[DeTomaso] 351 C Compression Question

[Göran Malmberg]

I also heard the same gossip from I dont know who. It probabley also has
some reality in some aplication for back up. However, myself I did grind the
closed chamber head up in a similar fashion to that of the Kaase head, but
this was not backed up by any dyno numbers.
It is also possible to fabricate good piston domes for the open-head that is
pushing up the charge closer to the plugg. We usually bought "blank" top
piston to make our own dome design at the time.
Goran.

----- Original Message ----- 
From: "tony DiGiovanna" <tonydigi at optonline.net>
To: <cengles at cox.net>; <JDeRyke at aol.com>; <detomaso at realbig.com>
Sent: Wednesday, December 10, 2008 5:12 AM
Subject: Re: [DeTomaso] 351 C Compression Question


>I had one engine builder say it was his experience that he could get more
> top end power out of open chambered Cleveland heads than closed chambered
> Cleveland heads, presumably from less valve shrouding that ensues. 
> However
> low end performance is often less due to decreased cylinder turbulence
> during compression.
>
> Opinions are like a......
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com
> [mailto:detomaso-bounces at realbig.com]On Behalf Of cengles at cox.net
> Sent: Tuesday, December 09, 2008 10:06 AM
> To: JDeRyke at aol.com
> Cc: detomaso at realbig.com
> Subject: Re: [DeTomaso] 351 C Compression Question
>
>
>
> Dear Jack and Tom,
>
> I have in my files an article from some hot rod magazine about two 
> allegedly
> comparable and similar 351C engines. One was built with quench heads and 
> the
> other was built with open chambered heads. They alleged that the open 
> heads
> made almost as much power as the quench heads. Interesting. It goes 
> against
> conventional wisdom. It might be true and it might not. I have been 
> educated
> that the dyno "tests" in many publications bear as much similarity to the
> real world and does the view from government! My suspiscion is that 
> properly
> chosen components can permit reasonable power from open heads, but less 
> than
> quench.
>
> Warmest regards, Chuck Engles
>
>
> ---- JDeRyke at aol.com wrote:
>>In a message dated 12/8/08 12:30:48 PM, tborcich at msn.com writes:
>>
>>>I have read conflicting reports that the Open Chamber heads had better
>>>flame travel because the plugs were not shrouded the way the quenched
> chamber
>>>plug was, but I have also read that the open chamber head was more
> susceptible
>>>to detonation.
>>>
>>Engine builders know a lot more about flame travel etc now than they did 
>>40
>>years ago, thats forsure. The open chamber is in fact more suceptible to
>>detonation, so you must back off ignition advance to compensate, and that
> ireduces
>>the power output. But the main power builder is the compression ratio, and
> with
>>an open chamber, its not physically possible to get much compression 
>>unless
>>you use domed or lumpy pistons. And once thats done, the dome or lumps
> changes
>>the way the flame front propagates- usually for the worse. Its all quite
>>exotic and for our old motors, what it mostly means is, one just can't get
> enough
>>power outa open chambers without a whole lot of trouble, dyno-tuning and
>>expense (like adding a blower). But even an amateur like me can get cheap
> power out
>>of a closed chamber head.
>>As for the dished piston, my August build '72 engine had cast flat-tops,
>>which I still have around in my shop, along with the original open chamber
> heads.
>>My understanding is, dished pistons weren't used until the smog laws got
>>really restrictive in late '73 thru '74, for the last run of Clevelands in
> the U.S.
>>Cheers- J Deryke
>>
>>
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