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By blocky - 5 Years Ago
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hi all , i have a problem with ,yes you guessed it ,pushrod length.i have purchased new tubular rods and of course they are slightly longer as i guess most of you would know.my idea is to use the little tin troughs from an old 55 motor i have under the pedestals and this will raise the gear about 55 thou and was thinking this would help or am i just panicking about nothing??? any advice would be very welcome.
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By Florida_Phil - 5 Years Ago
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I ran into this problem myself when I swapped heads on 1955 TBird. My engine originally had the small port 55 heads with low ratio rockers and the tin spacers under the pedestals. I swapped on a set of 1957 "G" heads with high ratio rockers. I had two different sets of push rods, One longer than the other. I don't remember the lengths. I do remember if I used the 55 push rods with the 57 heads, the rocker geometry was messed up and I had to make big adjustments to the value adjustment screws. I had to use the tin spacers in order to get this close. I eventually threw out the stock pushrods and went with a set of tubular pushrods, which are much thicker and stronger. With these push rods in the motor and the tin oil baffle spacers removed, everything was perfect.
Many people on this forum helped me with this issue. The oil baffle spacers were discontinued in later years. My motor doesn't miss them. The important thing is to get the valve train geometry right. If you don't, you will have problems. While you are at it, throw out those tiny stock push rods. They are trouble.
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By charliemccraney - 5 Years Ago
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Are they to long to fit, period or are you just observing that they are longer?
Another thing to realize is that overall length does not necessarily correspond to effective length. You can have two pushrods with the same effective length but a slightly different overall length but both should work just as well. Effective length is the distance from the tip of the ball, to the bottom of the cup and cannot be measured with typical hand tools.
Putting a shim under the stands will require a pushrod that is longer by more than the thickness of the shim. The reason is that the valve stays in the same position, so the rocker also has to rotate toward the valve on the shaft, moving the adjuster screw even farther away from the pushrod.
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By blocky - 5 Years Ago
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thank you for the info cheers
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By blocky - 5 Years Ago
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they are longer but now i have a few clues thank you all
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