5.0 Cobra intake swap made my car slower???

91foxbodygt · Apr 11, 2005

I upgraded to the 93 cobra intake and during the install i broke & replaced ONE injector to a 90's crown vic injector. well i kept stock throttle body and stock 19lb injectors.
i would run 14.8 at 95 with the stock intake and just and xpipe and dynomax bullets. i ran the car with the cobra intake, mac headers, moroso cold air intake and surprise 15.8 :/ !!!
what went wrong? am i supposed to upgrade to 24# injectors and 65mm tb with the cobra intake?
this intake just made my car a hell of a lot slower : (

5spd GT · Apr 11, 2005

Check for vaccum leaks. What is your timing set out? I'm assuming you removed the distributor and you may have not installed it at the correct timing. The weather and differences in driving can cause those changes as well...

91foxbodygt · Apr 11, 2005

i put 12* timing, i think its supposed to be 10*. i dont know about leaks, where do i check? also the car doesnt feel as strong off the line ( the rpm gomes up slow) , it wont spin the tires at take off, lost a lot of low end torque, now its like i need to try hard to peel out :/

91foxbodygt · Apr 11, 2005

i put 12* timing, i think its supposed to be 10*. i dont know about leaks, where do i check? also the car doesnt feel as strong off the line ( the rpm comes up slow) , it wont spin the tires at take off, lost a lot of low end torque, now its like i need to try hard to peel out :/

Shakerhood · Apr 12, 2005

What size throttle body did you put on it?

RFMustangGT · Apr 12, 2005

I put a 93 intake on my 95 GT and this is something you will have to live with or change intakes. if you want to keep the intake then you'll need to change heads to get your low end back. the intake is a longer runner than your stock intake and without heads it moved your torque curve towards the top end. you now have a car that is better in upper gears and higher rpm. I was so pissed when I stayed the time after 1500 in upgrades. I put an MSD distributor, wires and coil, 24# injectors, aeromotive fuel reg to add to my already C&L mass air kit and flowmasters and did not pick up any in the 1/8. my 6-ft times were slower but my ET was the same. I could feel the car pick up and go 3/4 way down the track but by then it was too late. if I had to do it again, I would probly would have waited to buy heads then the 93 cobra intake. only real positive thing I like about it is that it has made my car a much better interstate car. picks up great at high speeds.

Kerpal · Apr 12, 2005

Sounds like a vaccum leak or bad timing to me, while you might lose a little low end with that intake, it shouldn't be a full second slower.

lx2c6 · Apr 12, 2005

It def sounds like a leak or timing issue the intake shouldnt make that much of a diff i put a gt40 upper on top of a cobra lower (same as gt40 lower) and i felt a good diff in torque in positive way i think u definatly have a vac leak . listen for a very noticable sucking sound ( not the kind that a LS1 owner does ) but a loud hissing also to help diag a vac leak spray brake clean , throttle body cleaner or some kind of spray around any gasket surface where a gasket is in between and if u go over the spot where the vac leak is the cars rpm should jump and the hissing noise should change just for a sec though so do the spray n check in small doses so you know what area the leak is in ---good luck

darthcual · Apr 12, 2005

I think it your stocker heads because i've heard this story so many times. Guy does intake and car gets slower. Heard it a million times, remember your engine parts all must work together so if you have just headers going to stock exhaust thats still gonna bottle neck your hp. where as headers w/ x or h pipe hiflo cats and a nice straight thro muffler will see better results.
Oh well guess its time for you to get some heads, YAY!

Gremlin5.0 · Apr 12, 2005

sounds like vacumm. get a vacumm guage and see. I cant remember exactly what is supposed to pull, or just spray carb cleaner around the intake/heads to see if there is a leak.

When I put my RPM II on stock heads, my Torque suffered a bit but after 3000rpm it is mucho faster. It was worth it.

vristang · Apr 12, 2005

For a while I was running a similar set up. I switched from stock to Cobra manifold on the stock 302 w/ 24lb injectors. I noticed more power all over the curve, especially off idle. When I changed to the Comp Cams box upper I lost some low end, due to the shorter runners.

I think there are other problems. When I first swapped to the Cobra intake and bigger injectors I had better power and maybe even a little better economy, when I wasn't enjoying the power. Do you have any engine codes coming up. Are you running Mass air? I would think that during the swap some component was damaged and not noticed. The stock fuel injectors should be able to flow enough fuel for that intake, if they are functioning properly. Pulling an injector from another 302 shouldn't cause problem, again, if all is well.
Is there anything else that seems odd about how the motor is running? How long have you been running it since the swap?

eagle87 · Apr 12, 2005

Sell that Damm intake to me I'll figure it out then burn it....

1991vert · Apr 12, 2005

i had a cobra intake on my car before and i felt no difference in low end, but it pulled harder at like 2.5-3k+. make sure you check all of your vacuums...

here's a list of vacuum/lines:
1. PCV line from lower to underside upper
2. Fuel pressure regulator to vacuum tree
3. Vacuum from Vac tree to firewall
4. EGR vacuum

and im sure i missed something.

also get a timing light on it asap.

91foxbodygt · Apr 12, 2005

man thank all you guys for the info. the intake was from ebay with a 1 inch spacer for 255$$. anyways, another thing i noticed is that the car gets hotter now. the temp needle used to be up to the second line but now with the cobra intake, its up to the third line, i know, nothing big but it keeps rising.
the car has full 2.5 exhaust, mac equal headers, dynomax bulletts with dumps and no cats.
i have been running the car 2 weeks with the intake. when i go wide open throttle, its like if im driving it without punching it. sure the rmp goes up but slowly, also i punch it and it kinda pauses and then goes again. weird...
the car does sound louder since the install, but i dont know if that is normal.

we did have a problem installing the upper since we had to re-route all the pipes under it. i really dont know if we installed it right but it turned on so i guess its fine. we plugged the pipe coming out from behind the lower manifold and we got water in the oil. <-- dumb
that pipe was supposed to go to the tb spacer, so we just bypassed it straight to where its was supposed to go.
i dont know what to do. i just spend almost 300 bucks so the car can go faster and my car is super slower, but i will check for leaks asap.---thanks

91foxbodygt · Apr 12, 2005

right now the car has 12 degree timing, does that make a difference?
the car is a 1991 gt 5.0 with mass air

vristang · Apr 12, 2005

I'm not sure I really understand. What "pipes" did you have to reroute? I ask because of the coolant temp change you mentioned. If there is a point in the cooling system which is higher than the radiator, you will be more likely to form air pockets in the lines (at those high points), which will completely block flow. This caused alot of trouble for me a while back.
Have you checked for engine codes? Sometimes I have had some show up but the check engine light did not come on. Any codes may help point you in a direction.

BlackGT89 · Apr 12, 2005

I would not think that a Cobra intake by itself would kill your performance like that. Now if you were using a Performer RPM or similar intake with stock heads then I can see how you would loose low end torque. Keep diagnosing and maybe you will come up with what's ailing it.

91foxbodygt · Apr 12, 2005

you know how the stock manifold and the cobra uppers are different. they differ on the upper intake hoses.
also the pipe that comes from the lower manifold [in the rear] to the upper throttle body spacer in the stock intake, well on the cobra there is no tb spacer so that pipe, i had to connect it without passing it trough the tb spacer.

vristang · Apr 12, 2005

91foxbodygt said:
you know how the stock manifold and the cobra uppers are different. they differ on the upper intake hoses.
also the pipe that comes from the lower manifold [in the rear] to the upper throttle body spacer in the stock intake, well on the cobra there is no tb spacer so that pipe, i had to connect it without passing it trough the tb spacer.

It sounds like you routed the PCV valve hose to the underside of the upper manifold. The PCV vents crankcase pressure out of the aft end of the lower intake. Don't think that should cause you to much trouble.
How did you hook up the EGR valve? Are you still using EGR? In fact the performance that you describe sounds a lot like when the EGR pipe on my 2.3L cracked. The motor made very little power and stumbled and over itself unless I revved the crap out of it.

DMAN302 · Apr 12, 2005

May sound silly but make sure your TB is opening all the way when the pedal is depressed..perhaps your cable is binding and your only opening the TB less than 100%. Depress the pedal with the inlet pipe in place and confirm butterfly is open to max. You should not FEEL any loss with an intake swap like you have done...I think you likely have missed something, or routed a line incorrectly.

5.0 Cobra intake swap made my car slower???

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