1979 With AR 10.8 to 1 Pistons?

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Shadoobie
Posts: 83
Joined: Mon Mar 03, 2014 10:07 pm
Your car is a: 1979 Pininfarina Spider 2000

1979 With AR 10.8 to 1 Pistons?

Postby Shadoobie » Fri Sep 08, 2017 3:46 pm

Hey all, I found out Sunday that my piston rings on the number 3 cylinder have given up completely. Since I'm going to be removing the engine to deal with that this weekend, I decided to order Autoricambi's 10.8 to 1 piston set. I started reading on some threads about a potential clearance issue with the valves, so I ordered their thick head gasket just in case of any issues. My question is, should I be concerned about clearance? I spoke with Andy Truscott on Facebook about it and he's running the same pistons with no issues. I also couldn't find anyone that specifically saw that it couldn't be done. Csaba suggested that I might need to have the domes milled slightly as well.

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joelittel
Posts: 786
Joined: Tue Mar 08, 2011 6:53 pm
Your car is a: 1980 Spider 2000 FI
Location: Evanston, IL

Re: 1979 With AR 10.8 to 1 Pistons?

Postby joelittel » Fri Sep 08, 2017 8:28 pm

Do you know if your head or block have been decked? If so you could be flirting with danger.

Guy Croft outlines a procedure that uses plasticine to test tolerances. I don't have a link but a google search should find it.

BEEK
Posts: 1791
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: 1979 With AR 10.8 to 1 Pistons?

Postby BEEK » Fri Sep 15, 2017 10:24 am

The biggest issue with running a thick head gasket, while lowering the compression slightly it also ruins the quench area of the cylinder. This will cause a sever loss in power from combustion. I am also building a engine with those exact pistons. I am going to mill the block and tighten up the quench area. I will possibly have to mill the dome a slight bit. but i wont even check that until everything is dry built first. I have opened up the combustion chambers around the intake valves which will unshroud them some. Then i will check the valve to piston clearances. i may have to deepen the fly cuts some to make sure there is no contact there.
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, (5)and # 6 is on the way. 76 scorpions New Scorpion 24k original miles (Silver)
2014 500L Daily driver

131lover
Posts: 42
Joined: Thu Aug 16, 2012 5:14 pm
Your car is a: 131 supermirafiori

Re: 1979 With AR 10.8 to 1 Pistons?

Postby 131lover » Mon Sep 18, 2017 8:19 am

Hi!
These pistons are fitted as OE pistons in Lancia Prisma/Delta 1600Tc, Ritmo/strada 105Tc, and a few more 1600Tc.. Same bore diameter, 84mm..
They all had the 43,5mm intake valves and around 9,6mm lift in cams as OE, if not decked to much or skimmed head to much as in all Tc builds they should not be any valve clearance problem's!!

I agree fully with Beek about head gasket and squish effect!

Cheers
Alf

BEEK
Posts: 1791
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: 1979 With AR 10.8 to 1 Pistons?

Postby BEEK » Mon Sep 18, 2017 8:26 pm

in my case, I am not using stock cams or stock size valves so I must check the operational clearances. the valves are moving faster than the crank and a some points can actually hit the pistons during the down stroke.
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, (5)and # 6 is on the way. 76 scorpions New Scorpion 24k original miles (Silver)
2014 500L Daily driver

131lover
Posts: 42
Joined: Thu Aug 16, 2012 5:14 pm
Your car is a: 131 supermirafiori

Re: 1979 With AR 10.8 to 1 Pistons?

Postby 131lover » Tue Sep 26, 2017 4:48 am

No update??

scampbel98
Posts: 301
Joined: Mon Oct 04, 2010 7:45 pm
Your car is a: 1980 Fiat 124 carb
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Re: 1979 With AR 10.8 to 1 Pistons?

Postby scampbel98 » Mon Oct 02, 2017 5:46 pm

you can have the pistons shaved too.. I think Mark Allison or Juvius or someone had done the domed pistons and had them shaved 1 or 2 mm

Shadoobie
Posts: 83
Joined: Mon Mar 03, 2014 10:07 pm
Your car is a: 1979 Pininfarina Spider 2000

Re: 1979 With AR 10.8 to 1 Pistons?

Postby Shadoobie » Tue Nov 07, 2017 12:28 am

For those that are interested, the engine is back together and I have no problems whatsoever with the fancy new pistons. They are dished out by Persan so that the valves don't come close to touching the pistons. I'm also having no issues with detonation running 10 degrees of advance on 91 octane. I would highly recommend these pistons!

131lover
Posts: 42
Joined: Thu Aug 16, 2012 5:14 pm
Your car is a: 131 supermirafiori

Re: 1979 With AR 10.8 to 1 Pistons?

Postby 131lover » Tue Nov 07, 2017 6:33 am

Nice to hear, if piston pockets can take the 43,5 intake valve witch isn't available in the US from what I've heard,and with not to high lifted/duration there shall be no contact!
What thickness of head gasket did you use?
Do you have the rest of the engine stock?

Cheers
Alf


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