Exhaust crossover - question regarding flow

Have an interesting technique, tool or just anything related to porting? Post it here . . . please no bashing anyone for the model of engine they are working, we're here to share ideas . . .

Postby 75-1138604505 » Thu Feb 09, 2006 3:31 am

What affect does the exhaust cross over have on the flow of the port? Being more specific I am working on a set of heads for a ford 460 casting # D3VE. One port in each head has the exhaust crossover plumbed into the wall of the bowl creating a large open area on the long side. I do not need the exhaust crossover warm-up feature and will be block at the manifold. I am considering filling in the hole in the wall but would like to know if this hole affects the flow of the port before going to the extra work.
Kurt
75-1138604505
 

Postby maxracesoftware » Thu Feb 09, 2006 1:22 pm

Kurt.A wrote:What affect does the exhaust cross over have on the flow of the port? Being more specific I am working on a set of heads for a ford 460 casting # D3VE. One port in each head has the exhaust crossover plumbed into the wall of the bowl creating a large open area on the long side. I do not need the exhaust crossover warm-up feature and will be block at the manifold. I am considering filling in the hole in the wall but would like to know if this hole affects the flow of the port before going to the extra work.
Kurt

on "all" the various NHRA SuperStock Heads
i Ported ..i never had Heads welded in Exh Bowls
to "plug" heat-riser up.

and i never even "filled" the Heat-Risers with any
Grout/Epoxy/or melted materials

all i did was concentrate on making that Port
flow as close to the others as possible,
and usually that was achievable in all cases,
and as a side benefit to not plugging the Heat-Riser,
NHRA could never CHECK the CC's volumes of that
particular Port..so i was free to enlarge or shape
that Exhaust Port with the Heat-Riser like i wanted,
and was always successful in just about achieving the same
Flow Numbers as the other Ports.

on the Dyno and on the DragStrip ??
those Heads always ran as fast or faster than
other Porters who were spending a great deal of Time/Effort
to weld up the bowls and other parts of the Exhaust Ports.


on the Exhaust side of the Engine, its possible to
"correct" a low Exh/Int Flow Ratio with the
Camshaft to a great extent.

on the Ford 460 D3VE or DOVE , you should be able to get
more than enough Flow out of the Exhaust Ports
without having to weld or grout the Heat-Riser, and besides
the heat-riser will be automatically blocked-off with most
Single-Plane Intake Manifolds anyway.

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

i might add=>
the "only" time there is what i call a tremendous gain to be had with "Blocking" the Heat-Riser is in a Case
like NHRA SuperStock Chevy 305 cid Cylinder Heads
or like Heads...where you have (2) passsages interconnected
together joining into (1) Heat-Riser...then i have definetly
Dyno Test Data that HP is REDUCED by as much as 30+HP
with tight Centers/OverLap/Durations/Lift these Engines like
as the these (2) passages will begin to act like
a defective stuck EGR Valve and contaminate fresh mixture
with Exhaust gas residuals..and this is easily seen
in the middle (4) cylinder's EGT Temps on the Dyno as
well as noticing the -30HP Losses on what would
normally be a 515 HP + engine.
maxracesoftware
 
Posts: 132
Joined: Fri Mar 26, 2004 7:54 pm

Postby 75-1138604505 » Fri Feb 10, 2006 4:46 am

Thanks for the reply,
You just saved me a bunch of needless work. You even answered my underlying question of the exhaust gas contaminating the fuel charge during overlap. I was saving that one for further posts. Do you also read minds :laugh:
Kurt
75-1138604505
 


Return to Porting techniques?

Who is online

Users browsing this forum: No registered users and 1 guest

cron