SB Chevy rocker arms on a Magnum head?
#916138
01/29/11 12:55 AM
01/29/11 12:55 AM
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Joined: Apr 2007
Posts: 2,327 Glendale, AZ
69L78Nova
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I have pretty much gathered up all the parts needed to swap Magnum heads onto my 78 360. I have been reading about the use of small block Chevy 1.6 roller rockers on Magnum heads. If rollers would work, wouldnt 1.6 ratio stamped steel rockers work as well? Summit sells 3/8" stud kits for as little as $12, and a set of 1.6 ratio stamped steel rockers for $61. I have always liked the idea of adjustable rockers with a hydraulic cam, especially when a custom length pushrod is to be used. Also, am I correct in assuming a 1.5 ratio arm wont work? This is all going on a 78 360 shortblock with a Comp XE256 cam. Could I use the stamped steel units, or do they have to be rollers?
1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: Wedgeman]
#916140
01/29/11 01:03 AM
01/29/11 01:03 AM
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Joined: Apr 2007
Posts: 2,327 Glendale, AZ
69L78Nova
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Its just a cruiser. I picked up a set of brand new Magnum heads for free, and a dual plane Magnum M1 for next to nothing. Im just messing around with it and maybe looking to get a little more out of it. Its in a 4000lb 78 Fury so its not a strip terror or anything like that. Should I go ahead and still plan on using the aftermarket 7.65" pushrods as well too?
1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: Wedgeman]
#916142
01/29/11 01:20 AM
01/29/11 01:20 AM
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Joined: Apr 2007
Posts: 2,327 Glendale, AZ
69L78Nova
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Yeah the Comp lifters have the oil hole, and I do have the correct oil-through pushrods already. Am I stuck using 1.6 rockers, or can I use 1.5 ratio? The only reason I ask is because the 1.6s will increase my lift to .477/.485", and with 1.5s it is .447/.455". The advertised duration is 256/262, and at .050" it is 212/218. The car weighs 4000lbs, and Im running a 2400 converter, 3.21s, headers and 2 1/2" duals. I dont want to have any kind of a rough idle or lose what little bottom end I do have when I need to get this boat moving.
1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: Kern Dog]
#916146
01/29/11 10:32 AM
01/29/11 10:32 AM
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Joined: May 2005
Posts: 416 Franklin Co. Illinois
runinonmt
mopar
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mopar
Joined: May 2005
Posts: 416
Franklin Co. Illinois
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I use Magnum heads with the stock rockers (1.6)on a 360 with a Comp XE268 cam in my Duster. Idle is quite smooth and low end torque is plentiful. With a 256 I can't imagine a problem. Set up your Distributor so initial is at least 16 Degrees (mine is 19). Up to the point of spark knock the most advance will give you more low end grunt. I even use the stock converter. With the 2400 converter it may appear to be weak on the low end but I doubt it. That's pretty close to a factory performance converter. My Stepson has a 2800 in his roadrunner with the 268 cam and complained about this until I had him brake it to raise RPMs before launch. Kind of like slipping a clutch. After he had some seat time with it, he was happy. Drive ind enjoy it Ron
Last edited by runinonmt; 01/29/11 10:52 AM.
In sixty-five I was seventeen and running up one-o-one
I don't know where I'm running now, I'm just running on
Jackson Browne-Running On Empty
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Re: SB Chevy rocker arms on a Magnum head?
[Re: Wedgeman]
#916149
01/29/11 01:17 PM
01/29/11 01:17 PM
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Joined: Apr 2007
Posts: 2,327 Glendale, AZ
69L78Nova
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Thats the thing though. I dont want to run a higher stall or run some ridiculous low gears. This is a daily driver that Im just looking to get a little more power and torque, and take advantage of some of the benefits Magnum heads have to offer. I repeat, this is not a race car, and Im not loking to turn it into one. Its a stock 78 360 shortblock with an XE256 cam, headers and duals. But if the 1.6s would be better, then then Ill just go ahead and run them.
1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: 69L78Nova]
#916151
01/29/11 01:54 PM
01/29/11 01:54 PM
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Joined: Jan 2003
Posts: 20,149 Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
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Posts: 20,149
Park Forest, IL
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I don't think you'll see enough difference to even worry about.
"Everybody funny, now you funny too."
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Re: SB Chevy rocker arms on a Magnum head?
[Re: racincuda]
#916153
01/30/11 06:44 PM
01/30/11 06:44 PM
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Joined: Jan 2005
Posts: 12,406 Kalispell Mt.
HotRodDave
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Kalispell Mt.
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1.6 will only help not hurt in any way. Just slap the stock rockers on it and sleep well at night. I too have an XE268 with magnum heads on a 360 in my 68 cuda, 2.76 gears and stock 318 2bbl tq converter and it does not lack any TQ off idle even with an M1 single plane intake. Your cam is several sizes smaller and you have a dual plane intake so low speed TQ will not be an issue with the factory 1.6 rockers. If you want to run the chevy rockers you will also need guide plates that are magnum specific or some kind of adjustable ones, the stock ones don't use any of that junk.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: SB Chevy rocker arms on a Magnum head?
[Re: HotRodDave]
#916154
01/30/11 06:49 PM
01/30/11 06:49 PM
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Joined: Apr 2007
Posts: 2,327 Glendale, AZ
69L78Nova
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You're using the GM 3.1/3.4 springs and retainers too, correct?
1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: HotRodDave]
#916156
02/01/11 12:33 PM
02/01/11 12:33 PM
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Joined: Jan 2003
Posts: 16,122 Grand Haven, MI
patrick
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I Live Here
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Grand Haven, MI
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point of reference, in my 3950lb 5th ave, I had an LA 360 with a comp XE262 (~8:1) compression, 3.55's, and a MP166k converter that brake stalled to ~23-2400, flashed to 2800. moved the car along just fine. would light them up at will.
switched to a magnum headed 318 with a 259/259 roller, .506" gross lift, using hughes #1110 springs and stock magnum rockers. has the same power as the 360, would prefer the MP166k converter, but lives with the stock, low stall (~1400rpm stall) converter because of a crack I found in the snout of the 166k.
you'll be fine with the stock magnum rockers, GM3.1/3.4L springs or the hughes springs w/2.2L retainers with the gear, stall, & weight. with headers, it'll be a low-mid 14 second car, maybe even nipping into the 13's.
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: patrick]
#916157
02/01/11 05:00 PM
02/01/11 05:00 PM
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Joined: Apr 2007
Posts: 2,327 Glendale, AZ
69L78Nova
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Quote:
with the gear, stall, & weight. with headers, it'll be a low-mid 14 second car, maybe even nipping into the 13's.
Well, I already have the headers, 2.5" duals, 2200-2400 converter, and a 3.21 sure grip. Do you really think it would run that good with the stock pistons? I obviously can't use a spreadbore carb on the M1, so do you think a 600 Edelbrock will be ok? What do you think of the Hughes 7.64" pushrods?
1969 Nova 454/M21/3.31 Mild mid-11 second weekend cruiser
1994 F150 XLT Super Cab 2WD 5.0/4R70W/3.55 (Daily driver)
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Re: SB Chevy rocker arms on a Magnum head?
[Re: 69L78Nova]
#916158
02/01/11 05:11 PM
02/01/11 05:11 PM
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Joined: Jan 2003
Posts: 16,122 Grand Haven, MI
patrick
I Live Here
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I Live Here
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Grand Haven, MI
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both engines I ran/am running an eddie 1406 on an RPM air gap. my 360 was an LA headed, stock long block rering that I did a little bit of home porting to the heads with the XE262, it hung with a 300C (5.7L hemi) from 20mph roll. measured compression with the fel-pro gaskets in the kit was 7.9:1 magnum heads will boost that to about 8.5-8.7 depending on head gasket. if you can find some of the MP .028" thick gaskets, get them. the 318 is running a reground roller cam that is 208@.050, 127@.2" and .316 lobe lift (while .050 duration is 10 degrees smaller, at .2" lift duration is only 3 degrees smaller than a comp XE262, with .008" more gross lobe lift, almost .050" more lift at the valve). with stock pistons and the thin MP gaskets, I'm running a measured 9:1 compression. dunno about the pushrods, I lucked out an was able to reuse the stock magnum pushrods. I'd get a length checking one and measure your needs to be sure.
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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