Thoughts on Valve size?
The '1.88 intake valves in a 318 head' changes the shape from the seat to the top of the short turn so much, that you better know how to port heads-properly shape it, blend the roof/bowl/runner or it'll be weak and less than a stock 1.88 360 head...especially in the lower lift. If you don't do that work, you end up with possibly matching peak flow...the the entire way to peak could be 20cfm behind. As for the exhaust, there is a decent little port, it holds it's own with factory spec'd 1.50 in ported form to the 1.60 j or x in mildly ported form, so it will actually support a 1.78/1.88 int valve, and boy does that port move fast...
The 360 head at 1.88/1.60 with a good compression aka GOOD CYLINDER PRESSURE is an easy one, a lot easier than working a 318 head when it comes to making 350-400hp, because it just flows more air and will flow even more if you port them and at lower lifts...which is where this goes next.
It is easier and you just get more flow throughout the lift range with a 2.02 over a 1.88 in a 360 head, testing back to back factory 2.02 J vs 1.88 J , 2.02 wins, I have found it hard to get [email protected] lift from a 1.88 intake valve, but it was the casting I used. There are so many greater cylinder head guys out there, well...maybe not many...but whats said in this post is not the 'end all'
Someone mentioned the 1.94, the skinny stem idea, the valve shouding thing...
The 1.94 intake valve is a great idea, but in 11/32 stem "less weight" 1.60 exhaust valve and installed in the 360 heads you have, with a bit of bowl/guide porting they give 250/190 cfm.
Last for those who don't know. The factory 318 chamber valve de shrouding cut is about as big as the bore of a 340.
A lot has been said and covered already and some excellent points made, I'd like to add a little more, say..'dive further' into some of that.
The '1.88 intake valves in a 318 head' changes the shape from the seat to the top of the short turn so much, that you better know how to port heads-properly shape it, blend the roof/bowl/runner or it'll be weak and less than a stock 1.88 360 head...especially in the lower lift. If you don't do that work, you end up with possibly matching peak flow...the the entire way to peak could be 20cfm behind. As for the exhaust, there is a decent little port, it holds it's own with factory spec'd 1.50 in ported form to the 1.60 j or x in mildly ported form, so it will actually support a 1.78/1.88 int valve, and boy does that port move fast...
The 360 head at 1.88/1.60 with a good compression aka GOOD CYLINDER PRESSURE is an easy one, a lot easier than working a 318 head when it comes to making 350-400hp, because it just flows more air and will flow even more if you port them and at lower lifts...which is where this goes next.
It is easier and you just get more flow throughout the lift range with a 2.02 over a 1.88 in a 360 head, testing back to back factory 2.02 J vs 1.88 J , 2.02 wins, I have found it hard to get [email protected] lift from a 1.88 intake valve, but it was the casting I used. There are so many greater cylinder head guys out there, well...maybe not many...but whats said in this post is not the 'end all'
Someone mentioned the 1.94, the skinny stem idea, the valve shouding thing...
The 1.94 intake valve is a great idea, but in 11/32 stem "less weight" 1.60 exhaust valve and installed in the 360 heads you have, with a bit of bowl/guide porting they give 250/190 cfm.
Last for those who don't know. The factory 318 chamber valve de shrouding cut is about as big as the bore of a 340.
