cam for restrictor plate engine
cam for restrictor plate engine
(OP)
I am building a motor to run in a 2 barrel class that requires a restrictor plate with 1.750 bores. How do I figure out which cam will work best with this restriction ?
Motor is a 454 chevy with 15:1 compression . Carb is 625 cfm split dominator
Motor is a 454 chevy with 15:1 compression . Carb is 625 cfm split dominator





RE: cam for restrictor plate engine
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Raising CR with restrictor plate is going in correct direction !
but , are you really sure you actually have a measured 15:1 CR ??? because its very hard to get that knid of CR on a BBC 454 cid engine size even with decking and angle-milling
unless you are using other than OEM conventional valve angles/tilt and chamber design .
Many years ago i used the highest CR Speed Pro and TRW
pistons available for BBC-454
TRW and SP said their dome volumes were 50 CC ,
i was coming up with 44.5 CC at most ...it took about
half an hour to actually talk to an engineer at Speed Pro=Sealed Power ..he said they use a term called Effective Dome Volume ...which he said means they pour the dome with clay filling up valve notches ..and so the domes look better than they are .
So during that week many years ago , i also poured Manley's Pro Series Dome for BBC-454 ..they said it was 52 CC,
i told them i was coming up with 48 CC ....about a year later in Manley's next cataloge , i noticed the dome was rated at 50 CC ...another few years later in a newer cataloge , Manley rated the same dome to 48 CC
don't trust the piston people on dome volumes ..pour the domes yourself .
you'll be very lucky to get 15:1 CR with angle-milling and block decking and no flycutting, and small duration spread-center cams ,...thats what it will take to get 15:1 actual on a conventional head 454
Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/
RE: cam for restrictor plate engine
RPM = CFM / ( CID * .000289352 )
4755 RPM = 625 / ( 454 * .00028952 )
for 1.5 inches Hg vacuum and 100.0 theoretical Ve %
above 4755 RPMs , the engine will pull increasing vacuum
with increasing restriction and Ve % loss , so thats where CR becomes very important
97 to 99 jets for stock unmodified metering/carb (HP-1250)
0 tp 1900 Ft density altitude
Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/
RE: cam for restrictor plate engine
of the relevant info, such as tire size, gear ratio,
vehicle weight, etc...
RE: cam for restrictor plate engine
pistons are 46 cc dome . .010 below deck
.040 copper gaskets
bore is 4.280
I calculated this to 15.33
Am I missing something ?
RE: cam for restrictor plate engine
Am I missing something ?
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i come up with 15.334:1 CR same thing
all i meant was its takes angle-milling ,
block decking, a lot of real piston dome volume CC
and short duration cam with/without spread centers depending on actual duration @.050"
do you have a cam in the block right now to check valve-to-piston clearances ??
(spark plug-to-piston notch clearances ?)
have any current cam specs you are running now ?
Call Comp Cams or Cam Motion for cam recommendations for restrictor-plate engine .
Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/
RE: cam for restrictor plate engine
I was trying to understand if there are substantial gains by changing it , or maybe by changing rocker arm ratio on intake or exhaust side .
Also , how does the intake runner volume affect this combination ?