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Discussion Starter #1
Hi forum gurus,

Starting to think about the mustang this spring, curious, what do y'all think I have in terms of HP ballpark. Just curious.

351w circa 1978
rebuilt 1969 heads (PO mentioned he did this to raise compression numbers)
Original pistons, new rings and bearings. Rings were cast, he mentioned, for a quick break in period.
Edelbrock dual plane manifold (think it's performer 351w..)
Holley 1850 / 4160 vacuum secondaries 600 cfm
Comp cams XE268H-10 duration 268 intake 280 exhaust 110 separation .51 lift intake .512 lift exhaust
HEI distributor
Hedmen shorty conversion headers and magnaflow 2.5" exhaust with x pipe

Runs great, just was always curious ballpark

Thanks!
 

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So, the 4 barrel 1972 351W rated at 161 hp, up from 153 with a 2 barrel and did not change much for some time after that.

The heads were good, assuming they are 351W (on had 4 barrel) and not 302 heads with the C9 casting.

An old trick was using Chevy Valves and screw in studs, back then, so to speak. But with the vanilla 78 block, low compression engine, it is limited.

The other mods, (Carb, Cam, etc.) are good, but if it is a low compression (1978 engine with original pistons) it was not a high torque high horsepower era.

A lot of good bolt on items, but it is still a truck / grocery getter lower end.
 

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Discussion Starter #3
It was a four barrel and the addition of the 69 heads were to improve the compression ratio but not what compression that would be.
 

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There may be an online calculator that will give you an idea of what it's able to make, perhaps there's a dyno in your area? If you're happy with it, you only need one horsepower - the one on the grille. I'd like to go back and port my heads some more, but my engine runs so dang good, I'm happy with it, and I don't wanna mess with it until I have nothing else to do or spend time and money on. Haha!
 

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In those years was there not a good difference between the cars and truck engines to begin with?
You want to start your calculations from the right baseline.
 

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1966 Mustang GT 4spd
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Im guessing around 200hp?

Chris
 

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Im guessing around 200hp?

Chris
Really? Even at the rear wheels that would be low......He has a 9:1 compression 351 with one of the best iron windsor heads ford ever made and a fairly radical (for the street) cam along with an appropriate carb/intake.......200hp is more like an 8:1 302 with ****ty heads, an RV cam and small 4bbl
 

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Seek a Dyno. I can imagine you're "bored", like many I us at times nd just musing. But, three pulls on a Dyno, will tell you a bunch beside RWHP and RWTQ. You should add an O2 bung, so as, to have a chart of your AFR across the RPM run. Might find a little more performance knowing how the O2 burn is going
 

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1966 Mustang GT 4spd
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Really? Even at the rear wheels that would be low......He has a 9:1 compression 351 with one of the best iron windsor heads ford ever made and a fairly radical (for the street) cam along with an appropriate carb/intake.......200hp is more like an 8:1 302 with ****ty heads, an RV cam and small 4bbl
I dont know. The big question is how much compression he is making. I had a rebuilt 351w in my 69 Mach,9 to 1 compression, with intake, full length headers, carb, cam, etc and I turned low 14s (with a peg leg mind you). I was expecting a lot more. A big cam with no compression sounds great but the Performer intake is a torque intake not performance as one would think(it was the same one on my Mach). My friends stock 90 5.0 GT in high school regularly beat me, rolling or dead stop.

Me in high school lol





Chris
754528
 
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1966 Mustang GT 4spd
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Please delete post
 

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Discussion Starter #12
I tried one of the calculators at gofast.com and it spit out 300 based on the specs I put in. Only thing I guessed on was dynamic compression ratio which is something I might try to learn about.

Again, I am not caught up on a number and am perfectly satisfied with what I have. But, I have a bit of an engineering mind so part of my hobby here is to understand these things is all.
 

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Have it weighed and then take it to the drags and see what the trap speed is. You then take those figures and put them into an online calculator like those on wallaceracing.com and you will get a ball park idea. Much cheaper than a dyno. As an alternative you can take your weight and combine it with the acceleration numbers from a device like a "Dragy" and get figures as well.
 

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1967 Mustang Convertible
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320HP my guess.
 

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It was a four barrel and the addition of the 69 heads were to improve the compression ratio but not what compression that would be.

Compression for the 69 M code 351W 4V (I have a 69 Grande with this engine) is advertised at 10.7:1. Ford cut the decks to 9.480" to raise the compression. The heads are 60cc. All 351W heads from 69 to 76 have the same performance potential when modified. They're all the same basic casting. 1970 Ford raised the deck height to 9.500" which dropped the compression slightly.

The big problem with these heads is the exhaust port. It used the same size port as a 289 which is already a restriction on a 289 head. Despite having a larger 1.54" exhaust valve compared to the 289 1.45" valve, it doesn't flow any better.
 

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Discussion Starter #16
Thanks, this is interesting. I would have then the higher deck height given the block vintage of 1978. I don’t think any exhaust port work was done on the heads, that might be a fun project next winter, maybe a diy? I’m pretty handy!
 
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