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Topic: 1.6 or 1.7 RR's? (Read 1642 times) previous topic - next topic

1.6 or 1.7 RR's?

Yesterday I took my GT40p heads and lower intake to a local guy who does lots of port work on fords. I'm still going to run stock size valves but he thinks they should easily flow 200cc on the intake. He also seems to think that flow velocity at low rpms shouldn't be adversly affected and could possibly improve. I'm trying to decide if I should return my 1.6 Ford racing roller rockers for 1.7's. I will be using an E-303 cam and thought that with the extra flow in the heads and intake that I might benefit from a little more valve lift providing there will be no piston to valve clearance problems. I know I should just get a custom grind camshaft but the E-303 is brand new and already installed so I'm going to keep it for now. The shortblock is all stock 1997 Explorer so the hyperutectic pistons have valve reliefs.

Should I wait and test clearance with the stock 1.6 rockers and see if I can clear another .030" of lift, or just order the 1.7s?
GT40p 5.0 w/ vortech @ 9.5psi, 400rwhp

1.6 or 1.7 RR's?

Reply #1 –
Keep in mind that the GT40P heads dont flow all that well above .500 lift. They like more duration than lift.
It's Gumby's fault.

1.6 or 1.7 RR's?

Reply #2 –
The heads are getting ported, they should flow significantly more air than stock. I have heard that before about the heads not flowing well over .500" lift, but that is stock. I wont have numbers from the flow bench for over a month, does anyone know what these heads typically flow when ported?
GT40p 5.0 w/ vortech @ 9.5psi, 400rwhp

1.6 or 1.7 RR's?

Reply #3 –
Go 1.7s,the extra .30" lift should be worth a few extra ponies.

1.6 or 1.7 RR's?

Reply #4 –
Does anyone know of someone running a combo like this and if you can clear .529" lift with p heads and explorer pistons?
GT40p 5.0 w/ vortech @ 9.5psi, 400rwhp

1.6 or 1.7 RR's?

Reply #5 –
while your at it,, have a look at my diy link below.  you may wanna consider getting the 1.54 exhaust valve installed as well if your porting. 

i dono anything about the 40 or the 40p heads other than what research ive done.  I do know that you have that smaller exhaust valve that started in 97.

if you get any useful info that i could add to my diy link, please reply.

can you find your casting number please? and post it.  Check out the below link and see the mustang guys about flow numbers and such, they even have confussion on the the curiosities i had but ,,, they may know the numbers
see link>>>
http://www.foxtbirdcougarforums.com/showthread.php?t=11829




: )

1.6 or 1.7 RR's?

Reply #6 –
Quote from: jcassity;125156
you may wanna consider getting the 1.54 exhaust valve installed as well if your porting. 


I asked my guy doing the port work about larger exhaust valves. He is pretty experienced with fords and these heads. He said that it wouldn't be worth installing larger exhaust valves for a street application. If I was running a huge cam, short runner intake, full length headers, etc. then it would be something to think about. These heads are so efficeint that increasing vlave size is going to a pretty extreme level.
GT40p 5.0 w/ vortech @ 9.5psi, 400rwhp

1.6 or 1.7 RR's?

Reply #7 –
I'll try and remember to get my casting numbers tomorrow. I'll have to call Mr. Green
GT40p 5.0 w/ vortech @ 9.5psi, 400rwhp

1.6 or 1.7 RR's?

Reply #8 –
That sounds really strange to me man.
My edelbrocks are only performers and they have 1.90in and 1.60ex stock,there has to be a reason they up the valve size,and that reason is flow.
 

1.6 or 1.7 RR's?

Reply #9 –
Quote from: dominator;125284
That sounds really strange to me man.
My edelbrocks are only performers and they have 1.90in and 1.60ex stock,there has to be a reason they up the valve size,and that reason is flow.



now thats the ironic thing,, they downsized the valves in 97 and up.

the exhaust valves were bigger in the previous gt head years.

odd isnt it?

1.6 or 1.7 RR's?

Reply #10 –
Quote from: dominator;125284
That sounds really strange to me man.
My edelbrocks are only performers and they have 1.90in and 1.60ex stock,there has to be a reason they up the valve size,and that reason is flow.



Larger valves typically do flow better, but only if the runners can support it. The shape of the runners on the p heads creates a more effeceint entrance to the combustion chamber than older heads. I would have to do some extreme port work to justify larger valves on this style head. Edelbrocks are MUCH better heads all the way around and can make use of the larger valves without porting.

This is just my theory, not anything I can really proove
GT40p 5.0 w/ vortech @ 9.5psi, 400rwhp