DIY'ing a Big Valve Head

Hi guys.

Can anybody point me in the direction of a guide or information on making my own big valve head?

Got a spare cylinder head I figure I'm going to rebuild (for shits and giggles) and eventually want to match it up with a 2.0 litre block. H

Has anybody done their own bigger valve head and gas flowing?

Cheers

JD

Get a good book, i have a couple on cylinder head tuning and blueprinting that offer good guides. You'll need some specialist tools though. Are you just wanting bigger seats cutting? It isn't easy to do. Even with my knowledge I'd rather pay a machine shop with accurate equipment to do a proper job, very easy to make a balls up. Bigger seats with three angles, you could polish the exhaust and port the intake with a die grinder yourself.

I was thinking about fitting bigger valves alongside porting the intake and polishing the exhaust.

What books would you recommend? I may just read them for knowledge; like you say might end up realising it is easier for someone else to do it, but I enjoy the researching!

First of, as mentioned above, you need the right equipment…a high speed die grinder & carbide burrs as a minimum, along with safety equipment.

The first step of a big valve head is a 40.5mm inlet. This will fit on the std valve seat insert once its cut correctly to suit. Any bigger valve sizes will need the inserts changing. A 2ltr can run very well on the std 40mm inlet and can make around 150hp with the right combination of parts and a correctly ported head. I've done head's on 40.5mm inlet valves that make over 200hp on a 2ltr hillclimb spec engine so plenty of airflow is possible without changing seat inserts.

If you still want to go bigger and fit a 42mm inlet valve (the next common available size) the inserts will need changing at approx £150 for 4, plus the valves @ £20 a pop.

The most important consideration is the porting work. There is no point at all in fitting bigger valves unless the porting is done to suit…s correctly ported std valve head will give a better result than a badly ported big valve head…I've re-ported a fair few "big valve" heads that we'rnt giving the goods because the porting was insufficiant to suit the valve sizes used, and always released a flow & power gain.

If you go for a proper big valver you'll need bigger exhaust valves too to suit the much improved inlet flow.

The std 33mm exhaust valve can again, if ported correctly, provide enough exhaust flow on a road spec 2ltr up to around the 150hp mark. Like the inlet side, the common "35mm" upgrade is a waste of time unless the porting is sufficiant, and not needed unless a proper big inlet valve is used. A 35mm exhaust valve will need a bigger insert as well, plus the bigger valves, so another £150 for inserts & 4 x £20 for valves…so around £460 for seats & valves alone, before guide's & the actual porting and final machining is taken into account…a proper big valve head is'nt cheap!

If you want to proceed with the above now the fun begins!

The main inlet ports need a lot of work, along with a huge amount of material removal in the throat to get the full advantage of a big valve head, and correct shaping of the seat and short side turns…just smoothing off and/or polishing will not give any gain unless a good deal of material is removed.

Is there a noticeable difference between 40.5mm and stock valves? Or to notice any difference you would have to do a good amount of porting?

I think as a first timer to this for simplicity I'll probably use the 40.5 if they make a difference.

But I need to research it so I can figure out what equipment and what I'm actually going to do; do you know of any good resources i.e. a good book / webpage or maybe someones project porting a mk1 head?

Also, and I may show my naivety and dumbness, but I heard a rumour that bigger valves / flowed head can lose low down torque?

And you would suggest that if only going with a ported head head 40.5 inlet valves there would be no point in changing the exhaust valves? Keep them at 33mm and just polish the exhaust (alongside a better flowing exhaust obv)? How big could you go on the exhaust valves without changing the inserts?

And how hard is it to change the inserts / what is involved bar cost?

Oooh and where should I look for valves / springs etc. Not getting much joy googling on this one.

Sorry for blasting you with questions!

Downster32 said

Is there a noticeable difference between 40.5mm and stock valves? Or to notice any difference you would have to do a good amount of porting?

I think as a first timer to this for simplicity I'll probably use the 40.5 if they make a difference.

But I need to research it so I can figure out what equipment and what I'm actually going to do; do you know of any good resources i.e. a good book / webpage or maybe someones project porting a mk1 head?

Also, and I may show my naivety and dumbness, but I heard a rumour that bigger valves / flowed head can lose low down torque?

There is indeed…

A std GTi head with 40mm inlet valves flow 71-72cfm on average. A ported version makes 86-88cfm. A correctly ported 40.5mm inlet makes 93cfm, but all the ones I've seen to date only make 86-88 like the 40mm version.

I can help guide you….

It's just a rumor! As long as the port size is'nt too big relative to the valve size used then low end performance wont suffer. If a head is ported properly flow will increase as soon as the valve starts to open, so improved cylinder filling starts right away, and at all rpm points. If the port is made too big for the valve size used then low and mid range power can suffer and next to nothing gained at the top.

Downster32 said

And you would suggest that if only going with a ported head head 40.5 inlet valves there would be no point in changing the exhaust valves? Keep them at 33mm and just polish the exhaust (alongside a better flowing exhaust obv)? How big could you go on the exhaust valves without changing the inserts?

And how hard is it to change the inserts / what is involved bar cost?

If you can get the flow up to the max possible on the 40.5mm inlet then it's a close call. If your going to combine it with a performance cam then it'll be fine on 33mm valves as the increased opening/closing duration and lift will help. The rest of the engine spec will largely dictate whats needed, but and exhaust port thats a little down on flow wont loose a lot of power…I've run race engines on the dyno with lots of exhaust flow, and some with not so good flow, and the power does'nt change much…if a race engine can cope with less flow then a road engine can.

None…the next available size up from 33mm is 35mm, and the seat insert has to be changed to fit it.

The inserts MUST be changed by a professional machine shop that knows what they're doing.

Downster32 said

Oooh and where should I look for valves / springs etc. Not getting much joy googling on this one.

Sorry for blasting you with questions!

Blast away!

I can help once you know what spec your going to settle on regarding cam & valve sizes…the required engine power / spec / use will dictate the spec…what sort of power are you looking to achieve, what are you using it for, what engine size are you using it on…whats the basic engine spec going to be?

The plan I am formulating sounds like this;

Cylinder head with 40.5 inlet and 33 exhaust (for ease and cost). Ported and polished.
Going to use a 2.0 agg block (going to raise compression slightly; maybe pistons maybe skim, to somewhere between 10:1 and 11:1).
Get a 421 stainless exhaust.
As far is cam is concerned then I'd probably look for a fast road or try and find a torquey one from somewhere; want to keep the peak power lower down as I tend not to rag the balls of my cars.
And then it's just a question of carbs/custom injection. I like the idea of injection so I could run in lean when just cruising, but carbs would be easier to fit and set up.

So essentially what I'm after is a car that is quite torquey and a really fun 'street' drive; if I make 150bhp I'll be very happy.
If I can do it myself, bonus, I'll feel very chuffed. But if it is beyond me, I may just send it to someone to do for me (interested JMR? :wink: )

First port of call I think is to look into buying the gear and a book on porting. Also need to find some pics of someone who has done it on a mk1 8v head.

Or you just buy a 16v and have 150bhp straight away without having to drop mountains of cash in to an 8v. I'd only spend like that if i wanted to get an ABF to break 200bhp.

yes yes yes I know the whole drop a 16v in argument.

But

a) I'd be doing this a project I can learn on so less valve = less work.
b) I have a spare GTI 8v head, and an AGG block on the way that I got cheap
c) I like to do something slightly different

The tall block 8v 2.0 litre engines produce a nice amount of torque low down which would suit my driving style; 16v's have this and the power in the upper revs; I really don't drive in the upper revs so another reason why I don't need a 16v.

Downster32 said

The plan I am formulating sounds like this;

Cylinder head with 40.5 inlet and 33 exhaust (for ease and cost). Ported and polished.
Going to use a 2.0 agg block (going to raise compression slightly; maybe pistons maybe skim, to somewhere between 10:1 and 11:1).
Get a 421 stainless exhaust.
As far is cam is concerned then I'd probably look for a fast road or try and find a torquey one from somewhere; want to keep the peak power lower down as I tend not to rag the balls of my cars.
And then it's just a question of carbs/custom injection. I like the idea of injection so I could run in lean when just cruising, but carbs would be easier to fit and set up.

So essentially what I'm after is a car that is quite torquey and a really fun 'street' drive; if I make 150bhp I'll be very happy.
If I can do it myself, bonus, I'll feel very chuffed. But if it is beyond me, I may just send it to someone to do for me (interested JMR? :wink: )

First port of call I think is to look into buying the gear and a book on porting. Also need to find some pics of someone who has done it on a mk1 8v head.

More than interested if I can help yes…

Your thinking along the right lines, and a cam of between 270-280 duration will make for a grunty road engine without the need the rev it hard to get the best from it.

I've done a lot with carbs in the past and Im a big fan of them..my hillclimb 1800 8v runs 48 webers. .but i wouldn't recommend them for regular road use. There's nothing wrong with using them and most of the so called issues…poor low speed running, heat soak, regular tuning etc…is a load of old rubbish. .they work fine when in good condition and correctly tuned…old worn carbs poorly set up are a pain..good carbs set up properly arnt.

However for a simple road conversion i'd stick with K-jet where fitted, or use a standalone management system with digifant hardware but without the airflow meter…you can still make 150hp using either set up, but hp numbers arnt the way to think for a strong road engine…torque & power delivery are the most important factors.

Im more than happy to help, or if you think it's a bit much to tackle there's plenty of space in the workshop.  :wink:

Hhhmmm yes the carbs…..if you were to port and open up a cylinder head would it be pointless using something like a weber 32/34 or some sort of progressive carb (would they supply enough fuel?)
 
I remember my old transit had a weber 32/26 which was economic until you opened the throttle which then opened the second venturi so it could be run richer. If I was looking at carbs it'd be nice to find some that could do that, any ideas?

Or if I wanted something that could be run leaner when cruising but when opened up would put more in would I be better looking at  some sort of engine management system?

My car at the moment is a carb'd clipper so doesn't have any injection gubbins so I presumed it would be as much hassle to fit k-jet stuff as it would to fit megasquirt or something similar (not something I've researched yet).

Also, is there any 'engine porting kit' you'd recommend available on t'interweb? something like this;
http://www.demon-tweeks.co.uk/Product.do?method=view&n=1657&p=140097&c=215&utm_source=Google&utm_medium=Base&utm_campaign=Workshop%20Equipment

Could I use my drill for the bits (it revs to 2,500rpm) or is that not enough? I think I may have a hobbytool thing that may rev higher.

This is the book I'm eyeing up;
How to Build, Modify and Power Tune Cylinder Heads (Speedpro Series): Updated & Revised Edition: Amazon.co.uk: Peter Burgess, David Gollan: 9781903706763: Books


Cheers for all your help
Lots of love
Jd

Downster32 said

Hhhmmm yes the carbs…..if you were to port and open up a cylinder head would it be pointless using something like a weber 32/34 or some sort of progressive carb (would they supply enough fuel?)
 
I remember my old transit had a weber 32/26 which was economic until you opened the throttle which then opened the second venturi so it could be run richer. If I was looking at carbs it'd be nice to find some that could do that, any ideas?

Or if I wanted something that could be run leaner when cruising but when opened up would put more in would I be better looking at  some sort of engine management system?

My car at the moment is a carb'd clipper so doesn't have any injection gubbins so I presumed it would be as much hassle to fit k-jet stuff as it would to fit megasquirt or something similar (not something I've researched yet).

Also, is there any 'engine porting kit' you'd recommend available on t'interweb? something like this;
http://www.demon-tweeks.co.uk/Product.do?method=view&n=1657&p=140097&c=215&utm_source=Google&utm_medium=Base&utm_campaign=Workshop%20Equipment

Could I use my drill for the bits (it revs to 2,500rpm) or is that not enough? I think I may have a hobbytool thing that may rev higher.

This is the book I'm eyeing up;
How to Build, Modify and Power Tune Cylinder Heads (Speedpro Series): Updated & Revised Edition: Amazon.co.uk: Peter Burgess, David Gollan: 9781903706763: Books


Cheers for all your help
Lots of love
Jd

Engine management would be the better way forward yes. A Weber will do a good job tho…may cap you back to "only" 140hp in road spec trim tho!..

Bare in mind when fully open, you'd have a 32 & 34mm butterfly feeding the engine…the engine only inducts through one cylinder at a time…the restriction comes from the manifold shape/distribution…Ford Pinto 2ltr F2 stock car engine's make 160-165hp through a 32/36 Weber.

No not at all…you'll need a high speed electric die grinder as a minimum to get some serious metal cutting.

That's not a bad book…some good basics in there to get you understanding what's needed.

Most porting "kits" will contain a lot of stuff you dont need…like polishing mops etc. You'll need the grinder & some carbide burrs…tool suppliers like SGS can help there. You'll also need some emery flap wheels & emery tape….nothing at all needs polishing.

£60 for some grinding stones wow, you can buy them in halfords for £5. I have that book it is good to help you understand how you should go about the job. I find it quite therapeutic in a way:

You know what, i think.i've got some.of those somehwere…..

A couple of things;
If using a new camshaft is it best to find a solid lifter head as opposed to a hydraulic one?
Also, when installing larger valves, how do you enlarge the seat? Is that something best left to a professional or is it possible to due with home gear? Does the new valve kind of 'sit' on the old seat?
I'm starting to look forward to this

First off, and most importantly from a safety aspect…DONT use grinding stones on aluminium!!!

The aluminuim will clog the stone rendering it useless very quickly, and at the speed needed to remove any worthwhile material it'll explode in yr face…quite literally!!

Stones are ok for seat shaping…i.e the steel insert the valve sits on, and for porting old iron heads…Mini's, Ford's etc, but keep them away from alloy heads!

The only successful way to do it is with a high speed die grinder and carbide burrs. The burrs cut through alloy heads like a hot knife through butter, lubricate them with regular spray's of WD40 to minimise glogging and reduce wear…they dont last forever.

You ideally need a course cutter…recognisable by having less flutes, and a couple of double cut ones. Go for oval shape burrs to start with as they are the most usefull…get a flame shape one too to get between the guide boss & port wall.

If you want to get serious and open the ports properly then you'll need a long shank oval burr too to reach down into the port…or the collet nut on the grinder will clatter into the head…the std length burrs are not long enough to reach down into the ports.

Check out SGS, Lawson's, Roebuck, Morrissflex etc for carbide burrs.

The seats must be cut by a machine shop. The bigger the valve, the further out the contact point is on the seat insert…until you run out of space/seat diameter…thats why new inserts are needed for valves bigger than 40.5mm on the inlet.

I would advice anyone starting from scratch to start with a std valve size head. The seat inserts are one of the last opperations to be done. Always start head porting in order of importance…grind or cut out the inner diameter to the correct size relative to the valve size used, then the bowl is cut out to it's correct size…again dependant on the valve size used…followed by working the cutter gently down the side of the guide boss to open the gap between the boss & port wall…then open the wall back once there is room for the cutter not to jam. The main port between the manifold face down toward the back of the valve is the LAST section to modify…air does'nt have a problem flowing through round holes…it's changes of direction & going around corners it does'nt like, plus it need volume to flow through…hence increasing the area between the guide boss, around the bowl, and through the seat appature. I can give you all the sizes needed to produce a very positive result.

Porting heads is'nt rocket science, but, you have to do it methodically, and remove material in the right and most usefull places…polished and smooth corners wont gain a thing…correct material removal will…remember…bigger is'nt always better.

If it's likely to be a popular thing I'll put a basic guide up like I've done on other site's.