CAM Selection 4v OC |
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Danno
Member Joined: 05-March-2015 Location: Chesapeake Status: Offline Points: 129 |
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Posted: 08-February-2017 at 11:10PM |
351c rebuild, 9.5 CR, C6, 3.25 gear. What is a good off the shelf grind for a mostly street app? Power brakes and I don't want to lose any "drive ability."
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Danno
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MrSmog
Senior Member Joined: 21-January-2016 Location: Ky Status: Offline Points: 1407 |
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stock cj grind or similar if you just want a good street crusier. all the info you need is right here in these two links. do you have the stock higher stall in that c6? i think factory 4c/cj cars came with a 2500-2800 rpm stall stock.
http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/4181021846 http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/4591090956 |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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the biggest mistake you can make is too much valve overlap, especially with an auto trans and moderate rear gear
the large valves (even the small valves are large for displacement) and the canted angles they're on make for very good breathing and what G.Pence calls 'cross-talk', how well the intake & exhaust valve work together during overlap. because of the excellent cross-talk, Clevelands don't need anywhere near as much overlap as in-line valve engines. a lot of 'shelf' dual pattern (heavy exhaust bias) cams can get into overlap issues due to the added duration on the exhaust side another G.Pence link http://pantera.infopop.cc/eve/forums/a/tpc/f/5650045562/m/2601013795
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72 GT Ute
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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I probably went with slightly less cam than I could or should have but it sounded good when I finally fired it.
It's a dual pattern cam but only at 217I and 225E @ .050 and lift is only .571I and .577E. I figured since it's a street car I went a dual plane intake to keep the cylinders separated. I'm curious Rock, what's your opinion on this cam with 10.3 compression? Edited by lynchster - 12-February-2017 at 5:37PM |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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MrSmog
Senior Member Joined: 21-January-2016 Location: Ky Status: Offline Points: 1407 |
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Thats a odd cam, never saw one with that short a duration and such high lift. |
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Nuggets
Senior Member Joined: 07-November-2014 Location: UK Status: Offline Points: 869 |
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Short duration with high lift makes me think of a blower cam
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Barnaby
429 powered 73 Stripper.....no comfort, just noise! |
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californiajohnny
Moderator Group Joined: 05-October-2013 Location: winlock, wa Status: Offline Points: 14609 |
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JOHN
74 GRAN TORINO S&H CLONE 74 VETTE CUSTOM 90 S10 BLAZER 4X4 LIFTED 77 CELICA CUSTOM 75 V8 MONZA SUPERCHARGED 79 COURIER VERT. SLAMMED 75 VEGA V6 5 SPD 70 CHEV C10 P/U 68 MUSTANG FB CONVERSION |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Nope, no blower. However I did convert it to a roller cam set up. Howard Cams (233215-10) with Lunati lifters.
It was suggested to keep it under .600 since I didn't sleeve the lifter bores. If it helps the advertised duration is 270I and 278E Edited by lynchster - 13-February-2017 at 4:03PM |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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With the reading I've done I'd agree with a repop CJ cam dialed in without the 4 degrees retard in the 72-73's. I think Howards does one but the lobe center is at 115 instead of the factory 117. |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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Clevelands like their lift. and the short duration is exactly what i was getting at in my post regarding overlap. the canted valves get the job done with the short duration, more duration is the deal breaker unless you're running at Talladega or Bonneville
as far as the 10.3: static goes, you'd have to find the intake valve close point and calculate Dynamic Compression Ratio (DCR) here's a link to some formulas http://www.network54.com/Forum/136503/message/1333332712/Cam+Math+by+Randy+gt350hr actually all of the blower specific cams I've seen the specs to use very modest lift (not a lot) and the duration is tailored to adjust the desired power band. Crower lists a couple on their page and believe those are the same cams that BDS listed on their site also. unfortunately there were 3 at some point but probably the highest rpm power band cam is not listed any more 115* is crazy wide by todays standards, I've seen the stock Boss cams listed as 120* and more various different places. current available cam cores can't even be ground that wide because they'll break through the heat treat, if you really want a cam wider than 114* it may require using a 'full round' billet core, it's not cast as rough lobes but machined from a round bar then cam ground i had a custom Bullet cam ground from G. Pence's recipe, Mechanical Flat Tappet light weight EDM cool face lifters In lobe: F285/355 @ 112* mathematic center
Ex lobe: F295/358 @117* mathematic center
In gross lift .614" adv dur 285* Ex gross lift .619" adv dur 295*
LSA 114.5*
IVO = 30° BTDC
IVC = 75° ABDC
EVO = 85° BBDC
EVC = 30° ATDC "Its a hot street cam alright. Idle like a boss 351 & rev to the moon. The
powerband is a little like a 12 cylinder Ferrari back in the days when they used
Weber carburetors. A little soft on the bottom end, but when it hits it stride
it will crack your neck. Race car acceleration." ~ George Pence George likes the wide LSA for his Pantera, it's a sports car not a muscle street strip drag machine. he wants full range power band which he says is what the wide LSA provides, the TQ curve is much longer & flatter than a narrow LSA version of the same cam. it'll carry rpm longer after peak HP unlike narrow LSA's that drop off like a rock. I'm dying to check out this neck snapping race car acceleration in an M code basket case motor i picked up. only issue it has is broken ring lands from hydraulicing a couple cylinders from the PO washing the engine and getting water down the intake. Ooops. i guess it smoked a little and he heard some noise so he pulled it down, found the damage and replaced it with a 5.0. i have a Blue Thunder, stainless valves, spring kit from Alex's Parts, doing the Winkmiester lifter bore bushing job on it, boring .030" and forged flat top pistons i gotta figure a rough DCR calc for that |
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72 GT Ute
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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Thanks Rock, I think I have to get someone who knows what their doing or buy a program to figure it out. I tried a couple of free ones but I keep up with a dynamic ratio between 9.7 and 9.9 depending on the calculator. It seems a bit high to me. I thought I figured out closer to 8.9 - 9.0 before. It could just be me or a product of the cam and static compression. It seems to run fine in the shop with 93 octane and the factory dual point but I'm a little concerned about installing the recurved electronic distributor. What do I know? I do bodywork. Edited by lynchster - 18-February-2017 at 10:04PM |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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that's a LOT of DCR even at 9:1, George recommends a conservative ~7.8ish and the highest I've seen suggested is only a couple points over 8:1i think altitude has more effect than the calculators give it
Edited by Rockatansky - 19-February-2017 at 4:02AM |
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72 GT Ute
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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I'm guessing at the altitude I do it at 500 and 1500 feet. I've read elsewhere 8.5 - 9-0 DCR is the limit for high octane pump gas. The fact that it seems to run fine (in the garage) makes me believe I'm not doing the math correctly or I need a better program. Or the third possibility is it won't show anything until it's running with a load. I noticed a variance with the inputs required in the various free ware programs I've tried so far. Edited by lynchster - 19-February-2017 at 10:47AM |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Nuggets
Senior Member Joined: 07-November-2014 Location: UK Status: Offline Points: 869 |
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Wallace racing calculator is fairly accurate for a free one
I run 8.45:1 DCR and 10.65:1 Static but thats on closed chamber heads with flat tops, still has to run 99 though.....and I'm at under 500ft most of the time If I run on 95 or 97 I have to pull timing out to avoid pinking, load does change how the engine reacts. You might find yourself having to pull a little timing out to help the engine out once you're on the road I can probably pull out the equations if you really want to calculate it yourself though, will be in my thermo engineering books somewhere
Edited by Nuggets - 19-February-2017 at 11:40PM |
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Barnaby
429 powered 73 Stripper.....no comfort, just noise! |
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lynchster
Senior Member Joined: 07-January-2006 Location: Pennsylvania Status: Offline Points: 2150 |
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First off I want to apologize for jacking your thread Danno.
I figured out my DCR issue. My cam card list the intake closing at .050. between 8.49:1 to 8.57:1. Though not a guarantee, I'm in the theoretical money. Edited by lynchster - 20-February-2017 at 5:48PM |
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Chuck
72 Gran Torino Sport 13 Taurus SHO "Mr Pig" |
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Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6072 |
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DCR calc still applies to Danno too
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72 GT Ute
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