rover port size?

[kokkolanpoika]

What size rover stage 4 head port are?
Des hammill book say (page 114) inlet 47x28mm and exchaust 39x28mm.
(page 138) 44x27 inlet and axchaust 36x24mm? Are those smaller port for stage 3 port size?
Has anyone got stage 3 or 4 heads and can measure those port size??

What about seats thoart size? My valves are 43mm and 38mm i´m thinking to machine thoarts inlet about 37mm and exchaust 34mm?

Any info is welcome..

[HairbearTE]

This question is a tad tough to answer since some of the heads by different companies vary considerably despite being designated stage 3 or whatever by all. You should also realise that dimensions such as this on their own offer no indication of the quality of the work that has gone into the head. I've just measured 45x25 on a "stage 3" head i've got to hand. This is an RPI head and they dont do the porting themselves so may be the same as others.

[kokkolanpoika]

This question is a tad tough to answer since some of the heads by different companies vary considerably despite being designated stage 3 or whatever by all. You should also realise that dimensions such as this on their own offer no indication of the quality of the work that has gone into the head. I've just measured 45x25 on a "stage 3" head i've got to hand. This is an RPI head and they dont do the porting themselves so may be the same as others.

Thanks..
Just one think. is it possible that you measure exchaust too?

[HairbearTE]

Ok, just measured exhaust @ 40x26mm. They are slighty more square than stock. Actually these look quite good! Remember of course that the exhaust exits at an angle to the exhaust face so this dimension could not really be said to be the dimension of the port itself. Yes you can use these dimensions as a guide to what your port may look like from the outside but they are not the most important aspects of head modifications in themselves. The first 20-30 hp of potential in a stock head is around the bowl area, valve guide and valve seat area of the head. Fit bulleted guides, knife edge the approach to the guides in the port roof open the bowl area behind the valve a bit, get a 3 angle valve job and dont do anything that reduces the radius of the short turn (floor of the port) as a smaller radius here leads to seperation from the port wall of the inlet charge, this in turn leads to uneven mixture flow through the valve. There are a number of good books on the subject of head porting and flow and if you dont already have any then it would be worth the small cost of purchase if it helps you make a better head.

[kokkolanpoika]

Ok, just measured exhaust @ 40x26mm. They are slighty more square than stock. Actually these look quite good! Remember of course that the exhaust exits at an angle to the exhaust face so this dimension could not really be said to be the dimension of the port itself. Yes you can use these dimensions as a guide to what your port may look like from the outside but they are not the most important aspects of head modifications in themselves. The first 20-30 hp of potential in a stock head is around the bowl area, valve guide and valve seat area of the head. Fit bulleted guides, knife edge the approach to the guides in the port roof open the bowl area behind the valve a bit, get a 3 angle valve job and dont do anything that reduces the radius of the short turn (floor of the port) as a smaller radius here leads to seperation from the port wall of the inlet charge, this in turn leads to uneven mixture flow through the valve. There are a number of good books on the subject of head porting and flow and if you dont already have any then it would be worth the small cost of purchase if it helps you make a better head.

Ok.. Thanks again.

I have got shortened&bulleted bronze valve guides and valve stem diameter is 7.93mm. I bought those guides and valves from RPI.
My local machine shop just take off std guides. Now i have got more room to port those heads. After Xmas.
I must to port some material away from those guides area (knot area) inlet area almoust whole knot and exchaust area (roof) also 2-3mm. Then guides/port look very good..

[Boosted LS1]

It will help you if you make a dummy guide/s from a piece of copper pipe. Shape one end the way you want the port roof to look like. Then you can get all the inlets and exhausts identical to eachother

You need a tube for the inlets and a tube for the exhausts. Put a 'depth stop' on them

Boosted.

[stevieturbo]

sizes and stages mean nothing.

You cannot compare one companies stg1,2,3,4 to anothers.

Its all about airflow. Some guys are better at it than others. Huge ports arent necessarily the way to go, good shape that produces good airflow and high port veolicites IS the way to go.

[kokkolanpoika]

It will help you if you make a dummy guide/s from a piece of copper pipe. Shape one end the way you want the port roof to look like. Then you can get all the inlets and exhausts identical to eachother

You need a tube for the inlets and a tube for the exhausts. Put a 'depth stop' on them

Boosted.

I have got a "dummy" plastic guides from inlet and exchaust ports.
I just port all 8 exchaust ports and they look like identical and feel like identical if i but my finger in.

I dont know are they good or poor, but i´ll try my best.
port size is 40x26,5mm.

Guide looks good to me. Without porting, guide is inside the cast. Be seen about ~2mm, now it can see about hole "cone" area ~5mm?

ports size is same as mine earlier home ported head, but guide area are now ported, and 4,6 engine make 300hp with those earlier head.

seats are std size in this pick, first porting, then put new guides in + new seats and then porting seat area again.

[Boosted LS1]

I understand what you are doing At least they will all be the same.

Boosted.