i recently purchased a ghia 3 door fast back it has the 5.0 in it what is the stock compression for the 79 5.0 right now it has between 47 - 65 pound each cylinder except the #4 whitch has none i think its a stuck valve

 

I think they should have 8.5:1 compression, I know that I usually get 135-150PSI per cylinder on the newer 9:1 5.0s. I would think 47-65 is VERY low and the motor is probably old and tired. You would probably be better off swapping in a newer 87-up roller 5.0 and installing a cheap aftermarket dual plane 4bbl intake with a 600 vac secondary carb and a steel distributor gear to go along with the newer camshaft. There would be a HUGE performance gain, I think the 79 5.0 was rated somewhere in the 140-150hp range. With a good running 87+ 5.0 that can be had from $350-600, adding the intake and carb which should set you back another $100-150 you would be making at least 225HP with proper dual exhaust, if not more.
SS

 

thanks for the input ive found a HO351 4v 1n an 86 pickup for 350.00 i think im goning to go that way with the ghia

 

Cool! Before you buy it, do a compression check on that one as well. I suggest getting a small cam kit for it, something with .480-490 lift and about 215* duration and 112LS. I'm sure I could recommend something for you but I dont have my cam list here. Find some shorty 351W swap headers, get some drop motor mounts so you can stick it under the stock hood, 2.5" off road H pipe and cat back of your choice. You will also need a 351 into fox oil pan. If you can find a 10" 28oz flywheel you can get an '85 GT clutch kit and stick a T5 behind it. It will certainly make some very nice power and LOTS of torque.
SS

 

i was under the impression that 86 and under mustangs had higher compression because they have flat top pistons. Supposedly the 87-88 had 25 more horse but the 86 had more torque.

 

the 86 had the higher 9.2:1 compression....newer were the same pistons but factory fly cut(until 90 when they went with hyper-u-suck-****) , older had a different piston altogether

 

'86 had higher compression due to flat tops and smaller combustion chambers. 79-85 had the same pistons but larger combustion chambers. 92 and up received the hypereutectic pistons. Also, '86s didnt have more overall torque, they had more low end torque and peaked at a lower RPM. In any case, the '87 up 5.0s are faster in every sense.
SS

 

The switch to hypereutectic pistons was actually made sometime in mid/late 92 and was made because of cold start emissions on the forged piston cars. [forged needs a bigger clearance..]. 85's were forged as well, but flycut and 8.5:1 I think.

Oops, SS already beat me to the above.. sorry, I been up for 27 hours now... my bad

 

sorry...that 90 was supposed to be a 92....i'd like to say it was a typo but the 0 and 2 are so far apart....must have been sleepy.