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Push rod lenght question
Hi guys, i wonder If anybody could remember or tell me what lenght push rods I would need, I will make some changes to my stock 302 on a budget so I want to use my stock bottom hand,put a E303 cam, either GT40 heads with 1.6 roller rockers or E7 heads that have been professionally ported to match GT40 valve sizes with 1.7 SVO roller rockers on stiffer springs,some member is selling those for $400.00 with low milleage. Any info will be appreciated,thanks !
Michel |
should be able to use stock pushrods, or something pretty close.
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I am running the same combo (E303 cam w/GT40 heads, 1.6 roller rockers) in one of my mustangs, and we used the stock length pushrods.
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I would measure just to be sure...never can tell how much heads have been milled, what rockers are used, etc. Geometry can change very easily.
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pretty close cost me $800 a couple of years ago.
Measure them! Dwight |
Thanks guys I know the best way to be safe is to check but I'm just asking to save me time so I can enjoy driving my car.I could possibly buy ported E7 heads that have 1.7 roller rockers on them,would stock hardened push rods work.
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You need to check...
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Checking the appropriate length is pretty easy. I just did this for a 331 stroker I'm working on. Get a pushrod checker from summit racing, and you can find good instructions on the web for aligning the cam correctly to set the adjustment. Basically, you're centering the roller on the valve tip. (I centered mine, some will offset it based upon the direction the roller will move as the valve is pressed, but centering was fine for my lift.)
I bought two checkers (not necessary) to adjust both intake and exhaust. I also used these to check for clearance. Stock is 6.25". I ended up installing 6.50". DD |
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Then you end up with the smallest width contact patch from closed to fully open. |
This is a very critical part of the valvetrain geometry. As Gaz64 said the contact pattern should be centered on the valve stem. Mark the end of the stem with a felt pen and install the rocker and pushrod of choice & run it through 2 complete revolutions and check the mark on the end of the stem. Ideally it sholud be perfectly centered, if not valve guides will wear abnormally. Vernier calipers are a good tool to use for measuring small variance. Longer pushrods move the pattern towards engine centerline, (intake ports), shorter ones move the pattern towards outside (exhaust ports). Take your time, this is important stuff. Using an adjustable length pushrod will allow you to "Move the pattern" then measure the pushrod for correct length.
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Rick, when I switched to a different head and valve angle I had a very wide swipe near the center. I had to increase pushrod length to get my geometry correct and in doing so moved the swipe toward the exhaust side of the head. As I increased the pushrod length my swipe pattern decreased. Remember a large swipe indicates the roller is sliding across the valve tip and not moving in an arc that transfers the cam lobe lift directly to the valve movement. This also is where it loads the valve guides on the rocker axis.
It's more important to get the small swipe first while watching where it is located on the valve tip. You can run the swipe toward the outer 1/3 of the valve tip whether is toward the intake or the exhaust to get the geometry correct just keep away from the edge. I'm .050 from the exhaust side edge of the valve tip and my swipe is nice and narrow. All looks good and runs great. Also if you are increasing the pushrod lengths watch the rocker on the stud shank. You don't want it riding up too high and be on the threads. A longer stud or shank area would then be needed. Lou Lou |
I could be buying those E7 ported heads from a mustang forum member and they have the SVO 1.7 roller rockers installed using a stock roller cam but in my case I will put an
E303 cam so anyway I will need stiffer push rods because of the cam. Iwas hoping to reuse the stock push rods but I won't, I will measure I think it's the safest way to go,thanks guys ! |
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