Jump to content


Photo

Cylinder Head Witness Mark


  • Please log in to reply
17 replies to this topic

#1 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 06 October 2013 - 05:28 PM

Here is my 100 thou shaved 186 head witness mark picture:-

 

Attached File  Witness Mark.jpg   24.28K   8 downloads

 

this created 250 psi compression on a 202 short motor with a big cam. Dave I

 

p.s. the witness mark is at the bottom left of picture where the head gasket goes

p.p.s. the chamber is 44 cc


Edited by TORYPOWER, 06 October 2013 - 05:33 PM.


#2 rodomo

rodomo

    To advertise here, call 13TORANA

  • Members
  • PipPipPipPipPipPipPip
  • 18,019 posts
  • Name:R - O - B Dammit!
  • Location:Way out west of Melbourne Awstraylya
  • Joined: 10-December 05

Posted 06 October 2013 - 09:00 PM

I've seen your pic and I'm happy to be your witness Dave.

#3 Dave6179

Dave6179

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 577 posts
  • Name:David
  • Location:NZ
  • Car:HJ, VN, VX SS
  • Joined: 23-August 12

Posted 08 October 2013 - 08:28 AM

Dunno how much has come off mine over the years but my mark has almost gone completely. I have measured a difference of 4mm in the head thickness compared to the stock heads I have though. From 202 down to 149 and most inbetween.



#4 orangeLJ

orangeLJ

    Yes, yes I do post alot!

  • Members
  • PipPipPipPipPipPipPip
  • 10,261 posts
  • Joined: 02-May 06

Posted 09 October 2013 - 08:20 AM

yup, the head on my "good" motor (that I've just pulled out... again...) has no "thumb print" left at all...

 

constant problems with that head though (on multiple engines!), so its going on the shelf.

 

Pity though, it made good HP, just never reliable.



#5 _Macca97_

_Macca97_
  • Guests

Posted 09 October 2013 - 10:47 AM

If yours is 44cc and mine is about 40cc with a mild cam how much comp will i be running :/ think i might take abit more out of the chambers and/or run dished pistons



#6 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 09 October 2013 - 10:50 AM

If yours is 44cc and mine is about 40cc with a mild cam how much comp will i be running :/ think i might take abit more out of the chambers and/or run dished pistons

That will be fine Danny with Flat Top pistons using normal petrol, will go very well. Dave I

 

p.s. never worked out the compression ratio

 

here is the calculator:-

http://www.csgnetwor...m/compcalc.html

 

and the Dynamic C.R.:-

http://www.pcengines... Comp Ratio.htm


Edited by TORYPOWER, 09 October 2013 - 11:04 AM.


#7 _Ned Loh_

_Ned Loh_
  • Guests

Posted 09 October 2013 - 12:40 PM

yup, the head on my "good" motor (that I've just pulled out... again...) has no "thumb print" left at all...

 

constant problems with that head though (on multiple engines!), so its going on the shelf.

 

Pity though, it made good HP, just never reliable.

 

sell it to me cheap :D



#8 Dave6179

Dave6179

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 577 posts
  • Name:David
  • Location:NZ
  • Car:HJ, VN, VX SS
  • Joined: 23-August 12

Posted 09 October 2013 - 01:07 PM

I 've never checked my comp ratio. The block has had 20 thou taken off too. Spose I should get a syringe and measure the new head.



#9 orangeLJ

orangeLJ

    Yes, yes I do post alot!

  • Members
  • PipPipPipPipPipPipPip
  • 10,261 posts
  • Joined: 02-May 06

Posted 09 October 2013 - 02:45 PM

sell it to me cheap :D

 

maybe :P

its the one on the right.

pity the remnants of head gasket are there

 

2011-08-06_16-19-34_323.jpg



#10 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 10 October 2013 - 04:51 AM

I 've never checked my comp ratio. The block has had 20 thou taken off too. Spose I should get a syringe and measure the new head.

Sounds good Dave,
I've always played around, but never marked down the readings.
Always a first time. Dave I

#11 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 10 October 2013 - 05:05 AM

constant problems with that head though (on multiple engines!), so its going on the shelf.

Pity though, it made good HP, just never reliable.

I wonder why,
As it did perform well. Dave I

#12 _Macca97_

_Macca97_
  • Guests

Posted 10 October 2013 - 09:13 AM

Thanks for those calculaters dave, work it out to 12 to 1 comp than 9.6 dynamic comp, not sure if that totally correct, i used the crow 35665 cam as its about the size id want



#13 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 11 October 2013 - 11:15 AM

Thanks for those calculaters dave, work it out to 12 to 1 comp than 9.6 dynamic comp, not sure if that totally correct, i used the crow 35665 cam as its about the size id want

and Thank-you Danny,

With help, I have a calculator picture of what I am trying to achieve - 14:1 and a Bad Cam:-

 

Attached File  Dynamic Compression Ratio Calculator Rat Motor 2.jpg   311.91K   7 downloads

 

may well be not possible, and you never know unless we try. Dave I

 

p.s. the lower ring height is when the piston is machined to a dome which fits the head chamber.

p.p.s. the engine will run service station bowser E85 fuel



#14 _Macca97_

_Macca97_
  • Guests

Posted 11 October 2013 - 12:54 PM

i did a scanshot kinda thing but it wont let me post it :/

 

just did my one again, not sure if everything is correct, got 12.4 than 9.8  borrowed some of your specs dave, your motor would flog mine ahahah, mate in my car club is building a blown grey motor, so he gave me his specs and i got the exact same comp that he got using his pen and paper.

 

im guessing E85 means its 85% ethanol? abit like E10?



#15 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 11 October 2013 - 07:24 PM

i did a scanshot kinda thing but it wont let me post it :/    Has to be 1000 kB is size or less

 

just did my one again, not sure if everything is correct, got 12.4 than 9.8  borrowed some of your specs dave, your motor would flog mine ahahah, mate in my car club is building a blown grey motor, so he gave me his specs and i got the exact same comp that he got using his pen and paper.

 

im guessing E85 means its 85% ethanol? abit like E10?

Yep,

E85 is 85% ethanol and 15% fuel, where as E10 is 10% ethanol and 90% fuel.

Pen and Paper and reality can be close.

I want a lumpy idle mostly. Dave I



#16 _Macca97_

_Macca97_
  • Guests

Posted 11 October 2013 - 07:55 PM

I mainly just want abit of a lope at idle so I can have the best sounding car at school :) while still trying to have some kind of economy :)



#17 warrenm

warrenm

    Forum Fixture

  • Members
  • PipPipPipPipPip
  • 2,113 posts
  • Location:Central West NSW
  • Car:1972 LJ Torana
  • Joined: 08-November 05
Garage View Garage

Posted 12 October 2013 - 05:42 AM

Rather small combustion chamber at 26cc, the head deck might be a bit thin.



#18 N/A-PWR

N/A-PWR

    CABIN ENGINE CONTROLS GALORE

  • Members
  • PipPipPipPipPipPipPip
  • 9,629 posts
  • Name:Dave I
  • Location:Wooroloo, 65km's East of Perth
  • Car:'1969' LC RAT TORANA
  • Joined: 08-December 12

Posted 12 October 2013 - 10:36 AM

Rather small combustion chamber at 26cc, the head deck might be a bit thin.

Hi Warren,
That's probably why they have witness marks, to say this is where we stop machining.
Got to get the thinking cap going, and thank's for the heads up. Dave I




1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users