dovec porting question

If I grind out that bump and blend the exhaust and do a CJ intake match on my dove castings, how much material can I safely remove around the exhaust side ceiling? If I drill into the port with a bit to determine a stopping point... How far can we go? These are a pump gas build 460 and we were wanting some improvement to my castings that I haven't been able to sell so we will just use them up. I was thinking in my mind that removing the bump and taking another 0.020" would get some improvement in the turn and port shape.

The best advice is signing up for Scott Johnstons website.

colorado ford man wrote:If I grind out that bump and blend the exhaust and do a CJ intake match on my dove castings, how much material can I safely remove around the exhaust side ceiling? If I drill into the port with a bit to determine a stopping point... How far can we go? These are a pump gas build 460 and we were wanting some improvement to my castings that I haven't been able to sell so we will just use them up. I was thinking in my mind that removing the bump and taking another 0.020" would get some improvement in the turn and port shape.

Although it is possible to raise the roof of the exhaust port, if you are inexperienced then your best bet is to use the smog bump as your "grinding guide" and just grind it down until it is flush with the rest of the port roof and call it good. Becasue there are areas of the port roof that are thing as-cast.

That being said, contrary to popular belief you are far, far better off investing time executing a good exhaust bowl blend and short turn radius smoothing, and just leave those smog bumps untouched. Because if you forego smog bump grinding and instead execute a good bowl blend and short turn radius shaping, you will have an exhaust port that is good to at least 500 hp in a well planned engine combo. Grinding away the smog bumps and re-shaping them is a great deal of effort relative to the gains since most of the exhaust flow improvements are found upstream of the smog bump itself.  You will essentially find zero measurable power gain for or your "pump gas build 460 and we were wanting some improvement to my castings" by grinding out the smog bumps. So forget them and focus on the bowl & short turn only...unless you are building a 600-700 hp engine.

As far as a CJ port match (intake runners), I suggest you buy an electric die grinder, a couple of hundred dollars worth of 1-inch double-cut grinding bits, and commit to a minimum 8 hours (or more) of grinding and shaping them to they way they should be. I used to charge $200 extra for a CJ port match and then kick myself while I was doing the work. It is a very big undertaking which requires a lot of patience, perseverance, tooling, and expensive grinding bits. But it sure is cool when it's done....although again it is not necessary for the kind of engine you describe building.

To Paul's point, here is some guidance on how to achieve good results with the least amount of effort.

https://www.460ford.com/threads/simple-std-valve-dove-exhaust-187-cfm-pics.143753/

big thanks. I use air grinders and lifetime guarantee carbide burrs from matco tools. Give them a ring and they will stop you from using your consumable budget up too quickly. Asfar as the bowlblend is there much danger there to get into water or are we OK to go to town?

Here is a later D head to give you an idea what's going on in that thermactor hump area. I think this is a D8 head.

thanks for the pic.looks like the air passage is not too far from the coolant passage. I guess the bowl blend is not in an area to make much trouble.

Removing and shaping the thermactor boss is worth exactly 10 cfm.

For a mild application leave it and focus on the bowl and short turn radii.

Back cut BOTH intake and exhaust valves!!!

Run a cam with a proper IE split and call it good.

This is a good example of how much is enough.



https://www.facebook.com/pg/PpamLLC/photos/?tab=album&album_id=746402525737427



SJ
used 2b RHP

I recall a test they did in the old "Super Ford" magazine that pertained to this. It was actually an intake manifold test on a 460 equipped with these D0VE-C heads. They tested several popular aftermarket intakes, as well as a stock iron unit (which was very strong on the low end torque, but ran out of breath at 4200).
Then they were curious as to how much power it was worth, if any, to simply remove the thermactor bumps in each exhaust port....to simply grind them flush with the port roof, like Paul describes above. The result was right at a 20 horsepower increase ( I don't remember the TQ number), and this was with headers, not stock iron manifolds.

Wellat high elevation Wewant all we can get. It is NOTEASY building pump gaspower here. Bowl and back cut + remove and shape thermactor. Backto original inquiry. How much material can be removed? on the short turn and the thermactor boss?