[Roadsters] Head Porting

[Walter Peterson]

I second Keith's comments and add that with a big cam you need to get the
compression back up by either closing the head chambers (welding & grinding
to get better Squish which also reduces or eliminates pinging) and/or update
the pistons to do a similar job.  You know you've hit the best compromise
when the compression tester reads in the 205 PSI range and you don't ping.
Flat tops & closed chambers on my R16 head & H20 crank (R16 rods).

Walt Peterson in burned out Goleta.

PS I have a free pair of usable 1600 drums & backing plates, winner pays
shipping.


-----Original Message-----
From: datsun-roadsters-bounces+walter.peterson=cox.net at autox.team.net
[mailto:datsun-roadsters-bounces+walter.peterson=cox.net at autox.team.net] On
Behalf Of Keith0alan at aol.com
Sent: Thursday, July 10, 2008 8:00 AM
To: drlsmith at dccnet.com; datsun-roadsters at autox.team.net
Subject: Re: [Roadsters] Head Porting

In a message dated 7/9/2008 8:51:46 PM Pacific Daylight Time,  
drlsmith at dccnet.com writes:


Now  to be fair, part of the reason, I think, for having less detonation is
that  the longer duration cam will also reduce the effective compression  
ratio.

And something that really bothers me, after spending nearly  $2,000 on a
cam,
lifters, cam gears, porting gaskets etc. they gained only  14 hp at the 
wheels!
Up from 64 to 78........

My hopes of getting  100 hp at the wheels of my 1800cc stroker are looking
pretty damn  slim.......  :-(

Daryl



A longer duration cam will lower the effective compression ratio. I think I

might have milled the head a bit to pick the compression back up into the  
premimum range. Also, torque is generated by combustion chamber pressure, HP
is  
generated by RPM. You can increase chamber pressure to increase torque and 
bump  HP some but the real HP increase comes from higher RPM. Rather than
the 
stock  6000 RPM, build the engine to do 8000 RPM. With no increase in
chamber 
pressure  you will pick up 1/3 more HP. This sounds simple however there is
a lot 
that  goes into moving the peak of the torque curve from 6000 to 8000. Cam, 
port  sizes, balancing, strong rods, oiling and on and on. If you do the
port 
and cam  to peak at 8000 rpm then only run to 6000 rpm you have wasted a lot
of 
time and  money. You will see some gains but not nearly what you could.
 
Enough rambling for early in the morning.
 
keith



**************Get the scoop on last night's hottest shows and the live music

scene in your area - Check out TourTracker.com!      
(http://www.tourtracker.com?NCID=aolmus00050000000112)
You are subscribed as walter.peterson at cox.net

Datsun-roadsters mailing list

http://www.team.net/archive

http://autox.team.net/mailman/listinfo/datsun-roadsters