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Re: Longevity of 103's?

Posted: Mon Jul 01, 2013 6:03 am
by MegaRookie
Steve Arndt wrote:I will post pics of my heads and the plates.
Thnx! :D I'm very curious!


Re: Longevity of 103's?

Posted: Sun Mar 11, 2018 10:34 am
by E_bug
Sorry tonwake up this post but I think it's relevant. What are the specs for 103mm cylinders?
I have a basketcase motor with 103s srp pistons and those extra stud holes on the cyl liners.
Is it 103,050mm 103,150? I want to do cylinder bore measurements but dont know where to find the inspection specs. (Out of round, tapper etc)
Also whats a good piston ring end gap for a type 4 with 103mm n/a at a hot climate ?


Re: Longevity of 103's?

Posted: Sun Mar 11, 2018 4:59 pm
by wreck
"I did a 103 recently with JE forged pistons , it has Deutz cylinders and they were bored for .006" clearance . I have another 4.004" inch bore engine that runs cheap SBC Hyper pistons that was set up with .0015 " clearance that has not had any issues , I'm in Brisbane that has 35C summer days . Not quite as hot as what you can get up to in Summer . Both engines run cool . 120C CHT measured at the spark plug boss.
I checked the JE ring gap with the spec sheet but can't remember what it was . I'm sure it was in line with most gap calculators . sorry can't help you with the ovality /taper specs .

Re: Longevity of 103's?

Posted: Mon Mar 12, 2018 12:03 pm
by E_bug
Thanks for the info . I am trying to find the wear limits of the 103s . What would be concidered unusable .

Re: Longevity of 103's?

Posted: Wed Mar 14, 2018 5:33 am
by E_bug
So I measured stuff to make my own conclusions.. .

I have 0,060mm taper
I have 0,12 piston to cylinder wall clearence
I have piston ring end gap 0,85mm top ring and 1mm second ring.

I am tempted to fix the taper with a light hone at the bottom and give it a try. What do you all think?

Re: Longevity of 103's?

Posted: Wed Mar 14, 2018 1:01 pm
by Type 4 Unleashed
I wouldn't try to fix the taper, I would give it a light hone and run it.

I've ran as much as .010" piston to cyl clearance, and was manufacturer recommendation, .005" is generally what is used for Forged pistons.

Your ring gaps are larger than I like to run, most ring manufactures recommend .004 N/A and .006 with power adders times Bore. If your concerned about the heat then split the difference between N/A and Power Adders. Just go with some file to fit rings and go manufactures clearance recommendation, and add a little more for your heat concern.

Re: Longevity of 103's?

Posted: Thu Mar 15, 2018 3:34 am
by E_bug
Thank you very much for the Advice Richard

I have a tripod honing stone setup.. Its hard to find the ball hone at this side of the world I was using back in New Jersey! I will follow your advice with the light hone.
I would like to see what piston ring gap would be with new rings . The used ones seem like they where filed with a wood file :).

Oval measurements are Top 0,010mm
Mid 0,030mm
Bottom 0,010mm Would you call 0,020mm in the center barell shape cylinder?

Off to get new rings !!
I sprayed the piston skirts with molykote D321 for kicks and giggles..