4V pocket porting

i am building a forged turbo mark viii. i like the b heads

i am going to clean up the secondary, no egr.
i purchased 8 frpp stainless valves.(back cut, undercut stems.) i am going to spend my time doing a basic port of the primary. contour and enlarge it a tiny bit and use the new valves in the primaries and leave the stockers in the secondaries.

i am only out to get some flow on the backside of the primary ports that is factory limited.



1. back cut the exhaust seats to match ports.
2. removed flash in the exhaust ports
3. raised the exhaust port roof a tiny bit.
4. altered the inner short side.
5. removed a lot of the divider and knife edged it
6. more or less gave each exhaust valve its own gas path.

7. removed the shroud over the primary port in the chamber and laid it back to match the other port.

8. altered the primary bowl to change the gas angle more perpindicular. mainly after the guide.

the primary runner is really badly designed for power.

9. removed the short side bowl 'dam' and reshaped it resembling a short side.

10. where the primary port goes from square to round i lenthened that trasition from a 'step' to a ramp on the floor.

11. on the roof i eliminated the transition and raised the roof to the bowl.

12. removed the guide protuding into the secondary port.

13. blended ther runner to bowl

14. sanded it.

15. blended bowl to seat.

16. left the rest of it the hell alone.

all of that without removing a lot of meterial. gentle little alterations.

PICTURES.

yes there is. have you looked at the ports. pocket work will hardly hurt a disastrous factory design.

the factory design does everything possible to eliminate half of the valve. shrouded nearly against the valve.
a short side the has a SHELF. not a radius, but a straight edged shelf.
a bowl shaped more like a spoon than a radius.
a transition from square to round that is a full blown STEP.


even YOU can hardly argue it cant be mildly altered for better performance.

crap if i just short sided it and deshrouded it its a massive improvement. add racing valves and it is improved.

but the dyno will tell N/A, eh? it isnt like it has to be much better to be an improvement over 276ish rwtq bolt-on tuned B heads are known for.



just buy yourself a set of b heads and remove the valves. after that make a statement like 'you just dont know if its better or worse" please. these arent any where near my first set.

cragg clacks flow bench is sold so no numbers. i might try nashville and see what i can find.

B head stock numbers are typically 233intake at 28" .500 and 160 exhaust at .500".

well you are in luck. i funally found a flow bench in nashville that can flow 4 valve heads. ill get them done in the next week or so. and provide you with the basic info.

before number can be found anywhere for stock B heads. at all lifts. so really i will know what has changed. of course the valves bias low lift because of their design, but stock cams only lift .425 anyway so thats my only parameter.