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    1. 01-14-2019 12:16 PM #1
      Hello,

      I'm doing low budget block swap 1.8 8v to 2.0 8v [bubble block], keeping 1.8 8V head + weber carb (Audi 80 B3).



      Some things occupy me;

      - Do I change pistons to... X?
      - Do I use thicker head gasket?
      - Do I modify combustion chamber or keep it stock (bore goes 81->82.5)?

      Is there ANY way to fit mechanical fuel pump to 3A ? You can recommend electric pumps also.. Facet 60300 is what maybe good?



      Mechanical things in this project are no problem for me but this things..

      I'll certainly ask more later.

      Am I calculating correct??
      Last edited by DtiJ; 03-02-2019 at 11:05 AM.

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    3. 01-16-2019 09:28 AM #2
      it all bolts together just fine. make sure you use the 2.0 head gasket though. you cant use mechanical fuel pump as there is not cam lobe on the intermediate shaft to operate it. I'm doing the same build on a gti the 3a has slightly higher compression than the 1.8. 3a-10.5-1. 1.8-10-1. but you could adjust your ignition timing slightly if the engine knocks.

    4. 01-16-2019 10:19 AM #3
      Quote Originally Posted by garryt View Post
      it all bolts together just fine. make sure you use the 2.0 head gasket though. you cant use mechanical fuel pump as there is not cam lobe on the intermediate shaft to operate it. I'm doing the same build on a gti the 3a has slightly higher compression than the 1.8. 3a-10.5-1. 1.8-10-1. but you could adjust your ignition timing slightly if the engine knocks.
      Yes 3A with stock 3A head is 10.5:1 but with swapping head to 1.8 8V it goes to ~12.

      However with "G" cam or 3A stock cam dynamic compression is something like about 10,72:1 so it's pretty OK.
      with 276 cam dynamic it's around 10.07:1
      with very mild 1.8 8v stock cam it's around 11.84:1

      I've now calculated it zillion times and pretty sure about that. I used these:

      http://www.not2fast.com/vw/stuff/vw_engines.shtml
      http://www.csgnetwork.com/compcalc.html
      http://blackartdynamics.com/Compress...ompression.php

      I've found cometic makes head gaskets with very different thicknesses, but they cost €€€
      Last edited by DtiJ; 01-16-2019 at 10:28 AM.

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    6. 01-16-2019 06:51 PM #4
      I always thought the 3a head and the 1.8 head had the same cc's. and the difference was in the piston bowls. the last 3a engine I had, had a 1.8 head that had been skimmed about 1mm. gave 215psi in a compression test.

    7. 02-03-2019 06:59 PM #5


      2.0 8V out of donor car

    8. 02-03-2019 10:50 PM #6
      Quote Originally Posted by DtiJ View Post
      Yes 3A with stock 3A head is 10.5:1 but with swapping head to 1.8 8V it goes to ~12.
      I'm pretty certain you are a bit off base on this one.

      I'm pretty certain the 3A head and a standard 8v head [JH] has the same 30cc combustion chamber. Keeping all things the same, how is swapping the stock head with a 30cc chamber with a JH head with a 30cc chamber going to raise your compression?

      Simple answer, it will not.

    9. 02-04-2019 08:37 AM #7
      Quote Originally Posted by Butcher View Post
      I'm pretty certain you are a bit off base on this one.

      I'm pretty certain the 3A head and a standard 8v head [JH] has the same 30cc combustion chamber. Keeping all things the same, how is swapping the stock head with a 30cc chamber with a JH head with a 30cc chamber going to raise your compression?

      Simple answer, it will not.
      Do you think piston dimensions do not affect cr ratio? I'm going to change from 1.8L to 2.0L block. If combustion chamber volume does no go up, cr ratio goes up. Well piston dish also is effecting but in principle.

      BTW, i'm not using JH (stock 8.5:1) head, but 1.8 Audi PM (10:1 stock)

      Compression ratio is the ratio of the compression volume of the internal combustion engine to the sum of the stroke volume to the compression volume
      edit:
      1.8 8V stock piston should be this: http://www.partsdirect.nl/15908-thic...026107065n.jpg
      2.0 8V stock piston should be this: http://trshop.audi.de/konakart/image...053107065f.jpg

      There must be some difference in head, i'll report when i see...
      Last edited by DtiJ; 02-04-2019 at 08:53 AM.

    10. 02-04-2019 08:57 AM #8
      I think you are over thinking this way too much. Sit back, grab a beer and think about it slowly.

      You want a 2.0L, great, a lot of people want to go 2.0L when they have a 1.8L. Bigger is better, right? You also want to keep it simple and install your 1.8L head on it, no problem there. Use the stock 3A headgasket and bolt it right up. Whatever the compression ratio is in the 3A, it will be the same with the 1.8L head since the combustion chamber size is the same [30cc].

      This is what you need to grasp. Both heads have 30cc dimensions [there are tolerances and I'm not factoring this and you are not going to blueprint this too]. What makes you think the compression is going to change? Both rooms are 30cc. Grasp that fact, believe it, own it like it's yours. Once you believe that, the rest should make more sense.

      Your basically done with the modification. Simple easy.

      What your issues are going to be is getting the spark to work. You'll have to search about distributor adapters.

      Why you want carbs is beyond me but it's your engine and you want to do it your way. Good for you. I would not go with a mechanical fuel pump. Get an electrical low pressure pump. Electrical pumps are great at pushing but do not suck well so it should be as close to the tank as possible. The feed line should original from the bottom of the fuel tank. if your tank is not that way, then you may need a transfer pump. If you have a transfer pump, you may not need an additional pump at all since you could just use that one.

      I'm an auto mechanic. I own my own shop. I've worked on German cars [Mercedes/BMW] since 84, I was a top 10 Mercedes mechanic for 2 years and top 200 for over 20. I may not grasp the English language well, but I do know what I'm talking about. Put the 1.8L head on and enjoy the 10+ compression ratio. It will not change more than factory tolerances. Keep the fuel injection. It's so much better in EVERY level.
      Last edited by Butcher; 02-04-2019 at 09:04 AM.

    11. 02-06-2019 10:35 AM #9
      are you sure that's a 3a motor??? the oil filter looks very vertical to me. were they not angled back towards the gearbox?

    12. 02-07-2019 10:15 AM #10
      Quote Originally Posted by garryt View Post
      are you sure that's a 3a motor??? the oil filter looks very vertical to me. were they not angled back towards the gearbox?
      I think it is unless someone has swapped engine in donor car

      2 litre it is and 8 valve, thats for sure

      However pistons are like this, not flat:


      Always thought there is flat pistons in 3A.
      Last edited by DtiJ; 02-07-2019 at 10:35 AM.

    13. 02-07-2019 11:05 AM #11
      Quote Originally Posted by Butcher View Post
      What your issues are going to be is getting the spark to work. You'll have to search about distributor adapters.


      Whats problem with that?

    14. 02-07-2019 11:12 AM #12
      I have never done what you did. I have a lot of experience in my field. Keep that in mind with my comments.

      The 3A block has a bigger hole for the distributor. It is because the 3A distributor has a bigger gear. If you use a 3A distributor, you need to have an ignition system that will play with the distributor properly. I would imagine the 3A distributor has a hall effect sensor and the timing is all done in the ignition module. Some of the older VW engines, had all the timing done in the distributor and the ignition module just amplified the signal for the coil.

      I hope that makes sense.

    15. 02-07-2019 01:13 PM #13
      yeah them pistons look 3a. and the head gasket dowel is nearer the centre of the block ( further out on 1.8). if you are using a carb/ignition set up, you will need a mechanical advance dizzy with the 3a lower drive gear and a spacer ring

    16. 02-07-2019 01:32 PM #14
      Quote Originally Posted by garryt View Post
      yeah them pistons look 3a. and the head gasket dowel is nearer the centre of the block ( further out on 1.8). if you are using a carb/ignition set up, you will need a mechanical advance dizzy with the 3a lower drive gear and a spacer ring
      Do you know if I can combine distributor from 1.8 carb engine and this 3A distributor into one working unit?

      Is "mechanical advance dizzy" meaning it has centrifugal advance of spark and 3A motronic distributor does not have?

    17. 02-07-2019 01:39 PM #15
      Quote Originally Posted by Butcher View Post
      I have never done what you did. I have a lot of experience in my field. Keep that in mind with my comments.

      The 3A block has a bigger hole for the distributor. It is because the 3A distributor has a bigger gear. If you use a 3A distributor, you need to have an ignition system that will play with the distributor properly. I would imagine the 3A distributor has a hall effect sensor and the timing is all done in the ignition module. Some of the older VW engines, had all the timing done in the distributor and the ignition module just amplified the signal for the coil.

      I hope that makes sense.
      Car where this package is going has distributor with hall + 7 pin ignition module + big cylinder shaped coil. Basically same stuff than 3A donor.

    18. 02-07-2019 03:59 PM #16
      yeah if you are sticking with the carb set up, you will need the matching dizzy with a spacer ring and the 3a drive gear. if you are tuning the engine at all, you might be better with an early 1.8 gti dizzy. but if it's just a block swap, your original dizzy should be ok.

    19. 02-07-2019 04:02 PM #17
      don't forget to check the intermediate shaft end bearing for wear

    20. 02-08-2019 11:45 AM #18
      If you are using the 3A block, I thought you had to use a 3A gear. If you are using the older block, the stock intermediate gear must be shaved so the crank/rod won't hit it.

      Remember, I have not done this, but I plan on stroking an old block this year.

    21. 02-08-2019 04:19 PM #19
      Inlet valves are 2mm bigger in 2.0 8v. (40mm vs 38mm in 1.8 8v)



    22. 02-08-2019 04:34 PM #20
      yeah you need the 3a drive gear, 1.8 dizzy and a spacer ring.

    23. 02-08-2019 05:21 PM #21
      Quote Originally Posted by garryt View Post
      yeah you need the 3a drive gear, 1.8 dizzy and a spacer ring.
      I don't understand why I need 1.8 distributor

      I've read 2.0 is "electronical" but.. 2.0 distributor looks same except without vacuum retard. Is only that a reason?

      Vacuum retarding is just for better emissions during idle on catalysator cars (which my car is not, but it still has that vacuum thing)



      my 1.8 distributor is like this:
      Last edited by DtiJ; 02-08-2019 at 05:30 PM.

    24. 02-08-2019 07:21 PM #22
      there is a centrifugal advance mechanism inside the 1.8 dizzy. the advance in the 2.0 dizzy is controlled by the ecu. if you use the 2.0 dizzy on a carb'd engine without an ecu style management, you will have no ignition advance, and therefor, no power

    25. 02-08-2019 07:28 PM #23
      the vacuum advance unit gives the engine more timing during light throttle cruising (increases efficiency)

    26. 02-09-2019 10:41 AM #24
      Quote Originally Posted by Butcher View Post
      The 3A block has a bigger hole for the distributor. It is because the 3A distributor has a bigger gear. If you use a 3A distributor, you need to have an ignition system that will play with the distributor properly. I would imagine the 3A distributor has a hall effect sensor and the timing is all done in the ignition module. Some of the older VW engines, had all the timing done in the distributor and the ignition module just amplified the signal for the coil..
      I know this may not come out right, but you really need to grasp what you are doing because if you do not, then the project ends up in a disaster.

      The 2.0 and 1.8 distributors are different sizes. A 2.0 dist will not fit a 1.8 block and visa versa. I'm pretty certain the intermediate shafts are different too [since the dist gears are different]. The ignitions system are different because of the way to provide the correct ignition timing to the engine. If you use a 1.8 dist you will need a spacer ring.

      Just compare intermediate shafts and distributors. You should see the differences. Then the questions you are asking will seem elementary.

      Again, I'm not trying to sound like a jerk, but I do not grasp the English language well enough to sound like I'm a prince charming.

      There were different size valves on the 8V heads. They surely look to be the same size in the pictures, but a ruler certainly would do better than any picture. If I were to do that swap, I would install valves with the 7mm stem. It takes a few more parts but it should flow more air and you know what that does. Of course a good cam [not a high RPM version] and exhaust would certainly wake up that engine too.
      Last edited by Butcher; 02-09-2019 at 10:45 AM.

    27. 02-09-2019 11:21 AM #25
      Quote Originally Posted by garryt View Post
      there is a centrifugal advance mechanism inside the 1.8 dizzy. the advance in the 2.0 dizzy is controlled by the ecu. if you use the 2.0 dizzy on a carb'd engine without an ecu style management, you will have no ignition advance, and therefor, no power
      Thanks, that was exhaustive answer I was looking for. I am going to adapt 1.8 distributor to 2.0 block (with spacer, gear and so on). Makes more sense than adapt 3A ignition system to 1.8 carb car.


      Quote Originally Posted by Butcher View Post

      There were different size valves on the 8V heads. They surely look to be the same size in the pictures, but a ruler certainly would do better than any picture. If I were to do that swap, I would install valves with the 7mm stem. It takes a few more parts but it should flow more air and you know what that does. Of course a good cam [not a high RPM version] and exhaust would certainly wake up that engine too.
      Yes, I have 8mm valves (or actually ~7,9mm from shaft) and there is tiny bit of play between them and guides, especially #1 inlet valve. Didn't took accurate measurements, but about 0.5-1mm of movement when valve 5-10mm open. What is specs for measuring that?

      So it may be time for guide job anyway. Changing valves to 7mm, I need new valves, not so sure want to do that. Is it worth it? And does 7mm guides go straight to in place of 8mm?

      And for camshaft I think I'm going with 2.0 8v (3A) "G"-marked cam.
      Last edited by DtiJ; 02-09-2019 at 12:34 PM.

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