to the Figure 8 gasket question. I did
eventually hear back from Moss UK. They said their steel fig. 8's are 0.016
and their copper fig. 8's were 0.018. No explanation regarding the
different thickness other that they have not had reported problems with the
gaskets. I'm not sure where the 0.020 thick copper ones that I measured
came from or for that matter, the 0.016 thick copper ones I'm using.

Tim & Ryan Murphy
1961 ('61, it is Comm. No. 511 and was built in 1961 per British Heritage)
TR4 #317 BRG

-----Original Message-----
From: Fot [mailto:fot-bounces at autox.team.net] On Behalf Of Tony Drews via
Fot
Sent: Saturday, August 12, 2017 6:21 PM
To: fot at autox.team.net
Subject: [Fot] Grattan VSCDA next weekend?

Anyone else going to Grattan next weekend?

Vroom, vroom, Tony Drews

_______________________________________________
fot at autox.team.net

http://www.fot-racing.com

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe/Manage:
http://autox.team.net/mailman/options/fot/timmmurphh@gmail.com

_______________________________________________
fot at autox.team.net

http://www.fot-racing.com

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/fubog1@aol.com

_______________________________________________
fot at autox.team.net

http://www.fot-racing.com

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/toodamnfunky@comcast.net

_______________________________________________
fot at autox.team.net

http://www.fot-racing.com

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/fubog1@aol.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/fot/attachments/20170824/54448053/attachment-0001.htm>