Compression test - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

BeardWS6 · 06-02-2015, 06:47 AM

What should our motors hold on a compression test? I had the heads done and I think my push rods are to long. I got from 110lbs, 115,125,128, on just the driver side. Seems when we put load on the motor on the dyno I`m losing boost and the headers get really red where the heads go into the headers on all 8 cylinders . Like my exhaust valves are staying open. Whats your thoughts? Thanks!

white ZL1 · 06-02-2015, 12:50 PM

So after the problems you had with the last engine, who put this one together and what did they say?

Smittty · 06-02-2015, 02:55 PM

I get anywhere from 147lbs to 160 on mine.

BeardWS6 · 06-02-2015, 04:05 PM

I think I have the wrong length pushrods in. I had the heads ported and the short block built and put the 7.4 pushrods back in and I believe the valves are staying open!

97ChameleonTA · 06-02-2015, 05:15 PM

Out of curiosity, are you opening the throttle blade during your test? That can have a drastic impact on your readings.

Atomic Zl1 · 06-02-2015, 06:22 PM

Did you change anything in the tune after the mods?....Did you use GM head bolts?

BeardWS6 · 06-03-2015, 06:19 AM

Talking with my builder and then calling my head guy. We CNC`d my heads, cleaned the valves up and milled the heads. This put the valves closer to the push rod causing us to need shorter rods. He is sending me the info of how much was taken off the heads so we can order the ned push rods. Pat G is tuning the car and also has been a big help. I will keep everyone posted of results.

ZO6 Bryan · 06-03-2015, 07:43 AM

Didn't anyone measure the pre-load on the lifters when they built the engine? Hydraulic lifters adjust anyway unless they are completely bottomed out. Your valves will still close unless it is WAY off. And if that's the case you need a new engine builder.

FWIW glowing headers is usually do to the ignition timing being to far retarded. The combustion process hasn't enough time to complete and the fuel is still burning as it exits the exhaust port.

And what cam are you using? Does it have a very early exhaust valve opening? That also could cause glowing red headers.

BeardWS6 · 06-03-2015, 03:41 PM

Talking with my head guy the heads got a clean up mill and valve job. Looks like .015 was taken off my heads so I need to go with a shorter pushrod. Should have this completed tomorrow I hope.

BeardWS6 · 06-03-2015, 03:50 PM

Quote:

Originally Posted by ZO6 Bryan

Didn't anyone measure the pre-load on the lifters when they built the engine? Hydraulic lifters adjust anyway unless they are completely bottomed out. Your valves will still close unless it is WAY off. And if that's the case you need a new engine builder.

FWIW glowing headers is usually do to the ignition timing being to far retarded. The combustion process hasn't enough time to complete and the fuel is still burning as it exits the exhaust port.

And what cam are you using? Does it have a very early exhaust valve opening? That also could cause glowing red headers.

I had this cam in the car before I bent a rod. Made 704rwhp 694trq. Plugged cats killed the motor! Went back with a forged bottom end and ported heads with same set up. I had three different folks do the build. One did the short block, one did the heads and one put it together in the car. Seems we had some miss communication on what happen with the heads I believe. Cam is 227/242/520/590/122+6. Cam sounded totally different with the new build, this cam is quite. It wash`t when I got it running this time, which talking with someone could be a sign the valves are staying open. Cam is dot to dot per the folks we bought from. I have a very good tuner tuning her and so timing is good.

ZO6 Bryan · 06-03-2015, 06:39 PM

.015" too long is not enough to hold valves open. I'd look elsewhere.

Boother · 06-04-2015, 01:26 PM

Quote:

Originally Posted by ZO6 Bryan

Didn't anyone measure the pre-load on the lifters when they built the engine? Hydraulic lifters adjust anyway unless they are completely bottomed out. Your valves will still close unless it is WAY off. And if that's the case you need a new engine builder.

FWIW glowing headers is usually do to the ignition timing being to far retarded. The combustion process hasn't enough time to complete and the fuel is still burning as it exits the exhaust port.

And what cam are you using? Does it have a very early exhaust valve opening? That also could cause glowing red headers.

All of this

.

It would be an easy check to pull the valve covers and press down on the pushrod to see how much play there is left in the lifter.

BeardWS6 · 06-05-2015, 10:18 AM

Quote:

Originally Posted by Boother

All of this

.

It would be an easy check to pull the valve covers and press down on the pushrod to see how much play there is left in the lifter.

No play at all! TIGHT

BeardWS6 · 06-06-2015, 09:10 AM

Put the new pushrods in last night, a little more bolting up and fluids and she is ready to finish the tune. New compression test shows solid 140-142lbs pressure on all, this was on a cold motor. Looks like a little more than original was taken off the heads during the CNC and clean up milling of the heads and the valve job. I plan on finishing sunday and starting her up!
From what I`m told 140 on a boosted motor is pretty good. Before with the longer push rods we were getting 110-120.

06-02-2015, 06:47 AM	#1
BeardWS6 Drives: 01 WS6 Join Date: Jun 2009 Location: Texas Posts: 263	Compression test What should our motors hold on a compression test? I had the heads done and I think my push rods are to long. I got from 110lbs, 115,125,128, on just the driver side. Seems when we put load on the motor on the dyno I`m losing boost and the headers get really red where the heads go into the headers on all 8 cylinders . Like my exhaust valves are staying open. Whats your thoughts? Thanks! __________________ 2013 Red ZL1 Auto modded 2015 C7 ZO6 Luguna Blue stock

06-02-2015, 02:55 PM	#3
Smittty Drives: 2013 ZL1 Camaro 2000 SLP Camaro Join Date: Oct 2012 Location: Ruther Glen, VA Posts: 357	I get anywhere from 147lbs to 160 on mine. __________________ 2013 ZL1 748rwhp & 733 rwtq ( 93 tune )

06-02-2015, 04:05 PM	#4
BeardWS6 Drives: 01 WS6 Join Date: Jun 2009 Location: Texas Posts: 263	I think I have the wrong length pushrods in. I had the heads ported and the short block built and put the 7.4 pushrods back in and I believe the valves are staying open! __________________ 2013 Red ZL1 Auto modded 2015 C7 ZO6 Luguna Blue stock

06-02-2015, 05:15 PM	#5
97ChameleonTA Drives: 2013 ZL1 Convertible Join Date: Oct 2013 Location: Valrico, FL Posts: 515	Out of curiosity, are you opening the throttle blade during your test? That can have a drastic impact on your readings. __________________ 2013 ZL1 Auto Convertible - BRM Best: 10.829@127.15 FI Interchiller, Roto-Fab CAI, Big Gulp & Res, 9.1/2.5 Pulleys, PB&S, DeatschWerks 1500cc, Fore triple pump, Pfadt LT's, RD HX, MT DR's New times to come with E85 2016 2SS Auto - Hyper Blue Metallic Roto-Fab CAI

06-03-2015, 06:19 AM	#7
BeardWS6 Drives: 01 WS6 Join Date: Jun 2009 Location: Texas Posts: 263	Talking with my builder and then calling my head guy. We CNC`d my heads, cleaned the valves up and milled the heads. This put the valves closer to the push rod causing us to need shorter rods. He is sending me the info of how much was taken off the heads so we can order the ned push rods. Pat G is tuning the car and also has been a big help. I will keep everyone posted of results. __________________ 2013 Red ZL1 Auto modded 2015 C7 ZO6 Luguna Blue stock

06-02-2015, 12:50 PM	#2
white ZL1 Drives: none Join Date: Aug 2011 Location: DFW area Posts: 1,844	So after the problems you had with the last engine, who put this one together and what did they say?

06-02-2015, 06:22 PM	#6
Atomic Zl1 Drives: 2013 ZL1-Clean one owner Join Date: Apr 2015 Location: Upstate NY Posts: 86	Did you change anything in the tune after the mods?....Did you use GM head bolts?

06-03-2015, 07:43 AM	#8
ZO6 Bryan Drives: 02 Z06, 95 Trans Am, 2012 ZL1 Join Date: Mar 2012 Location: Southeast Posts: 1,838 View My Garage	Didn't anyone measure the pre-load on the lifters when they built the engine? Hydraulic lifters adjust anyway unless they are completely bottomed out. Your valves will still close unless it is WAY off. And if that's the case you need a new engine builder. FWIW glowing headers is usually do to the ignition timing being to far retarded. The combustion process hasn't enough time to complete and the fuel is still burning as it exits the exhaust port. And what cam are you using? Does it have a very early exhaust valve opening? That also could cause glowing red headers. __________________ Bryan 2018 ZL1 M6

06-03-2015, 03:41 PM	#9
BeardWS6 Drives: 01 WS6 Join Date: Jun 2009 Location: Texas Posts: 263	Talking with my head guy the heads got a clean up mill and valve job. Looks like .015 was taken off my heads so I need to go with a shorter pushrod. Should have this completed tomorrow I hope. __________________ 2013 Red ZL1 Auto modded 2015 C7 ZO6 Luguna Blue stock

06-03-2015, 06:39 PM	#11
ZO6 Bryan Drives: 02 Z06, 95 Trans Am, 2012 ZL1 Join Date: Mar 2012 Location: Southeast Posts: 1,838 View My Garage	.015" too long is not enough to hold valves open. I'd look elsewhere. __________________ Bryan 2018 ZL1 M6

06-06-2015, 09:10 AM	#14
BeardWS6 Drives: 01 WS6 Join Date: Jun 2009 Location: Texas Posts: 263	Put the new pushrods in last night, a little more bolting up and fluids and she is ready to finish the tune. New compression test shows solid 140-142lbs pressure on all, this was on a cold motor. Looks like a little more than original was taken off the heads during the CNC and clean up milling of the heads and the valve job. I plan on finishing sunday and starting her up! From what I`m told 140 on a boosted motor is pretty good. Before with the longer push rods we were getting 110-120. __________________ 2013 Red ZL1 Auto modded 2015 C7 ZO6 Luguna Blue stock