9500rpm and square lobes?

Don't know any street cars like that but I do know of some making over 110% VE.

We're talking airflow and port area right?

 

Me too.You will have to have cam lobes that look like the side of a cliff to keep from passing it all out the exhaust.That is very hard on the valve train.If you have ever seen a PS cam you will know what I am saying.I don't think a small block will reach MACH .55 at 7000RPM's Unless the port's are very,very small,in which case it won't feed itself at 7000RPM's Soo you are defeating your purpose IMO.A Pro Stocker will get there,but like I said 9500RPM's,500CID,and a different set up bank to bank and cyl. to cyl.

 

All I can say is for the car we were working on and what the Owner considered streetable they did not fit the bill

This was around three years ago and we were using a modified LT1 Intake.

We had ALOT of problems with the rockers. AFR told us we 'could' use regular rockers as they advertised but that we should really use Shaft rockers. The biggest problem was intake port interferance with the push rods. we had to have four ports welded back up so we could move them in to clear the push rods. We were using the CNC race ports on the AFR 220s. I do not know about now but back then they were definately not the same as the 210s.

Do I think big ports can be used on the street? Yes I am counting on it. It ALL depends on the owner/driver

 

Well, to kind of get back towards the original topic, deciding how big a port is too big depends on rpm (for a given displacement). A cam has a "comfort zone"of 3-4,000rpm. If you want to peak in the high 6,000's, which is the practical limit for an LT1 running the stock PCM, the car won't have much below 3-3,500rpm. This is true no matter what the port size, but the bigger the ports, the worse the situation will be. At the other end, if the port isn't big enough it won't make power up high or down low either! That is why a big cam in stock heads is a really screwed up setup. Better a big cam and ports that are "too big" than a cam that is too big for the ports, if you follow me.

A finished port in the 200-220cc range should be fine for a small block of less than 400ci running less than 7,000rpm. More rpm or more cubes needs a bigger ports. Less cubes and/or less rpm needs a smaller port. Stock displacement motors running stock cams do fine with 170cc ports, FWIW. Of course, they operate in the 1,500-5,500rpm range. A 383 operating at 7,000rpm needs ~40% more air than a 350 at 5,500.

Rich

 

Well this is all good but i still don't no how to pic the right head..

off the top of my head the set will be...
383
11-12.1
LT4 intake fully ported to the heads $$$$ to go to the Vic jr
With the LT4 intake i should peak in the 6500ish range and shift a little above that, i no the LT4 intake will not make power to 7000rpm

I will have to stay HR this year $$$$ but i think somthing in the 240/250 & 620lift on the x grinds should make a very nice set of the eng....

Whan the time comes i can go to the SR cam , port the heads, go to the Vic jr intake , fast and so on......

Will this work....the heads will be out of the box AFR's matched intake,cammotion cam, and so on.....

Is my thinking right here.

Could a HR cam work with the 220/227

thx

 

Who says a LT intake won't make power to 7,000?

Lets ask Mindgame what intake he had on his car with the 18* heads

May not be the best choice mind you...but when desent under the hood choices start at $1,500 and up.....

 

Get a set of 195cc or 210cc heads and have them ported!

Rich

 

Don't forget there was a spacer/adaptor between the head and intake,and a much worked on intake.The runner length and taper has to be right for your set up to make big power and if you want to put say $2500 in a LT-1 intake and have it remade,IT will make power.Wilson doesn't recommend it though,as there are other castings that will do a better job.

 

If the port velocity is high enough and the charge has enough inertia behind it, it won't ever make the turn to go out the exhaust valve. That's the whole point in getting the VE to high percentages... trapping the charge.

Doesn't really have much to do with the lobe shape as it does with the closing and opening events.

Based on my calculations, my own combination should be in the .5-.55 range near peak torque. VE peak was 111.2% (measured) which isn't too bad considering this aint the best intake manifold in that regard.

Speaking of the intake manifold. Even with the spacers and porting, I'm still quite a ways from the cost of a Hogans setup. And Wil$on... won't even go there. The CFE intake we just got back for a friends 355/215RR setup is sure pretty though. It was $pendy.

-Mindgame

 

QUOTE:
The CFE intake we just got back for a friends 355/215RR setup is sure pretty though. It was $pendy.



Show us some pics MG, I showed you some pics of the Wilson.Fair enough??


David

 

Aye, but the Wilson belongs to you.

I'm just putting this engine together for a gentlemen. I don't think he'd mind me taking pictures and posting em up but I definitely want to get his ok before doing so.

BTW, this one is sheetmetal. Not built out of a casting or anything. Looking for ~525 at the rear wheels with a cam in the 236-240º range! Am I crazy? You'll find out.

-Mindgame

 

Originally Posted by Curtis Leaverton, Developer of Dynomation wave action simulator
Researchhas shown that maximum port velocity through the minimum cross-section area of the runner should fall between 0.5 to 0.6 Mach, or about 600 to 720-feet-per-second. Port velocities above .6 Mach produce no further increases in volumetric efficiency.



Based on my calculations, my own combination should be in the .5-.55 range near peak torque. VE peak was 111.2% (measured) which isn't too bad considering this aint the best intake manifold in that regard.

Is this THEORY or fact.Has it been measured and has it made HP or is it all on paper. I would like to see it measured on a dyno.VE measurement's won't tell you intake velocity and the intake charge will go out the exhaust because it has a valve to help turn it out the port. This IS totally dependant on the cam.....

 

Dynomation
Vizard
Ricardo
Don Losito; Ultra Pro Machine
CF Taylor
Chuck R; PRED (has posted on this before)
Larry Meaux (has posted on this before)
More SAE papers than one could count
list goes on.....

Hey, they all concur that anywhere from .5-.6 is ideal and up to .7 is even feasible for extremely downdraft ports.

I have it on good authority that .5-.6 is a good target for 23º heads with that higher range going to the "high port" variants.

So, in answer to your question..... Fact.

Well if you say so LR.

Didn't mention much on camshaft lobe designs in there.

VE is indicative of intake and exhaust tuning, along with port velocity. If you have an intake charge that carries so little inertia that it would turn and go out the exhaust, then you have a problem. Either that or your just analyzing the situation in regards to low engine speeds.

-Mindgame

 

In your case, you could probably more than get by with the AFR 195. Then port as you need more.

-Mindgame

 

Well think what you want,but .5 mach and making HP is not attainable on a small block Chevy.You can have one or the other.I don't know who "THEY" are but I also know what makes HP below 7000RPM's.Ve does NOT tell you intake port velocity.....Look at the engine masters engines,READ a little more and you will see.
I thought this discussion was about small block Chevy's,not F-1 or Indy type engines.
If .5 MACH was the thing then people like WJ and Anderson would be doing it--They aren't.With the sewer pipes size runner's,2.500+intake valves,they ain't worried about MACH numbers.All they want is air and fuel in the chamber,the more the better.Like I said-more air=more fuel=more pop=more HP.
You have to have a rod piston combo to get those number's along with a port size that is very small.You don't have the bore or a 4" rod in a SB Chevy.
As far as sources I know and talk to people that are actually doing the port/head work on todays engines and not writing books about how to, and they don't agree and neither do I.I will say again much over .4-.43 MACH at 7000 and you are out to lunch.Bigger number's in this case are not better IMO and a bunch of other folks.
"O" you didn't by chance have a blower attached to your engine when you saw the .5-.55 velocity numbers did you??