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Thoughts on dual pattern custom cam grind
https://slantsix.org/forum/viewtopic.php?t=21698		 Page 1 of 4
Author:  AnotherSix [ Wed Jan 31, 2007 9:04 pm ]
Post subject:  Thoughts on dual pattern custom cam grind
With the erson deal happening I am looking at a custom grind. Something to work with a stock converter and 3.23 gears. I have been thinking about a 210 / 218 with 112 lobe centers, maybe 111. If they have another lobe around 215 I might use that for the intake and the 220 for the exhaust, but I did not see one listed. Any thoughts or experience with something like this? I want fairly smooth idle, broad torque and to actually pull up to about 5000 rpm. The engine is getting a ported head with 1.70 and 1.44 valves, 9-1 comp ratio and a custom 312.5 cfm progressive two barrel that does not exist just yet but I have worked out and resolved myself to making happen.
Author:  emsvitil [ Wed Jan 31, 2007 9:59 pm ]
Post subject: 
Image

a 254 254/266 and a 266 erson. same lobe seperation and centerline




edited 2015-02-25: fix link
Author:  Dart270 [ Thu Feb 01, 2007 4:48 am ]
Post subject: 
You should know that a few of the fastest racers use a cam with more intake duration than exhaust - the reverse of what V8 guys usually do. I would try that instead with those lobes.

Lou
Author:  emsvitil [ Thu Feb 01, 2007 5:24 am ]
Post subject: 
Quote:
You should know that a few of the fastest racers use a cam with more intake duration than exhaust - the reverse of what V8 guys usually do. I would try that instead with those lobes.

Lou
lowest torque of them all until 4500, then slightly better HP than 254 (lower than 266 & 254/266)
Author:  panic [ Thu Feb 01, 2007 5:58 am ]
Post subject: 
Yes, I'm wrong again.

It's so simple:

"exh flow on well ported heads is usually around 80% of intake flow, even at high lifts, and can be higher percentage at lower lifts"
Author:  Doc [ Thu Feb 01, 2007 8:33 am ]
Post subject: 
Quote:
...This is an extremely complex subject. If you guess wrong and you're lucky you'll never know what the engine might have done because you have no base line. If you guess wrong and not lucky (no power, no mileage) you get to do it all over again. ...
Unless you've discussed this with your head porter after a complete flow test you don't know what you need.
Oh so true. I have done some "best guess" dual pattern cams over the years and have not found one that "jumped-out" as a real break-thru from a performance standpoint.

I have come around to the "more on the intake" way of thinking for naturally asperated, non-NOS applications. I would "gamble" another $130.00 plus an engine build / install to try one of those.
After you "run the numbers, it still feels like "tossing the dice" every time I get one of these custom cams ground.
DD
Author:  NewLancerMan [ Thu Feb 01, 2007 8:37 am ]
Post subject: 
Doug, what are some of the numbers you have tried already? I'm sure people would be happy to hear.

Also, I know several people including Lou have run the stock Erson 270 & 280 and been very happy with them.

MJ
Author:  Dart270 [ Thu Feb 01, 2007 9:05 am ]
Post subject: 
I have not run any Erson cam - only thought the 270 looked to be a good choice for a streeter with stock (or close) converter. When Summit had them for $100 I had thought about buying one.

Note that all the "longer intake dur" cams I've seen (Doug's different?) are for long duration cams, like 250 to 270 @ 0.050".

I plan on getting a few custom cams made with more intake duration to try out. TIME is the biggest factor here...

For panic, the exh flow on well ported heads is usually around 80% of intake flow, even at high lifts, and can be higher percentage at lower lifts.

Lou
Author:  DusterIdiot [ Thu Feb 01, 2007 8:38 pm ]
Post subject:  Yep...
Quote:
I have come around to the "more on the intake" way of thinking for naturally asperated, non-NOS applications. I would "gamble" another $130.00 plus an engine build / install to try one of those.
After you "run the numbers, it still feels like "tossing the dice" every time I get one of these custom cams ground.

I've batted this subject around for a couple years now trying to get an idea of "where" to go on a cam for the hpak/efi/long rod motor...I got the feeling that my formula had to "fit" into the "longer intake" & "try to keep the overlap shorter to prevent reverb in the runners" & watch your lobe separation and duration to prevent too much "lump" for the computer to handle....


It really is like "throwing dice", I don't trust the computer simulation much considering it said rolling a 300 degree roller cam with the NA EFI slant would net me some "turbo" like power...I ended up having to "retune" the simulator with some head flow numbers off of here (I love how they think "oversize" = Cleveland valve sizes), using the "tuned port" for the Hpak intake, and calling the slant a stock chamber and not using "wedge" to get the numbers close to being real world (I double checked the results of these tweaks using the Beater Valiant and a G-tech, and now things are much closer to the real deal...).

What came up for a daily driver was something like a 268 intake with 258-260 exhaust, a 109 LSA and a moderate lift (under .50 not including lash).
Doc had a nice (low duration) dual pattern cam card he posted a copy of once with the caption "feels like 268 mopar cam", that looked like a good grind.

One thing that is known is the LSA and how you advance/retard the cam can affect your HP and torque peaks, as well as idle quality...


-D.Idiot

"It's a real hair tearing experience, I'll be bald before the engine ever gets built...but I'll be much more streamlined ,right?!??!"
Author:  Sam Powell [ Fri Feb 02, 2007 4:50 am ]
Post subject: 
The reason it is like "dice throwing" is because there are so few of us. I think the early SBC guys were throwing dice alot too, but it has all been documented to a fair-thee-well now. Not so with the slant six guys. The more we share information, the less dice throwing is involved. Of course not all SBC powered cars are equal, so there is still some magic formula found every once in awhile there too. :wink: But their baselinne of knowledge is certainly broad enough to eliminate most geussing. Keep asking these kinds of questions. I am always pretty impressed with the knowledge that shows up in subsequent replies.
Author:  emsvitil [ Fri Feb 02, 2007 5:13 am ]
Post subject: 
A longer intake duration would be applicable when you have an intake restriction due to the valves,ports,runners, carb..... (restriction devices in some racing classes)

It gives the air more time to make it through all the obstacles
Author:  DusterIdiot [ Fri Feb 02, 2007 6:21 am ]
Post subject:  Where's Vic when you need him?
Quote:
Of course not all SBC powered cars are equal, so there is still some magic formula found every once in awhile there too.
That's one thing that we do have going for us, the numerous "hot rod" cam swaps and dyno sheets and "how to turn the SBC junkyard 350 into a street machine"...there are a few articles that have some real world dyno plots that show what happens when they change the grind from a 106 LSA to a 112 LSA, as well as what happens to the curve- HP vs. Torque when you advance or retard the cam...

We need a "lottery winner" to do a "Vic Edelbrock" on an engine dyno with Doc one weekend like in the old days when Vic would take a 1967 383-2v engine and run it, then swap some cams in show the improvement on a graph then add bigger valves, etc... so we really do have numbers to see what the "small chamber/long stroke/small ports", really likes (of course turbo/blower and a useable roller cam would push the top of the envelope). Even then there would probably be an NA EFI grind vs. the Carburated grind since the EFI is a bit more tolerant/quicker to react to certain characteristics than the mechanical carb is...

Luckily most people are "doing something different" so he have some variety to see what's out there, but when it comes out of your pocket, research does get kind of $$$...


-D.Idiot
Author:  mpgmike [ Fri Feb 02, 2007 8:05 am ]
Post subject: 
Something that would make the whole cam choice a little easier would be infinately variable valve timing. I know you're thinking exotic, but here is something affordable that could make a killer cam perform like a stocker under peak VE while cruising etc., then allow the cam to wake up at the higher operating rev range.

http://powrehaus.com/2007/01/26/powre-valvz/

What do you think? I have 2 of these Valvz sitting on the kitchen table, and 3 sets on order. I've been researching them for a couple of weeks now. I'm totally blown away with what they're capable of.

Mike
Author:  Rug_Trucker [ Sat Feb 03, 2007 9:27 am ]
Post subject: 
Got some pics Mike? I am interested in these. They sound good in theory.

I just am like the guy from Missouri show me!
Author:  argentina-slantsixer [ Sat Feb 03, 2007 9:53 am ]
Post subject: 
I was considering those profiles (for custom profiles)

Valve Event Timings seat to seat / @ 050 IVO IVC EVO EVC

#1 20 62 76 31 / 3 37 45 -5 lift .480 using 1.5 rocker ratio
#2 25 59 85 35 / 13 49 75 25 .500 lift 112º LSA 107º IC
#3 25 59 80 30 / 13 49 70 20 . 500 lift 111º LSA 107º IC
#4 29 63 65 25 / 19 53 66 23 lift LSA LC same as above
#5 22 62 80 40 / 1 53 59 31 .510 lift 110º LSA same IC (110º)
#6 22 74 68 22 this is an OEM cam from our argentinian chrysler... I would only add more lift (original was .4 wich is low) LSA is 114.4 IC is 116 :shock: is "as is" measured from a cam extracted from a valiant 4 GT (dual carb manifold equipped at the factory) I'd add the most aggressive lobe profile that is acceptable to use on our .904 lifters. I don't have the valve timing chart @ 050 for this last piece

anybody interested in playig around send me an e-mail and I'll e-mail you the dyno 2003 cam files for this profiles.
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