Reply to "Identification & Advice Regarding My Pantera's Cylinder Heads"

That intake (M-9424-A331 Roush Version) was available as cast with either a C302 or A3 sized port window as was the M-9424-A351. They appear nearly identical but are slightly different intakes. The part numbers were the same so how you specified one over the other when ordering, IDK. The race teams usually picked up the phone or told their factory rep I suppose but there were all kinds of variation when it comes to these race parts.

I own the Torker style A331 in both A3, B3, and C302 size ports. The B3 may have just been a C302 version ported to that size but the A3 and C302 units are as cast runners. In fact, for the C302 runner version, I bet I could lifter finger prints and DNA matching several of the people that have posted in this thread.

Unless your A3 heads have been ported wider (than 1.75”), that intake can be ported to match them. 4V & Proud’s post shows the intake with the A3 port window. I can’t say for sure from the picture but the port window dimensions in your first post are pretty much as cast/stock for A3s. Have the decks been milled and do you know the combustion chamber volume? You mention a static CR of 10.3:1 but if it’s stroked I would think you’d need a dished piston or fairly thick gasket to get back down to that ratio.

With all due respect to the 4V purists, IMO the A3 is a better head in almost every respect than an iron 4V head. They are lighter, being aluminum and running a little cooler probably nets you another .5-1 point of safe pump gas compression ratio, the intake ports are (slightly) more energetic and flow better, the exhaust port is way better, and they all have screw in pedestals for adjustable valve train. Possible negatives are no egr if that matters to you, and the threads may not be as durable. In front engine cars with shock towers the exhaust port position is a problem but that is not an issue in a Pantera. They will require a purpose built header which you must already have because a 4v header won’t bolt up to the A3 heads properly.

The biggest issue with A3s is they are 30 years old and have typically been through so many hands and fiddled with so much you don’t know what you have without close examination. Do they still have the original iron valve guides or do they have bronze guides?

I’d be suspect of the whole engine as it appears to be a mish-mash of parts. That intake has been drilled for NOS foggers and slapped on the engine and was obviously worked for another engine. The heads look like they had been running pig rich. With that cam and fact it wouldn’t rev above 4krpm it could be something as simple as carburetion or ignition or it could be something very serious like tired or mismatched valve springs, though if the latter were the case I suspect you’d have even bigger problems to discuss. Is it a flat tappet cam and did you measure those specs or look them up? Are the lobes worn flat? Did you do a leak down test on each cylinder before you pulled it apart. -There's a lot of ground to cover here.


I’d recommend you seek out a Cleveland engine specialist, tell him how you want to use the engine and either have him build it or pay/take his advice on component selection. Even if you are an experienced engine builder there are nuances to every engine.

Take care,
Kelly