tarior
I had two Summit cams in a row do the exact same thing CJ5steve desrcribed. My springs were 105lbs on the seat. I went to a Crane cam, I didn't do ANYTHING different otherwise, not one single change, same oil, same springs, same pump, same cam bearings, that cam broke in just fine, and was perfect when I tore the motor down a couple of years ago. I honestly believe that the Summit cams have a very high rate of defective heat treatment.
cj5steve
im not so sure on the cam hardness #3 i ran for about a year in the motor before rebuild.the push rods are not bending.i think it may be a pushrod length issue but i dont understand how.the rocker tip is in the center of the valve tip.4wdrive hardware has pushrods listed for use with the edelbrock heads now.i looked them up and found the length i will compare to my current pushrods and see whats what.good info from all i appreciate all the help if anybody comes up with anything else let me know.im going to pull the motor and tear it all apart to get cleaned and new bearings now that all that metal is in there.
ironman_gq
I just read something about all of the cam blanks used to make cams by different companies are all made and hardened by two major companies and that the problems probably arent caused by defective heat treat but improper grind or breakin. cams could be getting hot and not being lubricated with the right oil and that might cause the cam to lose its temper and get soft.
cj5steve
well i think it is probably the pushrod length i dont understand to much about it but the pushrods that i ran with all 3 cam are 8.250 long.in the 4wheel drive hardware catalog they list pushrods for use with my heads and motor that are 6.936 long. when i figured out my pushrod length i got the adjustable pushrod and ran it to where the rocker tip was in the center of the valve at half lift.i thought this was correct but that is a huge difference.so even though i dont fully understand how that much difference can still ride on the valve where it is supposed to i think that is probably my problem.maybe?
grignac48
Interesting discusion. How would you determine if a push rod is too long? Or more importantly how do you know what length you need? On my 401 I had the heads milled 5 thou and suspect I will need shorter push rods at least 5 thou?
:-|
tufcj
Where'd you get those pushrods. Stock AMC uses the same as SBC, which is about 7.800 (7.794 actually)". For my 390 iron heads and crane rollers I used 7.900" to get the geometry right. I would think a pushrod that long would have the tip of the rocker way to the inside edge of the valve tip.
Bob
tufcj
grignac48
According to my AMC Shop Manual
The valve springs tension should be 80lb closed and 210-226lb open. That is standard for all 304,360, and 401 engines.
The pushrod, as cj5 says, you should see the push rod hit the center of the rocker arm. I would think that on close visual inspection you will see a misalignment problem. The length of my push rods new and old are 7.9 or so inches. 8 sounds long to me. :idea: Thats my two cents.
grignac48
According to my AMC Shop Manual
The valve springs tension should be 80lb closed and 210-226lb open. That is standard for all 304,360, and 401 engines.
The pushrod, as tufcj says, you should see the push rod hit the center of the rocker arm. I would think that on close visual inspection you will see a misalignment problem. The length of my push rods new and old are 7.9 or so inches. 8 sounds long to me. :idea: Thats my two cents.
cj5steve
grignac can you explain a misalignment issue to me.let me know what to look for.also i just read this whole post again,this is happening at random lobes everytime.
grignac48
Some of these guys who have built more engines maybe can answer. I really haven't messed with AMC's that much.
I would think that with the push rod in the lifter and centered in the head,(use something to hold in place) you should be able to set the rocker arm on the pedistal. Then look at where the push rod hits on the rocker. Rotate the rocker off of the push rod to see where it lines up on the rocker. As an additional check rotate the cam 360 degrees and see if the push rod travels in the same plane. It may take a couple of tries to pick the correct angle for the push rod. See if you see anything strange. I have heard of the lifter being ok but the lifter guide being wore and allowing side to side movement. ( not on an AMC tho) Then try it with the rocker arm partially tightened down. Look for sideways movement on the push rod. It will be a tedious process to figure out if it is a pushrod to rocker issue. It may be something totaly different. :smile:
tarior
Here's how I set up my valvetrain geometry on one of my 360's:
I made an adjustable pushrod and put it a pre-oiled lifter on the #1 inake lobe. I had it set at roughly stock length. I then took a black magic marker and painted the tip of the valve. I set the pre-load as per specification and turned the motor over by hand a couple of times. Then I took the rocker arm off and looked at the mark it made in the black. I adjusted the pushrod until the mark was in the center of the valve. I then measured what I had and looked through the Sealed Power catalogue until I found a pushrod that was within a few .001" of what I had.
This was on a set heads with large block mopar valves.
fuzz401
get your self a set of checking push rods and use them to set the length by how the rocker hits the valve tip 360 deg
now I have single studs and roller rockers this is how mine came out
grignac48
How do you make an adjustable push rod? Much better solution than mine, and more accurate. :sa:
tarior
Cut a section out of a stock pushrod, weld a nut on each cut end, use a piece of allthread for adjustment, with two jam nuts to lock it in place.
fuzz401
tarior
You could, but I'm cheap and have my own TIG machine :wink:
Holeshot
I would not be surprised to find that your oil pressure relief valve has opened up while starting the engine with cold oil, allowing all of the break-in trash to go directly into the oil passages in the block. VERY common problem. Time for another rebuild. Your lifters also have (or not?) oil passages in them that control oiling.
Modern, stock AMC V8s used three or four different pushrod lengths, with 1971s being all by themselves.
