4 cyl engine advice needed

[Tedscj at aol.com]

In a message dated 2/20/99 7:14:41 AM Eastern Standard Time, jguest at clara.net
writes:

> >You know, you can do a lot with those series B 4cyl engines.  Vizard has a
>  >good and extensive book on modifying the A series motor.  The B series (
> which
>  >is what you've got) is just a larger version of the same thing.  100hp is 
>  >easy
>  
>  Does the B-Series not have a cross flow type head on it?
>  
>  >enough to get out of a 1275cc A series, so I'd imagine you could get close
> to
>  >140 from your engine.  And you don't have to spend a lot of money.  The 
>  >key is
>  >a lot of work on your cylinder head (the information on how to do it is
>  >already out there.  You don't have to reinvent the wheel.)  And a VERY
HIGH
>  >compression ratio.  Like 12 to 1.  No problem on 91 oct.  Stock CR is, I
>  
>  Excuse my ignorance but I thought you could only run those sort of CRs 
>  with AVGAS or other such fuels. Is 10:1 about the best you can do on 91 
>  oct? Or is them some other means of preventing detonation at high CRs. 
>  Apart from backing off the ignition (bad for power output?)
>  
>  >think,  7.5 for a rubber bumper car like yours, which is pitiful 
> considering
>  >how much this engine can take, even with street gas.
>  >I think the saying goes "if you can't get the air in there, then squeeze 
> the
>  >hell out of what you got!"
>  >
>  >Ted
>  >
>  >
>  
>  Regards Justin



No, the B series engine does not have a crossflow head.
The reason you can run such a high compression ratio is that there is a
difference between the "geometric" compression ratio and the actual pressure
in the cylinder .
A whole bunch of factors determine the sort of "geometric" compression ratio
that one can use in an engine.  Like it's natural immunity to detonation, for
example.  In the case of the "a" and "b" series engines, it is the fact that
you can't get much actual air into them, therefore the actual cylinder
pressure is rather low compared to it's geometric ratio.  The actual cylinder
pressure is what you need to be concerned with.  Different "Geometric"
compression ratios can have different affects in different engines, though
they tend to be similar in most engines.

Ted