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Discussion Starter · #3 ·
Thanks, that what I thought. I didn't think Ford
made a 4V head in 1973. These heads are stamped with 4 in upper corner. I would like to see the bottom of heads. They are on my 70 Mach an appear not to be numbers matching for this car.
 

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mustang sally said:
I didn't think Ford
made a 4V head in 1973. These heads are stamped with 4 in upper corner.
351-4V (CJ, Q-code) was available until 1974 in the Cougar/Torino. You might even find 4V heads cast in '75 as replacement parts.


mustang sally said:
I would like to see the bottom of heads. They are on my 70 Mach an appear not to be numbers matching for this car.
Those are most likely going to be open chamber heads. You will find info that states if there is a dot cast next to the 4, it denotes an open chamber head. That is not true. I have fours sets of 4V heads, 3 closed chamber and one open chamber. ALL of them have the dot. The only way to be sure what you have, short of pulling the heads, is to pull the intake and use a mirror to get the casting numbers off the underside of the intake runners.
 

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Discussion Starter · #6 ·
I think this motor is 351 CJ low compression engine. I measured the value springs @ 1.77 across. I quess I could do a compression check. Wonder what horsepower this engine set up makes with elderbrock intake & holly 780.
 

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mustang sally said:
I think this motor is 351 CJ low compression engine. I measured the value springs @ 1.77 across. I quess I could do a compression check. Wonder what horsepower this engine set up makes with elderbrock intake & holly 780.
I have a late 73 Mustang with this engine in it. 70K original miles and never rebuilt. Has about 8.0 compression from the factory. I have replaced the intake and carb, unretarded the timing and tuned the crap out of it. Otherwise the long block is dead stock.

It's a real dog in stock condition. Ran a 16.25 second quarter mile when I got it. Part of the problem is that I won't rev it above 5000 rpm because the stock valves have a nasty habit of coming apart at high rpms. So I can't take advantage of the big ports.

If you upgrade the cam and the valve train and add some compression (have to change pistons) then these motors will run pretty well even with OC heads but you will have to rev it to make power.
 
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