Standard 2.0 TC, piston deck height and standard CR ?

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Kerem1967
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Standard 2.0 TC, piston deck height and standard CR ?

Post by Kerem1967 » August 10th, 2021, 9:14 pm

Dear Friends,

What should be the standard deck height with the flat top OE pistons in a 2.0 lt engine ?

Also, I would be grateful if you could advise the standard CR ratio for varios 2.0 lt TC engines.

Thank you
GC_90

M Faulks
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by M Faulks » August 11th, 2021, 6:33 pm

Hi Kerem,

CRs, I think for standard engine with standard cams, you are looking at around 9.5:1 ish with good fuel, high octane, probably run a shade more.

OE compression height is approx 33mm to the deck I believe, but be good if others chimed in too, as I can't give you the exact figure as Guy.

Hope that is of some limited help, welcome other folk correcting me if wrong :-)

Regards,
Martin
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Kerem1967
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Kerem1967 » August 12th, 2021, 7:14 pm

M Faulks wrote:
August 11th, 2021, 6:33 pm
Hi Kerem,

CRs, I think for standard engine with standard cams, you are looking at around 9.5:1 ish with good fuel, high octane, probably run a shade more.

OE compression height is approx 33mm to the deck I believe, but be good if others chimed in too, as I can't give you the exact figure as Guy.

Hope that is of some limited help, welcome other folk correcting me if wrong :-)

Regards,
Martin
Hi Martin,

Many thanks for your reply. Such a pity the great GC forum is quite quiet.

My current calculations gives me 9.25 CR with 1.50 mm headgasket and pistons running 0.36-0.37mm over the deck. And our pump fuel is not more than 95-97 octane. So I imagine 9.25 will be on the safe side for absolutely standard engine apart from the 40IDFs and headers. I asked Gloria what thickness GC quality gaskets available along the GC 12.9 head bolts.

Regarding the compression height, I think didn’t use the correct word. I meant to say that in standard 2.0 TC engines how much the pistons are over the block deck at TDC.

Regards

Kerem
GC_90

Wal
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Wal » August 15th, 2021, 1:04 pm

Kerem,

For info the CR for Fiat twin cams varied a bit:
• 124‘s ran about 9.8
• 131 and 132 ran around 8.9 to 9
• 105 and 130 were around 9.4
• Lancia’s were fairly similar being higher for the 1600cc and lower for the 2000cc
• Turbo and supercharged engines excluded as these were much lower around 7 to 8
• Putting a 1600cc piston (with dome) in a 2000cc engine (flat top pistons) could get the CR up to around 10

So at 9.25 you shouldn’t have a problem.

I don't know what the exact figure is for a standard engine but a good / reputable compressed gasket is probably about 60 thou (1.5mm) I would not expect the piston to come more than 20 thou (.5mm) above the block face. So again your values should be OK.

Regards,
Steven
Aka Wal

Kerem1967
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Kerem1967 » August 17th, 2021, 9:02 am

Wal wrote:
August 15th, 2021, 1:04 pm
Kerem,

For info the CR for Fiat twin cams varied a bit:
• 124‘s ran about 9.8
• 131 and 132 ran around 8.9 to 9
• 105 and 130 were around 9.4
• Lancia’s were fairly similar being higher for the 1600cc and lower for the 2000cc
• Turbo and supercharged engines excluded as these were much lower around 7 to 8
• Putting a 1600cc piston (with dome) in a 2000cc engine (flat top pistons) could get the CR up to around 10

So at 9.25 you shouldn’t have a problem.

I don't know what the exact figure is for a standard engine but a good / reputable compressed gasket is probably about 60 thou (1.5mm) I would not expect the piston to come more than 20 thou (.5mm) above the block face. So again your values should be OK.

Regards,
Steven
Aka Wal
Hi Steven,

Many thanks for your kind reply.

CR information and the piston deck height suggestion is going to be helpful.
Have you ever bought head gasket from GC ? I am in contact with Gloria but we couldn’t reach to a conclusion regarding the GC head gasket crush values. Apparently, GC has 2 types, one being around 1.75mm and the other one being 1.95 mm.
And I am not sure if any of the GC head gasket is the Astadur brand. ( 5951675 ) crushed thickness should be around 1,55 mm or so.
If I am correct older head gaskets do crush a lot ( up to 0,50 mm ) but would be great to identify which GC head gaskets crush how much.
I couldn’t locate this info in the GC book too.

Regards
Kerem
GC_90

Wal
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Wal » August 19th, 2021, 9:56 am

Kerem,
I have bought head gaskets from GC as I have 3 of his engines. But I don’t have any “loose” gaskets to look at. Unless someone has various used gasket types they can measure and provide the information it’s not possible to advise what the actual crush height would be.

In my opinion I would go for the thicker 1.95mm gasket just because it is thicker and unless you are racing seriously, the miniscule potential, power loss from .2mm is not worth it against a more durable head gasket.

It doesn’t directly answer your question but the following thread does give some additional detail that might assist:

viewtopic.php?t=2145

Similarly GC’s How To data sheet on “Head Bolts and Gaskets” mentions gasket makes:
OE polymer (incl Goetze Astadur brown polymer), FM/Payen & Ajusa/Nava/Spesso polymer.
Before torqueing down don’t forget to check the clearance between the piston crown and the valves to make sure there is sufficient running clearance, GC’s book describes this or briefly described here:

viewtopic.php?f=3&t=2882

Regards,
Steven

Kerem1967
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Joined: December 26th, 2012, 9:08 pm
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Kerem1967 » August 19th, 2021, 8:27 pm

Wal wrote:
August 19th, 2021, 9:56 am
Kerem,
I have bought head gaskets from GC as I have 3 of his engines. But I don’t have any “loose” gaskets to look at. Unless someone has various used gasket types they can measure and provide the information it’s not possible to advise what the actual crush height would be.

In my opinion I would go for the thicker 1.95mm gasket just because it is thicker and unless you are racing seriously, the miniscule potential, power loss from .2mm is not worth it against a more durable head gasket.

It doesn’t directly answer your question but the following thread does give some additional detail that might assist:

viewtopic.php?t=2145

Similarly GC’s How To data sheet on “Head Bolts and Gaskets” mentions gasket makes:
OE polymer (incl Goetze Astadur brown polymer), FM/Payen & Ajusa/Nava/Spesso polymer.
Before torqueing down don’t forget to check the clearance between the piston crown and the valves to make sure there is sufficient running clearance, GC’s book describes this or briefly described here:

viewtopic.php?f=3&t=2882

Regards,
Steven
Hi Steven,

Many thanks.I will read all these threads/topics carefully.

With the thicker gasket 1.9 one, I have to bring the pistons further up in order to have a good squish. And if I am not wrong good squish is vitally important in TC engines to make them deton. resistant.

The owner of this engine is going to bring me choice of gaskets as well apart from the one I am getting from Gloria. So, there will be a selection in hand to play around with the CR calculations and all the other parameters if needed. As far as I found out newer generation Fiat TC gaskets can crush up to 0.10mm but not more than 0.15mm which is logical and similar to Ford’s most used Victor Reinz, Elring brands.

Certainly an overkill option for a standard engine but I am also considering a MLS steel head gasket as well.

Although I am not familiar with Fiat 8v TC engines I am quite familiar with timing, checking the valve to piston clearances, piston height machining, valve pocket machining etc since I have built quite a few I4 8v and 16v engines including BDGs YBs etc.

Regards
Kerem
GC_90

Wal
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Wal » August 20th, 2021, 8:00 am

Kerem,
do keep us posted on your progress (with pictures).

Regards,
Steven

Kerem1967
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Joined: December 26th, 2012, 9:08 pm
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Re: Standard 2.0 TC, piston deck height and standard CR ?

Post by Kerem1967 » August 20th, 2021, 5:34 pm

Wal wrote:
August 20th, 2021, 8:00 am
Kerem,
do keep us posted on your progress (with pictures).

Regards,
Steven
Hi Steven,

I will do so.

Regards,
Kerem
GC_90

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