Ford Forums banner

1 - 14 of 14 Posts

·
Bum
Joined
·
19 Posts
Discussion Starter #1
I was looking at the specs and they are as follows.

91 Merc GM
5.0L 150 hp V8
Horsepower 150
Torque (lb-ft) 270
Displacement (cc) 4950
Bore X Stroke (in.) 4.00 X 3.00
Compression Ratio 8.9:1
Fuel Type/System MPFI

91 Ford Mustang LX Hatchback
4.9L 225 hp V8
Horsepower 225
Torque (lb-ft) 300
Displacement (cc) 4949
Bore X Stroke (in.) 4.00 X 3.00
Compression Ratio 9.0:1
Fuel Type/System MPFI

I am try to make some horsepower with my little 302. My question is why is the torque almost the same but the GM has 75 less hp? Is it the cam, heads? Seems like both engines are the same except for the hp. Just wondering where the extra 75 is comming from. Anyone know?

Thanks
 

·
Registered
Joined
·
160 Posts
well The mustang for one has better heads than the stock heads on your GM. Also the cam is different a little more aggressive. Also the mustang throttle body and upper intake is bigger than your GM. And the mustang is running bigger injectors.
 

·
Bum
Joined
·
19 Posts
Discussion Starter #3
Sounds right, but the injectors wouldent make since because they get the same gas mileage. The intake on the GM is the truck setup if im correct. The throttle is on one the drivers side. Im wondering if they made performace intakes for that setup for the 302. Would a replacement 91 mustang cam just go right into my block without a problem? Or should i just go with an aftermarket cam?
 

·
Registered
Joined
·
160 Posts
The injectors are bigger on the mustang. And no the GM does not have the truck intake the truck has bigger runners in it along with the mustang. And all the parts from a mustang will fit your car with no problem just go to a junk yard and pull the parts from a mustang. Also all you have to do is turn the mustang upper intake 180 and it will fit on your car, and yes them make performance intakes but I am not sure you can rotate them to have the TB on the driver side as compared to the TB on a mustang on the pass. side. For the cam you can use a stock one or an aftermarket one but if I was you I would stick with the stock mustang one for now or until you convert over to MAF computer.
 

·
Registered
Joined
·
160 Posts
I would go MAF than carb. All you have to do is go to a junk yard and find a mustang, or mark 7 with MAF then take the computer and the whole wire harness on the engine including the MAF sensor and then install on your car. Also if you have cruise control on your car now and you want to keep it you have to get the computer out of a mark 7, a mustang will make you lose the cruise control I forget why.
 

·
HO conversion guru
Joined
·
83 Posts
wow... where do I start.

first off, both engines have a 5.0L displacement. CV/GM/TC engines are standard output motors. Mustang and Mark 7 motors are High output motors.
HO motor uses the 351W ignition firing order. SO CV motor uses conventinal 289/302 firing order.

the block, crank and connecting rods are the same. CV motor gets cast, slightly dished pistons. HO motor gets Forged flat top pistons with valve reliefs. ALL 5.0L passenger car engines use hydraulic roller cam starting in 1986. HO cam is much more agressive with 266 duration and .444" lift. CV cam has 240/250 duration and .379" lift. for more info on cams, read here; 5.0 truck cam

HO motors use a different exhaust also. typically a factory style stamped shorty header with a 2.25" exhaust outlet and dual exhaust. CV motors use iron manifolds with a 2" outlet and dual exhaust was optional.

87 up HO motor uses E7TE cylinder heads. these have an open style, 64cc combustion chamber, which flows better compared to the close/swirl style 69cc combustion chamber on the E6SE heads used on the 86 HO and 86-91 standard output motors.
both motors use SEFI fuel injection (sequential electronic fuel injection) but the HO motor uses 19lb (orange) fuel injectors and the SO motor uses 14lb (grey) fuel injectors.
the EFI Lower intake is the same between the 2 motors. the upper air plenum/intake on the HO Motor is larger (63mm inlet) than the SO motor (53mm inlet). Of couse this means the throttle bodies are corresponding sizes also, 60mm on the HO (1987 and up) 50mm on the SO motor.
The ECM's between the 2 are different too, HO ECM is more aggressive and the fuel map is much different because of the cam and larger injectors.

You can swap the HO cam in the SO CV motor, but it requires you change the ignition firing order, install 19lb injectors and run an HO ECM.
Mark 7 ECM is the best in the CV/GM as 88 and up CV/GM uses an intergral cruise control system that is defeated if you run a Mustang ECM.

you can also swap to MAF but it requires the motor is convert to HO(cam and injectors) and run a Mustang MAF ECM.
mark 7's were never equipped with MAF, so you wont find an ECM there.
I hear 91-93 HO T-bird/Cougar MAF ECM's will work, but never tried it.
 

·
Bum
Joined
·
19 Posts
Discussion Starter #9
88grandmarq said:
wow... where do I start.

first off, both engines have a 5.0L displacement. CV/GM/TC engines are standard output motors. Mustang and Mark 7 motors are High output motors.
HO motor uses the 351W ignition firing order. SO CV motor uses conventinal 289/302 firing order.

the block, crank and connecting rods are the same. CV motor gets cast, slightly dished pistons. HO motor gets Forged flat top pistons with valve reliefs. ALL 5.0L passenger car engines use hydraulic roller cam starting in 1986. HO cam is much more agressive with 266 duration and .444" lift. CV cam has 240/250 duration and .379" lift. for more info on cams, read here; 5.0 truck cam

HO motors use a different exhaust also. typically a factory style stamped shorty header with a 2.25" exhaust outlet and dual exhaust. CV motors use iron manifolds with a 2" outlet and dual exhaust was optional.

87 up HO motor uses E7TE cylinder heads. these have an open style, 64cc combustion chamber, which flows better compared to the close/swirl style 69cc combustion chamber on the E6SE heads used on the 86 HO and 86-91 standard output motors.
both motors use SEFI fuel injection (sequential electronic fuel injection) but the HO motor uses 19lb (orange) fuel injectors and the SO motor uses 14lb (grey) fuel injectors.
the EFI Lower intake is the same between the 2 motors. the upper air plenum/intake on the HO Motor is larger (63mm inlet) than the SO motor (53mm inlet). Of couse this means the throttle bodies are corresponding sizes also, 60mm on the HO (1987 and up) 50mm on the SO motor.
The ECM's between the 2 are different too, HO ECM is more aggressive and the fuel map is much different because of the cam and larger injectors.

You can swap the HO cam in the SO CV motor, but it requires you change the ignition firing order, install 19lb injectors and run an HO ECM.
Mark 7 ECM is the best in the CV/GM as 88 and up CV/GM uses an intergral cruise control system that is defeated if you run a Mustang ECM.

you can also swap to MAF but it requires the motor is convert to HO(cam and injectors) and run a Mustang MAF ECM.
mark 7's were never equipped with MAF, so you wont find an ECM there.
I hear 91-93 HO T-bird/Cougar MAF ECM's will work, but never tried it.
thanks for the info. wow :hy:
 

·
Registered
Joined
·
2 Posts
If the firing order is different, then the cam AND the crank have to be changed right? Just checking... I am also interested in making the SO 5.0 in my 91 GM make better hp... it boggles my mind the hp is sooooo low! Torques are pretty good though.
 

·
Pantherholic
Joined
·
375 Posts
crank doesnt need changed... just the cam... changing the cam and the brain for the car changes the firing order of plugs the way they are fired... the HO firing order is same as the 351 W order if i remember right... it is also less harsh on the main bearings of the engine with the HO firing order compared to the factory way...
 

·
canuck
Joined
·
2,511 Posts
Top end as mentioned is upgraded in the Mustang variant of the same engine.

Dad bought a 91 Fastback LX 5.0 new and 225hp back then was quite a bit. Nowadays a modern V6 family sedan is just as quick and with similar HP.

If anything, search around RockAuto Auto Parts for mustang computer and if you're lucky, even a working engine that hasn't been tinkered with. Better go all out and throw in a 5 speed manual too. However, for the money it'll take to get even close to 225hp, you're best bet is to drop in a slightly used (perhaps fairly modern) 5.4L V8. Earlier variants had 260hp and later were upped to 300hp in truck applications. Some things such as engine mount locations may have to be modified, if you can wrench it yourself, it should be similar cost. Any cash left over can be put toward the 12mpg you'll knowingly get putting the pedal down :)
 
1 - 14 of 14 Posts
Top