[Land-speed] Still Asking Motor Questions, lol..

Rich Fox v4gmr at yahoo.com
Sat Mar 12 11:31:26 MST 2011


It seems the wrong thing to kill swirl. I usually want to make sure I build it
in. But with Vintage motors and blown motors sometimes you just can't. And
they seem to run OK anyway. Maybe not the best possible. But I have done it
and it seemed to work compared to what I was running against at the time. 

--- On Sat, 3/12/11, Larry Mayfield <drmayf at mayfco.com> wrote:


From: Larry Mayfield <drmayf at mayfco.com>
Subject: [Land-speed] Still Asking Motor Questions, lol..
To: "land-speed at autox.team.net" <land-speed at autox.team.net>
Date: Saturday, March 12, 2011, 10:19 AM


Not being known for motor building prowess, I rely on the list to help me
along.  Of late, I have been thinking about the use of a 289 Ford (what else?)
crank in the Mexican cast block I will pick up in June. I would like to use
the 302 Ford 5.090 rods rather than the hard to find 5.155 rod length of the
old 289 series motors. And I want to consider the use the 302 version of
pistons for the same reason as availability in race configurations. That puts
the piston down hole by 0.065 inches, however.  That would reduce the
compression ratio quite a bit.  But, I normally use dished pistons with about
a 13 cc dish anyway.  So if I use flat top pistors, I think I can maintain the
basic compression ratio, but, the "squish" would go away. At least I think it
would. I do run the turbo on the motor but What I would like to hear comments
on doing this.  Is this something stupid or actually reasonable to do on a
boosted motor?  Is it likely to run well or
 just so so?

No, I don't want to deck the block or mill the heads or find pistons with a
longer wrist pin compression height. I know I can do those things, so, the
question is can I do it the way described above and have a good performer?

So, you gotta ask..why? Well, I keep looking at the rule book about
displacement verification using the pump.  If the as pumped displacement is
within 3% of top or bottom of the engine displacement class size then
according to the book, it must be torn down for direct measurement.  That's
really the last thing I want to do. So if I can keep the motor size for a D
motor to 289 - 296 cid range I should always pass a pump check and never have
a tear down on the salt.  Not that I am worried about it because I don't think
me or the Sunbeam has the beans or aero to qualify or set a record but..just
in case, lol. And maybe someone else will benefit from this question in some
other situation.

mayf
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