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Author
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Topic: Mixing Rocker Ratios
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 11-18-2004 01:34 AM
   
I'm starting a winter engine project using some junk parts laying around the shop from the last year and trying not to spend anymore than I have to. I found a set of AFR 165 heads that has a couple of broken studs and a Victor Jr. that has some stripped threads and I also found a shaft roller rocker system that will work with these heads (yella terra). The problem is.. the rockers are a mixed bag of ratios and offsets. The only complete set I can put together with the correct geometry for the AFR's will have be all 1.60's on the exhaust, and (4) 1.60's & (4) 1.70's on the intake.
Here's the big finale... I was thinking.. (uh oh!)... Since the Victor Jr is known to flow about 5-6% better on the short middle runners, I could just use the (4) 1.70's on the 4 outside intake runners. What do you Ford racers think of that idea??   ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH [This message has been edited by bluestreek (edited 11-18-2004).]
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n2oMike
Gearhead Posts: 2419
From: Spencer, WV
Registered: Jan 2001
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posted 11-18-2004 06:37 AM
That's what I would do.  ------------------
Mike Burch
66 mustang real street
302 4-speed 289 heads
10.63 @ 129.3
http://www.geocities.com/carbedstangs/cmml_mburch.html
http://www.fortunecity.com/silverstone/healey/367
http://www.mustangworks.com/cgi-bin/moi-display.cgi?220
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 11-18-2004 12:06 PM
I guess what I'm asking is .. which cylinders do you think would really benefit the most from the 4 higher lift rockers (1.7). Thanks. ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH
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Rustang
Gearhead Posts: 733
From: Clarion PA
Registered: Nov 2000
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posted 11-18-2004 02:39 PM
This is kinda off the cuff but I think you'd want to "even" out the power from cylinder to cylinder. So the cylinders that are most starved for air should be the ones that get the increased lift. The increased lift should allow better cylinder filling.I suppose checking EGT from cylinder to cylinder would verify.  ------------------
'68 mustang 351 clevor- 10.92@124
'67 Stang, 351W -11.18@118
'69 351C Torino-14.90@100
'78 Pickup 351W-15.56@88
'79 Pickup 460 ET=??
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 11-18-2004 07:47 PM
I found 2 more 1.6 intake rockers but I don't know if that helps the situation or not. Anyone else have any thoughts/ideas on where to put these 1.7 rockers?? ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH
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Toronado3800
Gearhead Posts: 851
From: St. Louis, MO
Registered: Jul 2001
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posted 11-20-2004 03:15 AM
I can see it both ways, more agressive rockers on the "better" cylinders to maximize output, or on the "worst" ones to even it out. If you had a dual plane intake what would you do, and do any cam companies make uneven lobbed cams to match dual plane intakes?
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RogueS
Journeyman Posts: 31
From: Wichita, KS, USA
Registered: Oct 2004
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posted 11-21-2004 10:19 AM
I'd say that would probably cost a bit more money since it is much easier to have two different lobe grinds versus however many would be required to make it work best for the dual plane.
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bluestreek
Gearhead Posts: 1724
From: Athens,GA
Registered: Jul 2001
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posted 11-21-2004 02:02 PM
quote:
Originally posted by Toronado3800:
I can see it both ways, more agressive rockers on the "better" cylinders to maximize output, or on the "worst" ones to even it out. If you had a dual plane intake what would you do, and do any cam companies make uneven lobbed cams to match dual plane intakes?
An engine pulls and feels best when all cylinders are doing the same amount of work. I think that 289/302 dual planes are the worst there is as far as evening out flow to all 8 cylinders. When Edelbrock first introduced their RPM intake with more balanced runners, it was a vast improvement in the 2000-6500 rpm range, when compared the earlier split planes that had to use 4 long runners and 4 very short runners.
There's a lot of power to be gained if the flow into the cylinders can be equally balanced. The newer sequential port injection motors are proof. The ports can be balanced for peak HP at any rpm range with out compromising the length of the runners.
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1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank, rods and girdle, TFS alum. heads, Stealth 8020 intake, Xtreme 268 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)daily driver!
DanH
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