Thread: Big block valve train clatter

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BTW it's interesting you mentioned 1 & 8 intake as the rockers that are close as those were the rockers that were hitting on mine! Thanks again!

Originally Posted by bigred1957

BTW it's interesting you mentioned 1 & 8 intake as the rockers that are close as those were the rockers that were hitting on mine! Thanks again!

i built and machine alot of bbc over the years thats how i make a buck what pistons do you have and what heads on that 402? if you use a close rect port pistons on a O port head they hit a on the ex side of the dome seen many that hit

Hey Pat! I'm not sure what the heads and internals are, I was told that the 402 was stock to the truck and stock components. But some times you don't know unless you tear it down. I did adjust them and they don't hit the covers anymore, it idles really smooth so I don't think I have bent valves. I do think I might have found a weak spring today though, I slid the inner spring up and down with little force while it was installed. Do you know what the specs are on a stock dual spring? (open height, closed height, lb's of force measured)

you mean a single with a damper thats about 1.880 @ 100 lbs

Great! Thanks Pat! So I take it that the inner coil is the damper? That answers that. I know now for the next parts store run I need to make and it comes up again.

Thanks again!

Originally Posted by bigred1957

Great! Thanks Pat! So I take it that the inner coil is the damper? That answers that. I know now for the next parts store run I need to make and it comes up again.

Thanks again!

if the spring is flat it a damper if round wire it a spring and would be a dual

Is there a big difference between the two? I ordered a dual spring and should have got a single with a damper.

Originally Posted by bigred1957

Is there a big difference between the two? I ordered a dual spring and should have got a single with a damper.

well at best single 80to 100 .a dual with a damper 125+ on seat. i do not know what spring you pick up has abit to do with where it setup at .you can over spring a hyd cam as well i seen guys put 145 on the seat but you do not need this if a low to mild rpm engine

Sorry to bug you again Pat, or anyone who has ideas but I'm still having a knocking I can't figure out with my 402. I've checked out most everything we've discussed plus I've replaced a couple of valve springs that were under spec (but not by much). The timing chain has about 4 degrees of slop but I was thinking of checking it anyway. Also I was going to check if the cam has a retainer plate that could be getting loose. My thoughts are at the point of pulling the motor and tearing it down but until I find work I just can't afford to do it. My brothers a mechanic and mentioned the possibility of a stuck wrist pin, but wouldn't the knock be all the time? Help, I'm losing it.

your engine should not have a retainer plate stock? your engine could have a cam going bad or a rod bearing .or bad fule pump will make a hammer noise. bad rocker. bad piston, piston slap ? pistons domes hitting the chambers of the heads. lose auto fly wheel or crack in it

Once again----pull plug wires one at a time and see if there is a different sound on some cylinders
Rod bearing and wrist pin /piston noise will change--

My bet--dollar to a donut--you will find 2 rods bad on the same throw or 2 rods bad fed from the same main journal

Thanks Jerry, actually pulling the wires one at a time was one of the first things I tried. I learned that in HS auto mech. You know, back when we were hard on our hot rods, he must have thought it would have come in to use during our teen hood. However I might try it again just for the heck of it, not sure what else to do. I've driven it about 120 miles since (as it's my daily driver), I figured it should have puked something up by now if it were a main or a rod. Now if it's a wrist pin wouldn't it do it all the time especially when it's cold?