16v engine rebuild

[russlench 0]

I'm currently in the process of a complete 16v 9A rebuild (my first), and planning to document the process here - both to get help and advice from people in the know, and hopefully to provide a bit of a walkthrough for any other newbie wanting to dive in!

 

I hope everyone will feel free to join in - all comments are welcome!

 

Background

 

I picked the Corrado up almost two years ago, and have really only done what was necessary to keep it going, apart from a few cosmetic mods. It had travelled almost 180, 000 miles when I got it, and is now approaching 200k. A generally good motor that is only just staring to show signs of fatigue and a recently aquired thirst for oil; I have decided to take the time to restore it to it's former glory - maybe with a little more grunt than it had from the factory.

 

I am by no means a mechanic, though I do have a little experience working with aircooled VW motors - and am not afraid to get stuck in!

[davidwort 0]

excellent! be sure to take loads of pics, always good to follow work people are doing, a few of us on here have had valvers totally in pieces, so you should get some helpful comments and advice :)

[russlench 0]

Thanks davidwort for your post, as well as being my first build this is also my first contribution to the forum - so it would be good to get as many people involved as possible.

 

The Corrado is a daily driver so I thought it would be sensible to source a second engine, break it down and rebuild it, then swap 'em out.

 

Thanks to Rustynuts :salute: , I have a 9A block which is currently in the shop being machined out to 83mm. I also have a KR head complete with cams that I picked up a while ago from Ebay.

 

The block I will cover shortly, it came complete, so I stripped it down ready for acid tanking and machining but there has been a slight delay with the arrival of new pistons. I ordered a set of oversize Wisecos back in November which have yet to arrive - so I have concentrated mostly on sourcing the other parts required to complete the build.

[russlench 0]

I had a bit of time available this week so I decided to take a look at the cylinder head. I was fortunate enough when out in Australia a few years ago to stumble across a guy that built race engines for Beetles. I ended up staying with him for a few months and helping out on a few of the builds. I picked up the basics of head porting, so I thought I would try my luck on the KR head as I had managed to pick it up relatively cheap and decided that it was worth a go.

 

I read through quite a lot of the threads about which head to use with the 16v, 9A with KR inlet, abf, complete KR - as I have the KR complete with cams it seems only right to use it!

 

I have a few basic tools (and a few I've made to fit the purpose) and use of a small workshop, so on Saturday last week I set everything up and made a start.

 

With the inlet side of the KR already being quite open I concentrated on just roughing it all up, removing the casting marks, knife edging the runner divider and blending the runner into the valve seat. Below is a before/after comparison of one of the inlet ports:

 

[davidwort 0]

looks good, reminds me of when I first picked my 'worked' head up from the place that flowed it, very similar looking work done on the inlets, I spent ages staring at it from every angle (valves were out obviously), fascinating.

I've seen a fair few 16v heads just opened up far too much on the inlets which apparently ruins torque, they do respond quite well to careful headwork though.

[russlench 0]

I know what you mean! I too spent a lot of time staring at it and tried hard to resist the urge to continue or 'just take a little more off' running the risk of rendering it useless!

 

Obviously I started by removing the valves, springs and associated peripherals (misplacing a lower valve spring locator in the process! - thanks to Iverrrado for the spare! :salute: ), then tentatively warmed the entire head in the oven to accomodate the removal of the valve guides.

 

I made up a tool to act as a guide driver out of an old extended polishing mandrel (will post pics to explain this better!), this seemed to work quite well and the guides slid out relatively easily.

 

New guides and inlet valves were ordered from GSF and have now arrived, though I do have a question about the valves. Unfortunately I didn't notice before I jumped in and started smoothing the lip (green arrow) that they were three groove (blue arrow) not single groove stems :brickwall: . I have read that the three groove stem valves are used in the ABF head, so, my question is;

 

Can I use ABF collets with these valves and KR springs/retainers in the KR head?

 

Below is a photos of the new valve (left) and the stock KR valve (right). I would rather use the new valves if possible as A) they are new, B) I've paid for them and C) they do seem to be a slightly better shape in terms of flow (red arrow).

 

In terms of stem length, stem width and valve diameter they are identical.

 

Any help with this would be appriciated!

 

[davidwort 0]

from what I can see on ETKA (9A/KR and ABF) :

 

stem seal same

split cotter diff

top spring disc diff

outer spring same

inner spring same

lower spring disc same

ex valve ABF 97.95mm

ex valve 9A 98.2mm

 

there are some cross over parts on late 9A heads, with a different ex valve again 98.2mm but the same split cotter and top spring disc as ABF

 

interestingly the late 9A shares the same part number inlet valve (95.5mm) with the ABF

 

HTH.

[russlench 0]

Thanks davidwort!

 

So - with ABF cotters and retainers I should be OK?

 

Maybe one other problem that crossed my mind is: if the valve travels down far enough, could the lower of the three grooves impact on the stem seal? Or is there no danger of this?

[davidwort 0]

It's beyond my limited engine knowledge I'm afraid, I guess you really want someone like Vince from Stealth who's built many 16v engines, I'd Imagine he knows the ins and outs of part compatability, whenever I've been up to Stealth for rolling road days there's always a few 16v blocks kicking around :)

I do remember being told only to use VW stem seals though, as they use the best material, compared to some pattern parts.

[perky15 0]

i have just put my 9a together today. put a de-cat pipe on, kr inlet cam,panel filter, what a difference i love it even more now. maybe i will take the head back of and have it ported, does it make much difference?

[davidwort 0]

it depends on how well it's done, but generally a reasonable gas-flow, port and polish should give somewhere around 10-15% gains at the top end on a 16v head, the whole rev range should benefit but it will gain progressively more up the rev range.

I've found the car (once properly set up) is slightly more fuel efficient, the power delivery is nice an smooth and it will pull very strongly pretty much up to the red line, even on stock KR cams.

The downside is cost/benefit, there's a lot of work on a 16v head, so it's not cheap and compared to chipping a 1.8T it looks very expensive per bhp gained.

I've been fortunate to have my car rolling roaded enough times to compare the 1.8, 2.0 and flowed head on different rollers and my current setup is a good 20% more torque and even more on the power side over the standard 1.8. If you can believe the figures that's about 150lb/ft and 175bhp from a valver on KR cams which is enough to keep up with the traffic :)

[Jim 2]

Superb. Been hoping for a thread like this.

 

I plan to demote my Corrado 2.0 16v to 'weekend car' in the coming months so that I can spend a bit of time fixing stuff (or getting stuff fixed!) and an engine rebuild is something I had thought about. However when I went to see Vince @ Stealth he essentially said "If it aint broke, don't fix it" referring to the fact that my engine still pulls pretty well with no knocks or anything despite being 500 miles shy of 190,000 miles. But I'd quite like a few more ponies myself.. it was rollered last year at 140BHP despite having KR cams (had been previously been rollered at 157BHP) so it needs some kind of tune up at the very least.

 

So in short I may go it alone on the engine rebuild but just need the knowledge of someone like your good self to inspire me and make me feel confident enough to try such a thing!

[dirtytorque 0]

Thanks davidwort!

 

So - with ABF cotters and retainers I should be OK?

 

Maybe one other problem that crossed my mind is: if the valve travels down far enough, could the lower of the three grooves impact on the stem seal? Or is there no danger of this?

 

I was going to attempt to re-build a 16v head myself but in the end I gave it to a professional.I'll be interested to see you go at it.Keeps us posted.

:)

[russlench 0]

I spoke to Vince this morning, he said essentially if the valves are the same dimensions it should be OK. I spotted on GSF that they stock 3 groove cotters - I'll order a pair and mock up the valve assembly to see if there is any noticable difference.

 

I made a start on the exhaust side of the head yesterday - I'll try and get it as close to a mirror finish inside as possible: pics to follow.

[mattkh 0]

excellent! be sure to take loads of pics,

Hi

I was planning to take photos but could not.

How do you combine mucky hands with a camera that needs to stay clean. OK if u can hire a photographer.

[russlench 0]

Update - got the collets from GSF today, they sent the 8mm 3 groove for the G60. I'm pretty sure I'll need 7mm VR6 collets - will try again in the morning to get hold of a pair.

 

Unless anyone has a pair they could loan for research purposes?

[roo 0]

I've just rebuilt a KR head with ABF valvegear and it runs sweet as a nut. :clap:

The only obvious difference I saw between the KR and ABF valve gear was the valves, split collets and the top retaining cap. The actual length of the ABF and KR collets are pretty much the same, hence why there's no collision with the stem seal, it's just the ABF ones have 3 locating ridges instead of one.

 

I couldn't tell from your pics if you'd done this already, but aside from smoothing the inlet and exhaust ports I found that when I gasflowed my cylinder head, there was quite a bit of work to be done in blending in the back of the valve seats to the inlet and exhaust throats.

[russlench 0]

Thanks for the info roo, I have done quite a lot of work in the seat/throat area, will try to post pics later. Any idea where I can get abf collets/retainers?

[roo 0]

Unless you can find an ABF head to strip the parts from, you may have to go to VW for the parts you need. I can't imagine the collets at least being too expensive. Other than that I'd give GSF or Eurocarparts a ring.

[russlench 0]

Managed to get a bit of time today to finish the inlet side of the head and make a start on the chamber.

 

 

[russlench 0]

I ordered a single ABF retainer and pair of collets from VW and picked them up this morning. Below are a couple of pics showing the standards KR valve/retainer/collets (left) and the ABF valve/retainer/collets. The only real differences seems to be the amount of valve there is left above the retainer to contact the lifter and therefore the increased amount of valve from the underside of the retainer to the valve face. As the ABF uses the same lifters as the KR I can't see there being an issue with the reduced valve length up top. My logic would be that the increased length on the underside would mean that the springs are under less compression when the valves are closed, making it easier for the cam to open the valves as there is initially less resistance.

 

Would like to hear any thoughts on this.

 

 

[russlench 0]

Had the final bits to complete the head arrive on Friday - guides, and the rest of the cotters and retainers for the inlet side. Gave the chambers a light polish today and started pushing the new guides in.

 

 

 

[oldskoolkool 0]

hi what sort of task is it to gas flow your own head as i got a quote of £375 and wondered how much of a job it is for me to do ?? thanks

[davidwort 0]

hi what sort of task is it to gas flow your own head as i got a quote of £375 and wondered how much of a job it is for me to do ?? thanks

not being funny, but if you're asking those questions it's probably better if you don't attempt it.

It's a full top end strip down plus replacement of any worn guides and valves and then the careful porting, polishing and gasflowing of all 16 inlets and outlets plus combustion chamber and valve seats.

If you do a DIY job without the right knowledge you could end up with headwork that actually makes matters worse especially on the inlet ports.

TBH £400 quid for all that work is very good, I had mine done the best part of 10 years ago and that was £600.