Hi, i have just had a b18c built for boost with 9.01 CP's, manley rods,supertech valvetrain, arps etc. The compresion on cylinder 2 comes came out 20psi less than the other 3, so Ive run it in for about 1000 miles now and did a compression test it came out 170 170 150 170.
Now what the **** can this be?
(I also find a bit of oil on the floor where my car is parked in the morning- think its from the dent in my oil pan or could it be related to the low comp number?)

Should i just carry on and boost it, because i just cant be bothered opening it up for the 3rd time, whats the consequences?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by f1 vtec &raquo;</TD></TR><TR><TD CLASS="quote">Hi, i have just had a b18c built for boost with 9.01 CP's, manley rods,supertech valvetrain, arps etc. The compresion on cylinder 2 comes came out 20psi less than the other 3, so Ive run it in for about 1000 miles now and did a compression test it came out 170 170 150 170.
Now what the **** can this be?
(I also find a bit of oil on the floor where my car is parked in the morning- think its from the dent in my oil pan or could it be related to the low comp number?)

Should i just carry on and boost it, because i just cant be bothered opening it up for the 3rd time, whats the consequences? </TD></TR></TABLE>

I highly doubt that the dent in the oil pan has anything to do with the low compression on the #2 cylinder. If you are genuinely concerned, then you need to do a leakdown test.. Right now, all you have is an acceptable result from your compression test.. Remember, you are allowed a max variation of 20%...

.20 x 170 = 34psi

so, you are still within the limits and its nothing to be concerned about by any means. Anything under 136 would be cause for concern.

 

recheck your cam timing with the timing belt. also check valve lash on that cylinder. those things can affect compression numbers.

 

Valve lash is what I would check. Did you have the head checked for seal before you installed it? Sometimes older heads have beat up seats and they don't seal to well any longer.

 

ill have to check the Valve lash( sorry for the noob question but is it same as the valve clearance, how do i check for it).
Ill also check the cam timing. weird but my car is sounding like a subaru wrx on idle u know that boxer flat 4 sound?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">

I highly doubt that the dent in the oil pan has anything to do with the low compression on the #2 cylinder. If you are genuinely concerned, then you need to do a leakdown test.. Right now, all you have is an acceptable result from your compression test.. Remember, you are allowed a max variation of 20%...

.20 x 170 = 34psi

so, you are still within the limits and its nothing to be concerned about by any means. Anything under 136 would be cause for concern.</TD></TR></TABLE>

so should i check for the abve and if i cant find anything should i just go ahead and boost the thing.
thx for the replies

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by f1 vtec &raquo;</TD></TR><TR><TD CLASS="quote">ill have to check the Valve lash( sorry for the noob question but is it same as the valve clearance, how do i check for it).
Ill also check the cam timing. weird but my car is sounding like a subaru wrx on idle u know that boxer flat 4 sound?

so should i check for the abve and if i cant find anything should i just go ahead and boost the thing.
thx for the replies</TD></TR></TABLE>

No, If it sounds like a Subie something is wrong. If your valve lash is to tight and you go boosting you will burn a valve very quickly. Check your lash right away. Yes this is the same as adjusting the valves. .008.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by f1 vtec &raquo;</TD></TR><TR><TD CLASS="quote">ill have to check the Valve lash( sorry for the noob question but is it same as the valve clearance, how do i check for it).
Ill also check the cam timing. weird but my car is sounding like a subaru wrx on idle u know that boxer flat 4 sound?

so should i check for the abve and if i cant find anything should i just go ahead and boost the thing.
thx for the replies</TD></TR></TABLE>

I would focus more on the "subaru sound" issue right now. Check valve lash, thats fine.. but from what I have found, the "subaru sound" will occur also when spark plug wires pop off and you loose spark to one or more cylinders...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">

I would focus more on the "subaru sound" issue right now. Check valve lash, thats fine.. but from what I have found, the "subaru sound" will occur also when spark plug wires pop off and you loose spark to one or more cylinders... </TD></TR></TABLE>

Here are the main causes of the "Subie motor" sound.

1) Valve lash so tight 1 or two valves are barely opening if at all.
2) Fouled Spark Plug. What heat range and gap are you running?
3) Broken Ring Lands

Since this motor is brand new I am leaning toward number 1

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by asubennett &raquo;</TD></TR><TR><TD CLASS="quote">

Here are the main causes of the "Subie motor" sound.

1) Valve lash so tight 1 or two valves are barely opening if at all.
2) Fouled Spark Plug. What heat range and gap are you running?
3) Broken Ring Lands

Since this motor is brand new I am leaning toward number 1</TD></TR></TABLE>

1). If valve last was TIGHT then the valves would be opening too much and failing to close, thus leading to a burt valve
2). Again, going back to lack of or weak speak
3). This does not cause the subie sound. I had 30psi in one cylinder after I toasted it in my 99 Si. Sounded fine, idled a little rough yeah... but sounded fine

The sound is typically associated with an air pump type sound.. since the cylinder isn't firing, its just moving air and thus the "pump" type sound.

 

Broken ring lands make a B-Series motor sound horrible. Just like a boxer motor. Perhaps yours was the exception. I have heard the sound several times.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid93Eg &raquo;</TD></TR><TR><TD CLASS="quote">

1). If valve last was TIGHT then the valves would be opening too much and failing to close, thus leading to a burt valve
2). Again, going back to lack of or weak speak
3). This does not cause the subie sound. I had 30psi in one cylinder after I toasted it in my 99 Si. Sounded fine, idled a little rough yeah... but sounded fine

The sound is typically associated with an air pump type sound.. since the cylinder isn't firing, its just moving air and thus the "pump" type sound. </TD></TR></TABLE>

The valve lash part was a total typo on me. I mean to say closing instead of opening. Basically the Subie sound comes from a cylinder that isn't firing very well.

You said your motor only had 30 psi in one cylinder. You need at least 100psi to combust a mixture. So Your motor had to sound a bit off.