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Vanapplebomb
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Location: Holland, MI
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raygreenwood
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 Posted: Wed Oct 08, 2014 6:26 am Post subject: |
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Going off memory....not close to my books.
In the USA....for sure there was at least one series of 1.8L and they were all L-jet injected. That was EC case and had 7.3:1 compression and a slight dish in the pistons. I am pretty sure it was the exact same piston as the 1974 VW 412 with L-jet.
In the UK....the AN case # series was 8.6:1 compression with twin carbs on both the 914 and the 412 models. I believe that series had a slight domed piston.
There was another VW 412 series engine in the UK that used flat top pistons and had 7.8:1 compression.....the BRC series. I dont know if this was ever used in the 914....but it would drop right in. It also used twin carbs.
With US spec of 914 any of these pistons could be used. Because L-jet from the factory settings was slightly lean....I would tweak it a little to use 8.6:1 with it.
I eont know if the AN series was used in the US with L-jet.
Ray |
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Vanapplebomb
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raygreenwood
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| Posted: Wed Oct 08, 2014 10:11 am Post subject: |
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Again....going off memory....but the depth I think is, the same as the dished 1.7 piston. That piston is about 7.5-9cc. I think the 1.8 being slightly larger in diameter has about 9-10cc. Best way is a piece of plexiglass and a, syringe to cc it.
An alternate guestimate would, be.....knowing what the stock compression of a US 1.8 with dished pistons is supposed to be.....if you have the head cc and have the head off to measure deck....you can calculate compression as a flat top piston and then start adding cc's to the equation until have the correct listed compression. The qmount you add will bectu3 dish volume. Ray
Edit: bear in mind that all of these engines had a factory hear gasket whose crushed thickness added .026-.028" to the deck. All of them also had a gasket at the cylinder of about .003 after crush and a shim of about .005" or .010".
With this stack up.....most domed 1.7l from the factory had a deck measured at piston edge of about .075-.079". Most 1.8s have a similar deck of about the same.
Remove the head gasket and base shim and your deck is just about .040".
Typically on a 1.7 this bumps compression from 8.2:1 to about 8.5:1. |
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Vanapplebomb
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Location: Holland, MI
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Vanapplebomb
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raygreenwood
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Location: Oklahoma City
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| Posted: Thu Oct 09, 2014 6:32 pm Post subject: |
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| Vanapplebomb wrote: |
| Out of curiosity, how much different are they from 1800 bus pistons? |
I believe they are the same. The type 2/4 1.8l in my books and also in "Without guesswork" for types 1,2, 3, 4.....list the same, compression....7.3:1.....and since the head part # is the same on type 2, type 4 and 914 1.8l....and the combustion chamber and crank and rods are the same part #s.....I can only conclude that the piston dish size is the same.
I know California cars had even lower compression so there were some piztons out there with a deeper dish like 10-12cc. Dont quote me on the deeper dish. I may be mixing up 2.0 stuff here.
But it should be the same piston. Ray |
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