The V8 Owners Forum -

I am not familiar with the layout of the 300 heads, but if I was going to do that, I would find an old knackered head and play with that first. I would bore the holes out and totally dowel them to fill the holes and redrill on a milling machine to get my result.
That way, there is no chance of the head walking on oval holes.

Hi.

What about those?











Dowels are moved approx 5-6mm.. I think there is a risk to crack those heads.. 2mm is safe limit i think without seriously welding etc..

It's how little metal will be left when I oval the holes that concers me, angle killing will require this alone, think I will move another 1.5mm only. Maybee 2mm;-), but will it be worth it?? Gut tells me yes with 1.77 inlet valves. Are those vizzard heads??? Would live to know what figures he got on thise, he has obviously welded the roof (I have gone through these in the past) and raised the floor. Why the oval I always wonder???

Working on the assumption that quality control was lax at best, I'd say that wall thicknesses would be a bit of a lottery.

Best advise would be "suck it and see", I think. Make friends with a good ally welder, just in case....

Yes, I think you are right. 1mm at a time. Interested in those vizzard heads thought. Wonder what they made in terms of power and flow. Why the oval roof I always wonder? Is the sacrifice in CSA worth it for the more laminar flow and better velocity through the range

If i remeber correctly, they flow better than race ported wild cats, approx 260cfm i think. Inlet valve is 50-51mm and exhaust valve is 40-41mm.
5.5L engine produce ~505hp@7600rpm.?
Not even 100hp/litre..