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Putting bigger valves in the WW okrassa heads
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Finnbarr
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PostPosted: Fri Oct 18, 2019 4:48 pm    Post subject: Putting bigger valves in the WW okrassa heads Reply with quote

Hello everyone,

I am building a 1397cc motor for my 54 beetle and I have the WW Okrassa kit.

I can get a local machine shop to machine the heads for larger valves and i have read in another post that 37mm exhaust and 32mm intake are about as big as you can go with-out welding.

So i have 2 questions:
1 - are these sizes correct ( it was an old post) so has anybody used these sizes?
2- where can i buy these size valves from ( i am in Australia so opportunity locally is very limited or at least my knowledge of retailers is )

I guess this question might have been raised before and if it has i am sorry to re-ask, but i could not find a post about this exact topic.

Any help you guys can offer up, is greatly appreciated.
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sled
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PostPosted: Fri Oct 18, 2019 7:20 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

maybe a more relevant question is do you really need 37x32?

37x32 will support a lot of horsepower from a MUCH larger engine with much better ports.

over-valving your engine and ports is not advantageous.
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PostPosted: Fri Oct 18, 2019 8:29 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Joe Ruiz" mr.okrasa" made /use to sell bigger intake valves try hitting him up ..and see if he still has any forsale he may help you ..
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Finnbarr
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PostPosted: Sat Oct 19, 2019 3:47 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

So 37 and 32 are too big for thid size motor.... now I know, that answers question one .... a follow up question would be .... if i am to go bigger valves than what's stock in the WW okrasa heads... what would be the right size to increase the valves to ? ... just looking for advise from the people who know more than I do ... just want to make my motor the best version of it, it can be ... any shared wisdom is appriacted.
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PeteSC
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PostPosted: Sat Oct 19, 2019 4:47 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

When Joe Ruiz built my 1397 we included his 35/33 intake exhaust valves. Joe has them custom made and does offer them for sale; I bought a 2nd set to have in my parts stash....reach out to him through here (username is Mr. Okrasa).

Image may have been reduced in size. Click image to view fullscreen.


Video of engine running at link below. It performs great, has about 4,000 miles on it in last year, and gets driven 2-4 times per week year around. I can’t say how much difference the valve mods make; I would presume with the 36 Dells (26mm vents) and Speedwell intakes that the larger valves are a benefit.

https://www.instagram.com/p/Bo4TsOsD8B5/?igshid=1afbqz3ob5pjb
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PostPosted: Sat Oct 19, 2019 11:59 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Thank you PeterSC ... really appreciate you sharing... very helpful
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Alstrup
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PostPosted: Sun Oct 20, 2019 5:21 am    Post subject: Re: Putting bigger valves in the WW okrasa heads Reply with quote

Hello.
To try and help clarify a little about valve sizing in the Oksasa heads I can contribute a little theory and experience.
As a general thought (from my side) the stock Okrasa/WW heads begins to work well with a little more displacement such as for instance the 80 mm bore over the std 77. This enables you to unshroud the intake vcalves juuuust a litle bit more than stock, which makes the intake valve works significantly better.

The 33 x 30 mm valve combination can easily support 80-85 hp in a functional street set up. (Race is different) It does however require the intake port to be good for the valve and seat. It also requires the intake valves to be lifted up in the 0,450 to 0,475" range to create enough flow and time area for the filling. In a 36 hp set up that kind of lift is a bit of a challenge. Not impossible, but it will require a little more than what the average tuner is prepared to invest in it.

Now, if we go back and look at what is, shall we say normal and easily obtainable valve lifts in these heads we typically end up in the 0,370 to 0,410" area. Now it makes sense to increase valve size to get closer to the desired time area to get the proper filling of the cylinder. In say a 80 mm bore the outer 8% of the valve will again be somewhat inefficient, but the increased area of the rest of the valve is still significantly better than the 33 mm valve, so you will need less lift to get to the same flow potential. Also, looking from a street engine point of view, as I have menthioned elsewhere, the intake port works relatively better with a 35 mm intake valve/seat, because the shape and port volume matches the larger valve better.

WRT the exhaust side. The 33 mm exh. valve is a little bit large for the set up, but as long as the cam duration stays low it doesnt matter that much. If cam duration is increased it will soon create an overscavenge situation which makes the engine less efficient and also harder to get in a proper tune. The exhaust system can of course compensate for this to some extent.
These observations are in relation with at least 2 sgl barrel carbs or better.

If you want to increase performance and driveability with a stock(ish) centermount carburettor and improved sgl ports you need to be very carefull not to make the exhaust side too efficient. Even the 33/30 valve set up can be enough, because at the end of the day the stock type intake manifold is very restrictive. The switch to a manifold from a 40 hp engine will give you the immediate potential of 4-6 hp more. That´s about it.
It is possible to pull 43-45 hp through a 40 hp manifold on a 1200 cc engine, but it requires A LOT of work and a healthy compression ratio. 7 years ago I built an experimental 1200 engine like that for a low light Ghia, keeping the stock cam, but changed the advance (retarded it a little) welded heads, 33 x 30 valves, 8,5 CR. homemade 1,1 rockers on intake, stock on exhaust. 40 hp manifold reshaped for the narrower engine, modified 28 mm PCI carb and gutted stock exhaust. This engine pulled a solid 44 hp but that was it. Not a lot for the work involved, but the engine runs well, looks stock and cruises nicely at 125 km/h on the Autobahn with a little power to spare for hills and the occasional overtaking, and that is what the guy wanted.

To the OP. With a 80 mm bore I would not recommend going with a 37 mm intake. 35 mm is plenty as to my explanation further up.
Hope this helps.
T
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Finnbarr
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PostPosted: Sun Oct 20, 2019 9:12 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Alstrup,

thank you ..... very helpful information, which was the sort of commentary I was hoping for.
I am relying on the knowledge of others and help from friends with this build , as i am learning my way when it comes to engine building.

I might not always ask the right question, but i seem to end up where i need to be in the long run.

Here is a list of whats going in my motor if that will help clarify any thoughts or comments from you and others: it might raise more questions too ? lol

36hp case going for 1397cc
WW 69.5 crank
WW Okrasa heads (not using the rest of the kit on this motor)
AA 80mm pistons and barrels
AA 5.110 connecting rods
Mr Motorhead stage 2 cam
DPR flywheel for 200mm clutch
Speedwell 1.25 ratio rockers
S&G twin carb manifiolds
Gene Berg Carb linkage
2 x 40 IDF carbs 26mm venturies
vintage speed exhaust
full flow oil & external oil cooler

Will be moving to:
CB Performance EFI with twin IDF style throttle bodies
CSP exhaust




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Mr. Okrasa Premium Member
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PostPosted: Sun Oct 20, 2019 10:55 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

PeteSC wrote:
When Joe Ruiz built my 1397 we included his 35/33 intake exhaust valves. Joe has them custom made and does offer them for sale; I bought a 2nd set to have in my parts stash....reach out to him through here (username is Mr. Okrasa).

Image may have been reduced in size. Click image to view fullscreen.


I have 1 set left available here:

Image may have been reduced in size. Click image to view fullscreen.

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VW www.Okrasa.com
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PostPosted: Mon Oct 21, 2019 1:11 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Alstrup-

I've been talking to my engine builder about valve sizes, but he's been hesitant to commit. He’s done a lot of Formula VEE and Porsche 356 work, but this will be his first set of Okrasa heads.

I’m using Porsche 356 crank & rods, and the bore will be 82.5 mm.

I’m planning on using Stefi.g’s Zenith 32 NDIX manifolds. If they don’t flow well enough I’ll consider switching to Speedwell manifolds & 36 DRLA’s.

I have a set of 1.4:1 Speedwell rockers. I’m hoping to hit .4” lift.

Once I have my flow numbers, I plan on going to Dima Elgin and have him grind a cam for my engine. I’m thinking of something like a 356 super cam. 5000 RPM would be max.

If I have to choose between max power and low end torque, I’ll choose torque. I want something that’s enjoyable to drive!

What size values would you suggest? 35/32? 35/30?

Cheers,

Paul
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PostPosted: Tue Oct 22, 2019 11:48 am    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

With dual carbs definitely 35 x 32 mm. Just have him aim for an I/E ratio of 70-73%
Dimitri makes good cams. - I did´nt think he was still active. He´s an elderly gentleman by now.
If you want torque over hp you probably do not want the 356 Super cam, because you will have trouble getting enough static compression unless you get a little creative. Bolt together with a 0,5 mm flycut is about 8,2. (Depending on what pistons you are going to use of course.) The super cam needs 9-1 to make decent torque. You will most likely like the 75 hp cam better.
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PostPosted: Tue Oct 22, 2019 4:42 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Alstrup-

Thanks! Your comments about Pre-A Super cams sound on target.

"The stock 1500 Super used a cam very similar to the later Super cam but ground on the early two-piece case billet...A call was made to Dema Elgin and he had two options, a 270 and 280 degree. The 270 was chosen because of the carb and exhaust limitations...A compression ratio of 9:1 was needed to match the new Elgin cam".

http://www.willhoitautorestoration.com/1500_super.php

Cheers,

Paul
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PostPosted: Wed Oct 23, 2019 1:54 am    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

I was toying around with Honda Goldwing valves in a 36hp head but never went anywhere with it.

https://www.thesamba.com/vw/forum/viewtopic.php?t=437391&highlight=goldwing

eQ

I just noticed the day I originally posted that, weird!
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PostPosted: Wed Oct 23, 2019 12:43 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

The 270 is the Porsche 102-16 grind with 0,320" lift at the cam. Yes it needs 9-1 to work well. He mosty likely grinds it on a lower LC to make it pull well in a smaller engine.
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PostPosted: Wed Oct 23, 2019 2:36 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Alstrup-

Do you know anything about the Elgin 66509-19 (AKA Maestro Grind) cam? The specs are somewhere between a normal and super 356 cam. I've read that it's very drivable, but starts to poop out ~ 4800 RPM. Elgin claims "excellent power from 1000-5000 RPM".

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And yes, I realize that the grind would have to be altered to work on a 2 piece billet. Wink

Cheers,

Paul
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PostPosted: Thu Oct 24, 2019 3:44 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

Hello.
Yes I am familiar with some of his grinds and works. For the vintage Porsche world his cams work well. With the Maestro cam. Have never used it myself, but a couple of my colleagues have. It basicly pulls the lower rpm power that a 356 SC should have done, pulls about the same hp as the 102-16 but cuts off significantly sooner. Doesnt pull as much over the curve.

I have used the 102-15 grind in a small 1200 with 33 x 29 mm valves and 8-1 CR with a modded 28 PCI carb. It had a somewhat rough idle and needed some timing at idle to do it within reason. The power was better than I expected. 2 years lateer the crank broke, so the guy swopped to a WW crank and kept the rest of the heart. This gave us about 8,5 CR. At the same time the induction was upgraded to 2 32 mm PCI´s and a 4 tip exhaust. That engine runs really well. It has never been dynoed, but I dare say a solid 45 hp with a very nice powerband.
I have used the 102-16 in a regular WW replica Okrasa engine with stock 7,5ish CR. It runs great as such, and most likely just about the way they did way back when, but it lacks torque. It is more of a rpm engine. It´ll do 80 mph no problem, but it takes time.

I have also used the 102-16 in a 74 x 77,20 engine, using NSU TT pistons to get more compression and a little narrower engine. That engine has 9-1 CR with slightly detailed Okrasa heads and 1,25 rockers added, and 32 mm PCI´s. This engine is a totally different animal. Everything seems to work so much better with the slightly larger displacement. Again, unfortunately no dyno time, but I wouldnt be surprised if it pulls 65 hp.

Whether it is 74 x 77 or 69,5 x 80 doesnt matter much I don´t think. That is merely a matter of where it peaks with power and torque within a couple of hundred rpms. The 35 x 32 valve combination will definitely work better with the 80 mm bore.

With the other Elgin cams. I have used the 7010-17 in 1720 cc´s with good succes. Loads of power for the engine size. (In fact I am to build a 1720 twin spark with that cam this winter)
The 7508-18 has been used in 1904 cc 912 based engines. Pulls well. Usually in the 130 hp area
Used the 7208-17 in another 1904, but this engine had only 8,7-1 CR. this engine was not worth writing home about. It may be the lack of CR compared to the recommended. It may be the grind that is not suited for the engine entirely, I don´t know. Ultimately it was taken apart again and we instralled the 7508-18 along with 10-1 JE pistons and off we went.

I sincerely hope Mr Elgin has a talented apprentice, because it would be a real shame if his knowledge should vanish.
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PostPosted: Fri Oct 25, 2019 5:53 pm    Post subject: Re: Putting bigger valves in the WW okrassa heads Reply with quote

I am doing a similar build to yours, and using the WW heads.
Whilst I don't intend to increase the valve size it has been recommended to me that I get a good cylinder head guy to go over them and probably relap the valve seats as they are perhaps a bit naff "as supplied"
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