# Oversized valves worth it?



## vwnut82 (Sep 21, 2000)

Are the benefits worth the time and money spent to upgrade from a 40/33mm valves to 42/35? This is on a 3A shortblock with a solid lifter GTI head.


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## JeffB (Nov 28, 1999)

*Re: Oversized valves worth it? (vwnut82)*

Are you building a true race engine and planning to go racing?


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## vwnut82 (Sep 21, 2000)

*Re: Oversized valves worth it? (JeffB)*

daily driver, weekend racer


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## JeffB (Nov 28, 1999)

*Re: Oversized valves worth it? (vwnut82)*

Not even close to being needed. The expense will be high and the gain will be nothing.


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## A1Rocco (Oct 6, 2001)

*Re: Oversized valves worth it? (JeffB)*

Well that's one opinion.
I too will be using the exact same set-up, 84 GTI airshroud head on a 2.0L 3A block with an Audi 5000 Turbo intake manifold. I have been reading up on this set-up since 1995 and read a test article in a British mag where they tested a head with and without. The gains were noticeable with the 42/35's and at the time it was a pricey swap. Since then and especially with the strenght of the US $ it is not so pricey for you, for me it sucks, I'm in Canada. Personally I can't afford it but could do it locally if I wanted to, My machinist/rebuilder that I use can do it and does all the rebuilt performance heads for RPI and Momentum Motorsport. I feel that the bigger the cam the more benifit you will get from the bigger valves. Cost is all relative. I find VW guys are the cheapest car tuners there are. They want everything at 1980's prices or forget it. If you feel a need for that little extra and you will be using the biggest cam you can run and like to run it up to the redline alot then do it and don't even complain about the cost. I guarantee you will be getting it cheaper then other car makes.
Go for it if it seems appropriate and good luck.
I will look for the article I was referring too and reply with some stats if I can find it.
James. http://www.autocross.net. 


[Modified by A1Rocco, 3:34 AM 11-11-2001]


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## mk1classic (Feb 28, 2001)

*Re: Oversized valves worth it? (vwnut82)*

Go for large exhaust valves 35mm. It's the exhaust that's too small on the original 1.8L GTI engine according my engine tuner. He said that the most gain would be in getting larger exhaust valves, but this was for a 1.8L engine 
(He’s been tuning VW for 25years air-cooled and water-cooled)
Another possibility together with larger exhaust valves and a port and polish job, is to go for intake and exhaust valves with 7mm stem to keep the airspeed up but with less restriction in the intake.


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## JeffB (Nov 28, 1999)

*Re: Oversized valves worth it? (A1Rocco)*

quote:[HR][/HR]I will look for the article I was referring too and reply with some stats if I can find it.
James.[HR][/HR]​Please do that as I would be very interested to see how this expensive modification would help a daily driver that races on a weekend or two a month. That money could be well spent in many other places.
jeff


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## Vdubs (May 16, 2001)

*Re: Oversized valves worth it? (vwnut82)*

Cost is always an issue, if you're going to take the head off strip it and just do bigger valves it's expencive for not much gain. If the head's off and being ported, polished, cam and springs ect you'd be mad not to put in bigger valves.


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## A1Rocco (Oct 6, 2001)

*Re: Oversized valves worth it? (Vdubs)*

See, these British guys know whats goin' on, I believe it was Tim Stiles or was it Steve Creswell, damn where's that article(still looking), that built the motor. Also the European Car project GTI from 1995? used bigger valves and I beleive they were 7mm stems.
James.


[Modified by A1Rocco, 5:55 AM 11-12-2001]


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## 2035cc16v (May 18, 2000)

*Re: Oversized valves worth it? (JeffB)*

quote:[HR][/HR]The expense will be high and the gain will be nothing.[HR][/HR]​wrong on both counts.


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## A1Rocco (Oct 6, 2001)

*Re: Oversized valves worth it? (A1Rocco)*

I found the article in the British mag, it's May '95 VW Motoring. They used a Eurospec head with 42mm intakes/36mm exhausts. Wow, I didn't know you could get those two in there. Anyway this article doesn't have enough technical info so it's not the one I'm thinking of so it must be in European Car. They did say the car used to have 41mm intakes/35mm exhausts and that it was a lot faster now with the Eurospec head. I have an article on the old set-up somewhere too. I'm looking.
James.


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## Peter Tong (Jun 17, 1999)

*Re: Oversized valves worth it? (A1Rocco)*

James, did they have flow data for that head. I talked to Steve when I purchased my VSAM unit from him and he was one of the few tuners over there that was running the Eurospec head...


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## TBT-Syncro (Apr 28, 2001)

*Re: Oversized valves worth it? (vwnut82)*

going 1mm larger and going down to 7mm will gain you more then 10% flow on almost every VW head. In some cases you'll see up to 20% more flow.... this is without any head work.


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## Peter Tong (Jun 17, 1999)

*Re: Oversized valves worth it? (TBT-PassatG60)*

I can attest to this - gained 22% in the midrange of lifts with a backcut, unshroud, and undercut stems... I think I'll get larger valves put in the next time I have this head off...


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## YetiMan (Jul 25, 2001)

*Re: Oversized valves worth it? (TBT-PassatG60)*


_Quote, originally posted by *TBT-PassatG60* »_going 1mm larger and going down to 7mm will gain you more then 10% flow on almost every VW head. In some cases you'll see up to 20% more flow.... this is without any head work.

What he said


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## ABA Scirocco (May 30, 2001)

*Re: Oversized valves worth it? (A1Rocco)*


_Quote, originally posted by *A1Rocco* »_ They used a Eurospec head with 42mm intakes/36mm exhausts. Wow, I didn't know you could get those two in there. 


I don't think you can on a stock head but the Euorspec head isn't made using a stock casting, they have their own castings made.

_Quote, originally posted by *TBT-PassatG60* »_going 1mm larger and going down to 7mm will gain you more then 10% flow on almost every VW head. In some cases you'll see up to 20% more flow.... this is without any head work.

I'm planning to do this on my next engine, I've already bought the valve from TT


_Modified by ABA Scirocco at 9:49 AM 12-20-2003_


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## Fox-N-It (Jul 23, 2003)

Who sells the oversized valves? bigges ones i can find are 41/35. How much machine shop work do i have to pay for to have this done?


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## '84GTI-Spence (May 17, 2003)

http://www.bertilsengines.com


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## Fox-N-It (Jul 23, 2003)

when going down to oversized 7mm TT valves what valve seats, retainers and guides should be used?


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## Slow1.8 (Oct 9, 2003)

*Re: ('84GTI-Spence)*


_Quote, originally posted by *'84GTI-Spence* »_http://www.bertilsengines.com

35.0 mm 102.6 mm 8.0 mm 
44.0 mm 102.6 mm 8.0 mm








Would those fit in the same head?


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## ABA Scirocco (May 30, 2001)

*Re: (Fox-N-It)*


_Quote, originally posted by *Fox-N-It* »_when going down to oversized 7mm TT valves what valve seats, retainers and guides should be used? 

The stock valve seats can be opened up enough to fit and you use 16V or ABA guides and OBD1 ABA retainers and keepers.

_Quote, originally posted by *Slow1.8* »_
35.0 mm 102.6 mm 8.0 mm 
44.0 mm 102.6 mm 8.0 mm








Would those fit in the same head?









No, not even close. 


_Modified by ABA Scirocco at 6:18 AM 12-21-2003_


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## Slow1.8 (Oct 9, 2003)

*Re: (ABA Scirocco)*









First the old valve seat is milled out. 








After careful cleaning, the recess and inserts are checked for fit








The new hardened seat is then pressed into position.








The new seat is then cut to the correct angle for the valve face.









Finally the valve and seat are lapped to ensure a perfect seal


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## Slow1.8 (Oct 9, 2003)

*Re: (ABA Scirocco)*


_Quote, originally posted by *ABA Scirocco* »_No, not even close. 

I thought they wouldn't...








But why does he make such big valves if they won't even fit...








ABA_Scirocco: How many Millimeters do we have to work with untill you can't go no more?
3mm? 5mm?












_Modified by Slow1.8 at 11:39 AM 12-21-2003_


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## ABA Scirocco (May 30, 2001)

*Re: (Slow1.8)*

I'll have to double check the measurement but I think the valves are about 39mm apart centre to centre so any combination that adds up to less 78mm should work. If that 39mm is correct 42 and 35 would be about as big as you'd want to go, the space between the valve heads would be about .5mm. 
BTW, those 44mm intake valves would fit if you kept the stock sized 33mm exhaust valves but I'm not sure there would be much point in doing that.


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## DanielAdams (Aug 22, 2002)

*Re: Oversized valves worth it? (mk1classic)*


_Quote, originally posted by *mk1classic* »_Go for large exhaust valves 35mm. It's the exhaust that's too small on the original 1.8L GTI engine according my engine tuner. 

I'd agree with that. I did a fair amount of research before building my 2.1 8v (or, more precisely, having it built for me) and I heard the same thing all over - went with 40/35
Dan


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## stock77 (Aug 28, 2001)

*Re: Oversized valves worth it? (DanielAdams)*

With proper bowl work (as described by Peter Tong), the larger valves and smaller stems are a good way to go. I wish I could give a better before and after comparison of my 35mm exhaust valves ( I also agree with the exhaust valves first theory), but I changed other things at the same time, so I didn't have any scientific method to judge with. 
At a certain point larger valves in a 8V head get to the point of diminishing returns. You start to have to seriously siamese the valve seats and the valves start to shroud each other a little bit. And you also run out of room to get them in the head of course.








Just my .02...... 
The same person that A1Rocco is talking about, did my larger valves and also did my shim-under bucket conversion for my Eurospec head. If I am not mistaken he machined my valves from blanks and cut the stems and groved them for the keepers. So this type of work and the corresponding parts are able to be sourced relatively easily. 
edit: one last thing, the cost factor is relative, one person's prohibitive cost is another person's cheap must have... So I can't comment on that.


_Modified by stock77 at 5:13 PM 12-22-2003_


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## Fox-N-It (Jul 23, 2003)

I just foudn out the head i might buy already has 41/35's with a port and polish and 3 angle valve job. Only one problem.....there is a slight crack in the area between 2 valves......not sure how $$$ it will be to repair but the head was pulled from a running car. 
any ideas?


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## Slow1.8 (Oct 9, 2003)

*Re: (Fox-N-It)*


_Quote, originally posted by *Fox-N-It* »_ has 41/35's with a port and polish and 3 angle valve job. Only one problem.....there is a slight crack in the area between 2 valves

I guess I'd have to say that 41/35 is not a safe way to go... Darn.


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## Fox-N-It (Jul 23, 2003)

*Re: (Slow1.8)*


_Quote, originally posted by *Slow1.8* »_
I guess I'd have to say that 41/35 is not a safe way to go... Darn.









Forgot to add the crack is under spec meaning it still held compression perfect. It was on a turbo G-60. I would like to have it fixed just incase tho.


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## Slow1.8 (Oct 9, 2003)

*Re: (Fox-N-It)*

Please tell use when you slap that thing on!!!


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## Fox-N-It (Jul 23, 2003)

*Re: (Slow1.8)*

Back from the dead.
That head was deemed very costly to repair by the cylinderhead specalist at my college. Im in the process of getting a big valve head to play with in hopes of recreating the same specs. Maby stick with 40mm intake instead of 41 and 35mm exhaust.


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## fwdvw (May 12, 2000)

*Re: (Fox-N-It)*


_Quote, originally posted by *Fox-N-It* »_Back from the dead.
That head was deemed very costly to repair by the cylinderhead specalist at my college. Im in the process of getting a big valve head to play with in hopes of recreating the same specs. Maby stick with 40mm intake instead of 41 and 35mm exhaust.

Thanks for bringing this back cause it good reading and I have been very courious as of late. Keep us up to date.


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## Fox-N-It (Jul 23, 2003)

*Re: (fwdvw)*

So to get this strait.
41/34 valves will fit on stock seats but will need to be ground for seal?
I would need ABA/16v stem seals, ABA/16v retainers and ABA/16v keepers for the 7mm stem diameter?
What size valve guides? ABA/16v?
The 8mm Lightened retainers I'm using wouldnt work for this would they


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## Fox-N-It (Jul 23, 2003)

*Re: Oversized valves worth it? (vwnut82)*

Bump


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## ABA Scirocco (May 30, 2001)

*Re: (Fox-N-It)*


_Quote, originally posted by *Fox-N-It* »_So to get this strait.
41/34 valves will fit on stock seats but will need to be ground for seal? 

Yes, according to Colin at TT, bore the seats .060" oversized for a street engine and .070" for a race engine

_Quote, originally posted by *Fox-N-It* »_I would need ABA/16v stem seals, ABA/16v retainers and ABA/16v keepers for the 7mm stem diameter? 

For seals, yes either ABA or 16v seals will work, but for retainers and keepers it depends on the valves you're using, for the triple groove valves use ABA stuff and for single groove valves use the 16v stuff. The TT valves for instance are triple groove so with those you'd need to use the ABA retainers and keepers.

_Quote, originally posted by *Fox-N-It* »_What size valve guides? ABA/16v? 

Yes, either.


_Quote, originally posted by *Fox-N-It* »_The 8mm Lightened retainers I'm using wouldnt work for this would they








 
No, they wouldn't.


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## Fox-N-It (Jul 23, 2003)

Thanks thats mostly what I thought just good to have some conformation.


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