Pushrod length?
Thread Starter
Racer
Joined: Oct 2010
Posts: 474
Likes: 0
From: Bishop CA
Pushrod length?
I'm just getting around to putting on a new set of IK-180 Brodix aluminum heads on my 1975 small block. They say that I need to measure the distance for the correct length pushrods. I'm not sure how they want me to do this. The block was decked slightly during rebuild, not sure how much. Other than that I'm using same rockers. Should there be that much of a difference in length from the stock pushrods that are in it. I am going with hardened rods. Any help on how to measure them will be helpful, and how critical is this measurement? Thanks in advance.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Basically, you take a pushrod length checker which is a pushrod that you can lengthen, and rotate the motor a couple times.
Good article here: http://www.circletrack.com/techartic...gth/index.html
Good article here: http://www.circletrack.com/techartic...gth/index.html
Drifting
Joined: Dec 2002
Posts: 1,946
Likes: 28
From: Long Beach CA
Or.....first of all, you need to get a solid lifter. Either by using a solid lifter or taking apart a hydraulic lifter and putting a washer inside so it's now solid. Install that in the engine with your current pushrod, with the cam on the bottom of the circle (valve is closed). Use a magic marker to mark the top of the valve stem, then install the rocker arm just tight enough to take up all the clearance, no tighter. Rotate the engine through a couple of revolutions with your wrench on the pulley bolt. Then remove the rocker arm and look at your mark on the top of the valve stem. If the mark is evenly on both sides of center, then the pushrod is OK. If it's toward the outside (exhaust side of the engine), the pushrod is too long. If it's toward the inside (intake side), the pushrod is too short (not likely). The length is important because if the rocker arm is not riding correctly on the valve, it puts a side load on the valve and will wear out the guides and seals faster.
Thread Starter
Racer
Joined: Oct 2010
Posts: 474
Likes: 0
From: Bishop CA
Basically, you take a pushrod length checker which is a pushrod that you can lengthen, and rotate the motor a couple times.
Good article here: http://www.circletrack.com/techartic...gth/index.html
Good article here: http://www.circletrack.com/techartic...gth/index.html
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Built a '75 350 with Brodix IK180 heads and a Comp XE-274 cam with Comp's roller tip rockers. The pushrod length that produced the best pattern on the valve stem tip was 7.9" (+.100").
Cheers!
Cheers!
