mk3 bottom end for a mk1

[alex g]

is there anything i need to know when getting a 2l bottom end from a mk3 for my mk1 to be maited up to a 16v head, are they all interchangable

[Golfwise]

Lots to know really.
Need 16v pistons
Block is taller for a start and generally the inlet manifold / throttle body won't allow the bonnet to close properly.
It would be interesting to know if there would be enough material on the top of the pistons to machine the clearance needed for the valves ????
Anything is possible as the head will mate up basically.

[alex g]

so the mk3 is a tall block is it

[Golfwise]

Yes

[VanKronenburg]

What you need to know if putting 16v head on the 8v block is that the compression ratio will drop to 8.2:1 Excellent if you want to turbo or supercharge but hardly that special if you are leaving it normally aspirated

The tall block 16v will fit, but it is very tight - especially with K-jet throttle body. You need hard engine mounts otherwise the engine will rock back and hit the throttle body on one of the bonnet braces.

[VanKronenburg]

Why don't you fit a complete 16v engine... I don't really understand why you want to do this?

The only people to perform this are the yanks with their ABA 8v crossflow motor. They build an "ABF" 16v by using the tall ABA block with ABF pistons, head and so on. I don't know why you would do this either as I know you have the ABF in Australia.

[alex g]

i want to run a 2l 16v on dellortos if it get to hard to run the bottom end i will run a 1.8 but i am looking to make this one nice and old school fast, so clearance shouldnt be an issue as the head will be manifoldless in the traditional scence

[VanKronenburg]

i want to run a 2l 16v on dellortos if it get to hard to run the bottom end i will run a 1.8 but i am looking to make this one nice and old school fast, so clearance shouldnt be an issue as the head will be manifoldless in the traditional scence

There is no difference in difficulty to run a 1.8 or 2.0 block - the point is that if you fit a 16v head to an 8v block, you will be building a low compression motor.

There are still clearance issues with throttle bodies or twin carbs in a Golf 1 with certain DCOE manifolds and a tall block 16v. Some of the long port manifolds reach out so far that the airbox or filter socks you need to run will touch the front of the bonnet.

If using a tall motor, you'll need one of the shorter port manifolds, like a Dbilas Tuning one. If you need contacts for these parts, send me a message.

Also, with the carb setup, you will not gain much power or torque with the standard cams. Twin 45s are great with a ported head and mild cams and will get an honest 180ps - not like the UK cars we all read about with stock 16v and 190hp :roll: Rubbish. :!:

[alex g]

so boring a 1.8 bottom end sounds like the go and the head will be having work done aswell

[VanKronenburg]

Yes the 1.8 16v bottom end would be the best choice. Bored to 1.9 they are better than the 2.0 if you are building a normal aspiration motor - they rev better mainly. The 2.0 head is best to use to modify if the machinist has little experience as there is more material to work with. All the heads produce very similar results if they are well modified, though.

[finemk1]

pls pls if you choose to go for the 8v bottom end, get the pistons cut down for the valves like someone said befor or get a spacer and another head gasket to raise the head a few mm

hey vankronenburg whats the best choice pistons if you were to bore the 1.8 to 1.9 ?

[VanKronenburg]

pls pls if you choose to go for the 8v bottom end, get the pistons cut down for the valves like someone said befor or get a spacer and another head gasket to raise the head a few mm

hey vankronenburg whats the best choice pistons if you were to bore the 1.8 to 1.9 ?

If you use a spacer, you only lower the compression further - why would he do this

In terms of pistons, we like to use Mahle or JE; both will make any specification. 11.5:1 is the best street compression ratio for a mild tune 16v. It is both safe and provides a decent boost in mid range. It is possible to go right up to 13.5:1, but this requires modification to the block to set the head at an angle for valve clearance. Remember that the motor will run hotter if bored to 1.9 with higher compression: of course the compression boost creates more heat but there is also less space in the cylinder walls for this heat to be stored. A remote oil cooler is a good idea.

[finemk1]

If you use a spacer, you only lower the compression further - why would he do this Question

was recomended to me after i had a boo boo, i think he was as smart as me at the time and just looking for answers........ ie. not very smart hey

[Golfwise]

Fine it appears you used normal 8v pistons and the valves when open had no where to go but through them.Thats why 16v pistons are different You take too much notice of bad advice.