3400 G Engine

[catrat]

Old Magnet SJ or any one that can help. Have sure got a lot of good info. here need some more. What is the corect pressure for the valve springs on the 3400 engine. Intake and exhaust the same. Need to find some new springs. One engine shop here may help if i know the pressure needed.
Thanks
catrat

[Old Magnet]

Can't seem to find my specs on the D3400 which I am guessing would be the same as the G3400. On the D311 the outer spring is 45 lbs @ 2-5/8 in. and the inner spring is 9 - 11 lbs @ 2 - 13/32 in. Should be in that range, maybe somebody can help verify.

Correction: Those are the specs for the D3400.....didn't realize I was looking in the D3400 manual.

[catrat]

Thanks Magnet that is what i needed. I got some time today to hunt some in my garages[just moved] And found my R2 parts book. Found the springs and numbers called Cat ordered 4 of each. will be in local dealer on june 19. I could not belive it this machine is 67 years old
catrat

[SJ]

I,ll bet you ordered the springs from Cleveland Bros. didn,t you. I,m sure your aware that a while back they bought out Beckwith Machinery in the western part of Pa. so now CBE has around 25 dealer stores (branches) or more now.I worked at the Wilkes Barre branch here in Northeastern Pa. for 36 yrs. for them in the engine dept. Just where are you located at in Pa? My town is just outside of Wilkes Barre west of it.

[catrat]

SJ i am near Altoona central PA. I picked up the springs yesterday and installed them today. No difference still coughs spits and sputers backfires through carb. What i have done ckeck spark about 1/2 in nice blue. Put new intake and exhaust gaskets new springs on intakes, cleaned carb, This enging ran real good till it ate a valve. I took it down and replaced one liner piston and all the rings and new seals on all liners. It has me beat Any and all help welcome
catrat

[Old Magnet]

If the carb, mag, and timing is correct I would still suspect the valve springs. What does the installed height of the springs check out to on the engine? Cat doesn't say much about it but most engines require valve spring shims as the seats recess or are ground. Were you able to tell what the cause of the original valve ingestion was? Still wonder about the valve stem clearances, again at .012 maximum or more you can expect valves to not properly seat. That's about all the additional thoughts I can offer.

[SJ]

I,d first try setting each cyl. on TDC firing stroke & see if the valves has clearance & if they are ok You might try pressure testing each cyl. on TDC but you,d have to take an old spark plug & remove the top & weld a nipple on it & then get a pressure gauge & an air line shutoff & attach an air line to the nipple & with an air regulator to pump in some air & shut the line supply off & see if it leaks down immediatly or holds ok & only drops very slowly.If you do this air test it would be best to put the tractor in gear & lock the brakes each time you make the test on each cyl and make sure the throttle is off.I,d think to set the air regulator not more than about 75 lbs. I had this setup made at the shop for diesel engines & it told you alot about what a problem could be.It could be just an intake valve not seating correctly but just guessing & giving you an idea.Also I didn,t mention but install the shutoff before the air regulator so the regulator tells you if there is a leak down.Also take the plug wires off the plugs that your not testing too.

[catrat]

Magnet SJ THANKS can't say what the instaled height is. The orignal head that let valve go valve head came off. I thought it was old age. This head has brass guides for the intakes and the side movement may be .08 th it can just be felt. From what i can see this head was rebuilt exhaust valves are different style that ones in old head and intakes same style as old ones but look new.[Old head has all cast guides.]
I set the valves with piston at top dead center. With plugs out turned it over by hand with wire in hole till move ment stoped then set valves. I do have a plug with a air line set up made up used it to change the springs. I will play with the carb and raise float setting to see if it get better or worse.
If that don't help i am going to pull this head and reinstall the orignal have cleaned up the seats and put in two other valves will put the new springs on them two valves just in case.

[edb]

Hi catrat,
just wondering if there could be crossfiring going on in the intake from a problem of carbon tracking on the maggie distributer cap or rotor button face. Had a radial engine once that had faulty spark plugs and it would crossfire through the old plug leads. This sort of phenomina in the intake could cause a pressure rise and blow an intake valve open and cause it to contact the piston and bend, a carefull failure analysis of the failed iron from the previous valve failure could show a bent valve type failure, the sure sign would be possible beach marks on the stem with a shear lip at the site of final failure--a bending fatigue failure-- Failure analysis was a big part of my Senior Mechanics job at the Dealer, my old Cat school books are in a shed out back so will see if I can post a pic tomorrow of the failure type mentioned.
Proper failure analysis seeks out the root cause of the failure and not just fix the resultant damage for a repeat failure to recur.
I do stand to be corrected.
Some food for thought here as sometimes things are not as straight forward as we would hope, there can be other factors at play, our Failure Analysis Instructor at C of Oz said, "Beware of preconcieved ideas."
Cheers,
Eddie B.

[Old Magnet]

It may be a mute point but valve stem to guide clearance is measured by measuring the actual diameter of the valve stems (in several places) and actually measuring the bore of the guide. The wear clearance is usually higher when the valve is in the open position then when closed so wiggling the valve stem when installed is not always a good check.
Your situation seems to be more orientated to run mode so I'm not sure the static air pressure leak down test will reveal anything. Ignition tracking could certainly be a culprit. Whose spark plugs and what designation are you using?