Choosing a cam for a 363 SBF

[Ohio Rob]

Hello all.
I’m building a 363 SBF drag engine. No class specific requirements and it’s going in a Fox body mustang that weighs 2950 (3140 with me in it). Automatic C4 with a trans brake and an ATI converter that flashed at 5100 RPM (347 with 300 RWHP currently). The gear is a 4:10 and the tire is 26.5 tall.

I’m looking to maximize the effort with the parts I’ve been collecting for years.
Here’s what I’m working with so far:

Dart SHP block with factory cam architecture (4.125 bore)
3.400 stroke
Internal balance (neutral)
14.7:1 compression with the piston .010 in the hole (calculated with measured numbers)
Trick flow twisted wedge R heads with measured 51 cc chambers
Manley nex tek springs 221433-16
Trick flow 4150 flange intake with direct port injection.
1000 CFM Holley T-body
1-7/8” kooks headers
1.7:1 comp steel rocker arms (pro magnum) with stud girdles
.875 comp solid tie bar roller lifters

Engine will be a dry sump oiling and Will be run NA. I want to spin it as much as possible with what I have.
Here are the flow numbers and the info on the springs I have on the heads.

Any help, criticism, ideas are welcome.

Thanks,
Rob

[LSP]

You mentioned wanting to spin it as much as possible, what connecting rods do you have?

[Ohio Rob]

I have a set of lunati rods.
They have ARP 2000 bolts
Here’s the part number and card

[Walter R. Malik]

You mentioned wanting to spin it as much as possible, what connecting rods do you have?

And, that valve spring number 221433-16 you mentioned is for a 4.6L or 5.4L cylinder head so, what is the correct number...?
221443-16 is more likely.
What is the maximum valve lift your heads will accept before the retainer will contact the seal...?
What material are the valves made from...?

[Ohio Rob]

Sorry about the bad spring number.
Yes, 221443-16 are the springs I have.
Stainless valves.
I don’t know about the retainer to seal data.

[LSP]

I have a set of lunati rods.
They have ARP 2000 bolts
Here’s the part number and card

Those rods seem quite robust, your short block should be 8500 rpm capable. Did you ever order those rings?

Those springs don't have enough rate for an average intensity roller profile with your valves at that rpm IMO.

[Ohio Rob]

Thanks for the reply LSP.
I haven’t ordered the rings yet.
I do plan on using the gas ported ones you suggested.

What kind of spring rate would you suggest for my application?

[LSP]

Thanks for the reply LSP.
I haven’t ordered the rings yet.
I do plan on using the gas ported ones you suggested.

What kind of spring rate would you suggest for my application?

100+ lbs. more rate, the PAC 1325 installed .100" from coil bind looks good to me if you do want to get in the 8500 rpm range.

I'd get your converter loosen up to flash another 1200 or so rpm too.

[Ohio Rob]

You mentioned wanting to spin it as much as possible, what connecting rods do you have?

And, that valve spring number 221433-16 you mentioned is for a 4.6L or 5.4L cylinder head so, what is the correct number...?
221443-16 is more likely.
What is the maximum valve lift your heads will accept before the retainer will contact the seal...?
What material are the valves made from...?

I took a valve out and measured the bottom of the retainer to the top of the seal.
The distance is .850.
I also weighed the intake valve and it came in at 131 grams. It’s a 2.08” stainless valve.

Thanks,
Rob

[Walter R. Malik]

You mentioned wanting to spin it as much as possible, what connecting rods do you have?

And, that valve spring number 221433-16 you mentioned is for a 4.6L or 5.4L cylinder head so, what is the correct number...?
221443-16 is more likely.
What is the maximum valve lift your heads will accept before the retainer will contact the seal...?
What material are the valves made from...?

I took a valve out and measured the bottom of the retainer to the top of the seal.
The distance is .850.
I also weighed the intake valve and it came in at 131 grams. It’s a 2.08” stainless valve.

Thanks,
Rob

With that heavy of an intake valve, a camshaft which is not so aggressive at high lifts near the nose would be best for RPM.
Something along the lines of a mild drag race cam or high speed, long oval track lobe profile would probably be what you need.

That valve spring will coil bind at a little over .750" lift so, A guess would be something near .420" lobe lift about 276/284@.050"

[bob460]

I took a valve out and measured the bottom of the retainer to the top of the seal.
The distance is .850.
I also weighed the intake valve and it came in at 131 grams. It’s a 2.08” stainless valve.

Thanks,
Rob

With that heavy of an intake valve, a camshaft which is not so aggressive at high lifts near the nose would be best for RPM.
Something along the lines of a mild drag race cam or high speed, long oval track lobe profile would probably be what you need.

That valve spring will coil bind at a little over .750" lift so, A guess would be something near .420" lobe lift about 276/284@.050"

Didn't Kaase use this spring 221443-16s on his BBF 598ci SR-71 1200+HP build using a .480 lobe comp cam 250lb seat pressure and 750lb open and a 178 gram 2.375 intake valve?