Briggs & Stratten new heads did leak down test

(24 hp engine on a Cub Cadet mower. V-twin. 2004 vintage 274 hours.
Left side of engine (looking from the carburetor) had bent push rods. On the intake valve the valve guide got displaced and locked up the rocker arm.
Decided to buy 2 new heads from Amazon due to hours on engine.
Installed both heads, proper torque and valve clearance.)
Heads included valves, springs etc. all assembled.
Did the leak down test at 15 psi. Both cylinders leak an equal 25% which, on my gauge, means "low leakage".
If I depress the valve springs with my fingers (during the test) I obviously get great leakage at that valve.
Curious thing: I upped the pressure to about 80 psi and the push rod (all 4 push rods are brand new) on the exhaust valve came out from under the rocker arm and fell to the ground.
Maybe I should stop wiht this engine and simply try to start it.
There was a respondent on this group that thought 0 compression is valid.
Thank you all. Now I have a new tool (Lead Down Tester)
Ivan Vegvary
Reply to
Ivan Vegvary
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That'll do it. Stuck valves and water/gasoline filling the cylinder (-very- unlikely on a mower) are the top reasons for bent pushrods on ICEs.
Ouch, how much?
Yes, very curious, considering that you adjusted the valves. Having heard VW engine heads bouncing up and down off the cylinders as said POS drives down the road, I know some cylinder studs will stretch, but that's not a mower engine.

Refer them to CONgress, as they are truly clueless fidiots. (Unless the head is off the engine. ;)
New tools are always welcomed by most of us here.
Reply to
Larry Jaques
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Sounds like the valve lift screw needs to be adjusted so there is enough contact even at full-open on the valve to keep it captured.
Unless something has happened to the camshaft, too.
Adjust the valve clearance on each first. It sounds like the adjustment was set very loose from the factory -- perhaps for ease of assembly -- with the understanding that it would be adjusted after installation.
Also -- make sure that the thing does not lock up through two full turns -- just in case something is wrong with the camshaft.
*Then* try to run it. :-)
Good Luck, DoN.
Reply to
DoN. Nichols
No, that's bent CONNECTING rods.. The stuck valve will bend a push-rod - but I've never seen or heard of hydrolocking bending a push-rod. Over-reving (stuck governor) will do it. So will a worn/damaged rocker arm assembly. Anything that will let the push rod get out of it's proper position.
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Check to make sure you are getting full valve opening (or lift). Whatever broke/bent the camshaft MAY have damaged the cam - or the damaged cam MAY have allowed the push-rod to get out of position and bend.
The Intek twins on riding tractors seem to have a real problem with bending push-rods - generally traced back to overheating due to having the cooling fins blocked with grass seeds and dust.
Oil is another problem. I reccomend you use nothing but all-fleet or deisel rated oil - or oil specifically designed for air-cooled 4 stroke ngines that contains a good amount of Zibc EP additive. (ZDDP) and only hooch-free gasoline (I use Shell Premium exclusively on my small engines)
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You're right. Man, has it been that long since I had my head under a hood? I guess so. I'm in disconnect!
Valve spring retaining clip, where the valve goes thru the piston.
Reply to
Larry Jaques

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