Cyl Head Port to RPM???

[NJSPEEDER]

i was wondering if anyone wouyld know if/where i can find either a chart or a good formula for comparing the cc's of intake and exhaust ports to the best operating rpm for the heads.

-thanks

[Batman]

:shrug: I think that would also depend on how the heads were ported. I don't know if there is a given formula for that :???:

[NJSPEEDER]

i was wondering the same thing.
i am not sure though. it takes a certain volume in the intake and heads to satisfy the draw volume of the cyl as the piston cycles. would it need to be a total volume formula relating intake runner + intake port to cyl draw or would it be a straight draw vs demand formula just for the head?

this is one of those times i am sorry i dropped out engineering in college.

[johnjzjz]

the guys who know the info you are talking about dont shair it -- as you already know the motor size the cam duration and valve size all play -- as small a change like back cutting the underside of the valve head would thro off the game - and can only be checked on a bench machine at .000 to.100 lift - matching the parts in full on racing porgram like you guys do bigger is more power always -- of course to a point the computor programs give it a good stab but will never match real time -- the only way i was able to figu out what the V Twin wanted in port loacation and size is with fuel dye in the gas and real time racing than tear it down and feness the ports it got us their but it took an entire season of racing in small steps that turned into a #1 plate -- but it was time and very hard -- jz

[WildBillyT]

Tim, this isn't really what you asked for, but maybe you can analyze the numbers and draw some conclusions... :shrug:

http://users.erols.com/srweiss/tablehdc.htm

[best of both]

There is a good book that you can get from a book store or possiblt from Summit or Jegs, It is called How to Build & Modify Cevrolet Small-Block Cylinder heads By David Vizard. To answer your question The Cross Sectional area of an intake port and the size of the engine determine the rpm range of every cylinder head, there are math formulas in the book that you can use to figure out your own heads. To answer the comment on the guys who know wont tell. It is more because you can spend eight hours talking about what makes a head work and why and still never know it all. Flow numbers are not always the best way to pick a head. Watch who runs good and find out who did the head work. There are a lot of as cast heads that work great for a lot less money than you would pay for port work and a good valve job. I have two Chevrolet powered Race cars and a 96 Z28 for a driver. My Malibu is a mid ten second car with a 331 inch motor with a head the most would use for scrap but I have more time in them than I should have spent. If you have any more questions just ask.

[johnjzjz]

There is a good book that you can get from a book store or possibly from Summit or Jegs, It is called How to Build & Modify Chevrolet Small-Block Cylinder heads By David Wizard. To answer your question The Cross Sectional area of an intake port and the size of the engine determine the rpm range of every cylinder head, there are math formulas in the book that you can use to figure out your own heads. To answer the comment on the guys who know wont tell. It is more because you can spend eight hours talking about what makes a head work and why and still never know it all. Flow numbers are not always the best way to pick a head. Watch who runs good and find out who did the head work. There are a lot of as cast heads that work great for a lot less money than you would pay for port work and a good valve job. I have two Chevrolet powered Race cars and a 96 Z28 for a driver. My Malibu is a mid ten second car with a 331 inch motor with a head the most would use for scrap but I have more time in them than I should have spent. If you have any more questions just ask.

A very good friend and customer of mine has a 1965 mustang super stock car NHRA the year before last he had the ( GUY ) as they are called do his heads and he got the national record for 2 or 3 months i think, its a 289 automatic 450 CFM orig 4 brl carb orig weight car 10:97 at a cost of $4500 for the porting alone, than the parts and valve job work -- i though this was the guy -- guys i was referring too -- been racing and doing this almost 35 years even guys i know 20 years or more do not talk about how they achieve high flow #s -- but maybe it happens you can walk up to a guy who you are racing and he is winning and ask him who does his work and he will tell you the truth ( right ) but today most like AFR will sell you a set of heads CNC Ported that will rival anything anyone is doing buy hand at a cost if 1/3 a head port shop would have charged you -- and i have a collection of very interesting math books on all the parameters you are looking at -- but you will get lost in a sea of confusion -- so many things are relative to so many other things -- dizzy is the term after reading, it does help but, keeping focus on the issue you started to look at becomes a blur -- you want to do some reading its all formulas or i can give you the name of the book and the author ( Tim ) and answer some questions but most of it is out their -- jz

[best of both]

I believe the fastest piece I put together in the last few years went 7.60s at 185. When I was still with the Hot Street Car in the NMRA we were known for answering peoples questions, even repairing transmissions and cylinder heads for others in the class. When it comes To Super Stock it is a whole new ball game.The Cars are using many trick parts to make them work without tons of horsepower. They are limited in the cylinder head castings they can use so of course they are not going to share head numbers. A lot of the heads are not even close the modern castings. I have at least a dozen friends who run Super Stock. How do you think we ran within a tenth of the fastest cars in Hot Street with as much money in our car as the other guys were spending on motors.

[johnjzjz]

I believe the fastest piece I put together in the last few years went 7.60s at 185. When I was still with the Hot Street Car in the NMRA we were known for answering peoples questions, even repairing transmissions and cylinder heads for others in the class. When it comes To Super Stock it is a whole new ball game.The Cars are using many trick parts to make them work without tons of horsepower. They are limited in the cylinder head castings they can use so of course they are not going to share head numbers. A lot of the heads are not even close the modern castings. I have at least a dozen friends who run Super Stock. How do you think we ran within a tenth of the fastest cars in Hot Street with as much money in our car as the other guys were spending on motors.

good for you dude / for me its the fun part getting a few wins here and their makes it all worth while --- i hate the big high powered motors they make you a hero and a villain in the same sentence in a split second -- as far as super stock goes its only money and its not mine hahahhahahaha -- jz

[best of both]

I couldnt agree more. I have a 10 second Malibu and a mid 8 second Mustang with a Small Block Chevy and F1r Pro Charger blow thru setup. I have more fun in the Malibu at the track and the most fun in My Z28 on the Street. The Fast car I mentioned belongs to a long time friend and engine customer. I spoke to him this afternoon The Car is a Haas Prostock Chasis and he actually went 6.90s with NOS a month or so ago and I didnt even know. Cars for me are not an Ego thing. The amount of people I have helped in my life takes care of that, I only see my motors run about once a year or so since most of my customers are Ford guys. I prefer the NMCA or NSCA even more than an NHRA event. Joe