Interesting effect of valve coking - ZR-1 Net Registry Forums

XfireZ51 · 07-30-2015

This was displayed in a thread on the C7 forum discussing issues w Direct Injection and effect of not having fuel sprayed on valves.
The dyno chart demonstrates the gradual loss of power over time. I suspect something like this may also happen if you're not using ur secondaries very often especially since oil fumes are quite present in the LT-5 air intake.
The third and fourth run show difference in same motor after de-coking of valves. Fairly dramatic.

XfireZ51 · 07-30-2015

Informative YouTube

http://youtu.be/7Pz0zTQ1bz0

XfireZ51 · 07-30-2015

Also very interesting comments in this vid regarding effect of oil in throttle body

http://youtu.be/Mk4e5XFe47A

Paul Workman · 07-30-2015

And, another video on YouTube is "Oil Catch Cans: Myth or Must Have?"

I'll save you some time... They're a MUST HAVE, especially high rpm as in WOT or engine braking.

One of the (several) striking things I see as result of deleting my SPTs is the lack of coking on the intake valves; second only to steam cleaning.

As also mentioned in the video (first one) the amount of oil ingested and thus coking (I surmise) is reduce by 90% as result of the oil level being down almost/about a quart. True, the motor in the video was a modern LT1 w/ dry sump (read: different animal), but this is also true of the LT5s far as oil dumping into my catch can when the dipstick level is at the FULL line.

Windage/frothing is probably the culprit. So, I wonder what harm there is to maintaining the oil level as some point below the "FULL" line; say at the bottom 1/3?

Or, should I not worry about it, being fooled into thinking all is well because I have a catch can in place (on my 90, at least, and soon on the 91 too)? I'm leaning in favor of the catch can. I guess the question is, just how efficient is it, i.e., does it capture just a token amount of oil, or is it really very practically removing it "all"? Which can(s) are most effective?

XfireZ51 · 07-30-2015

Justa point of clarification

The dynos are of a BMW 3 series, not LT1, but its indicative of a motor w DI.

07-30-2015	#1
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,662	Interesting effect of valve coking This was displayed in a thread on the C7 forum discussing issues w Direct Injection and effect of not having fuel sprayed on valves. The dyno chart demonstrates the gradual loss of power over time. I suspect something like this may also happen if you're not using ur secondaries very often especially since oil fumes are quite present in the LT-5 air intake. The third and fourth run show difference in same motor after de-coking of valves. Fairly dramatic. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX Last edited by XfireZ51; 07-30-2015 at 08:58 AM.

07-30-2015	#2
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,662	Re: Interesting effect of valve coking Informative YouTube http://youtu.be/7Pz0zTQ1bz0 __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

07-30-2015	#3
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,662	Re: Interesting effect of valve coking Also very interesting comments in this vid regarding effect of oil in throttle body http://youtu.be/Mk4e5XFe47A __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX Last edited by XfireZ51; 07-30-2015 at 12:40 PM.

07-30-2015	#4
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Interesting effect of valve coking And, another video on YouTube is "Oil Catch Cans: Myth or Must Have?" I'll save you some time... They're a MUST HAVE, especially high rpm as in WOT or engine braking. One of the (several) striking things I see as result of deleting my SPTs is the lack of coking on the intake valves; second only to steam cleaning. As also mentioned in the video (first one) the amount of oil ingested and thus coking (I surmise) is reduce by 90% as result of the oil level being down almost/about a quart. True, the motor in the video was a modern LT1 w/ dry sump (read: different animal), but this is also true of the LT5s far as oil dumping into my catch can when the dipstick level is at the FULL line. Windage/frothing is probably the culprit. So, I wonder what harm there is to maintaining the oil level as some point below the "FULL" line; say at the bottom 1/3? Or, should I not worry about it, being fooled into thinking all is well because I have a catch can in place (on my 90, at least, and soon on the 91 too)? I'm leaning in favor of the catch can. I guess the question is, just how efficient is it, i.e., does it capture just a token amount of oil, or is it really very practically removing it "all"? Which can(s) are most effective? __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry Last edited by Paul Workman; 07-30-2015 at 10:52 AM.

07-30-2015	#5
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,662	Re: Interesting effect of valve coking Justa point of clarification The dynos are of a BMW 3 series, not LT1, but its indicative of a motor w DI. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX