Mythbuster: continuing project thread of my 1303 '75

[70Turbobug]

So Walter, if I am reading between the lines correctly...you´re planning on a larger engine?

[Wally]

Originally Posted by effvee

Hi Walter, I have noted your up-grades and congrats. Question, when is enough on your current engine, before you have a major failure? You have done very well, I'd hate to see you engine let loose.

I hear you! But that is also the nature of me: I'd like to improve untill I think there is no gain to be had. And imo there are still loads of thinks to improve upon and the type 4 case is much stronger than 400 hp. Swedish lunatics (and I mean this in a kind way ) have gone 600+ on the type 4 casing with a drag-race-only engine, so I think there are possibilties to extend that to track-driving with a little less hp, but for longer duration

The car itself is still very drivable too. Its not scary when you step on it, so also because the handling can handle it, I think more power is possible.
If I can keep it 'in tune' (and I am getting rather well at this, even if I say so myself), there is no reason it should break with more hp, although I am getting more and more surprised the alu cylinders keep up

Another thing to consider: this (much) bigger turbo is more gentle on the engine at comparable boost then the smaller turbo was due to lesser backpressure...
So more power at less stress for the engine! How can you pass up on that?

[Wally]

Originally Posted by 70Turbobug

So Walter, if I am reading between the lines correctly...you´re planning on a larger engine?

Of course! But that will take a while as its a lot of $$. The stroker crank however has already been 'heat treated', a forged (stock 914) flywheel seems to be able to be used for 228mm enlargement and a set of 'virgin' 914 2.0 heads is in storage for some time already to get the 'treatment' once funds are available
After all, the current engine was only made from left overs of the 2,7 carnage and therefore not 'all i can be'...

[70Turbobug]

Sounds good! I think the heads you have now will do just fine.Or are planning with bigger valves and welded ports,etc.? You could sell your current engine,that would give you enough money for the next build.I´m sure you would find a buyer for it.

[Wally]

Originally Posted by 70Turbobug

Sounds good! I think the heads you have now will do just fine.Or are planning with bigger valves and welded ports,etc.? You could sell your current engine,that would give you enough money for the next build.I´m sure you would find a buyer for it.

I agree: the current heads flow well, even with just 0,500" valve lift. The 'new' set would be about the same, but with a tiny bit more porting, maybe Be-seats and upgraded valve train package. They would have a little more beef left in the heads as I would start with virgin heads and like a bit more CR, so they would get a little better in all aspects. Then a cam with more lift and you have more potential. At least thats my thinking.

I don't think I want to sell the current engine as I can use lots of its parts from it and I am VERY curieus how its looks on the inside. Only if I can see what it looks like will I be able to judge how well certain solutions have worked out.
But thats all in the far future due to $$ needed

[70Turbobug]

I wanted more "beef" on the exhaust ports,since that is a weakspot imo.That´s why I chose the CU heads.They have a thick chamber and enough room for big valves.The square ports allow a better seal at the header.I´m also curious what your motor looks like inside,mainly the cam and lifters.The crank and rods will be fine I´m sure and should show little wear.I´m anxiuos to see what size engine you will build.

[effvee]

Originally Posted by Wally

Then a cam with more lift and you have more potential. At least thats my thinking.

Walter, in regards to more cam, how about a set of Pauter ratio rockers in the mean time. I believe that would allow a sort of more cam/results for a short investment. And later you can still use the ratio rocker in your next build?

[Wally]

Originally Posted by 70Turbobug

I´m also curious what your motor looks like inside,mainly the cam and lifters.

I have DLC'd the tool steel lifters from Thorsten, so the lifters are the least of my worries
Personally I would like to see how the pistons are wrt skirts in relation to the clearance they had and of course the head seal

[Wally]

Originally Posted by effvee

Walter, in regards to more cam, how about a set of Pauter ratio rockers in the mean time.

That would give too much lift with this cam... its a fine balance

[1302 S]

Hello Wally
I like your combination of short stroke and large bore in your engine. And it seems to be very realibly, you have realy succeeded.
I have read your thread but I cant find what valve size you use in your heads? I could have missed something....

// Anders

[Wally]

Originally Posted by 1302 S

Hello Wally
I like your combination of short stroke and large bore in your engine. And it seems to be very realibly, you have realy succeeded.
I have read your thread but I cant find what valve size you use in your heads? I could have missed something....

// Anders

Its 46x40mm

[Wally]

Slowly but surely the new parts for the new intake and exhaust side are coming together:





Changing the springs to CB650:


The double Berg springs had 3 saisons on them and were VERY much down on spring pressure, so this was/is a good thing to do either way.

[paul_f]

Nice one Wally! Did you put rope inside the cylinder to hold the valve or did you use air pressure?

Great idea with the jubilee clips, that would made it much easier for me if I had thought of that!

[Wally]

I used air pressure Paul. Killed an old compression measuring device for that a few years ago

[Wally]

The Berg double springs were about 35% down on spring pressure

Check your springs after about 2 years of driving I'd say...

Anyways, back tp building the twin scroll header:
Trial fitting: