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Engine out...what next
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RichardinNZ
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PostPosted: Tue Aug 28, 2012 2:14 pm    Post subject: Engine out...what next Reply with quote

I have the 36hp out of the '58 Bug and will be taking the heads off to fit new push rod tubes and seals. I will be adding twin 28pci carbs on express manifolds and a 019.

Is there anything else I could do whilst the headsa are off. Should I be looking to increase the compression ratio?

Thanks
Richard
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Kjell Roar
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PostPosted: Tue Aug 28, 2012 2:23 pm    Post subject: Re: Engine out...what next Reply with quote

RichardinNZ wrote:


Is there anything else I could do whilst the headsa are off. Should I be looking to increase the compression ratio?

Thanks
Richard


Yes, if you want more power. Quite easy engineering job for those who can. The intakes in the heads also should have a little port-job to flow better.
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PostPosted: Wed Aug 29, 2012 4:18 pm    Post subject: Reply with quote

How about some basic work, such as-
-chasing all threads on your head's exhaust studs (M8 x 1.25mm) and those for the intake manifold studs (M6 x 1.0mm, I think)
-replacing all exhaust valves as a precaution, and lapping the new ones to the seats
-chasing the heads' spark plug threads with a threading tool/restorer
-pre-stretching the new pushrod tubes to the factory spec, cleaning them with solvent or brake cleaner spray; then painting them with flat-black paint
-having the heads cleaned with solvent, then bead-blasted
-measure your heads' combustion chamber volumes as a baseline for determining your compression ratio
-measure each piston's deck height
-verify that the two cylinder's top surfaces are level and flat on each side of the engine
-check each valve spring for presence of rust blisters, and replace if found
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RichardinNZ
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PostPosted: Thu Aug 30, 2012 1:20 pm    Post subject: Reply with quote

Thanks for the help; will try to speak to some people here about a suitable machine shop. Also considering adding large intake valves at the same time, despite trying to keep my costs down!

Richard
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RichardinNZ
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PostPosted: Mon Sep 10, 2012 5:53 pm    Post subject: Reply with quote

Can anyone offer advice regarding the bigger intake valves? I'll be running 2 x 28PCI carbs and wonder whether I should add 33mm intakes?
Thanks
Richard
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Kjell Roar
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PostPosted: Tue Sep 11, 2012 3:09 am    Post subject: Reply with quote

RichardinNZ wrote:
Can anyone offer advice regarding the bigger intake valves? I'll be running 2 x 28PCI carbs and wonder whether I should add 33mm intakes?
Thanks
Richard


You can take up the original seat insert to 27mm (from 25 original) and still use the original valve. That wil probably be enough for a nice daily driver with 28 PCI's.

The Okrasa-set got 33mm IN valves, with 28 inner in the inserts, and you can probably put in an Okrasa-valve and take up the original insert to 28 mm. If you want more, you need bigger carbs.

But I hope someone can confirm that the Okrasa-valves can be used that way. I just talked to a guy who is a specialist in valve seats and porting (not much VW), he said it would work. As long as the insert's outer is not smaller than the valve, it should work, and get the angels right. But he didnt want to go any wider than 28-29mm without putting in bigger seat inserts.
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RichardinNZ
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PostPosted: Tue Sep 11, 2012 12:54 pm    Post subject: Reply with quote

Thanks for the information; I've been to see a cylinder head specialist who (although not a VW specialist) instantly recognised them as 36hp heads...so I'm feeling confident in him! He is going to open up the seats on the intakes and hopefully we can use the 33mm valves.

Flycutting...is 2mm usual? Does anyone know what compression this gives with otherwise stock heads?

Thanks
Richard
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PostPosted: Tue Sep 11, 2012 1:38 pm    Post subject: Reply with quote

If you cut 3mm, you get around 37cc in the head instead of 45-47cc, and you will get 8.2:1 comp. with deck height around 1 mm. I think original deck height is 1.25 mm. will give 8:1.

Back in the 80'ies, I heard that 2.5 -3 mm was a good maximum cut, for a street engine.

Engine calculator:

http://cbperformance.com/enginecalc.html

I am planning my own 36 hp engine, will try to build it next year. Have saved up some parts for it, so its soon time to start building it.
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RichardinNZ
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PostPosted: Mon Oct 08, 2012 12:20 am    Post subject: Reply with quote

OK; moving forward now that my parts have arrived (thanks Mr Motorhead). The heads are at the head specialist; as I mentioned he recognised them as 36hp but isn't a VW specialist and I'm far from an expert too! He says that if they were later heads he'd (my words) flycut the face and also in the bore...both by a similar amount. But what about the recess for the copper rings that sit around the barrel. Are these needed and how accurate do they have to be? It'll add more labour time to have them and therefore more cost!

Thanks
Richard
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RichardinNZ
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PostPosted: Mon Oct 29, 2012 11:32 pm    Post subject: Reply with quote

Heads back...2mm flycut and 33mm intakes in new seats. Measure at just under 41cc which gives me about 7.5:1 compression ratio. Also installed new exhaust valves and new exhaust guides. I won't use copper rings around barrels (and no heater) so didn't need to machine for these. Hope to get the heads on and engine reassemled at the weekend, mock up the manifolds and carbs and work out the linkage and try to get the correct jets for the carbs....see my other posts!

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

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

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PostPosted: Tue Oct 30, 2012 2:15 pm    Post subject: Reply with quote

Nice pictures! I like that your getting a little quench in to the combustion chamber when you flycut some more, which helps too Wink
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RichardinNZ
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PostPosted: Wed Dec 05, 2012 6:08 pm    Post subject: Nearly complete! Reply with quote

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Mr. Motorhead
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PostPosted: Wed Dec 05, 2012 11:36 pm    Post subject: Reply with quote

Nice, Richard! Have you taken it for a spin yet?
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PostPosted: Thu Dec 06, 2012 12:45 am    Post subject: Re: Nearly complete! Reply with quote

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

That looks great. Any picts of the linkage and what did you use? I have a set of 30 manals that I have been looking into building some manifolds for.
I really like what you have done here. Cool
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RichardinNZ
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PostPosted: Thu Dec 06, 2012 2:20 am    Post subject: Reply with quote

A few bits and pieces to complete; may be out for a spin at the weekend but very busy on other things at the moment. Can't wait, but also very pleased with how it looks (the Mr Motorhead stacks set it off).

Will post some linkage photos next week....

Richard
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RichardinNZ
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PostPosted: Thu Jan 03, 2013 9:35 pm    Post subject: Reply with quote

OK...made no progres on this as have hit some problems and have had little time to look at it....I have no compression! The barrels don't seem to be sealing in the heads although there appears to be good clearance between the fins/face of the head and the barrel. To ensure this is the case I have clearanced this part of the head further (many hours carefully cutting a step in the head around the barrel area with a dremmel).

I'm wondering whether the push rod tubes are too long and pushing things apart? Compressed they measure 152.5mm. The official manual states that uncompressed they should be 154/155mm on stock engine...does anyone know what they compress to usually (with stock, non-skimmed heads) as mine should be compressing to 2mm shorter than this I guess?!

Many thanks
Richard
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PostPosted: Sat Jan 05, 2013 2:26 pm    Post subject: Reply with quote

Push rod tubes should not bee the problem, I cut my heads 3mm without any tube problems. Good luck with finding your troubble.
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RichardinNZ
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PostPosted: Sun Jan 06, 2013 12:18 am    Post subject: Reply with quote

Hi Bengt
Thanks for that; very helpful. Will look elsewhere now!! Will track down the problem soon.
Richard
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Flavio
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PostPosted: Sun Jan 06, 2013 3:30 am    Post subject: Reply with quote

Hi Richard
Are you sure that the pushrod tubes you have are the correct 25/36 Hp ones ?
Flavio
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PostPosted: Mon Jan 07, 2013 12:57 am    Post subject: Reply with quote

Hi Flavio
Yes...correct ones.

Will post again at the weekend when I have done some investigating!!
Thanks
Richard
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