Hey guys, I really don't know how to ask the question.

What I'm asking is.....for the size of the intake port on the head....like, lets say, 190cc.....what would the RPM range be of the head? 2000 to 6500RPM or 2500 to7500rpm?

I have looked high and low for the awnser to this and I can't find anything.

Is there a chart? Would the compression ratio have anything to do with it?

I hope I make sense, let me know if I don't.

What I am trying to do is match my parts so everything will work together.

Thanks guys,

Joe

Generally as the Intake runner size increases the RPM range is shifted up. Really good head design can offset this which is where good after-market heads can really make some gains.

My suggestion if you want to look at intake runner size and get an idea of the RPM range is take a look at Dart, AFR or Brodix heads with different runner sizes and see what range they say the heads are.

Compression ration also plays into it, but often heads will be rated for a range of Comp ratios.

You trying to match all your parts together is the way to go, making sure your Comp Ratio, Intake Runner length, Cam, gearing, etc is all matched to the same RPM range will net you the most HP from those components.

Good luck!

The size of the engine also has an effect.A 400 needs more air flow at 6000 rpms than a 350 does.Port design also plays into this some smaller volume ports will out flow larger ones.No cut and dried answer.

Joe there are so many things to consider, but if you know what rpm range you want to make peak torque in it'll help. I think a lot of guys run too large an intake port killing their bottom end and mid range. I found my last car had too small of intake ports, 171 for a 355, but it really responded well in the midrange, but ran out of umph up high. I'd go small again before I'd go too large. I've driven many SBC with too large a port and it isn't fun on the street.

This may help in your decision. Minimum port cross sectional area = rpm x stroke x bore x bore / 190,000. For example a 420 cid sbc that'll operate to 6500 rpm will require 2.28 cross sectional area, where a 355 cid sbc to operate at the same rpm only requires 1.93 cross sectional area. These are square inches. Some guys try to correlate this to the cc of the intake port volume, while some are close it doesn't really work (1.93 sq in doesn't mean you need a 195 cc intake port, but it's close to the best choice IMO, although a 200 or 210 may work well also). I had a chart that showed the relationship to cross sectional area and intake port volume that spelled out the correct size port volume based on cross sectional area, but I couldn't find it tonight. I'll look again.

When picking your heads don't get tricked into looking at the max lift flow numbers, you engine only operates at max lift momentarily. Mid lift flow numbers are much more important IMO. Also try selecting heads that offer 70-85% exhaust to intake flow numbers. This relationship tells a lot about a head and make sure the numbers don't look too good due to a weak intake port.

Just decide where you want to make max power, do the math and then a lot of research. Again I'd opt for an intake port that is slightly under rather than going too large on a street car. It'll be more responsive in the range that you use it on the street.

I would argue that cam sizing has more effect on RPM limits than head runner size. Look for the smallest cc runner that offers the most cfm flow. It's real easy to make this way harder than it needs to be.

Maybe we could be more specific if you let us know why it is you are looking into this. New heads? New combo? Wanting more power? The more info you can give us the better.

I would argue that cam sizing has more effect on RPM limits than head runner size. Look for the smallest cc runner that offers the most cfm flow. It's real easy to make this way harder than it needs to be.

Maybe we could be more specific if you let us know why it is you are looking into this. New heads? New combo? Wanting more power? The more info you can give us the better.

Wanna know? Well, It's not for me, it's for a buddy. He just bought a set of 190cc intake port heads with 58cc chambers. We are simply trying to match the intake to the heads and the cam to the intake/heads.....otherwize, match all parts together to make it run better.

If it makes any difference, it's a .040 over 327 with 4V flat top pistons.

Joe

A cam anywhere from 224-236 @ 50 should work good. Find a flow chart for the heads, they probable peak at .525 or so. Get a good converter too( call them up and tell the guy what you got). I had afr 195 with a 218@ 50 crane cam and it just died at 4800. rpm will be your friend with a 327 and 190 heads.