I think some of the pov spec mech head cams run no valve overlap

Is this what is required for using a G-lader Gaz?

Cheers for the additional info

I believe so, I seem to recall a discussion years ago that talked about similar issues that went along the lines of too much overlap just means the boost goes straight through the engine, while on a turbo this is less of a problem as it helps spool the turbo. I'll admit I don't know alot about the subject but thought I'd mention it anyway. :)

That makes a lot of sense, thanks fella :-D

Ahhhh, just had a think about what you said maxmax, is that the def of capacity then: distance travelled by all 4 cylinders in one stroke? Makes sense then how CR is not related. Tanks for that, clears a lot of things up

Call me max , not maxmax.

Yes, the displacement of a piston engine is exactly that. That's the reason why all the 1272cc engines found in mk2-3 engines have different compression ratio's, the combustion chamber is different, whilst the displacement stays the same.

The 3F engine is a good example, 1272cc's but higher CR lets is extract more mechanical energy from the combustion process than the AAV

That's what's always confused me, ce would have had to have made loads of different piston/head/crank combos to achieve all of the 1.3's with different CRs. Thanks chief

Anyhow, anyone know how easy afh heads go onto early bottoms?

That's what's always confused me, ce would have had to have made loads of different piston/head/crank combos to achieve all of the 1.3's with different CRs. Thanks chief

Anyhow, anyone know how easy afh heads go onto early bottoms?

There was a thread that accumulated some knowledge on the theory a while back,

Sure it was about this topic too - building a 16v engine capable of taking boost reliably and on the cheap. I'm sure it ended up not being achievable though

Mechanical headed G40.... that's how the cup cars roll isn't it?

using a mech head (hk,gk,gl) on a g40 block is possible but i cant really see the point due to the valves been smaller, you cant fit sodium filled valves and you cant buy suitable cams off the shelf compared hydraulic head, you can actually buy solid lifters for the hydraulic engines aswell

some info here on building a 16v g40

http://www.clubpolo.co.uk/forum/index.php?...=203246&hl=

since then I've found another posible way of building a 1300 16v, consists of

1272cc block overbored to 76.5mm

late engine 1292cc iirc? crank

1.6 16v 136mm rods, preferably uprated although could probally take abit of boost, as seen on charged lupos etc

afh pistons

either a afh or late roller rocker 16v head, with suitable cambelt conversion

then youd have to sort fueling and turbo, manifold etc, a sinktrap design comes to mind utilisting the original vw cast mani

Edited 15 July, 201115 yr by willsalter1000

The turbo manifold is not an issue. And it would be running on an r5 carb, so theres the fuelling. I'm just looking for alternative heads and whether any are viable.

I know there have been folk asking about 16v taking boost, but iirc most were wanting to use the afh block and head. I have a g block, so all of those internals I know will survive a turbo. It's just the head now that needs sorting.

Just read above link, good stuff.

Anyone ever calculate the CR using afh head and hh pistons?

ermmmm shoot me down in a ball of flames here ........if the head reduces the compression ratio- would it be possible to run a 1W bottom end for your 1.4 and then the mechanical head will reduce the compression.....

question is how much it reduces it by!

could be an amazingly good way to run a turbo setup

ermmmm shoot me down in a ball of flames here ........if the head reduces the compression ratio- would it be possible to run a 1W bottom end for your 1.4 and then the mechanical head will reduce the compression.....

question is how much it reduces it by!

could be an amazingly good way to run a turbo setup

You will need to work out the CR if using the 1W pistons/bottom end with either an AFH or an 8v mech head with combustion chambers, but with the right head gasket it could give a good CR for forced induction. A 1398cc turbo is worth looking into mate if you haven't already purchased your accralite forged pistons?

is the 1w a 1.4 then? That's the diesel bottom end right?

Yep, that's right.

To work out if you can do it or not, you'll need to understand the theory behind it.

http://en.wikipedia.org/wiki/Compression_ratio

The calculation on the wikipedia site can be simplified a little to:

CR-1=(engine cc / no of pistons / combustion space at TDC) or combustion space at TDC = engine cc / no of pistons / (CR-1)

Some rough calculations for working out combustion space at TDC from compression ratio:

For the 1398cc 1W engine (compression ratio is 22.5:1 or there abouts, to calculate combustion space at TDC, you need to subtract 1 from the compression ratio as above, hence 21.5:1, this represents the ratio of swept volume to the compression volume)

Combustion space at TDC = 1398/4/21.5=16.25 cc

Because it's not possible to theoretically determine where the combustion space comes from (it can come from the head, headgasket and the dish in the piston) we have to make some assumptions that mean the results may not be 100% accurate.

Some of this combustion volume will be taken up by the headgasket. Diesel headgaskets are very thick, ~1.5mm

A 1mm thick headgasket of 75mm bore will add approx 4.4cc to the compression volume, assuming the pistons stop at TDC and don't occupy the headgasket space like they do on the GT and ABD engines.

I measured the combustion chamber in the head of an early mech head enigne several years ago and found it to be about 20cc (I was going to put one on a 1.6 bottom end)

Assuming a flat head on the diesel (zero combustion volume) and using the diesel headgasket, you end up with a compressed volume of 36.25cc (one or two cc's in the diesel head would reduce this value as you won't have increased the combustion volume by as much)

resulting compression ratio = (1398/4/36.25) +1 =10.6:1

So those numbers aren't too bad for N/A but a bit on the high side for forced induction.

Anyone follow that? Think it's time I went to the pub.

Also, the 268/268* newman camshaft i'm using at the moment is actually intended for a G40 or G40T but works well in normal N/A applications so they must be quite compatible.

Actually the other way around! The 268° deg cam and similar items in their range are designed for the N/A Polos, but it just so happens that N/A cams work fairly well in turbo'd cars - and the 268° is a good match for a K03 turbo on a G40 engine. Put one on a G-lader powered G40 though and it'll be a sack of shit.

Are you sure?

I ask because when i purchased it, the spec sheet stated it was for turbo g40 engines, and when i asked they said exactly what you have quoted.

It's designed for F/I but works well in N/A

I'm 110% certain. The 268/268° Newman isn't advertised formally by them, and they're normally a bit shy to flog it - because it's a copy of a Schrick 268° cam which was designed for N/A cars.

Rewind 4 years or so, and PSD were playing with the first K03 turbo'd Polo they'd built - and I put one on my 1341cc bottom end around the same time. Steve Pitt and I both reached the same conclusion that using a GT cam with a smallish K03 was a waste of time.

I spent many hours trawling German forums to find out what they were using - and Schrick 268° cams for N/A cars were a popular choice for turbo cars too. Schricks were expensive, Steve had an account with Newman - so he had a couple made to see how they fared - one went in John Marchant's Mk1 Polo 1272cc K03 motor, and the other in mine.

In the past if you rang Newman and asked for a "turbo" cam you'd get an evasive answer, I guess they're being a bit more open now if they realise that it's common knowledge! I suppose Newman see it as a turbo cam, but it's a copy of a Schrick designed originally for N/A.

I think some of the pov spec mech head cams run no valve overlap

Is this what is required for using a G-lader Gaz?

Cheers for the additional info

I believe so, I seem to recall a discussion years ago that talked about similar issues that went along the lines of too much overlap just means the boost goes straight through the engine, while on a turbo this is less of a problem as it helps spool the turbo. I'll admit I don't know alot about the subject but thought I'd mention it anyway. :)

Overlap is bad for a turbo cam, fine for G-lader though in my experience.

But 16v turbo does sound very interesting, not something I had considered. Ate these heads flat bottomed?

6N2 gti head

The afh is the same kind of design. Tbh if I was going to 16v an 8v I'd use the gti head as the cam belt only operates one pulley on the head rather than 2 like on the afh. I guess that would simplify things a little?

^^ that does sound like a good idea, if the belts are compatible etc that is. Combustion chamber still in the head though. To remedy that, can you modify dished pistons e.g weld up the dish? Or is this a bad idea?

Could you not just use the 16v pistons in the 8v block?

sometimes you can, just depends what capacity your after, in my last post in ths thread I've said how to build a 1.3 16v using a early 8v block(from aav/u, nz, py 3f etc) and 16v pistons

Edited 17 July, 201115 yr by willsalter1000

You could, but how would you know they would survive the boost pressures? Using the py bottom end assembly basically gaurantees it will survive a turbo

i meant using the g40 internals on the 1w bottom end! so it wouldnt be 22:1 cr to start with. might be able to get it closer then 10.6:1

You could, but how would you know they would survive the boost pressures? Using the py bottom end assembly basically gaurantees it will survive a turbo

the only way is to try, the setup i mentioned would probally take boost fine, and the rods would be ok up to a certain point

yes, the py bottom end is strong, you just need to run different pistons to sort the CR out

either HH, yet to find out what CR is created when used in conjunction with a 16v head, although i could find this out tomorow

or custom piston if hh pistons are no good

regarding which 16v head to use, both have been fitted to g40 style blocks before

afh heads need cambelt alterations

roller rocker heads need waterway and cambelt alterations

Back from the dead, but I may have a solution to the original problem of low compression when using a solid lifter head with combustion chamber in it. The 1w pistons (from the diesel) are flat headed too. I've just been to collect a spare set. If I can get a solid head, i'b be up for having a look at this again.

Another issue, valve sizes. Any one know of them for the solid and hydro heads, so we can compare?

i read through the thread there. (alot to take in) I'm in the middel of looking an solid lifters from the likes of a mk1 golf and putting them in to a 3f head. vw's hydraulic tappets all seem the same. for example i hav the tappets from an AFN 1.9tdi and they are the same as 3f 1's.

so would that not save the need for using the older head?

Andy

The solid lifter heads in polo's are totally different to the hydraulic heads (and I'm sure the Golfs are the same engines as polos) so I'm not too sure what your wanting to swap across.

The issue isnt about needing new lifters, they are easy to get. The solid lifters are apparently more suited to higher revs as they eliminate valve bounce. Plus its something different, and I like the idea of a period motor in my old 'loon

The solid lifter heads in polo's are totally different to the hydraulic heads (and I'm sure the Golfs are the same engines as polos) so I'm not too sure what your wanting to swap across.

The issue isnt about needing new lifters, they are easy to get. The solid lifters are apparently more suited to higher revs as they eliminate valve bounce. Plus its something different, and I like the idea of a period motor in my old 'loon

Yeah, the design of the solid lifter heads is completely different to the hydraulic heads. The solid lifter heads have adjustable rocker arms which the cam lobes push against, whereas the hydraulic heads have an oil filled bucket which the cam pushes on.

I think its less about solid lifters eliminating valve bounce, because thats what the double valve springs will reduce. Its more to do with the hydraulic support in the tappet failing and therefore the valve not lifting the amount that it should. In which case you'll get fuck all air getting in or out of the engine and therefore fuck all rpm'zzzzz.

I am the same as you dude, I want a period looking engine