Blowby... - Team Camaro Tech
Engine General Engine Discussion.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 18 (permalink) Old Feb 10th, 08, 08:17 AM Thread Starter
Senior Tech
Paul
 
Join Date: Sep 2001
Location: Queen Creek AZ
Posts: 3,677
Blowby...

So for the second time I popped the front and back seal on my intake. The first time I thought that I hadn't put down a sufficient amount of RTV, so I pulled the intake a couple weeks back to have a look. I had plenty of RTV but what is happening is that at high RPM apparently there is too much crankcase pressure and it is pushing oil out the front and back of the manifold.

I do have a pcv in the drivers side cover and a breather in the passengers side cover.

I did a leak down test about a month ago and all cylinders tested out good, but you can hear air getting past the rings. I changed the valve springs out a week or so ago and aired up the cylinders and there is enough air getting past the rings where you can feel it coming out of the breather and pcv holes....but no different than when I did the leak down test.

So...I can't have my motor pushing oil out the front and back seals of the intake, not gonna work for me. Unless I can improve my pcv somehow I think that I'm going to have to yank the motor and install some new rings. If memory serves me correctly we used KB hyper pistons with standard rings. I'll have to talk to my buddy and see if he remembers any better than I do.

The specs on my motor are:

-350 4 bolt block bored 30 over
-steel crank
-stock 5.7 rods
-KB hyper flat top pistons
-The rotating assembly was balanced and the block was clearanced and zero decked

Assuming that everything is good in there what kind of rings would I want to go with? I'd like to run something proven that will have less blowby than the current standard rings....some kind of file to fit rings?


Anywho, the rest of the specs on my engine are:

-Edelbrock performer RPM heads 70cc
-Crower solid flat cam .242/.248 .482/.504 114/110
-1.6 rockers
-Holley Stealth Ram intake
-58mm TB
-30 lb injectors
-C950 ECU
-GM CC small body distributor
-Thorley tri-y headers
-2.5 x-pipe and 2.5 exhaust

On a side note, I made my first 12 second pass the other [email protected]

Best of 1.55 - [email protected]
paulm is offline  
Sponsored Links
Advertisement
 
post #2 of 18 (permalink) Old Feb 10th, 08, 09:09 AM
Senior Tech
 
Join Date: Mar 2002
Location: Austin, TX, USA
Posts: 5,277
Re: Blowby...

I would expect your leak-down test to have shown something if you're getting that much blow-by. What were your leakage numbers for each cylinder?

Dave
========================
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
dnult is offline  
post #3 of 18 (permalink) Old Feb 10th, 08, 09:23 AM
Senior Tech
Eric
 
Join Date: Oct 2005
Location: Ohio
Posts: 437
Re: Blowby...

First thing that comes to my mind is a broken ring or two....

Were the leak downs consistant?

'68 Coupe 383 Small Block
4 speed Muncie (M 21)
12 bolt rear end (4.10)
Old school slappers
Old School L-60 Mickey Thompson's


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
EC's 327 is offline  
 
post #4 of 18 (permalink) Old Feb 10th, 08, 10:59 AM
Senior Tech
Ed
 
BigBlock1969RS's Avatar
 
Join Date: Jun 2007
Location: Los Angeles, CA
Posts: 2,083
Re: Blowby...

What kind of pressure were you using on the leak-down test? And did you try putting some oil in the cylinders to see if that made a difference in ring sealing?

Ed

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
BigBlock1969RS is offline  
post #5 of 18 (permalink) Old Feb 10th, 08, 11:06 AM
Senior Tech
Tim
 
77wolf10.85's Avatar
 
Join Date: Mar 2007
Location: Oklahoma
Posts: 3,222
Re: Blowby...

No insult intended here Paul, but are you sure you did the leakdown test correct and read it correct? There are at least 3 different style testers I am aware of, and the gauges are the main diff. Enough ring leakage to feel leakdown test air flowing out the breather is significant is what I want to say but that is probably subjective. Kinda would need to hear and feel it to say that for sure. If it leaks it has to go somewhere huh

There's more than 1 orifice size PCV available.

PCV won't really pull on the crankcase at WOT. It will equalize pressure though if there is a differential(that's all it's doing anyway), and if the orifice is large enough to permit equalization.

If I had an engine I thought was good, but blowing out manifold endseals, I would lose the silicone and go down to O'reilly and buy a $15 cheesewhiz tube of The Right Stuff. 1/4" bead of The Right Stuff on the ends and up onto the intake gasket a little, let it skim a minute or less, set the intake straight (some do this with the use of dowels but I usually just decide to see how good I am), start the bolts but leave them just snug about 15 minutes, then barely tight about 15 minutes, then put the **** to them. The Right Stuff is like silicone on steroids. You really don't even need to let it skim or do the stages of tight but I usually do just so I'm sure I get some crush on the solidified poop.

If I thought I needed rings I would also need honed at the least. That means complete disassembly to me cuz hone crap is nasty crap and you can't get it out of the cyls without powerwashing and brushing. And yes, file fit rings always but they get double money for them. Especially with KB hypers, you don't want too little gap with them. Lots of good rings available. I have expensive tastes on engine guts so I won't recommend you a set of rings that costs more than your pistons. If I was in your shoes I think I would see how much gap I had with a set of .030's, might work out perfect and save you 50 bucks or so.

Tim Smith
77wolf10.85 is offline  
post #6 of 18 (permalink) Old Feb 10th, 08, 11:23 AM
Gold Lifetime Member
Steve
 
Farm Boy's Avatar
 
Join Date: Feb 2005
Location: The California Republic
Posts: 1,720
Re: Blowby...

I kind of doubt blowby pressure is pushing out the manifold seals. If you had that much crankcase pressure you would have smoke coming out of the breather and you would be able to see and smell the blowby while driving around.

I suspect you have a problem with the way the intake manifold fits on the engine. Did you have the heads shaved or the block decked? Could the manifold be warped? How big is the gap you are filling with the silicone?

Steve

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

I drove it for the first time in 1972 when I was 15.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Better looking than a '56 Ford or Plymouth.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Farm Boy is offline  
post #7 of 18 (permalink) Old Feb 10th, 08, 11:36 AM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Blowby...

I'm with Steve on this one, I think.

My old 327 had both compression rings broken on #2. On the highway, she'd blow a quart out the breather in 4 hours. Real messy stuff. Ventilation was same as yours, pcv on one side breather on the other.

She never blew a gasket out.

I think either...
Your manifold isn't sealing properly for reasons yet to be found, or...
Your crankcase ventilation is suspect. Are you sure the air can flow out that breather? Maybe the darned thing is clogged? Or snapping down right on top of the baffle so it gets plugged up that way? This could be happening on the pcv side too, depending on the valve covers and baffles.





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #8 of 18 (permalink) Old Feb 10th, 08, 12:13 PM Thread Starter
Senior Tech
Paul
 
Join Date: Sep 2001
Location: Queen Creek AZ
Posts: 3,677
Re: Blowby...

Quote:
Originally Posted by dnult View Post
I would expect your leak-down test to have shown something if you're getting that much blow-by. What were your leakage numbers for each cylinder?
The were all in the "set" area or like 10%...like this picture (except not 20% plus like the picture).

http://www.carcraft.com/techarticles.../photo_09.html


Quote:
Originally Posted by EC's 327 View Post
First thing that comes to my mind is a broken ring or two....

Were the leak downs consistant?
Yes


Quote:
Originally Posted by BigBlock1969RS View Post
What kind of pressure were you using on the leak-down test? And did you try putting some oil in the cylinders to see if that made a difference in ring sealing?
Whatever the instructions said....was it like 90 or 100 PSI and no oil added? I could do it again for grins, it my buddys tester and I could grab it from him.


Quote:
Originally Posted by 77wolf10.85 View Post
No insult intended here Paul, but are you sure you did the leakdown test correct and read it correct?
Oh no, I could never ever make a mistake, LOL!


Quote:
Originally Posted by 77wolf10.85 View Post
PCV won't really pull on the crankcase at WOT. It will equalize pressure though if there is a differential(that's all it's doing anyway), and if the orifice is large enough to permit equalization.

If I had an engine I thought was good, but blowing out manifold endseals, I would lose the silicone and go down to O'reilly and buy a $15 cheesewhiz tube of The Right Stuff. 1/4" bead of The Right Stuff on the ends and up onto the intake gasket a little, let it skim a minute or less, set the intake straight (some do this with the use of dowels but I usually just decide to see how good I am), start the bolts but leave them just snug about 15 minutes, then barely tight about 15 minutes, then put the **** to them. The Right Stuff is like silicone on steroids. You really don't even need to let it skim or do the stages of tight but I usually do just so I'm sure I get some crush on the solidified poop.

If I thought I needed rings I would also need honed at the least. That means complete disassembly to me cuz hone crap is nasty crap and you can't get it out of the cyls without powerwashing and brushing. And yes, file fit rings always but they get double money for them. Especially with KB hypers, you don't want too little gap with them. Lots of good rings available. I have expensive tastes on engine guts so I won't recommend you a set of rings that costs more than your pistons. If I was in your shoes I think I would see how much gap I had with a set of .030's, might work out perfect and save you 50 bucks or so.
Good input, thanks!


Quote:
Originally Posted by Farm Boy View Post
I kind of doubt blowby pressure is pushing out the manifold seals. If you had that much crankcase pressure you would have smoke coming out of the breather and you would be able to see and smell the blowby while driving around.

I suspect you have a problem with the way the intake manifold fits on the engine. Did you have the heads shaved or the block decked? Could the manifold be warped? How big is the gap you are filling with the silicone?
Could be warped I guess. Heads were not shaved, I put the intake gaskets on dry, put a couple of flashlights in the lifter valley and set the intake on....Didn't see any light coming out, except from the dist hole. No burning oil driving around...just oil out the breathers at WOT, high RPM once on the dyno.


Quote:
Originally Posted by JimM View Post
I'm with Steve on this one, I think.

My old 327 had both compression rings broken on #2. On the highway, she'd blow a quart out the breather in 4 hours. Real messy stuff. Ventilation was same as yours, pcv on one side breather on the other.

She never blew a gasket out.

I think either...
Your manifold isn't sealing properly for reasons yet to be found, or...
Your crankcase ventilation is suspect. Are you sure the air can flow out that breather? Maybe the darned thing is clogged? Or snapping down right on top of the baffle so it gets plugged up that way? This could be happening on the pcv side too, depending on the valve covers and baffles.
Could be clogged I guess...



Bottom line is that my motor has more blowby than my buddies who used "file to fit" rings. You can hear the difference although the leakdown doesn't show much difference.

Best of 1.55 - [email protected]
paulm is offline  
post #9 of 18 (permalink) Old Feb 10th, 08, 01:26 PM
Gold Lifetime Member
Jim
 
Join Date: Dec 1999
Location: Yorkville, Illinois USA
Posts: 22,121
Re: Blowby...

Yer just looking for an excuse to go thru 'er, ain't ya Paul?

Well just do it then, yank 'er outa there and check 'er out. Nuttin to lose but time and money, lots to gain. And it's always so much fun.





To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
New website for my vert is coming together. Do ya like the slide show on the home page?
JimM is offline  
post #10 of 18 (permalink) Old Feb 10th, 08, 01:51 PM Thread Starter
Senior Tech
Paul
 
Join Date: Sep 2001
Location: Queen Creek AZ
Posts: 3,677
Re: Blowby...

Quote:
Originally Posted by JimM View Post
Yer just looking for an excuse to go thru 'er, ain't ya Paul?

Well just do it then, yank 'er outa there and check 'er out. Nuttin to lose but time and money, lots to gain. And it's always so much fun.
Well....I am definitely not opposed to pulling it out and going through it but it would be good to know why I am popping end seals on the intake BEFORE I pull it out. I mean at least have a good theory before getting crazy.

So, so far theories are....

1. Error doing leakdown and there IS a problem.
--Do test again to double check.

2. Bad seal on intake due to warpage or ???
--No way to check this without disassembly but everything looked okay when I resealed a couple of weeks ago.

3. Bad PCV setup.
--I'll check it out....this would be an easy fix huh?


I have learned a bunch over the past few years, but I don't have any clue about picking rings. So what do I need to know about my pistons inorder to determine what my options are on rings? What are good rings for street/strip?

If I do pull it apart I want to change the timing chain too. I have a double chain that had 3-4 degrees of slack when I checked when I changed to the crower solid flat cam. What is a better chain that won't stretch? I read about a Cloyes true roller? Is that a better option?

Best of 1.55 - [email protected]
paulm is offline  
post #11 of 18 (permalink) Old Feb 11th, 08, 11:34 AM
Senior Tech
 
Join Date: Jan 2001
Location: skiatook, ok
Posts: 3,692
Re: Blowby...

Keep in mind that the KB hyper's use a considerably larger ring gap than a standard cast piston...if your doing your leakdown/air pressure test with a cold engine I would certainly expect you to feel or hear more air bypassing the rings.
You might try simply disconnecting the PCV system and either run an open hole or some sort of breather where the PCV valve normally resides. This will give full ventilation on both sides of the engine, then you can see if the problem remains.

I've had excellent luck with the speed-pro plasma-moly ring sets, and they aren't that expensive. Just pay close attention to your rind end gap as the KB's are special that way.

"This is not a cheerocracy...I make the cheercisions around here"
travis is offline  
post #12 of 18 (permalink) Old Feb 11th, 08, 12:01 PM Thread Starter
Senior Tech
Paul
 
Join Date: Sep 2001
Location: Queen Creek AZ
Posts: 3,677
Re: Blowby...

Quote:
Originally Posted by travis View Post
if your doing your leakdown/air pressure test with a cold engine I would certainly expect you to feel or hear more air bypassing the rings.
That's true the engine was cold when I swapped the springs.


Quote:
Originally Posted by travis View Post
You might try simply disconnecting the PCV system and either run an open hole or some sort of breather where the PCV valve normally resides. This will give full ventilation on both sides of the engine, then you can see if the problem remains.
OK...It can't hurt to try! I've never not run a PCV...will no PCV hurt the motor at all or was it simply an emissions thing?


Quote:
Originally Posted by travis View Post
I've had excellent luck with the speed-pro plasma-moly ring sets, and they aren't that expensive. Just pay close attention to your rind end gap as the KB's are special that way.
Well, my buddy says that he doesn't remember KB pistons. He said that he remembers TRW hyper pistons...



I did some fine tuning yesterday for idle and off idle. The motor is running so sweet that I hate to pull it out just yet. I suppose I can live with a couple of drops of oil out the front and back of the intake until I confirm that there is a "real" problem.

Best of 1.55 - [email protected]
paulm is offline  
post #13 of 18 (permalink) Old Feb 11th, 08, 04:42 PM
Senior Tech
 
Join Date: Jan 2001
Location: skiatook, ok
Posts: 3,692
Re: Blowby...

With the engine fully warmed up, if there is any blowby you will see it with the PCV valce removed and an open PCV hole in the valve cover. I certainly wouldn't leave it open, but it won't hurt anything to drive it for a while with the hole open. Heck, I've seen people do it for years!
The only reason I mentioned the thing about the ring gaps is because KB's hyper pistons definately use a wider than normal ring gap than any other piston out there, including speed-pro/trw hypers. Once the engine is warmed up, the larger ring gap with the KB's closes down to normal.

"This is not a cheerocracy...I make the cheercisions around here"
travis is offline  
post #14 of 18 (permalink) Old Feb 11th, 08, 07:20 PM Thread Starter
Senior Tech
Paul
 
Join Date: Sep 2001
Location: Queen Creek AZ
Posts: 3,677
Re: Blowby...

Quote:
Originally Posted by travis View Post
With the engine fully warmed up, if there is any blowby you will see it with the PCV valve removed and an open PCV hole in the valve cover.
Yup, there is definitely blowby! Thanks for the simple test!

Best of 1.55 - [email protected]
paulm is offline  
post #15 of 18 (permalink) Old Feb 12th, 08, 03:04 PM
Senior Tech
 
Join Date: Jan 2001
Location: skiatook, ok
Posts: 3,692
Re: Blowby...

Quote:
Originally Posted by paulm View Post
Yup, there is definitely blowby! Thanks for the simple test!
Well that sucks Congrats on getting well into the 12's though, FWIW

"This is not a cheerocracy...I make the cheercisions around here"
travis is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome