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perf-list Digest Tue, 29 Aug 2000 Volume: 2000  Issue: 133

In This Issue:
Re: Ignition options & also pinging
Re: Ignition options & also pinging
Re: Ignition options & also pinging
Re: Ignition options & also pinging
Re: Ignition options & also pinging
Re: Ignition options & also pinging
Re: [compression ]
A/F ratio tester
Re: Ignition options & also pinging
Re: Ignition options & also pinging

----------------------------------------------------------------------

From: "Dave Resch" <Dave.Resch sybase.com>
Date: Tue, 29 Aug 2000 09:59:00 -0600
Subject: Re: Ignition options & also pinging

Yo Derrick:

I just wanted to add a little more info to Tom's post.

The formula for compression ratio is SV/CV+1=CR

where SV is swept volume and CV is clearance volume.

SV = cylinder volume displaced by piston: ((pi*r^2) * stroke), where r is
bore/2.

CV = (combustion chamber volume + head gasket volume + deck clearance + piston
top relief)

Head gasket volume is calculated like volume of a cylinder, and height of the
compressed gasket is the cylinder height.

Deck clearance can be calculated by (deck height - (crank throw + rod length +
piston compression height))

Crank throw = stroke/2

Piston compression height is the distance from center of piston pin to the top
of the piston (not counting any dome).

Piston top relief is an important factor in determining clearance volume.
Unless the piston top is totally flat (i.e., no valve relief), you need to
determine the relief volume.  That (and compression height) should be in the
piston specs.

You need to have all these numbers to accurately determine the static
compression ratio.

Dave R (M-block devotee)



------------------------------

From: "Jeff Keahey" <Jeff airboatfanatics.com>
Subject: Re: Ignition options & also pinging
Date: Tue, 29 Aug 2000 12:58:00 -0500

The formula SV/CV+1=CR is only good if you have an RV type cam or can
guarantee that bother valves are never open at the same time. My Ch# 350
was running 12.3CR but with the cam I had, it would run on reg unlead. Most
aftermarket cams will have both valves open to sweep out burnt gasses
completely and therefore you loose compression but gain efficiency.
Compression is a good place to start when figuring parts for a rebuild but
you can go much higher than the regular limits with the right cam. Cylinder
pressure is more the "tell tale" measurement that will determine output. I
am rebuilding my Ch# 350 now and am going back down to 11.5:1 domed piston
with a smaller cam(but not much) and I would assume my cylinder pressure
will be about the same. If you have any question the cam manufacturer can
clear up what an estimated CR would be for a particular cam.

Jeff


----- Original Message -----
From: "Dave Resch" <Dave.Resch sybase.com>
To: <perf-list ford-trucks.com>
Sent: Tuesday, August 29, 2000 10:59 AM
Subject: [perf-list] Re: Ignition options & also pinging


> Yo Derrick:
>
> I just wanted to add a little more info to Tom's post.
>
> The formula for compression ratio is SV/CV+1=CR
>
> where SV is swept volume and CV is clearance volume.
>
> SV = cylinder volume displaced by piston: ((pi*r^2) * stroke), where r is
> bore/2.
>
> CV = (combustion chamber volume + head gasket volume + deck clearance +
piston
> top relief)
>
> Head gasket volume is calculated like volume of a cylinder, and height of
the
> compressed gasket is the cylinder height.
>
> Deck clearance can be calculated by (deck height - (crank throw + rod
length +
> piston compression height))
>
> Crank throw = stroke/2
>
> Piston compression height is the distance from center of piston pin to the
top
> of the piston (not counting any dome).
>
> Piston top relief is an important factor in determining clearance volume.
> Unless the piston top is totally flat (i.e., no valve relief), you need to
> determine the relief volume.  That (and compression height) should be in
the
> piston specs.
>
> You need to have all these numbers to accurately determine the static
> compression ratio.
>
> Dave R (M-block devotee)
>
>
> =============================================================
> To  unsubscribe:   www.ford-trucks.com/mailinglist.html#item3
> Please remove this footer when replying.
>
>


------------------------------

From: "wish" <wish ford-trucks.net>
Date: Tue, 29 Aug 2000 17:35:49 GMT
Subject: Re: Ignition options & also pinging



>The formula SV/CV+1=CR is only good if you have an RV type cam or can
>guarantee that bother valves are never open at the same time.

Actually this is the one for STATIC compression ratio, that assumes the valves
are closed and such (never heard them called brothers :)  ... the one you're
referring to is a DYNAMIC ratio, which is the one the motor actually "sees"
when running.  A huge cam can be used to "bleed off" compression so you can
run a higher static ... that's what they tried to do with my truck, but I'm
only able to run about 6° of timing even with the beefy cam.

>Compression is a good place to start when figuring parts for a rebuild but

>you can go much higher than the regular limits with the right cam.

True, but you need to consider combustion chamber shape and material, and spark
plugs, and all that other stuff, or you can go on a base assumption that will
be "safe" if you're on a budget or just want to get started with the ideas,
once you know the specs then you can play with them, but you need a starting
point ... From what I remember the general rule of thumb is 9.5:1 static for
an iron head and 10.5:1 static for an aluminum head.  Of course with cams and
such you can fudge this, but be sure of what you're doing (I aimed for 9.5 and
got much closer to 10, and it pings like all get out with any sort of timing
advance)

Just my $.02
wish

96 Mustang GT 5spd 4.6L
73ish 1/2ton 4x4   6.4L
http://www.ford-trucks.com//lc/lc.php?action=do&link=http://www.public.iastate.edu/~wish

Ford Truck Enthusiasts
http://www.ford-trucks.com

------------------------------

From: "Hogan, Tom" <Tom.Hogan kla-tencor.com>
Subject: Re: Ignition options & also pinging
Date: Tue, 29 Aug 2000 12:26:54 -0700

What is the "+1" for?

Tom H

> -----Original Message-----
> From: Dave Resch [mailto:Dave.Resch sybase.com]
> Sent: Tuesday, August 29, 2000 8:59 AM
> To: perf-list ford-trucks.com
> Subject: [perf-list] Re: Ignition options & also pinging
>
>
> Yo Derrick:
>
> I just wanted to add a little more info to Tom's post.
>
> The formula for compression ratio is SV/CV+1=CR
>
> where SV is swept volume and CV is clearance volume.
>
> SV = cylinder volume displaced by piston: ((pi*r^2) *
> stroke), where r is
> bore/2.
>
> CV = (combustion chamber volume + head gasket volume + deck
> clearance + piston
> top relief)
>
> Head gasket volume is calculated like volume of a cylinder,
> and height of the
> compressed gasket is the cylinder height.
>
> Deck clearance can be calculated by (deck height - (crank
> throw + rod length +
> piston compression height))
>
> Crank throw = stroke/2
>
> Piston compression height is the distance from center of
> piston pin to the top
> of the piston (not counting any dome).
>
> Piston top relief is an important factor in determining
> clearance volume.
> Unless the piston top is totally flat (i.e., no valve
> relief), you need to
> determine the relief volume.  That (and compression height)
> should be in the
> piston specs.
>
> You need to have all these numbers to accurately determine the static
> compression ratio.
>
> Dave R (M-block devotee)
>
>
> =============================================================
> To  unsubscribe:   www.ford-trucks.com/mailinglist.html#item3
> Please remove this footer when replying.
>

------------------------------

From: "wish" <wish ford-trucks.net>
Date: Tue, 29 Aug 2000 19:32:43 GMT
Subject: Re: Ignition options & also pinging



>What is the "+1" for?
>
>> The formula for compression ratio is SV/CV+1=CR


It comes from factoring out a variable divided by itself in the original equation
... I think I've got the entire derivation somewhere, or can come up with it
pretty quickly if someone needs it, but basically its initial volume over final
volume equal compression ratio, then you just start plugging in equations for
figuring each of those volumes ...


Just my $.02
wish

96 Mustang GT 5spd 4.6L
73ish 1/2ton 4x4   6.4L
http://www.ford-trucks.com//lc/lc.php?action=do&link=http://www.public.iastate.edu/~wish

Ford Truck Enthusiasts
http://www.ford-trucks.com

------------------------------

Date: Tue, 29 Aug 2000 18:19:47 -0500
From: Ezekial <ezekial mmind.net>
Subject: Re: Ignition options & also pinging

The motor is all stock size rods and crank. The bore is 4.030 which
would be the stock 4.0 bore and then bored out .030 over for my TRW's.
The head gasket is a stock sized Fel-Pro replacement. You don't have to
go to the trouble of figuring it out totally for me. I was just looking
at a balpark figure to make sure I wasn't getting into high compression
where then I would need to run expensive fuel. I am kind of leaning
towards the spark plugs being my problem but I am not sure. I think I
raised the compression about 1 point over stock. So does anyone know a
rule of thumb to go by? I used the next degree colder then the stock
plug. Maybe more?

Also anyone with after-market ignitions and give me some pointers on the
right direction.. I am looking at either the Crane HI-6S and MSD 6, 6A,
or 6AL and in both cases purchasing the incab timing adjustor.

Thanks..


> > Maybe someone can help me on this on too..
> > I built a new motor and upped the compression rato. I used 9:1 pistons
> > and had the block decked to .008. I figure I have around 9.4:1 or so??
> > anyone know if I am guessing wrong?? and I am wondering if I should go
> > to a colder plug. I am using stock minus the degree colder??

>
> Derrick
> There isn't enough info above or in the web page to calculate compression
> ratio.  When I  get home I will look in my shop manuals for engine specs.
> The info needed to calculate compression ratio is:
>
> Crank throw (stroke)
> Rod length
> Deck height
> cylinder bore
> compressed thickness of head gasket
> volume of combustion chamber
>
> If you know how close to the top of the deck the piston is at tdc that
> measurement can be used instead of rod length and deck height.
>
> Tom H.

--

Ezekial (Derrick)
93 F-150 4x4, 351, SC, SB
66 Fastback Stang, 289HP, 4sp
96 Conv. Stang, 3.8, lil add ons
www2.mmind.net/ezekial/

------------------------------

Date: 29 Aug 00 20:06:38 EDT
From: Tim Turner <ManicMechanicNC netscape.net>
Subject: Re: [compression ]

"William Whited (Tony)" <f10074 ford-trucks.com> wrote:
> I'm looking at a 74 truck that has a 460 and engine compression is
> between 90 and 145.  Do you guys think it is a problem?  The engine has
> around 115,000 miles on it.  TIA

Sounds like 115K hard miles...  As others said the cyl-cyl. variation is too
extreme.  The 90 bothers me as well; many years ago I was taught that anything
under 100 was a dead hole (at least in modern engines).  It's proved to be a
fairly viable rule of thumb for me.  I'd re-test the compression wet in the
low cylinder(s) to try to isolate the problem to rings or valves, a vacuum
guage could be of some help as well.

Sounds like it's time for an infusion of cash into that engine though.  :-(

Tim

____________________________________________________________________
Get your own FREE, personal Netscape WebMail account today at http://www.ford-trucks.com//lc/lc.php?action=do&link=http://home.netscape.com/webmail

------------------------------

Date: Tue, 29 Aug 2000 18:08:09 -0700
From: scott <scott ford-trucks.com>
Subject: A/F ratio tester

>>Either way you go you need to get or have a A/F ratio tester
>>for about $20 at AutoZone it is well worth it.

Now that is a good tip.I did not realize I could get one that cheap.
Thanks,Scott

------------------------------

From: "Jeff Keahey" <Jeff airboatfanatics.com>
Subject: Re: Ignition options & also pinging
Date: Wed, 30 Aug 2000 06:29:05 -0500

I do not know what type ignition you have now but both of the ones you asked
about are very expensive and only worth the money if you are going
7000+RPMs. If this is a daily driver I can bet you will see no improvement
over your stock ignition. Now if your stock ignition is going bad you are
better off to get a new (better) replacement coil rather than complete
replacement. You can usually get a high powered coil at an autoparts store
with more than enough power for less than $50 ($20 on a Chevy). If you do
not believe this to be accurate go down to a race track and ask around and
see how many are use stock distributors/coils/caps/rotors you will be
surprised.

Jeff
----- Original Message -----
From: "Ezekial" <ezekial mmind.net>
To: <perf-list ford-trucks.com>
Sent: Tuesday, August 29, 2000 6:19 PM
Subject: [perf-list] Re: Ignition options & also pinging


> The motor is all stock size rods and crank. The bore is 4.030 which
> would be the stock 4.0 bore and then bored out .030 over for my TRW's.
> The head gasket is a stock sized Fel-Pro replacement. You don't have to
> go to the trouble of figuring it out totally for me. I was just looking
> at a balpark figure to make sure I wasn't getting into high compression
> where then I would need to run expensive fuel. I am kind of leaning
> towards the spark plugs being my problem but I am not sure. I think I
> raised the compression about 1 point over stock. So does anyone know a
> rule of thumb to go by? I used the next degree colder then the stock
> plug. Maybe more?
>
> Also anyone with after-market ignitions and give me some pointers on the
> right direction.. I am looking at either the Crane HI-6S and MSD 6, 6A,
> or 6AL and in both cases purchasing the incab timing adjustor.
>
> Thanks..
>
>
> > > Maybe someone can help me on this on too..
> > > I built a new motor and upped the compression rato. I used 9:1 pistons
> > > and had the block decked to .008. I figure I have around 9.4:1 or so??
> > > anyone know if I am guessing wrong?? and I am wondering if I should go
> > > to a colder plug. I am using stock minus the degree colder??
>
> >
> > Derrick
> > There isn't enough info above or in the web page to calculate
compression
> > ratio.  When I  get home I will look in my shop manuals for engine
specs.
> > The info needed to calculate compression ratio is:
> >
> > Crank throw (stroke)
> > Rod length
> > Deck height
> > cylinder bore
> > compressed thickness of head gasket
> > volume of combustion chamber
> >
> > If you know how close to the top of the deck the piston is at tdc that
> > measurement can be used instead of rod length and deck height.
> >
> > Tom H.
>
> --
>
> Ezekial (Derrick)
> 93 F-150 4x4, 351, SC, SB
> 66 Fastback Stang, 289HP, 4sp
> 96 Conv. Stang, 3.8, lil add ons
> www2.mmind.net/ezekial/
> =============================================================
> To  unsubscribe:   www.ford-trucks.com/mailinglist.html#item3
> Please remove this footer when replying.
>
>


------------------------------

From: FLR150 aol.com
Date: Wed, 30 Aug 2000 12:34:21 EDT
Subject: Re: Ignition options & also pinging

In a message dated 8/30/00 7:25:41 AM Eastern Daylight Time,
Jeff airboatfanatics.com writes:

<< I do not know what type ignition you have now but both of the ones you
asked
about are very expensive and only worth the money if you are going
7000+RPMs. If this is a daily driver I can bet you will see no improvement
over your stock ignition. >>


Jeff,
I have to differ with you here. I DO race my truck, and I have the MSD6AL. I
have never seen 7k rpms, but I did see a HUGE difference in the time my plugs
last and an increase in my MPG and a SIGNIFICANT increase in off the line
acceleration (both on and OFF the track). I had no more stumbling, no more
occasional missing, and cleaner valves when I have to pull the heads. So
there is a HUGE difference between the stock and aftermarket ignition
systems. And besides, for a 1-3 mpg city increase, I think $180 is not a bad
deal at all for the 6AL. It'll pay for itself in no time.



Later,
Wayne Foy
NLOC #484
94 Flareside SC
#2 Top Truck
Atlanta GA ....

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