400 pistons

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pedro
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400 pistons

Post by pedro »

I have seen two different types of 400cc pistons, one with the valve cut outs and squish area similar to a 350, the other with an open bowl type of combustion chamber with the raised area only around the edges. Can anybody enlighten me about these pistons please.
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MarkB
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Re: 400 pistons

Post by MarkB »

My Sport has the 'open bowl' type, although nobody's been able to identify them. The conversion was done by Alex at NLM about 20 years ago. The engine certainly pulls well!
"I'll have a V please, Bob."
pedro
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Re: 400 pistons

Post by pedro »

Interesting Mark, I would imagine that the compression ratio must be considerably lower with the open bowl (for want of a better description)
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MarkB
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Re: 400 pistons

Post by MarkB »

You must be right, Pete. Now that the engine's been rebuilt I'll give it a compression check.
"I'll have a V please, Bob."
harrymuffin
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Re: 400 pistons

Post by harrymuffin »

Are you going to pipette it?
MickeyMoto
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Re: 400 pistons

Post by MickeyMoto »

... I only have two... :)
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72degrees
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Re: 400 pistons

Post by 72degrees »

harrymuffin wrote:Are you going to pipette it?
You are the ghost of Phil Irving and I claim my five pounds ;)
harrymuffin
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Re: 400 pistons

Post by harrymuffin »

You won, the only person who a)knows who Phil Irving and B) knows what pipetting is. You follow up questions what engine did he design/ modify that won two world Formula 1 champion ships, where did he learn about motorcycle engines and which engine did he do most of the design work that was also a Vee Twin and his nationality?
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72degrees
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Re: 400 pistons

Post by 72degrees »

harrymuffin wrote:You won, the only person who a)knows who Phil Irving and B) knows what pipetting is. You follow up questions what engine did he design/ modify that won two world Formula 1 champion ships, where did he learn about motorcycle engines and which engine did he do most of the design work that was also a Vee Twin and his nationality?
I have a well thumbed copy of "Tuning for Speed" on my bookshelf. On page 3 he talks of using a burette but I imagine a suitable pipette would be easier with the engine still in the frame. I'm not sure about all of your questions but if I remember correctly he was heavily involved in Vincents.

I know a 'compression tester' won't tell the whole story but out of interest, what sort of PSI would you expect from a well screwed together 350 Sport (with standard cam) in tip top condition?
harrymuffin
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Re: 400 pistons

Post by harrymuffin »

The compression test and actual compression ratio depends on when the inlet valve closes so if you have a cam L5 then your actual CR will be lower and subsequently so will be the pressure compared a standard engine when you perform a compression test. Regarding the the Morini I would think 150 - 170 would be good for a well used engine, but what is important is that the pressures on each pot are within 10 -15 of each other, I am more than happy to be corrected on these pressures so maybe people should get measuring and a sore thumb approximation could be ascertained for people to go by. As you know owners of Velocities would perform a compression test by standing on the kick start and seeing how long the pedal would suddenly go down. I do remember a long time ago when after putting in a fast road cam into my Cooper 'S' the compression pressures were lower than the with the standard camshaft, but it did go better once the revs were up.
The answers to my questions is yes he did do the design and development on the Vinnie, he converted the Buick/Rover 3 1/2 ltr V8 to 3ltr (and the 2 1/2 Repco Tasman engines) and designed SOHC Heron heads for the engine when working for Repco, he served his formative years at Velocette working on the SOHC, DOHC and Roarer engines and he is (or was) Australian. He admitted that after the second championship win and the engines producing around 360bhp that unless the heads are redesigned that engines with Heron heads were at their maximum development. This equates to about 120bhp/litre which is about what the sport engine produces on exaggerated Italian horses and the 7ltr Jaguar V12s were producing, I think they had about 600ish bhp. Most of his public known work seems to based on V's and Heron headed engines.
harrymuffin
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Re: 400 pistons

Post by harrymuffin »

P.S. You can only really achieve a meaningful compression test if you can get the engine to freely turn over at cranking speed, so I don't know how you would do it with a kick starter unless you do one pot at a time with it running on one cylinder by freewheeling down a big hill in 2nd gear or on starter rollers.
pedro
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Re: 400 pistons

Post by pedro »

OK Fella's, Interesting, but does anybody know anything about 400 pistons please?
What did Morini use in the 400 Dart?
I have heard that one of the models was deliberately de-tuned and was slower than the 350, it's something that I would like to know the answers to, I know so far that Mark has the open bowl type pistons and that Jem has the original (Asso) type but larger. Can anyone help?
There are definitely two types at least out there.
Steve Brown
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Re: 400 pistons

Post by Steve Brown »

pedro wrote:OK Fella's, Interesting, but does anybody know anything about 400 pistons please?
What did Morini use in the 400 Dart?
I have heard that one of the models was deliberately de-tuned and was slower than the 350, it's something that I would like to know the answers to, I know so far that Mark has the open bowl type pistons and that Jem has the original (Asso) type but larger. Can anyone help?
There are definitely two types at least out there.
I think the detuned 400 would have been for the German market where they had/have? a 27ps (hp) class for insurance purposes. Sadly I can't say how it was detuned, vielleicht weisst Norbert die antwort?

Would the pistons you have be the Volkswagen ones that are mentioned here from time to time? And are there no markings inside the piston that may help identify them?
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morini_tom
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Re: 400 pistons

Post by morini_tom »

The 400 dart had 'proper' heron pistons, like the 350, in a 66mm nikasil bore.

The factory claimed only a 1hp increase (36hp) for the 400. But they were 'detuned' with smaller valves (for the Japanese market I believe).

So 400 dart pistons and barrels with 350 heads would be the way to go.

Unsurprisingly, finding 400 dart pistions would be near on impossible
pedro
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Re: 400 pistons

Post by pedro »

In a web conversation with an Italian ebay seller, we were talking about 400 pistons and I got the following reply, might be worth contacting them to see if a batch could be made if enough people were interested.

my friend Paolo says that asso pistons aren't avaiable from years. He says that few years ago he gave the drawings to http://www.woessner-he /start/

Apparently they made him half a dozen some years back, all gone now.
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