Agreed - the cam manufacturer should be able to tell you what effect their
cam will have on cylinder pressure.
I've honestly never seen a factory engine that made the compression it was
advertised with. Generally the block and heads have more material on them
than the minimum (less machining) so that 10:1 motor is lucky to be making
an honest 9:1. Next time you take your engine apart, check the downfill
volume and chamber volume, then plug the numbers into the standard formulas.
Prepare to be amazed. That's also why you hear a lot of "it never spark
knocked before" stories, as after the block has been decked and the heads
cleaned up the compression comes up 1/2 point or so.
That's how the stock/super stock guys made power back in the '60's, by
"blueprinting" the engine... Basically setting all clearances to optimize
performance. The sanctioning bodies had to counter by setting minimums, to
keep racers from "over-blueprinting".
SC
-----Original Message-----
From: 65 [mailto:65Val@xxxxxxxxx]
Sent: Thursday, January 21, 2010 11:49 PM
To: 1962to1965mopars@xxxxxxxxxx
Subject: Re: 273 Rebuild status and how much compression we can run on pump
gas w/10.5 m
""The engine never pinged on me before, but I was running 87 or 89 octane in
it. I know they're not quench pistons, but I have to wonder why it didnt
have pinging problems before.""
Engine was probably tired enough to not make an honest 10.5:1 comp.
I would think the hotter cam would bleed off a bit of cylinder pressure,
minimizing the ping in the new engine.
Darwin/BC/Canada
--'65 Cdn.Val.Custom 100 'vert
--'67 Dart GT 'vert...
Check'em out... http://s41.photobucket.com/albums/e285/65val
----- Original Message -----
From: "Tom Watters" <tomwatters@xxxxxxxxxxx>
To: <1962to1965mopars@xxxxxxxxxx>
Sent: Thursday, January 21, 2010 8:32 PM
Subject: Re: 273 Rebuild status and how much compression we can run on pump
gas w/10.5 m
Gary, thats a good question.
I'm putting back in it what was in it, just a little larger bore. The
stock hipo 273 pistons came above the deck, looks like a pretty snug fit
into the head.
The engine never pinged on me before, but I was running 87 or 89 octane in
it. I know they're not quench pistons, but I have to wonder why it didnt
have pinging problems before.
If I do have pinging problems, Rebel does have high-test that I can
experiment with. ie, 12 Gals of 92 octane plus 2 gallons of 100 octane
would probably do it.
I hope to not be doing the octane boost thing. We'll just have to see how
it is once built.
:-)
Gary Pavlovich wrote:
Tom,
With 10.5 pistons you will raise your compression considerably more than
most pump gas will handle. What fuel will you be using and will you be
adding an octane booster or a bit of "race" fuel?
I have been researching the correct octane level for 10 to 10.5 to 1 true
compression motors and would appreciate any research/experiential input
from our list members.
Gary Pavlovich
----- Original Message ----- From: "Tom Watters" <tomwatters@xxxxxxxxxxx>
To: <1962to1965mopars@xxxxxxxxxx>
Sent: Thursday, January 21, 2010 7:54 PM
Subject: Re: 273 Rebuild status
Steve,
Good Point. The New pistons will require that, even with all the manual
checks Egge does, there's still the need when adding pistons and pins
that something might be askew. Dont want to flub up the forged crank.
Will have to add it to the list. Appreciate it.
--Tom
Steven Charette wrote:
Tom,
You got money tucked away to rebalance the rotating assembly?
SC
-----Original Message-----
From: Tom Watters [mailto:tomwatters@xxxxxxxxxxx] Sent: Thursday,
January 21, 2010 10:14 PM
To: 1962to1965mopars@xxxxxxxxxx
Subject: 273 Rebuild status
Well, it looks like I'll be rebuilding the 273 rather than just a
refresh
(Rings & beargings). Needs boring, which means pistons and the like.
After bumping around on the phone, I got some good recommendations of
friend
of the the local car club president for a machine shop. It seems to be
on
the high end of average, but I can tell he does know his stuff. When I
talked to Nellis Machine or Las Vegas Crank and Machine, they didnt
leave me
with a comfortable feeling about taking in my original block to them.
I
told HBR Competition Engies I will be dropping off the Block, Heads,
Crank
and Pistons tomorrow afternoon. Total for Bore (175-200)/Crank Turn
(95)/Cam Bearing install
(75)/re-condition rods (25-35) is at a 500-600, depending.
This will cause me to buy pistons. Only one company makes (egge) the
10.5:1s, Those will run about $300
Cam/Lifters from Racer Brown is now on Order $235+Tax. Ordered #
ST-1 -
Mechanical Cam. Its a little lumpier than the stock HiPo Cam (450 lift
instead of 425), but not as big as the D-Dart race cam (495 lift). It
should give me what I want.
So barring a ton of head work, the rest of the parts I'm looking at
will be
about $300 (Timing Chain, Teardown set, Freeze Plugs, Bearings, Rings,
etc)
Total for a full rebuild minus head work, I'm looking at $1435. if I
need
head work, Usually about another $200-$500
If He were assembling, it'd be another 1000 or so.
Now to get the taxes submitted so I have the funds to pay for it with
my
return. ;-)
Regards and Happy Moparing.
--Tom
----
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1962 to 1965 Mopar Clubhouse Discussion Guidelines:
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----
Please address private mail -- mail of interest to only one person --
directly to that person. I.e., send parts/car transactions and
negotiations as well as other personal messages only to the intended
recipient, not to the Clubhouse public address. This practice will
protect your privacy, reduce the total volume of mail and fine tune the
content signal to Mopar topic. Thanks!
1962 to 1965 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html and
http://www.1962to1965mopar.ornocar.com/general_disclaimer.html.
----
Please address private mail -- mail of interest to only one person --
directly to that person. I.e., send parts/car transactions and negotiations
as well as other personal messages only to the intended recipient, not to
the Clubhouse public address. This practice will protect your privacy,
reduce the total volume of mail and fine tune the content signal to Mopar
topic. Thanks!
1962 to 1965 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html and
http://www.1962to1965mopar.ornocar.com/general_disclaimer.html.
----
Please address private mail -- mail of interest to only one person -- directly to that person. I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic. Thanks!
1962 to 1965 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html and http://www.1962to1965mopar.ornocar.com/general_disclaimer.html.
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