Most high quality valves have the stem "necked down" at the valve head. And yes, it does improve flow.

Rich

 

Yes, I know. I think it's called back-cutting (?). LS1 valve stems are a smaller diameter than LT1/SBC 1 valves. Is there anything to be gained here in addition to back-cutting?

 

I think 450 should be cake for a 383 with the right setup and good heads. I know my 355 made 440 rwhp with lt1 castings and a solid roller through a 9" with 4.71 gears. Put a stock rear with 4.10s in my car and i would be in the 455-460 range. I'm with mindgame on his thinking. There are alot more 430-450 rwhp 350-355 cubes motors showing up so its time for the stroker motors to show their stuff also. Look at the complete combo of the motor and you should reach your goal.

My heads are off the car now and I'm going to lt4 castings resulting in going from 175ish CC runners(still to be measured) to 205 ish and from a 2.0 valve to a 2.05 valve. I guess we will have results soon on what those kind of changes will do.

I also believe that peak flow numbers are concentrated on too much here. A head that flows 270 at .700 will do nothing for you. No one runs a cam to hit that lift. A perfect example of this is the head flowing 248 peak but makinig 440 rwhp. Those heads are obviously very efficient and have good velocity to make that kind of power. I will bet you that my heads don't flow much more than that....assuming i even match those flow numbers. Another example would be SAR2k...his heads flowed alittle better than the above heads and made 452 rwhp. I would bet both of those heads aren't a big intake runner CC head. A good flowing head with a smaller runner will outperform a high flowing head at high lift numbers that had to open up the runners alot to get that peak flow number. There is ALOT more to a head than peak flow bench numbers guys. Not to even get into the fact that those numbers can be skewed to begin with and that every bench flows different just shows how silly flow bench racing is.

Back to the original question...AFR is a good head, I would go with a 210 over the 195s any day from seeing the out of the box numbers. You may even get some gain out of a 220 head on a big cube motor with the right seteup. But you may be getting a bit on the ragid edge of a good mannered street car with those heads and the correct setup to use them. A hand blending is usually going to get you some HP even over a race cnc ported head.

 

do you have the 195s already?? why not just go with the 210s?

 

As stated previously by a few other people before me in this thread...if you think that the 195 AFR heads are the same as the 210's or 220's. You are mistaken. I would listen to 95bird and engineermike, because these guys have actually flowed these heads on a real flow bench under controlled conditions and aren't biased. I would also say that you are going to have a more streetable car making 450rwhp with a slightly larger head that flows more and a smaller cam as opposed to a smaller head that flows less and compensatory cam change required to get you to that power level. Just my opinion though. We'll find out in a couple months when I pick my motor up if I've done it right.

 

the primary thing is that the 210 is 80cc exhaust port vs 65cc exhaust port on the 195... not to mention the intake size port.

 

I agree.

 

95Bird or even SAR2k- take your topend and put it on a 383 with the right "matching" camshaft, Do you think you could push the numbers over the 450 mark.

Or how would you achieve this.

 

That's one way of looking at it but let me propose another....

What is wrong with using a cylinder head that is just large enough (volume wise) to feed an engine of given displacement and turning "x" rpm?

This cylinder head, if sized properly sized in the minimum cross section area, would have higher average port velocity and in that would likely produce higher volumetric efficiency, correct?

In my mind there is a close to optimum size and erring to the too-large-and-lazy port is probably more detrimental to street engine performance than perhaps being too small.

-Mindgame

 

I believe SAR2K has already been over 450 rwhp.

Mike

 

I know that with a 383 I could be well over 450 rwhp with the right cam. I would change my head setup to feed more air since the larger cubes could use it. And as mike said above SAR has already been there. Put my current motor on a stock rear with 4.10s and it would be over that number already also. YOu still wouldnt need a head that is ported for max numbers in the .700 lift range since you would have a lazy port in my opinion. Honestly if I built a NA 383 and wasn't in the 480-500 rwhp range I would be alittle dissapointed. Listen to what people are saying here and do some research and your 450 rwhp should be easy. I always said..if you want to go fast..find people already going fast/making power and listen to them.

 

The problem is ...how do we find the optimal size for X cubes/rpm?

 

Easy... I ask Arty Ross at lunch, LOL.
Steve...

 

Go flow my old heads..get to work sucka. Oh..and ask him what runner volume for my motor..I think you know the specs

 

Yeah, I second that "get to work sucka" remark! I need an LT4 intake ported!!