gonna troubleshoot a motor KNOCK..need some help

[wilde1j]

Re: gonna troubleshoot a motor KNOCK..need some help

My money would on that hole ran lean. Most common cause of heat damage.

 

[83ebbtide]

Re: gonna troubleshoot a motor KNOCK..need some help

Craig-, if he resleeves the one cylinder will he still need to deck it or do the sleeves fit flush?

 

[bob johnson]

Re: gonna troubleshoot a motor KNOCK..need some help

My money would on that hole ran lean. Most common cause of heat damage.

other than engine damage forensics....

how can you diagnose a single lean cylinder?

I have a somewhat over -warm issue going on with my 115 and after new T-stats, and water pump and a new cleaned up set of heads....

I am wondering if i need to just blindly go rebuild the carbs....the motor runs great....just runnign at 180 ish when the other side is running about 150 ish

is there a sign there??

if you pull a carb can you specifically test it somehow for not letting the propper amount of fuel through?

thanks

bob

 

[bob johnson]

Re: gonna troubleshoot a motor KNOCK..need some help

Craig-, if he resleeves the one cylinder will he still need to deck it or do the sleeves fit flush?

the bore is standard.... and not damage much at all( didnt check for out of roundness yet)...why would a sleeve be needed???

you can bore those sleeves out .040" I thought...



bob

 

[Craig-]

Re: gonna troubleshoot a motor KNOCK..need some help

Craig-, if he resleeves the one cylinder will he still need to deck it or do the sleeves fit flush?

Would have to be cut.

 

[Craig-]

Re: gonna troubleshoot a motor KNOCK..need some help

the bore is standard.... and not damage much at all( didnt check for out of roundness yet)...why would a sleeve be needed???

you can bore those sleeves out .040" I thought...



bob

Doesn't need a sleeve if it is still good. Hone it out or bore it if you see the need. Figure out what made it run hot or you'll be doing it again.

 

[83ebbtide]

Re: gonna troubleshoot a motor KNOCK..need some help

Bob, I thought I read where someone mentioned releeving the cylinder which is what raised my question. Can you just redo one cylinder? Not to take over your thread but I may be rebuilding mine and thought if you bored one hole you did them all.

 

[Faztbullet]

Re: gonna troubleshoot a motor KNOCK..need some help

What cylinder is that piston from??? If #1 it could be a glue line leaking in block but its kinda rare in the V-4. Make sure you install the late model t-statssas they cool a lot better(ficht style).

 

[wilde1j]

Re: gonna troubleshoot a motor KNOCK..need some help

the bore is standard.... and not damage much at all( didnt check for out of roundness yet)...why would a sleeve be needed???

you can bore those sleeves out .040" I thought...



bob

.... and perhaps more than .040". Resleeving is used where you can't bore BC to much metal is already gone.

If you can ID which carb fed the damaged cylinder, examine carefully before cleaning. You may find partially plugged jets or passages. More motors are damaged by lean conditions than any other cause.

 

[Craig-]

Re: gonna troubleshoot a motor KNOCK..need some help

I did a comp test on the motor last feb when i bought it...they were all 120's

...
how can you be sure about the over heat??

I know thats the result....pistons out of roundness and galling...

bob

No doubt it got too hot. I'm thinking it was from water, based on a previous thread of yours, if this is the same hole that had salt in it. A lean burn may have started the problem but it got wet after that, from what I saw in the pictures. Your feb comp #'s are good enough not to touch the other cylinders if you can't measure any damage now that it's opened up. If you want to replace good pistons for your peace of mind, it's your money.

 

[bob johnson]

Re: gonna troubleshoot a motor KNOCK..need some help

ebbtide....you certainly can just bore one cylinder..and leave the rest stock if all the specs are in..I have a 1995 115 motor that is the same style as this 90 and it has three standard bore and an .03" oversize piston in the other cylinder!!

Fazt...its the number 2 slug...

and what is a glue line???


bob

 

[bob johnson]

Re: gonna troubleshoot a motor KNOCK..need some help

No doubt it got too hot. I'm thinking it was from water, based on a previous thread of yours, if this is the same hole that had salt in it. A lean burn may have started the problem but it got wet after that, from what I saw in the pictures. Your feb comp #'s are good enough not to touch the other cylinders if you can't measure any damage now that it's opened up. If you want to replace good pistons for your peace of mind, it's your money.

different motor Craig...i have a 1995 115 ocean runner on the boat that was getting salt deposits


this motor was on before that one and is an 1997 Ocean Pro 90 .

how does water cause an over heat?? by washing the walls??

in automotive motors they add water to cool the motor!!


bob

 

[83ebbtide]

Re: gonna troubleshoot a motor KNOCK..need some help

Thanks Bob! That could certainly save me some money, assuming the other cylinders check out. Good Luck!

 

[Craig-]

Re: gonna troubleshoot a motor KNOCK..need some help

different motor Craig...i have a 1995 115 ocean runner on the boat that was getting salt deposits


this motor was on before that one and is an 1997 Ocean Pro 90 .

how does water cause an over heat?? by washing the walls??

in automotive motors they add water to cool the motor!!


bob

More like steam cleaning and also raises temps in water jacket.
Water/meth injection in hot rods cools the air charge, condensing it, packing more oxygen into a smaller space, then more fuel has to be added so not to be too lean. Results in lower combustion temps allowing more timing advance without detonation.