Floating Valves. Need help and advice.

[charat]

hey guys.

so a while back. i discovered i have floating valves. at first i thought it was the timing chain guides and blah blah. but i had a mechanic look at it and he says its the valves that are floating. i couldnt afford an engine rbuild at the time so he said to run a thicker oil. but the problem seemed to persist through the thicker oil. i think its just one (set?) of the valves? anyways. im planning on doing an engine rebuild soon. but i was thinking, could i just rebuild the head? i dont feel like pulling the whole engine out. would retiming the engine fix the problem or is that a bunch of bull? (<- my friend suggested it)

thanks for all the help guys. sorry if i sound noobish but yeah...

[rioredstang]

If you are floating the valves as he claims then you need to replace the valve springs. You can pull head off and take to a good machine shop. Tell them what problems you are having and let them inspect the head and advise of what repairs your head needs. I don't know the mileage on the head, most likely a standard valve job, Shim the springs or replace, resurface head,and readjust all clearances.

[IanS]

Something isn't adding up.

Thicker oil would have no effect on valve float. Im not even sure how he would know you had floating valves.

I think you have bent vavles. This will require a head rebuild at the very least, if not a full engine rebuild, depending on what caused them to bend.

How did the engine actually get in this condition?

[charat]

Something isn't adding up.

Thicker oil would have no effect on valve float. Im not even sure how he would know you had floating valves.

I think you have bent vavles. This will require a head rebuild at the very least, if not a full engine rebuild, depending on what caused them to bend.

How did the engine actually get in this condition?

uhm... floating valves are actually common on 240sx's. all that needs to happen is a spring or two wearing out (not enough push on the valves themselves) bent valves are a less common problem. the only way a bent valve can occure is if the combustion cycle misfired and bent teh valve. a spring wearing out is much more likely. also, my engine is in fine condition. only problem is the floating valve. (i think there are only 2-3 floating)

[tyrodtom]

I noticed a loss of power in my 240. When I did a compression test the #1 cylinder read around 70 psi. I at first thought blown head gasket, even though there was no other sign. I took the head off, could see no sign inside of a blown gasket. Finally noticed the #1 exhaust valve was sitting farther down in the seat. When I poured water in the upside down combustion chamber the water would run right out.I finally determined the valve was floating, and pounded the valve down into the seat and didn't seal anymore. I tested the springs with a valve spring tester, and that spring was noticebly weaker. I had 2 other heads , I went thru all the springs with the tester, used the 12 strongest springs, lapped all the valves. Put it back together.That was in 2008, I circle track race this car. The car won 7 races this year.

[moso]

i think you have a poor mechanic. i agree that ka's can suffer from valve float when the motor reaches higher milages, especially if it has been abused, and when pushed to extreme high revs. i also agree that you would have a hard time proving that you have valve float, without bending a valve, and would really like to know how you came to that conclusion. nothing is going to help your valve float problem short of new valve springs, anyone suggesting anything else to solve valve float should be politely told to shut up. you can definitely do a head only rebuild although i would decide on the lower half after you open it up. my kade had significant out of roundness and it only had 150k on it when i rebuilt it. good luck with your 240.

[liquid_cool]

uhm... floating valves are actually common on 240sx's. all that needs to happen is a spring or two wearing out (not enough push on the valves themselves) bent valves are a less common problem. the only way a bent valve can occure is if the combustion cycle misfired and bent teh valve. a spring wearing out is much more likely. also, my engine is in fine condition. only problem is the floating valve. (i think there are only 2-3 floating)

well..where to begin...#1 valve's float under higher rpm in 240's..thats common....but...the ka is not build for high rpms to begine with...this is a manufactrer's weekness built into the car from inception..its not delibrate..just a weekness...there is only 1 way to solve valve float at higher rpm's...and thats with duel spring combo's..Brian Crower makes an afordable set..thats what i run....

#2. if you have valve damage like you state..then your timing was off and you smacked a valve with your piston..dont fret...this is common with ka owners who are new at timing the KA-DE's...here is some advice after you get a rebuild done..rotate the engine by hand with a wrench from the crank..if it suddenly stops..your timing is off...

#3. your mechanic is full of it..adding heavy oil wont ever fix a valve problem..and that leads to this quiestion...did he say valve float.....or valve clearence?..this question is verry important..as the valve clearence noise can be reduced with heavyer oil...

options: you WILL need to pull the head off of the car..no matter what!

you need to change the damaged valves and reseat them...if the seats are not ovald out..you can just use lapping compound to seat them yourself..

you should allso change the valve seals while your at it.

my last recomendation...duel springs...duel springs are an outer spring with a smaller spring in the center..this is commonly used race aplication to stop valve float in performance engines for what ever racing you know of..its all the same..or you can stay oem and just get new springs cheep..

last but not least..you may not need to deck the head depending if there is warpage or not...and when ya install the head gasket..i recomend you use a head gasket sealer like "indian head" brand on both sides..

thats my advice..good luck.

[charat]

well..where to begin...#1 valve's float under higher rpm in 240's..thats common....but...the ka is not build for high rpms to begine with...this is a manufactrer's weekness built into the car from inception..its not delibrate..just a weekness...there is only 1 way to solve valve float at higher rpm's...and thats with duel spring combo's..Brian Crower makes an afordable set..thats what i run....

#2. if you have valve damage like you state..then your timing was off and you smacked a valve with your piston..dont fret...this is common with ka owners who are new at timing the KA-DE's...here is some advice after you get a rebuild done..rotate the engine by hand with a wrench from the crank..if it suddenly stops..your timing is off...

#3. your mechanic is full of it..adding heavy oil wont ever fix a valve problem..and that leads to this quiestion...did he say valve float.....or valve clearence?..this question is verry important..as the valve clearence noise can be reduced with heavyer oil...

options: you WILL need to pull the head off of the car..no matter what!

you need to change the damaged valves and reseat them...if the seats are not ovald out..you can just use lapping compound to seat them yourself..

you should allso change the valve seals while your at it.

my last recomendation...duel springs...duel springs are an outer spring with a smaller spring in the center..this is commonly used race aplication to stop valve float in performance engines for what ever racing you know of..its all the same..or you can stay oem and just get new springs cheep..

last but not least..you may not need to deck the head depending if there is warpage or not...and when ya install the head gasket..i recomend you use a head gasket sealer like "indian head" brand on both sides..

thats my advice..good luck.

willl do. lastly, how long do you think it will take, on average, to do all that? (pull head, rebuild, etc.)

[IanS]

uhm... floating valves are actually common on 240sx's. all that needs to happen is a spring or two wearing out (not enough push on the valves themselves) bent valves are a less common problem. the only way a bent valve can occure is if the combustion cycle misfired and bent teh valve. a spring wearing out is much more likely. also, my engine is in fine condition. only problem is the floating valve. (i think there are only 2-3 floating)

You should check your sources.

The valve float that is common is caused by over revving, and it only occurs at higher RPMs.

Valve springs dont often wear to the point of allowing the valve to float off the seat unless an engine is severely abused. More often then not they break before they wear out. Ive seen a handful of Ford V8s come in with broken springs, with less than 150,000 miles on them.

There are a number of ways a valve can become bent. Foreign objects, incorrect timing, timing chain failure, or last but not least, floating the valves into pistons via over revving. If someone did float a valve into a piston, then it is likely bent.

Not to mention a bent valve is not the only thing that can cause a leak. As l_c stated, ovaled valve seats can leak, as well as burned valves.

It has been mentioned that you need to find a new mechanic, this may not be true. I would find it much more believable that one of two things happened. Either you misunderstood what he was saying because he was being too technical for you, or because you weren't listening. Or he attempted to dumb it down, and accidentally used incorrect terminology to explain it to you. I would bet, given the chance to explain himself here, things would be much clearer.

Come to think of it, we are trying to help solve your problem, buy you have yet to actually tell us what the symptoms are. Its tough to diagnose a problem based on hearsay. Especially when your info does not seem to add up.

Is it ticking?

Is it lacking power?

Is it consuming excessive fuel?

Does it smoke?

Does it smell?

Does it run rough?

Is the problem better or worse at idle?

Is the problem better or worse at mid RPM?

Is the problem better or worse at high RPM?

Is the problem better or worse at a constant cruising speed (60 mph)?

Just for future reference, try not to talk down to those attempting to help you. Especially when you are just repeating what your friend told you.

You weren't even in high school when I bought my first 240SX

[liquid_cool]

ian...valve float is common in the ka-de's past 65oo rmp due to spring rate..my info was valid for this specific issue with the info he gave in his statement.

[IanS]

ian...valve float is common in the ka-de's past 65oo rmp due to spring rate..my info was valid for this specific issue with the info he gave in his statement.

The valve float that is common is caused by over revving, and it only occurs at higher RPMs.

For a KA, 6500 is borderline overrevving. They were never meant to rev that high. I may have worded it poorly but hey, Im human.