quote:Originally posted by 4V & Proud:
it does get complicated, what doesn't?
another number 5145 different diameter & back-cut
https://www.ebay.com/itm/Ferre...AOSw86JaWfxk&vxp=mtr
5045 = 1.71" = 12 Deg Under Cut-Dish Head
5145 = 1.76" = 9 Deg Flo-Dish Head
plus length exhaust valves are only available in Competition Plus series
https://www.ebay.com/itm/Ferre...AOSw86JaWfxk&vxp=mtr
not sure on intake, possible a 5000 or 6000 series BBC valve will cross over with the desired length?
is the 1.76" diameter a deal breaker in a serviceable factory seat,
does the valve need to be reduced or the seat opened up?
You probably can't use a 1.76 exhaust valve. It depends on the space that is left between the existing valves.
It also depends on the accuracy of the location of the existing valve guides. Most production heads vary from cylinder to cylinder on the location.
For instance, on my 302 Ford heads I enlarged both the intake and the exhaust. The new intakes are 1.94 and 1.60, intake and exhaust.
About half of the cylinders had the guides located where a 2.02 intake would fit, half not.
As far as enlarging the valves, it isn't just the size of the valve that increases flow, you need to open the pocket under them the corresponding amount.
When you get in to the assembly and modification of the heads, it's fun. I wouldn't use the term "complicated" but maybe "exacting" is closer to the facts?
You need to remember that Ford "cut" the heads to use production parts, a low lift, low duration camshaft and with the exception of the Boss 351, never intended even the CJ to turn more then 5500rpm.
What everyone is doing is providing for more cam lift, more air flow through the ports and substantially more rpm.
The Cleveland heads are up to the challenge with relatively little modification. The one exception to that is the bad exhaust port.
The cast iron heads are also much easier to work on then the aluminum ones are. The aluminum just clogs all the cutters, stones and sanding drums.
One of the current advantages is that all of these valve brands are FAR superior to the originals as are the balancers, not to mention roller rocker arms, etc.
It's really easy to unleash the original intent of the 4v Cleveland as a true high-performance/race engine as the original design intended.