Cobra or HO wont start

SCMBOB · March 1st, 2011, 10:14 PM

ok i bought a 91 mustang with a supposed "COBRA" swap!! so as excited as i was i swapped my running 5.0 HO out with this cobra. after i swapped it an got everything setup double and triple checked everything. when i began to do the timing it cranked and cranked when i opened the throttle body fully it glugged and then backfired and thats when i stopped. i made sure the number 1 piston was at TDC and then followed the instructions on the rest of the firing mode for the HO motor. could this be that this is not a cobra motor? or do i have the firing mode wrong? what is the correct firing mode for a cobra motor? how can i even tell this is a cobra motor? i heard that you can tell by looking at the serial number and it should have an R in it. in all reality im pissed im stuck and need sime help o and i kept the motor map instead of changing over to maf is that my problem

FastStang91Lx · March 1st, 2011, 10:30 PM

Start over... What year is your car? And if your timing is way off, then it will backfire. Lastly, is this 'cobra' motor supposed to be just a stock spec 93-95 cobra motor?

SCMBOB · March 1st, 2011, 11:08 PM

the car is an 87 gt the motor came out of a 94 or 95 mustang cobra has a 303 cam and under-drive pulley and a water pump pulley under-drive is smaller than the stock one and the water pump pulley is about the same size car cranks just wont turn over also has new bbk upper and lower with high flow fuel rails and a kirban fpr that has never been set to proper psi. should i put stock fpr on until i get it fired up?

gripthenboost · March 1st, 2011, 11:23 PM

Are you sure the motor is getting fuel and spark?

fogged306 · March 2nd, 2011, 12:30 AM

Are you sure you're at TDC on the compression stroke? How are you checking?

ryanw · March 2nd, 2011, 12:36 AM

Originally Posted by fogged306

Are you sure you're at TDC on the compression stroke? How are you checking?

Can you just put it at 0 TDC and drop the distrubtor in ? Going by the marks on the balancer ?

fogged306 · March 2nd, 2011, 12:39 AM

If the balancer hasn't spun, yea. If it has, you could be way off on your timing.

Firaga · March 2nd, 2011, 02:48 PM

BBK upper and lower intake mani? Isn't that like.. taking a step backwards?

SCMBOB · March 2nd, 2011, 04:01 PM

it am chacking through the number one spark plug hole and then placing the distributer accordingly and then after it fires i can spin my distibutor to adjust the timming ever so slightly but it had a HO upper and lower on it thats the reason for the changing of the intake manifold. also yes i am getting fuel and spark therfor the result of a backfire

fogged306 · March 2nd, 2011, 05:59 PM

What I'm getting at is how are you making sure you're not at TDC on the exhaust stroke.

SCMBOB · March 2nd, 2011, 11:36 PM

ok i got it to fire runs smooth also found out it is not a cobra it has a non HO motor and i am very pissed. i paid $2200 for a damn van motor good thing i still have my old 302 "HO"

fogged306 · March 3rd, 2011, 01:33 AM

So what was your issue?

The only differences between an HO and a non-HO are already changed, so you've technically got an HO engine in there. The heads, block, and rotating assembly were the same. The cam, firing order, computer, and I believe intakes were the only things different. The alphabet cam you have is the HO firing order and you've already got a different intake, and you're running the HO computer if you're running the stock mustang one.

It's not a GT-40 combo (cobra) but as of now, there's no point in doing a swap.

Also, you got hosed bad even if that was a real cobra motor. 2200 is beyond ridiculous.

SCMBOB · March 3rd, 2011, 01:32 PM

i am running the stock gt computer and it wont fire on the HO firing order and it will on the non HO firing order and it doesn't even sound like a v8 it sounds like a camed out 4 banger. ima try a few thing tonight and see what happens.

fogged306 · March 3rd, 2011, 01:44 PM

Are you sure it's a 303 cam then? Because those are HO firing order cams. If it is not an HO cam, then the HO computer won't work either because the injector firing sequence is different also. I believe it's only 4 cylinders that are different so this would explain exactly what you are describing to be a non-HO cam too. If that's the case, then all you would need then is to replace the cam with any performance aftermarket cam, go back to the HO firing order and you would be set.

SCMBOB · March 3rd, 2011, 08:04 PM

its weird to me im stumped the computer that it had in it before was running on a a9l or an ap9 and it sounded mean now it sounds like a junker but ill get it figured out

March 1st, 2011, 10:14 PM	#1
SCMBOB Newbie Join Date: Jan 2011 Posts: 44 iTrader: 0 reviews	Cobra or HO wont start ok i bought a 91 mustang with a supposed "COBRA" swap!! so as excited as i was i swapped my running 5.0 HO out with this cobra. after i swapped it an got everything setup double and triple checked everything. when i began to do the timing it cranked and cranked when i opened the throttle body fully it glugged and then backfired and thats when i stopped. i made sure the number 1 piston was at TDC and then followed the instructions on the rest of the firing mode for the HO motor. could this be that this is not a cobra motor? or do i have the firing mode wrong? what is the correct firing mode for a cobra motor? how can i even tell this is a cobra motor? i heard that you can tell by looking at the serial number and it should have an R in it. in all reality im pissed im stuck and need sime help o and i kept the motor map instead of changing over to maf is that my problem

March 1st, 2011, 10:30 PM	#2
FastStang91Lx I Post Entirely Way Too Much 1991 Mustang LX 5.0 Join Date: Jan 2010 Location: Minnesota Posts: 5,572 iTrader: 2 reviews	Start over... What year is your car? And if your timing is way off, then it will backfire. Lastly, is this 'cobra' motor supposed to be just a stock spec 93-95 cobra motor? __________________ Point made in less than a few hours with minimal response. http://www.moddedmustangs.com/forums...ml#post4465184

March 1st, 2011, 11:23 PM	#4
gripthenboost Hardcore Enthusiast 91 Mustang GT 1991 sliver GT Join Date: Apr 2010 Location: New York Posts: 1,213 iTrader: 0 reviews	Are you sure the motor is getting fuel and spark? __________________

March 2nd, 2011, 02:48 PM	#8
Firaga Regular 1993 Mustang GT Join Date: Jan 2009 Location: San Diego Posts: 413 iTrader: 0 reviews	BBK upper and lower intake mani? Isn't that like.. taking a step backwards? __________________ I have a 93 5.0 I love my car, and all my friends hate it. AEM Brute Force intake, BBK 75mm TB/EGR, C&L 75mm MAF, Trick Flow Street Upper/Lower, Custom exhaust with Dynomax SuperTurbos, Tokico Rear Shocks

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March 1st, 2011, 11:08 PM	#3
SCMBOB Newbie Join Date: Jan 2011 Posts: 44 iTrader: 0 reviews	the car is an 87 gt the motor came out of a 94 or 95 mustang cobra has a 303 cam and under-drive pulley and a water pump pulley under-drive is smaller than the stock one and the water pump pulley is about the same size car cranks just wont turn over also has new bbk upper and lower with high flow fuel rails and a kirban fpr that has never been set to proper psi. should i put stock fpr on until i get it fired up?

March 2nd, 2011, 12:30 AM	#5
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Are you sure you're at TDC on the compression stroke? How are you checking?

March 2nd, 2011, 12:39 AM	#7
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	If the balancer hasn't spun, yea. If it has, you could be way off on your timing.

March 2nd, 2011, 04:01 PM	#9
SCMBOB Newbie Join Date: Jan 2011 Posts: 44 iTrader: 0 reviews	it am chacking through the number one spark plug hole and then placing the distributer accordingly and then after it fires i can spin my distibutor to adjust the timming ever so slightly but it had a HO upper and lower on it thats the reason for the changing of the intake manifold. also yes i am getting fuel and spark therfor the result of a backfire

March 2nd, 2011, 05:59 PM	#10
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	What I'm getting at is how are you making sure you're not at TDC on the exhaust stroke.

March 2nd, 2011, 11:36 PM	#11
SCMBOB Newbie Join Date: Jan 2011 Posts: 44 iTrader: 0 reviews	ok i got it to fire runs smooth also found out it is not a cobra it has a non HO motor and i am very pissed. i paid $2200 for a damn van motor good thing i still have my old 302 "HO"

March 3rd, 2011, 01:33 AM	#12
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	So what was your issue? The only differences between an HO and a non-HO are already changed, so you've technically got an HO engine in there. The heads, block, and rotating assembly were the same. The cam, firing order, computer, and I believe intakes were the only things different. The alphabet cam you have is the HO firing order and you've already got a different intake, and you're running the HO computer if you're running the stock mustang one. It's not a GT-40 combo (cobra) but as of now, there's no point in doing a swap. Also, you got hosed bad even if that was a real cobra motor. 2200 is beyond ridiculous.

March 3rd, 2011, 01:32 PM	#13
SCMBOB Newbie Join Date: Jan 2011 Posts: 44 iTrader: 0 reviews	i am running the stock gt computer and it wont fire on the HO firing order and it will on the non HO firing order and it doesn't even sound like a v8 it sounds like a camed out 4 banger. ima try a few thing tonight and see what happens.

March 3rd, 2011, 01:44 PM	#14
fogged306 MM Fanatic 89 GT Join Date: Apr 2007 Location: NY Posts: 4,875 iTrader: 2 reviews	Are you sure it's a 303 cam then? Because those are HO firing order cams. If it is not an HO cam, then the HO computer won't work either because the injector firing sequence is different also. I believe it's only 4 cylinders that are different so this would explain exactly what you are describing to be a non-HO cam too. If that's the case, then all you would need then is to replace the cam with any performance aftermarket cam, go back to the HO firing order and you would be set.

March 3rd, 2011, 08:04 PM	#15
SCMBOB Newbie Join Date: Jan 2011 Posts: 44 iTrader: 0 reviews	its weird to me im stumped the computer that it had in it before was running on a a9l or an ap9 and it sounded mean now it sounds like a junker but ill get it figured out

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