68 Mustang Lacks Power

C

captainmorgan

Member
Joined
Jun 1, 2008
Messages
13
Location
MN
I just replaced the motor in my 68 Mustang. It is a new 302 crate engine that dyno'ed at 352 HP. I also put a shift kit in the Auto transmission and installed a 2500 RPM stall convertor. It also has a new detroit locker rear with 3.55 grears. The first time I took it out I was able to spin the tires no problem. Now It just does not have any power :hissyfit:. I adjusted the timing so that I have 36* all in by 2800 RPM. I took it out and the first time I was able to spin the tires and had full power. I tried a second time and no power again:hissyfit: :censored: :banghead:. Anyone have any ideas on want could be wrong?

Thanks
 
Last edited:
id you check if the distributor slipped? Verify timing remains as set, if that's not it we need more details. What carb, what kind of ignition and so on.
 
bobs77vet said:
check your fuel supply.......maybe you are having a fuel deprivation problem or vapor locking.
Click to expand...
How would I know? Would the fuel pressure be low? I have a fuel pressure gauge under the hood and it shows that the fuel pressure is fine while sitting in the driveway (I'm not able to see the fuel pressure while driving).
 
Do you have a fuel pump with bypass ? Mechanical or electric pump ? Do you have a return line or a aftermarket (Holley for example) pump without return line ??
 
A friend just had that same problem. he brought it over for me to check the timing,it was still set where i put it earlier,got too checking around and found the vac advance can had already went bad. Give it a check.
 
kwplot34 said:
A friend just had that same problem. he brought it over for me to check the timing,it was still set where i put it earlier,got too checking around and found the vac advance can had already went bad. Give it a check.
Click to expand...

I checked and the mechanical and vacuum advance is working fine. 12* vacuum advance and 24* mechanical advance.
 
captainmorgan said:
MYBAD79 said:
Do you have a fuel pump with bypass ? Mechanical or electric pump ? Do you have a return line or a aftermarket (Holley for example) pump without return line ??
Click to expand...

Edelbrock mechanical fuel pump without return line.
Click to expand...

I've heard that you often get vapor lock without a return line. I have a mechanical Holley pump and I use a pressure regulator with a reducer in the return line - works fine. The regulator is basically just a "T" - supply from pump is 6AN hose, same size line to the carburetor and return but the return has a plug installed with a 2.5mm (.100") hole in it...
The guy I got this pump from had nothing but problems and he was not running a return line.
 
MYBAD79 said:
captainmorgan said:
MYBAD79 said:
Do you have a fuel pump with bypass ? Mechanical or electric pump ? Do you have a return line or a aftermarket (Holley for example) pump without return line ??
Click to expand...

Edelbrock mechanical fuel pump without return line.
Click to expand...

I've heard that you often get vapor lock without a return line. I have a mechanical Holley pump and I use a pressure regulator with a reducer in the return line - works fine. The regulator is basically just a "T" - supply from pump is 6AN hose, same size line to the carburetor and return but the return has a plug installed with a 2.5mm (.100") hole in it...
The guy I got this pump from had nothing but problems and he was not running a return line.
Click to expand...

Where do you have the "T" in stalled? Is it installed before or after the pump? How do you install a plug in one end of the "T" and connect a hose to it at the same time? Do you have a picture?

Thanks,
Kevin
 
how close is the fuel line running next to the exhaust system or headers (for vapor lock)? i would be looking at fuel flow rather then fuel pressure, perhaps take the fuel line off and crank the engine and see what kind of flow rate you are getting (use a stop watch and a gallon fuel jug) if the car loses power it could be that the flow rate is not sufficient to compensate for the rate the gas is being used, it could be a piece of gunk floating around in the gas tank or the fuel line. how much rubber fuel hose are you using and what size is the fuel lines? could the rubber fuel lines be collapsing? are these the original lines for a six cylinder? does the carb have any float bowl glass sights that you can see if there is gas in the float bowl?
 
Last edited:
captainmorgan said:
I just replaced the motor in my 68 Mustang. It is a new 302 crate engine that dyno'ed at 352 HP. I also put a shit kit in the Auto transmission and installed a 2500 RPM stall convertor. It also has a new detroit locker rear with 3.55 grears. The first time I took it out I was able to spin the tires no problem. Now It just does not have any power :hissyfit:. I adjusted the timing so that I have 36* all in by 2800 RPM. I took it out and the first time I was able to spin the tires and had full power. I tried a second time and no power again:hissyfit: :censored: :banghead:. Anyone have any ideas on want could be wrong?

Thanks
Click to expand...

Maybe it's the "shit kit" (sorry, I had to).

When you say that you "took it out the first time", this is the first time after installation of the engine? And the second time is the very next time you drove it? So, something happened between these runs and it has been down on power since, correct?

Apologies for all the questions, just trying to understand the circumstances.
 
Yeah, it seemed to have plenty of power the first time I took it out after the break in procedure. The next time I could not even spin the tires. I played around with the timing on Saturday and the first time I tested it I could spin the tires, so I drove it around the block and into a parking lot and tried it again and it was a dog again, no power.
 
captainmorgan said:
Where do you have the "T" in stalled? Is it installed before or after the pump? How do you install a plug in one end of the "T" and connect a hose to it at the same time? Do you have a picture?

Thanks,
Kevin
Click to expand...

The regulator or "T" is between the pump and the carburetor.
I drilled and threaded one side of the regulator fitting and plugged it with a bolt, then drilled the bolt.... I'm sure epoxy would do just as fine....
 
I haven't had time to look at it. I have been working on the fuel line of my Vette.

I hope to have time this weekend but I don't think that it has a return line to the gas tank.
 
You must log in or register to reply here.

Latest posts

Back
Top