 1.8 - 2.0 Frankenstein, Using 2.0 C&Ps on 1.8? |
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| SteveNMaine |
 Oct 18 2025, 05:31 AM
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#1
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Member  Group: Members Posts: 94 Joined: 12-August 24 From: Maine Member No.: 28,288 Region Association: None  |
Last winter I built a 2056 using a 1975 2.0. This winter I am rebuilding a 1974 1.8.
The 1.8 has one trashed C&P so I am wondering if I can use the old 2.0 C&Ps for my rebuild, using all four of course. Everything seems to fit; head to cylinder register, cylinder to block register, wrist pins for connecting rod, etc. There is only a +1mm difference in bore diameter. I am not trying to build a HP engine just something close to stock. Any insights? |
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| Mike D. |
Oct 18 2025, 10:15 AM
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#2
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OK, It runs now, and pretty good too! Group: Members Posts: 1,456 Joined: 3-January 03 From: Santa Clarita, Ca Member No.: 85 Region Association: None 
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IIRC, I think you would have very low compression. check wrist pin position between the 1.8 and 2.0 pistons.
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| brant |
Oct 18 2025, 10:18 AM
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#3
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914 Wizard Group: Members Posts: 12,106 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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Agreed. The wrist pin height is different
Get a crank/rods/pair of heads and make a 2.0 |
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| SteveNMaine |
Oct 18 2025, 11:24 AM
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#4
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Member Group: Members Posts: 94 Joined: 12-August 24 From: Maine Member No.: 28,288 Region Association: None |
QUOTE(Mike D. @ Oct 18 2025, 10:15 AM)  IIRC, I think you would have very low compression. check wrist pin position between the 1.8 and 2.0 pistons. Yeah, that is one thing I had not checked. The top to the cl of the pin is different. |
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| SteveNMaine |
Oct 19 2025, 06:19 AM
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#5
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Member Group: Members Posts: 94 Joined: 12-August 24 From: Maine Member No.: 28,288 Region Association: None |
So, I see two different part numbers for 1.8 pistons and cylinders for 1974, 022 198 075 A and 021 198 075 D.
I have seen the D described as a higher compression design, but will it fit? Also, the 021 198 075 D is listed as 1.8V and the 022 198 075 A is listed as 1.8 in the Model/Option/Info column of the Porsche parts diagram, what is the difference? |
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| chmillman |
Oct 19 2025, 06:24 AM
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#6
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Member Group: Members Posts: 249 Joined: 15-June 24 From: Switzerland Member No.: 28,183 Region Association: Europe
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QUOTE(SteveNMaine @ Oct 19 2025, 02:19 PM) So, I see two different part numbers for 1.8 pistons and cylinders for 1974, 022 198 075 A and 021 198 075 D. I have seen the D described as a higher compression design, but will it fit? Also, the 021 198 075 D is listed as 1.8V and the 022 198 075 A is listed as 1.8 in the Model/Option/Info column of the Porsche parts diagram, what is the difference? As far as I understood, the V is for carbureted versions (V=Vergaser). I think those were only non-USA cars? |
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| Dave_Darling |
Oct 19 2025, 07:56 PM
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#7
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914 Idiot Group: Members Posts: 15,298 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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That's correct. The 1.8V engines ran something like a full point more compression than the regular 1.8 engines. I think it was all in the pistons, as well.
That's the main reason the carbureted 1.8s were rated at 85 HP and the injected ones were rated at 76 HP. (Both DIN spec.) The 1.8V engines also required high-octane fuel, while the regular 1.8s do just fine on regular-grade. --DD |
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