VW Vortex - Volkswagen Forum banner

2.0 8V (3A) + 1.8 8V head etc?

25K views 63 replies 6 participants last post by  DtiJ 
#1 · (Edited)
2.0 8V (3A) + 1.8 8V head compression etc (project)

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??
 
See less See more
1
#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:thumbup: 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.
 
#3 · (Edited)
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/Compression/EngineCompression.php

I've found cometic makes head gaskets with very different thicknesses, but they cost €€€
 
#8 · (Edited)
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.
 
#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.
 
#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.
 
#21 · (Edited)
I don't understand why I need 1.8 distributor :screwy:

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:
 
#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:thumbup:
 
#25 · (Edited)
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.


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.
 
#26 ·
if it's a budget build then you might want to stick with 8mm valves. unless you can get a second hand head and swap it all over. if you are having porting/valve job done, then the 40mm inlets will fit the 1.8 head and work well if done right. the 3a camshaft is an identical spec to the digifant gti engine, so you might be better with a gti dizzy. also, I wouldn't skim to much off the head as you have no knock control.
 
#28 ·
now you mention it, i'm not certain if it's the same seats for the 38 and 40mm valve. but you can make the 38mm valve flow pretty good with the right porting and valve angles. the later mk2 gti had the same power output as the earlier one, but the valves were up to 40mm. so the increase in size was obviously not night and day. I think what you need to do is decide, how much you want to spend? and how much power you're after?
 
#29 ·
Being old also means I'm slow.

I forgot you are putting in the VW head. If the valves are smaller, the seats will not work. Replacing the seats are really a bad idea. I would suggest you just get a big valve head and rebuild that.

With a bigger 2.0 engine, I believe the larger valve head is the only way to go. They made a big difference with the 1.8 engines, I can only imagine that they would be good for the 2.0 too.
 
#36 · (Edited)
30 usd
+ shipping $48.41 usd
vat 16,87 eur

total 87,15 eur

:mad::(:(:sly::rolleyes::eek::banghead::screwy::what::thumbdown:

I'll combine 1.8 8v carb distributor internals to 2.0 8v dist or something like that. :sly:


Got new piston rings + main bearings + big end bearings + timing side oil seals

Someone stupid has changed main bearings wrong (other side should have oil hole and other not. They were put like random there, some blocking oil passage :banghead:)

 
#37 ·
I would invite you to my country, but they are in the process of building a wall. :p

The dimensions cannot be that difficult to fine. The OD must fit inside the block, the ID must be large enough for the small distributor to fit. If you have both items, a hunk of aluminum, and a lathe, you should be fine.
 
#40 ·
Thanks a lot!

soon it's time to focus on getting the distributor fitted.

Already have put

- bottom together
- intermediate and crank seals
- breather stuff and seals
- oil cooler seals
- water pump and thermostat + cover + o-rings replaced


 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top