FAST 90 intake manifold crack
Thread Starter
Instructor
Joined: May 2007
Posts: 214
Likes: 4
From: Sweden
FAST 90 intake manifold crack
How wrong can man go???
After battery change and short circuit I posted to forum and asked help because of MAF, bad battery and bad idle.
Time has passed as well as some $$$ and I changed MAF and TPS sensors hoping that it would help. Same symptom remains. When starting engine it won't start but only gives a "promoise of 2 seconds".
Now I got new MAP sensor and that's why I took off intake manifold to install it.
To my big surprice I found that the bottom part of intake manifold that is plastic is broken.
There is a 10" long and 1,5" wide crack on the bottom of the plastic part of intake.
Obviously it results an air leakage.
I was able to separate metallic top part of intake and plastic (PVC?) bottom part of intake.
I am not familiar with LS1 and I need help and advice how to fix the damaged plastic bottom part.
Please advice!
Cheers
Jan
After battery change and short circuit I posted to forum and asked help because of MAF, bad battery and bad idle.
Time has passed as well as some $$$ and I changed MAF and TPS sensors hoping that it would help. Same symptom remains. When starting engine it won't start but only gives a "promoise of 2 seconds".
Now I got new MAP sensor and that's why I took off intake manifold to install it.
To my big surprice I found that the bottom part of intake manifold that is plastic is broken.
There is a 10" long and 1,5" wide crack on the bottom of the plastic part of intake.
Obviously it results an air leakage.
I was able to separate metallic top part of intake and plastic (PVC?) bottom part of intake.
I am not familiar with LS1 and I need help and advice how to fix the damaged plastic bottom part.
Please advice!
Cheers
Jan
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Who installed this manifold??
If the button-head bolts for the valley cover were not installed before putting that thing on, be ready for the same thing to happen on the replacement (or repaired) manifold.
You MUST use these:
Thunder Racing sells them under part # 99-VCB-FAST
If the button-head bolts for the valley cover were not installed before putting that thing on, be ready for the same thing to happen on the replacement (or repaired) manifold.
You MUST use these:
Thunder Racing sells them under part # 99-VCB-FAST
Thread Starter
Instructor
Joined: May 2007
Posts: 214
Likes: 4
From: Sweden
I guess the bolts are ok because I measured the cap and it is less than 0.01574803" according tot the digital meter I have :-D 
´
It should be ok.
Is there a prooven method to "weld" the bottom?
´It should be ok.
Is there a prooven method to "weld" the bottom?
Last edited by Janfun; Sep 8, 2012 at 03:37 PM.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
If the bolts are OK, then something was laying on the valley cover when the manifold was torqued down. Loose bolt? Nut? Is the LS1 type metal cooling tube still installed?
If I were repairing, I would use JB Weld epoxy as has been suggested. Sand and clean with alcohol first. Sanding, to roughen up the surface is important.
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Thread Starter
Instructor
Joined: May 2007
Posts: 214
Likes: 4
From: Sweden
You must mean 0.1574803".
If the bolts are OK, then something was laying on the valley cover when the manifold was torqued down. Loose bolt? Nut? Is the LS1 type metal cooling tube still installed?
If I were repairing, I would use JB Weld epoxy as has been suggested. Sand and clean with alcohol first. Sanding, to roughen up the surface is important.
If the bolts are OK, then something was laying on the valley cover when the manifold was torqued down. Loose bolt? Nut? Is the LS1 type metal cooling tube still installed?
If I were repairing, I would use JB Weld epoxy as has been suggested. Sand and clean with alcohol first. Sanding, to roughen up the surface is important.
Melting Slicks
Joined: Apr 2002
Posts: 2,631
Likes: 2
From: Clever, MO aka SOMO
To fix this, I'd pull off the throttle body and use something to reach inside the opening to push down on that cracked "flap" of plastic to try and get it to lay flush with the area around it. It only has air running thru it creating a vacuum so I'd try to mix some 2 part epoxy, from Auto Zone or Kragen etc. and reseal the cracked area from the bottom side only. Maybe even get some fiberglass mat to place over that area first, then layer the epoxy over it, or even use fiberglass resin. Those parts stores sell small fiberglass repair kits cheap. Sand the whole area first then clean it really good before doing the repair. Read the instructions well first. Don't be afraid of fixing stuff yourself before blowing cash on more items.
Good luck!
Good luck!
Burning Brakes
Joined: Sep 2009
Posts: 1,239
Likes: 2
From: Naples FL
St. Jude Donor '12
To fix this, I'd pull off the throttle body and use something to reach inside the opening to push down on that cracked "flap" of plastic to try and get it to lay flush with the area around it. It only has air running thru it creating a vacuum so I'd try to mix some 2 part epoxy, from Auto Zone or Kragen etc. and reseal the cracked area from the bottom side only. Maybe even get some fiberglass mat to place over that area first, then layer the epoxy over it, or even use fiberglass resin. Those parts stores sell small fiberglass repair kits cheap. Sand the whole area first then clean it really good before doing the repair. Read the instructions well first. Don't be afraid of fixing stuff yourself before blowing cash on more items.
Good luck!
Good luck!
You get the award for the best idea so the day!
I once used that same method to repair a broken car top carrier and it worked very well.
Team Owner
Joined: Jan 2007
Posts: 29,063
Likes: 1,839
From: cookeville tennessee
ttt
Hate it for you guys here. Something went wrong for sure. I have not heard of these going bad unless someone tq the bolts down to much. Are unless you how a blower on the car on the old fast 90... Good luck with the fix let us know how it comes out on the repair..Robert
Burning Brakes
Joined: Feb 2008
Posts: 949
Likes: 1
From: Tampa fl
St. Jude Donor '14
Hate it for you guys here. Something went wrong for sure. I have not heard of these going bad unless someone tq the bolts down to much. Are unless you how a blower on the car on the old fast 90... Good luck with the fix let us know how it comes out on the repair..Robert
Thread Starter
Instructor
Joined: May 2007
Posts: 214
Likes: 4
From: Sweden
Here it is. A JB Weld fix with Glassfiber net. Applying JB to crack and then putting a glassfiber net on top and pressing so that JB gets through the glassfiber net. So far it requires some Dremelling or sandpaper but result is quite good. I tested it and it takes 22 lb pressure.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I have expierenced numerous types of EPOXY repair products.
When your working with ANY used plastic/Nylon intake manifold, you MUST be aware that the plastic is oil saturated, The engine oil that coats the inside of the manifold MUST be properly removed before you use ANY epoxy or your just wasting your time. Use a quality degreaser first and then clean the area with a solvent that will remove any remaining oil film. BRAKE PARTS cleaner works well.
The absolute BEST plastic Epoxy that I have ever used is Devcon
http://www.itwconsumer.com/devcon-pr...C%2025%20ml-23
Here is the professional way to fix it:
http://www.youtube.com/watch?v=UNa3T...eature=related
Make sure that you properly roughen up the surface inside and out, feather the edges of the crack and apply the epoxy to ONE SIDE, let cure, regrove the other side and apply epoxy to that side. Sand the inside smooth.
When your working with ANY used plastic/Nylon intake manifold, you MUST be aware that the plastic is oil saturated, The engine oil that coats the inside of the manifold MUST be properly removed before you use ANY epoxy or your just wasting your time. Use a quality degreaser first and then clean the area with a solvent that will remove any remaining oil film. BRAKE PARTS cleaner works well.
The absolute BEST plastic Epoxy that I have ever used is Devcon
http://www.itwconsumer.com/devcon-pr...C%2025%20ml-23
Here is the professional way to fix it:
http://www.youtube.com/watch?v=UNa3T...eature=related
Make sure that you properly roughen up the surface inside and out, feather the edges of the crack and apply the epoxy to ONE SIDE, let cure, regrove the other side and apply epoxy to that side. Sand the inside smooth.
Tech Contributor
Joined: Jan 2007
Posts: 19,450
Likes: 1,155
From: Dyer, IN
Here it is. A JB Weld fix with Glassfiber net. Applying JB to crack and then putting a glassfiber net on top and pressing so that JB gets through the glassfiber net. So far it requires some Dremelling or sandpaper but result is quite good. I tested it and it takes 22 lb pressure.
Should be interesting to see how long it lasts, considering the difference in CTE.
Race Director
Joined: Sep 2005
Posts: 11,060
Likes: 291
From: Pasco WA
One thing you never mentioned was when the manifold was installed. If it ran for months/years with the FAST installed, and working fine, then the cracking in not due to using the wrong bolts. My money is on the crack happening at the install, which was recently.
Team Owner
Joined: May 2001
Posts: 36,836
Likes: 244
From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
Here it is. A JB Weld fix with Glassfiber net. Applying JB to crack and then putting a glassfiber net on top and pressing so that JB gets through the glassfiber net. So far it requires some Dremelling or sandpaper but result is quite good. I tested it and it takes 22 lb pressure.
JB Weld withstands over 500° F so your good there as well.