compression numbers

[TurboBusa]

Is this normal? i just got my engine rebuild and its 30 over, je pistons, big vlvs ported stock heads etc..... I finally got 2500 miles on it and even ran it at the track, it ran really good. anyways
i checked the compression on all the cylinders and it is 170 to 175
all the way. i checked it also while it was hot. is this too high?
i am also using NGK UR5 gapped at 32 the plugs look good. it looks kind of hot should i get a colder plug? what do you all think?
huh?

 

[tybob]

hi i have 160 in all cylinder cold ....if you take hot it is normal you have i little more try it cold.... and all gauge dont give exacly the same psi...but i think for a new engine .030 over it's ok bob

 

[TurboBusa]

thanks Bob i'll try that later on today.

 

[Blown&Injected]

Did my .030 over engine cold and on about the third compression stroke it was already about 170. The gauge took settled about 175 after a few more pumps. If I let it crank it would pick up another couple psi.

Seems a bit high to me only because I do not recall reading others results in that range - seem to come in around 130 - 140 psi. BTW there was no carbon build up in the engine for sure - pulled the heads right after the compression check.

BTW, your numbers are very close, as were mine, which is good. I still had three cracked pistons

 

[TurboBusa]

thats what i thought the range was around 130 to 140's. thats why i thought i'd ask.
Cracked pistons! how did you do that? even with cracked pistons you had that high of numbers?

 

[Turbo Brian]

When you bore out an engine, you increase the static compression ratio. If 140-150 is normal, with a cold stock engine, 170 seems in the ball park for a warm motor that has been bored out .030.

 

[Blown&Injected]

Originally posted by TurboBusa
thats what i thought the range was around 130 to 140's. thats why i thought i'd ask.
Cracked pistons! how did you do that? even with cracked pistons you had that high of numbers?

Engine was running VERY good in every respect except the oil pressure gauge was screaming warning! Wiped cams killed the crank. Thought I would reuse the old pistons but three were cracked below the oil ring so the compression rings and area of the piston were still doing their job - All 6 were within 5 psi kinda scary!

My engine was .030 over, .040 over now, but that is such a small increase that it does not seem capable of taking a 3.8 from 135 to 175 psi

 

[TurboBusa]

crap man! that is scary! what was your oil pressure at the time? another question, what is the range the pressure should be for our cars? at cold i get about 65psi, when hot at idle 15 but mostly 20psi. when i hit the gas even just a little bit, it jumps to 40. and when cruizin at the highway at 165 temp its usually 45 psi. seems normal to me.

This is my first time dealing with a new turbo buick engine (fresh).
before the rebuild it had gobs of mileage and track times with nos and a newbie lerning how to tune. you know how that goes. finally i went lean and wasn't paying attention to the gas gauge.
Went lean and blew both head gasket at #6 and #3. now new engine and new set up still trying to learn this thing.
I think the most scariest part was starting the new engine, because of the stories of cams wiping out etc... i thought there was something wrong with the engine at first lots of clacking but no indication of knock, oil press came up quick. clacking went away after about 1 min then i just let it run for 20 in at 3200 rpm.
hopefully this will hold up.

 

[Blown&Injected]

Your oil pressure sounds just fine. Mine would start at about 65 psi but fall to 9 after just five minutes and it would not jump back up.

This might sound like a PITA, but I would pull the valve cover and fire it up and make sure the push rods are spinning especially the number three exhaust lifter.

 

[TurboBusa]

OK blown your starting to scare me. I don't think i want to do that now, but i will first chance i get to play with it tomorrow. darn this is going to be messy huh? another question what do you use for plugs? so #3 exhaust huh, make sure its spinning.
i'll do that.
i really want to see what this thing can do. thing is i don't really know how to play with this trans + and extender chip dill.
i'll figure it out somehow.
my set up is as follows.
109 .030
214 crower cam
ported stock heads with big vlvs
poston headers
ported intake
rjc plate
65mm TB
precision upper plenum
thdp 3"
83's
T+ and extreame extender
3.5 lsi mas
precision FM
no A/C
GTQ 70
3800 stall 7 disc Vigilante and trans brake
DRW tranny
Nos, but haven't used yet will only use 50 but too scared to use.

 

[Blown&Injected]

Do not recall what part number I use; what ever the GN T-Type org says is good for a mid 11 second car, always AC Delco or Autolite.

Your setup sounds great!

Since I do not have a MAF Trans, I do not know how to use it, but it sounds like there is just a base line that just looks at the chip plus switches that will add and subtract timing and fuel, maybe in different areas of the rpm range too??? Sounds like enough tuning to go very fast.

Pull just that one valve cover and make sure the #3e is turning as it is running - should even spin by turning engine over by hand.

 

[TurboBusa]

blown #3E spins so its good right. i watched all of the rockers go fully up and down. darn that was messy!

 

[Peeds]

hey ive got a question on compression numbers as well. my cars engine was rebuilt less than 2 miles ago then all the sudden it started smoking real bad white smoke. so i figured blown head gasket. just got done the compression test. on the passanger side one of the cylinders was 140 and the others were 150. one cylinder on the drivers side was 155 and the other two were 160. is the 140 to low since all the others are 150+. any help is appreciated, im young and new to this whole car thing... thanks
-Paul