[Half-Inch Stud]

Fill the Head crossover. Do not simply block the Intake manifold crossover with a metal plate.

Metal Plate block magnifies reversion in every other 1crank rotation 43657218
Reversion alarms: Because Exhaust #6 bombs 4 during 4's overlap. Exhaust #5 bombs 3 during 3's overlap. Explains why carbon Spits up to coat some Carb throttleplates.

Filled crossovers allows the bigger cam to shine, uniform CYL HPs across all 8, and cleaner plugs.

any thoughts for/against?

[25stevem]

Your not even mentioning that headers will not tune as they should with out totally filling the crossover!

In a pinch one time I made T shaped block off plates that bolted together out of 3/8” Aluminum plate that I shaped with a couture gauge to sit against the head bolt boss very well, and then shaped the other plate to fit the intake flange crossover hole itself.

It took me all of 1.5 hours per head to make and probably sealed off both exh ports by 95% .

This method of course as compared to a pouring a plug will not let you reshape the rear of each center valve bowl so as to have them flow the same as each end port, but it sure helps power non the less.

[Half-Inch Stud]

Baby steps.

OMG. I tried to make 1/2 of a Y to plug the Head port, while on the car. Out of a block of teflon. No go.

Success was met with pouring Aluminum, with 0000 steel wool in each valvebowl. No reshape needed. Steel wool held in by valvestem is the perfect cool stop + shape set.

"Improved" success was met with casting a ceramic slurry. Some reshape was needed.

[Cliff R]

Turkey cooker (burner), some old cast pistons, cast iron pan, steel block off plate and it really helps to warm the heads for about 20 minutes on an Old Coleman gas camping stove.

I remember those days, years before KRE start making aluminum cylinder heads.

I've also tried the steel wool packed into the port area behind the valve stem. Either way works fine, less mess and clean-up pouring in with the block off plate but you really have to pay attention so you don't poor in too much...........

[Half-Inch Stud]

Oh yea, the pour is performed to a medium rare Head, on a bbq grill.

Since i ginned-up the 0000 steel wool packing with valvestem on my own, that is favored.

Ceramic pour: 1 Exhaust bowl developed an 1/4" erosion indentation, from being torched in service.

Aluminum pour: no troubles in service. Wondered about thermal expansion stresses, but no harm in extreme cold or heat.

Ideal x-pipe or h-pipe can only occur with the 4-5 exhaust crossover path. Fill 3 & 6. Smooth crossover tube under Intake. But no idea what it that be worth.

[Tandyman]

Ok Guy's , so does anyone have an idea on how much power this is worth ?
Say on a 450 HP build or is this only worth it on a max effort deal ?

Glenn

[25stevem]

Assuming your 450 hp motor is already breathing thru headers , and headers on such a motor add about 20 hp out of the total of 8 cylinders I will venture a guess that since we are taking about improvements pertaining to just 4 cylinders that your looking at a 8 to 10 hp gain at like 5500 rpm.