Camshaft suitability for my Ford 302 + Weber 48 IDA setup (37 mm chokes) — advice?

[Joep Leeuwenburg]

Hi all,
I'm currently building a Ford 302 for my GT40 project and would like some opinions on whether my camshaft choice is well-matched to the rest of the engine, and how to best configure my Weber 48 IDAs (using 37 mm venturis). Car will be street orientated with occasional track.

Below is the full spec of the engine so far:

• Block: 302ci, 4.020" bore, 3.000" stroke (roller-ready block)
• Compression ratio (target): ~10.0:1
• Heads: SRE R+R aluminum heads
  • 185cc intake runners
  • 64cc combustion chambers
  • 2.02" / 1.60" +0.100" valves
  • Hydraulic roller–compatible springs (140 lbs seat / 425 lbs open, 0.600" max lift)
• Rocker arms: 1.6 ratio aluminum
• Induction: 4 × Weber 48 IDA on a Pierce 99008.907 manifold
• Exhaust: Bundle-of-snakes
• Ignition: MSD Pro-Billet distributor (8579) + MSD 6AL + Blaster 2 coil

Camshaft Choice
I’m planning to run the Comp Cams XR276HR-12 (PN 35-518-8)
Specs:

• 224° / 232° @ .050"
• .555" / .565" lift with 1.6 rockers
• 112° LSA

Is this cam a good match for a Weber-fed 302 aiming for strong midrange and ~375–400 hp?
Will the 112° LSA and 224/232 duration provide stable vacuum and good drivability with 48 IDA’s?


Weber 48 IDA Setup (37 mm chokes)
I am rebuilding my IDA’s. My IDAs only have two progression holes
Here is the Weber setup I am planning to start with (baseline):

• Chokes: 37 mm
• Aux venturi: 4.5
• Main jets: 165
• Air correctors: 190
• Emulsion tubes: F7
• Idle jets: 65F10
• Idle jet holders: 120
• Pump jets: 50
• Pump exhaust: 50
• Needle valves: 200

Is this a good potential baseline or any recommended changes?

 

[Cliff Beer]

Hi Joep, real basic response here, based solely upon my own 1st hand experience (not extensive).

1. Regarding camshaft, my only input would be don't select one with a ton of overlap. The 48 Webers have modest/limited ability to handle upstream pulses in the inlet and throttle bodies typically brought about by large overlap. Too much overlap can stall a consistent vacuum, which in a IDA is the primary means by which fuel is drawn into the throat.
2. Regarding setting up the 48 Webers, I highly recommend buying and studying Pat Bradens "Weber Carburetors" book. Everything you need to know to tune the 48's for your 302 is in there, including all the jet setting. Be aware (as you probably are) not all 48 IDA's are the same. Beyond the jetting they can vary by the progression holes drilled in the throats. So, good to start with the right/best 48's so as to not have to do too many gyrations to get the right AFR across the spectrum from idle to WOT.

Have fun, and good luck!

Cliff

 

[Mike Pass]

I would also suggest a cam with lift rather than overlap if you want the IDAs to run well at low rpm. They like a strong signal.
The only way to get them set up is to be able to read the air fuel ratio so rolling road or an air/fuel gauge. Anything else is just guessing. A/F gauges are not expensive but need a bung welding into the exhaust for the O2 sensor. (no exhaust air leaks also). Once you know what the air/fuel ratio is at the full range of throttle rpm etc. you can work out what to change and by how much. It can get expensive as there are 8 of everything to change. It just takes a bit of testing and thought. They can be set up to run really well. A roller cam will dodge any cam scuffing issues.
Cheers
Mike

 

[Mark H.]

Why not use a LeMans cam? H/M still grinds them. After all this cam got its name from where they were used and in the 40. I use a H/M LeMans in a 66 GT350 that is street driven, but with a 4 barrel carb. I’m sure H/M could advise you best.