61 replies to this topic

[EunUCh]

The math seems to be correct,,I would think 295bhp at 7k @ .9 VE would be
a reasonable target to aim for.
Roller cam would probably be nice but they dont come cheap.
400 hp is almost 100hp/litr on 253,,it can be done but comes back to $$
If i read correct this is a "sort of" give a go budget build,and why not give it a go!
I doubt if the hq racing boys an girls will give out too much on what makes
the 253 go a bit.
Compare the 2o cylinder vol. to the "fitty 3",,there is about 2 ci difference.
Then compare valve/throat/port size.
I am sure i saw a thread somewhwere on air speed.

[Struggler]

400 hp out of a 253 is up there, But I think its achievable, sure I have some hurdles.
I also have VT heads with 58cc chamber for better compression if need.
Not sure about your formula though ? If my 355 is using 2414000 cubic inches of air per minute which ( if I am rite ? ) = 1396.990 CFM. All this threw a 750 carby ?
Thanks

As Bomber said, Holley carbs are rated at a pressure drop, which they need to draw fuel.

Don't get too tied up in the maths, it was just a quick way to illustrate how hard you need to spin the smaller engine to ingest the same amount of air and therefore, theoretically, produce the same amount of power.

Personally I don't like VN heads on 304/308's, much less on 253's due to the large port volume. Its even worse when you dont have a long runner intake like the stock bunch O' bananas.

Anyway, build it, rev it and have some fun !

[ACJ]

Sorry, I don’t mean to be Skeptical about your thoughts as I take it all on bord, archerley I love it. It’s a good way to learn.
Probably you are right with the VN heads to, but if I come away and other with more knowledge its all good to.
Some times it hard to determine good advice from crap.
But the best advice is, build it, rev it and have some fun !
And yes the bigest hurdle for me is “give it a go budget” and use as many bits as we have
Thanks

[rodomo]

Stuff and links in here relating to Commodore Cup engines: http://www.aussiev8....-253-specs.html

These I think? are from an old post on this forum.

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Edited by rodomo, 15 January 2012 - 07:16 AM.

[ACJ]

Thanks rodomo, I have read both article. Good food for thought.
What about you, have you made a start yet ?

[Struggler]

Sorry, I don’t mean to be Skeptical about your thoughts as I take it all on bord, archerley I love it. It’s a good way to learn.
Probably you are right with the VN heads to, but if I come away and other with more knowledge its all good to.
Some times it hard to determine good advice from crap.
But the best advice is, build it, rev it and have some fun !
And yes the bigest hurdle for me is “give it a go budget” and use as many bits as we have
Thanks

No problem !

I hear what your saying about internet advice..... I could have no idea !

Looking forward to seeing how it turns out.

[makka]

Crank the compression up and run it on e85, and bore it .060 or more, .060 will give you 261 cubes

[EunUCh]

Got to admit that numbers can become a bit over whelming and boreing at times.

But sometimes having even a small ammount of theory from all quaters we can build a bit
of an idea of where to go.
In the past we tried to get everyones input even if it sounded like utter bullshit at the time
and then build a bit of a "mental" model of what we were trying to gain.
Sometimes the most ridiculous suggestions when mixed up,shaken(but not stirred) and let to settle
ended up being a starting point.
On a budget,,,got to give credit for givin it a go,good on ya,,not many would bother.

[Rainman]

So old thread, what happened Adam ? Did anything happen ?    Ray