Thread: cylinder head maths /// Make selection easier

Originally Posted by EH179

It was mentioned earlier in the thread, to close the lash on the exhaust valve further, down to .018-.016".
My concern would be reducing the seat time on the exhaust, allowing the valve/seat to start burning causing damage and increase the water temp' for a street driven engine.
On a race engine, not so much an issue as they would run cooler fuels and get pulled down and inspected often.

Well a hydraulic roller has zero lash, and it doesnt burn the valves or the seat.. If you have an earlier exhaust valve opening it will also take more heat out of the engine and decrease the water temp, decrease the heat on the rings and ring lands its a win win.. You can get a series of lobes that have a lash range of .014-.018 which wouldnt burn the seat more vs a lobe that is .022-.026. You would worry more if the lash ramp on the lobe was .010 and you had a 1.6 rocker and specs called for .016 (lash ramp x rocker ratio) and you set that to .024 which is off the ramp, which would make a stuff up the velocity curve of the lobe sending it out of control no matter what spring you had.. When you see something that specs to .028-.030 lash it just tells you what the lash ramp is, you can go tighter with no harm but not looser..

Originally Posted by swampy

HI
Easy to say about LS when an early chev head has the capabilities of a vacuum cleaner .

Huh?

Hi
Big LS heads are flowing 350 easily upto 400cfm . Early Small block chevy [23 degree] dream of that .
Admitedly the LS is a different angle of head . The LS motor is a culmination of all the earlier chev motor designs . So better flow is no surprise .

HI
Comp Cams plastic dizzy grs last way longer than brass . There claiming 300%.

Cast cams eg flat tappet use cast iron or plastic

Austempered roller cametc or nitride can use plastic and steel dist gear.

Melonised gear canbe used on both above

Billet cams refer comp

MSD Pro Billet Dizzy chev comes with cast iron dizzy gear


Gear arrangement canbe different for different brands of cam

Originally Posted by swampy

Hi
Big LS heads are flowing 350 easily upto 400cfm . Early Small block chevy [23 degree] dream of that .
Admitedly the LS is a different angle of head . The LS motor is a culmination of all the earlier chev motor designs . So better flow is no surprise .

Doesnt really matter, you only want 450-500HP the AFR 195 you have will do this... Its more about the size of the port than flow, if you had 250-260CFM who cares that is enough.. The port size on the 195 is around 1.9 square inches.. For a 383 or 400 chevy you are good for 6000RPM peak HP

Hi
Yea from what I have read as long as I get 250-260 cfm once assembled with head and manifold together I will get there . A real 500hp 500tq .
Seen evidence of low rise singles flowing 250-260cfm . The new AFR mani should flow well and possibly above this .
Although the heads might flow 310cfm I doubt I will ever achieve more than 550hp with a 236/242 242/248

I have seen a Joe Sherman motor push around 600hp with these heads . The cam was a 260 @ 50 Circle track . USA dyno fudge figures so = approx.

Disappointing really as u can ask many head makers and u will get as many answers It all tends to revolve around 195---220cc . The MCSA ranges 2.2---2.4

EG
version A 2.4mcsa revs past 8000rpm .. I doubt this for a 400 cuin maybe just make it
Version B 2.2 mcsa peaks at 6500 revs to 7000 for a 400cuin ------- more believable of the two

Inbetween 2.1 peaks around 6300 with 400 cuin

Version B work out on dyno as well as in theory with the smaller port of 1.9.. peaking at 5700-5800 on a 400cuin


All version B style have about 500rpm left in them over there peaks and seen a lot of evidence of this .

You cant just flow a manifold on a bench without attaching it to a head the number is meaningless... Its just like flowing an exhaust port and thinking that flow number has anything to do with an actual real world scenario, that number is more meaningless..

A 2" port on a 383-400 could rev past 7500 it wont make peak power there but it will rev there, 2.2 rev up to 8000+ ..

Originally Posted by swampy

Hi
Big LS heads are flowing 350 easily upto 400cfm . Early Small block chevy [23 degree] dream of that .
Admitedly the LS is a different angle of head . The LS motor is a culmination of all the earlier chev motor designs . So better flow is no surprise .

Yeah I already knew that, thanks.

I was just at a loss trying to work out how you got that I was comparing LS and early model heads from reading my comment about Tony Mamo.

You would be better of adopting an LS based philosophy as opposed the early stuff...

Originally Posted by paulzig

You would be better of adopting an LS based philosophy as opposed the early stuff...

Big induction and exhaust and short cam specs?

yeah i agree dont have to do too much, swapped out the cam for a 216/220-degrees duration at 0.050-inch, 0.525/0.532-inch lift, and an LSA of 114. decent exhaust and a tune. 412 horses.

Originally Posted by Deuce.

Big induction and exhaust and short cam specs?

Problem with saying that is that you see something as short but if you take into account the lobe separation and then work out each individual valve event, look at the lift, and lobe area the cams end up sort of big really...

I'll do an example when I get back later tonight..

Originally Posted by HQ308Ute

yeah i agree dont have to do too much, swapped out the cam for a 216/220-degrees duration at 0.050-inch, 0.525/0.532-inch lift, and an LSA of 114. decent exhaust and a tune. 412 horses.

I’m guessing this 412 HP you speak of is from an LS with the above mentioned cam as I can’t see a 355 Holden punching out those numbers with such a small stick.

Originally Posted by 46Crab

I’m guessing this 412 HP you speak of is from an LS with the above mentioned cam as I can’t see a 355 Holden punching out those numbers with such a small stick.

OK so for the Holden 355 with a set of well ported VN heads 2.02 valve, lets say 280CFM.. Cam that is 232/236 106LSA+2 hydraulic roller could you see it making that power?

All I've changed is the IVO and EVC or overlap, the IVC and EVO is the same as the 216/220 114LSA cam at IVC40 EVO46 Only difference is overlap...

Originally Posted by paulzig

OK so for the Holden 355 with a set of well ported VN heads 2.02 valve, lets say 280CFM.. Cam that is 232/236 106LSA+2 hydraulic roller could you see it making that power?

All I've changed is the IVO and EVC or overlap, the IVC and EVO is the same as the 216/220 114LSA cam at IVC40 EVO46 Only difference is overlap...

With those heads and cam (232/236 106LSA+2 ) a 355 would piss in 412hp and then some. I was more asking (maybe I should have read further back) if the 412hp was based on on an LS engine with the 216/220 114LSA cam as it sounded more like a mild LS Cam not a Holden V8 cam.