The combustion chamber mods recommended by Vizard are very similar to the
difference between the standard and Holbay cylinder heads. The compression
ratio lost due to the increase in chamber volume can be recovered by using
flat top pistons in place of the 1725 dished pistons. The only other major
difference between the standard and Holbay head is the intake runner
diameter. The Holbay intake port is the same size as the standard exhaust
port.
I have a standard and Holbay head and am in the middle of building a new
engine with the Holbay head and Weber induction setup, the Holbay cam sold
by Sunbeam Specialties, .060 over flat top pistons, and the two piece
"early" exhaust header also from SS. In the interest of knowing our Rootes,
I am putting both the cylinder heads on the flow bench to reveal the
differences. I expect for this to happen within the next month or so. I
will post the results to the list. I am also planning to put the finished
engine on the dyno. I will post those results as well.
Tom Hill
-----Original Message-----
From: owner-alpines@autox.team.net
[mailto:owner-alpines@autox.team.net]On Behalf Of Barbara Blue
Sent: Wednesday, March 07, 2001 7:40 PM
To: Jarrid Gross; alpines@autox.team.net
Subject: Re: More Power from the 1725
Yep, Mr. Vizard admitted you loose compression reshaping the combustion
chamber. He claims the object is to make hp, not have a high compression,
so it is more than worth the trade off.
Webbers expensive, you bet your bippy! I think that's why they were not
highly recommended, as the whole article came off as a low buck way to
enhance the 1725.
BLOCK No more than 40 thou overbore! Why? Gee Jarrid, I was hoping you
would explain that one to me!
I thought that for $200 you could get a new head gasket, and with a LOT of
sweat equity, do the head job. $50 for a cam grind similar to the SB2, some
unidentified exhaust mods, and you would be on your way. His did not
propose reving over 6500, which he claims the stock valve train can handle.
>From my limited experience with cams, I would think the Alpine valve train
could handle the SB2, and from what I have seen on the computer, the SB2
doesn't care to go over 6000, anyway. Don't know any of this for a fact,
though. I know all about what a person "ought to do". The next thing you
know, all you have left of the original engine is an expensively modified
block.
Glad for your comments.
Bill
----- Original Message -----
From: "Jarrid Gross" <JGross@econolite.com>
To: "Barbara Blue" <the_blues@worldnet.att.net>; <alpines@autox.team.net>
Sent: Wednesday, March 07, 2001 7:39 PM
Subject: RE: More Power from the 1725
>
>
> >HEAD Reshape the combustion chambers.
>
> Yeah but you loose compression here.
>
>
> > Skim head 60 thou
>
> To make up for the loss in compression due to combustion chamber mods.
>
>
>
> >CARBS Stromberg 150's for street use.
> > Weber 28/36 is smoother, slightly less hp. Not recommended
> over
> >the Strombergs
>
> Totally disagree here, constant depression carbs are more restrictive
> than conventional carbs. This due to the spring loaded and gravity
> loaded venturi pistons that must be lifted by partial manifold vacuum.
>
> The weber 28/36 flows enough to make 120BHP.
> 150CDs are at thier limit on a 1725.
> Volvo 1800s used 175CDs, as did the TR7.
>
> If you want real bolt on potential, get the 32/36 DGEV, or better yet
> a 40/40 DGAS.
>
> Either will add flow potential and are a set and forget affair.
>
>
>
> > Weber DCOE 40 for ultimate power if camshaft is modified
>
> Yes of course, but this is the most expensive mod short of building
> a hot shot motor.
>
>
> >BLOCK No more than a 40 thou overbore!
>
> Why?
> Bigger pistons means more than just more displacement.
> It also adds compression ratio.
> .060 pistons are available, and if you have a tired .040 I wouldnt
> hesitate to overbore to .060, I mean, what do you have to lose?
>
>
> >Using Webers on the 1600, he claims 100hp without the Holbay camshaft!
It
> >appears that with a hotter cam, a person can get really nice results for
> >something like $200.
>
> I dont know what you could do with $200.
> You could grind a cam I suppose, but that is an incomplete proposition.
> Along with the cam are a great deal of other things that "ought" to get
> done to, and by the time you are done, it will cost $1500 to make
> an honest 100BHP.
>
> Hosepower costs money, and its a log curve.
>
> You first 92 BHP costs $1200 (basic rebuild).
> The next 10 adds $300 (cam and port work)
> 10 more adds about $600 (more head work, real pistons).
> 10 more adds about $1200 (carrillo rods, light piston pins, dynamic
> balance).
> 10 more adds about $2400 (big valves, and light springs, serious head
work).
> 10 more adds about $4800 (lightened flywheel, tilton clutch,destressed
> block, multi-stage oilpump).
> The costs go on and on....
>
> I'd say that a 150BHP alpine motor would cost at least $5000.
> 175BHP perhaps $10000.
>
>
> BTW, the 150BHP holbay rally special used a stroked 1725 engine with a
> billet steel crank,
> an E128 camshaft, cast flat top pistons and twin webers.
> This engine displaced 1840cc, and was good to 7000 RPM.
> The last time the package was available the crankshaft itself cost
something
> like $3500 USD.
>
>
> Jarrid Gross
|