Vacuum problem/AFR Cobra Intake, please help???

[$uperstang]

Just got done building by 325 stroker and now I have a serious mysterious vacuum issue! So I hook evrything back up like stock except the cobra intake has different fittings that go to the vacuum tree on firewall and the PCV system. I used 1262 felpro gaskets as AFR recommended when I called them but whe I get the instructrions it says to use 1250 WTF?? I hope that is not my problem? Here it is: At first I did not realise that my pcv hose was simply off (not connected to the valve in the lower) by accident and the car ran fine. The only mystery was that while idling I pull the dip stick out and it sucks like crazy meaning there is so much vacuum it pulls the dipstick back in if I have it out like 1/2" and let it go!? So then I buy a new PCV valve for some minor added security and go to install it that is when I realised I never had the hose hooked up. So I hook it back up and now my car starts and just idles for like 5 seconds and stalls! But when I remove the PCV hose with the valve still in the lower intake and simply put a bolt to plug the end of the hose the car runs fine. But still when I pull the dip stick out it sucks real hard like a shop vac. WTF is wrong here? where the hell is the vacuum coming from if the PCV is not hooked up and plugged and would this be related to the 1250 1262 AFR intake gasket discrepency. PLEASE HELP?? I am ready to pull the entire intake back off and figure this mess out or is there an easier fix!!!

 

[91lxttrim]

I'm having the same problems after a trick flow install(although I haven't checked the dipstick thing). I'm going to try messing with my PCV junk and see what happens. I think mine might be related to the AIC or TPS though.

Good luck

 

[$uperstang]

I just spoke with AFR and they suggested that there is a problem with the way my intake is matting on the head surface as well and may need to have my intake machined to create a level surface.

 

[jrichker]

The suction is because you have a bad vacuum leak from the lower intake manifold not mating up properly with the heads. The gasket may have slipped out of place when you put the lower manifold on.

My favorite trick that saves time and effort is the stay in place gasket. Be sure that you scrape (don't use a wire brush) all the old gasket material off, then clean all the surfaces with acetone or MEK.

When the surfaces are clean, use weather strip adhesive on the head to manifold surface, and on the side of the gasket that mates to the head. Follow the instructions on the tube or can and when it gets tacky, press the gasket down on the head.

Clean the area where the rubber rails mount to the block in front and in the rear with more acetone or MEK and do the same trick with the weather strip adhesive that you did to the heads.

Coat the rubber seals and the gasket area around the water passages with lots of Blue Silicone gasket sealer and put it together. Wala! no leaks, and no gaskets that shifted out of place.

If you reuse the injectors from your old setup, a repair kit is available from most auto parts stores if needed. Coat the injector body "O" rings with oil before you use them and everything will slide back together. Take the other advice you got here and run with it.

Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $2.74 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:

http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

Most of the links above have store locators for find a store in your area.

Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber.

 

[vristang]

What he said.

I have done this, and it can be quite difficult to troubleshoot.

Here is what it looked like
http://forums.stangnet.com/attachment.php?attachmentid=37227&d=1123979724

The Front intake gasket did not seal against the block. That intake runner was leaking to the lifter valley.

Good Luck
jason

 

[$uperstang]

Thanks people I took it apart and it was the 1262 intake gasket and the cobra ports being smaller leaked right at the top edge of the lower portion of the gasket. I am going with new stock gaskets and getting the cobra ported now.