496 combo help

[hitchcock]

I am attempting to turn a 3700 pound car into a ten second drag car. It is a 73 vette that has a 9 in. ford ladder link, and coil overs. I am building a 496 (4.31 borex4.25 stroke) with 6.385" h-beam rods. I have two sets of world products heads both are 2.30 intakex1.88 exhaust and have 11/32 stem diameters, with 119cc chambers, one set is Grumpy Jenkins 320 cc. intake runner with d-port exhaust the other has 345 cc intake runner and square port exhaust. I have a Dart, holley strip dominator, and a Victor junior and a Tr2x Edelbrock tunnel ram intake. A holley 950 cfm HP series carb. And between 11.5 to 1 and 12 to 1 compression. Can anyone reccomend a head intake combo, and a cam? Gear ratio will be selected after I pick a cam and heads. The is my first big block project, any input would be very helpful. Thanks.

[cboggs]

I would use the 320cc heads as the 345cc heads would be too
big for the combo, .. too much cross sectional area.

I'd also mill them to reduce the chamber size and try to get the compression
up, .. 13.1 or so.

Intakes, .. hummm, .. I like the Dart stuff ported, and I like the Victor
manifolds as well, .. I'll have to check some notes but the Victor Jr should have
a smaller cross section and would work better to a point.

I'll leave the cam recommendation to one of the awesome cam people
on the board.

73 Vette, sounds like fun.

Curtis

[ou812]

If it were me Id mill the heads down for 12.5 compression min.
If the cam is solid roller, then Id use a comp grind, single pattern around 270 @.050 with .714 lift. Stick it on a 110 lobe center. Id use the victor jr as well but I would think the 950 would be a little small, even for that weight.
Brian

[hitchcock]

thanks for all the advice, but could someone explain what the cross section area is, saw some one with a bigblock pontiac talking about it.

[cboggs]

thanks for all the advice, but could someone explain what the cross section area is, saw some one with a bigblock pontiac talking about it.

Yea, .. simple terms, .. the cross sectional area, .. or CSA is what
determines the air speed along with the volume ( cfm )
It's a simple measurment of the area or "window" the air has to
flow through in a port.
For a simple square or rectangle port, height x width gives you
CSA.

So cylinder head guys & engine builders look at the CSA to find the
air speed, .. and find a head the right size.

just going by CC's of a port doesn't work because if the ports are
different lengths it makes the CC numbers useless for air speed comparisons.

There are several threads here on Speedtalk that get really in depth
on CSA if you want more information.

Curtis

[Trev]

Curtis

My new heads have a 53 x 34 mm rectangular port
Does this mean the CSA is 1802 mm

Given that info what can u determine, ie size of cam and cubic inches etc etc required.

Thanks Trev

[sbrown]

No need to reinvent the wheel on this package. I would use the smaller of the 2 heads, port them if they are not already, mill the heads to get 11 to 1, and use the victor intake. I prefer dominators on these combo's though. I would do a custom street roller in the high 250's, low 260's at .050. I can do the camshaft for you. Should get you well into the tens with 4.10 gears and a good 9.5 race converter. Pump gas friendly and easy mid ten second passes. I have a Mopar customer with a similar package running 10.30's @ 130 (3700lbs) with 4.10's , exhaust to the axle, no N2O and a single dominator. It has ported Edelbrock heads that flow 307 on the intake. He drives it 30 minutes to the track each way. He went 10.28 last week on a drag radial.

Scott
Straightline Performance
www.straightline-perf.com

[cboggs]

Curtis

My new heads have a 53 x 34 mm rectangular port
Does this mean the CSA is 1802 mm

Given that info what can u determine, ie size of cam and cubic inches etc etc required.

Thanks Trev

2.86" x 1.338" = 2.791 csa.

on a 466 ci engine this would put peak / max airflow / choke point
around 6500 rpm.

As long as this is the Minimum CSA in the port, ..

On a 406 small block, .. 4.155" bore x 3.75" stroke, .. would put
the peak / choke around 7500 rpm.

Curtis