Replaced valves now will not run right.

[dougiefresh]

my timing belt snapped and i had to replace the valves.
the motor ran perfect before , had it tuned by English racing.
now after i replaced the valves. i installed the motor and tried to start it, just cranking it would not work i have to give it gas. it runs horible sounds like a harley. timing seems horible. with my v3 dsmlink if i just have on injectors 1 by it self or 1 and 2 or 3 it runs better but if i turn on 4 it kills it at idle . i have a 4g63 motor 2g with a 1g cas. when i put back the motor i kept everything the same as it cam out so what is going on? what do i need to check, do, or fix!?! any and all help is welcomed or if anyone could help that lives near pittsburg cali. i would love the help.attached is a link file of it running . i do not know if it will help.

 

[Stnmstr]

I'm not a guru on dsm's by any means but this caught my eye because I had a very similar thing happen to me. It turned out that one of my rockers was lightly kicked and stuck one of my intake valves open. Take it with a grain of salt but might be worth popping the valve cover to check

 

[greekgodchaos]

I had an injector resistor pack go bad on me once and I had similar symptoms to what you are describing, but that seems to be a rare thing to go bad...just something to make sure is functioning correctly.

 

[ZenkaiRacerDsM]

Did you install the valves yourself? Did you at least lap them?

 

[dougiefresh]

Zen I did them myself I pull this motor apart a few times, hut what do you mean lap them?
For the rest of you guys I have sparkvijust checked commpression I have 0psi in number 4 but 100 in yhe rest . What did I miss .??

lapping. cleaning the seal of valve area yes.

 

[ZenkaiRacerDsM]

Yeah, you can't just drop in new valves and have them seal. Maybe they weren't lapped enough? I would imagine that new valves would take quite a bit of lapping to get to seal.

By lapping I mean, using a lapping compound your almost sanding/grinding the valves and seat area so they match. Theres videos of how to do this on youtube.

If you did already do that, then I would guess they are still leaking. Unless you verified they sealed with some water or fuel?

 

[5150DSM]

I'm wondering if you bled down the lifters before you fired up the car? Also, how sure are you on your mechanical timing?

 

[dougiefresh]

well you are correct i just came out of the garage from working on it i bled the lifters. now i have 120psi in 1,2,3 but 4 is still zero... any ideas? tomarrow im going to get a air tank and postive pressure them. but any ideas are more then welcome. and ill keep it updated. thanks for all the help guys

and also i hope i lapped them well enough . we will see, i do have a ? since its not a warm motor due to the fact it wont run bc of this. how low from 170 should it be ?more then 120?

 

[BogusSVO]

Some reading for you.

http://www.dsmtuners.com/forums/articles-engine-fuel/341636-how-lap-valve.html

http://www.dsmtuners.com/forums/newbie-forum/420313-how-fluid-test-4g63-cylinder-head.html

Sounds like one of a couple things could be going on in #4

1) Valve is bent

2) HLA is pumped up holding the valve off the seat

3)the guide center line is off from bending valves, ( cracked guides)

4) valve tip height is off and not allowing the valve to fully close.

 

[bigpatofpa]

Try putting air on the #4 cylinder using your compression tester and air source (compressor).remove fuel rail and injector s listen for air. Or pull 02 sensor or crack downpipe and listen for air . Try rotating the crank to make sure you're on the compression stroke

 

[dougiefresh]

well guys , i did a down compression test and ended up tearing it all apart. to find the valves not sealing. looks like i bent them, but how did i end up bending only that cylinder ???

 

[11secDSM]

The bent valve was most likely hanging open...probably from a pumped up lifter that wasn't bled down.

 

[g4ebguy90]

Lapping valves??? Is used to check valve to seat contact NOT FOR valve job.

Lapping shows you contact area on the seat. If you use lapping compound as a way to do a POOR mans valve job, you are making the angles the same for ex. 45/45. usually you want a degree difference, that is the point. EX. 44/45 45/46 degrees

When you use lapping compound * to do cheap valve job* not only do you create the same angle on the seat as on the valve, but you also destory the valve margin, which Is needed to help disipate heat.

You pretty much triangle out the valve face.

Idk if you did this, but just so everyone is clear. Cause alot of ricer boys do this.

 

[ZenkaiRacerDsM]

Yep, a lot of people do it this way. Lapping is how it was done back in the day, and how most people do it these days if they are doing it themselves since they don't have the tools for machining.

 

[g4ebguy90]

It cost about $20-30.00 to get your valves done. Probaly close to the same for a cut on the seats, there really is no excuse for not getting it done properly.

Not saying you did it, but these guys are in my view, ruining there valves, and there ability to get rid of the heat they store. It may run for a bit, but eventually they will burn, and the cyl will lose compression.

Those prices are with removing them of course. *valves*.

 

[ZenkaiRacerDsM]

Hmm, I have a Honda engine I'm putting together and have been debating putting the new valves I got for it in, or just keeping the current stock valves that are in it to forgo machine work. I didn't know it was that cheap. I bet it will take a lot of time though with the speed at which the machine shops around here work.

 

[dougiefresh]

Ya I found out I must of skipped those lifters they were still hard unlike the others

 

[g4ebguy90]

O you forgot to bleed the lifters before install?

 

[bryanwheat]

It cost about $20-30.00 to get your valves done. Probaly close to the same for a cut on the seats, there really is no excuse for not getting it done properly.

Not saying you did it, but these guys are in my view, ruining there valves, and there ability to get rid of the heat they store. It may run for a bit, but eventually they will burn, and the cyl will lose compression.

Those prices are with removing them of course. *valves*.

I have yet to find a machine shop that will cut all seats and valves for under 100 bucks with the head disassembled. It's funny that you talk about lapping valves and that you are so sure that it will cause a burn't valve. I've been lapping valves for 15 years on many many head jobs, and put hundreds of thousands of miles on them without a single failure. I can get a better seal on the valves than i have been able to get from any local machine shop. If the valves or seats have serious pitting, than of coarse you are going to want to machine them, but for a little minor pitting lapping works fine.

 

[g4ebguy90]

I have yet to find a machine shop that will cut all seats and valves for under 100 bucks with the head disassembled. It's funny that you talk about lapping valves and that you are so sure that it will cause a burn't valve. I've been lapping valves for 15 years on many many head jobs, and put hundreds of thousands of miles on them without a single failure. I can get a better seal on the valves than i have been able to get from any local machine shop. If the valves or seats have serious pitting, than of coarse you are going to want to machine them, but for a little minor pitting lapping works fine.

I had my done on my first build ever, now the seats I did, the valves cost like $1.50 $2.00 each to have machined. I forgot why I had to outsource it, think the machine at school was not functioning right.

Now the cut was nothing fancy. I assumed if you have the head removed and ready, the job SHOULD be able to be done quickly and cheaply.

As far as using lapping compound to cut your valves. I doubt you are doing what others are, there are videos of people, usually honda boys grinding there valves and seats with this compound for about 30-40 minutes. They literally triangle out the valve, so if your trying to tell me * which not saying you are* that this is GOOD and has no ill effect on anything with the motor please don't waste your time at least trying to convince me.

I assume you are careful and probaly don't go all out like the others.

But I disagree with you thinking your getting a better seal with a straight cut with the same angle on the seat as on the valve, which is what you do.

 

[martindoom]

Just a tought here but.. wouldn't a tune WHILE the bad valves were in run down the new ones?

 

[DSMnoobsause]

On all of the race heads we build we cut the seats and lap the valves.Its Just like having the head and block surfaced and then laping the head and block.

 

[g4ebguy90]

On all of the race heads we build we cut the seats and lap the valves.Its Just like having the head and block surfaced and then laping the head and block.

No no, people are using the lapping compound to CUT there seats. They spin the valve against it for like ever until they have grinded the metal down way to far, then run it.

 

[BogusSVO]

If you spend more than 10-20 seconds per valve lapping it to get it to seal, then there are other issues that need to be addressed.