428PI vs 390

[KF100TK]

What are your opinions on the difference between a 428PI and a 390 4bbl with a modified cam?
I am debating a swap in my 70 F-100 shortbox 2wd.

[Dragon]

Depends upon what you want to do. Of the pair the 428 will pull more power unless you went to a 390 stage 3 cam group in the Crower line. I used a Crower 535 lift cam in a 390 and then when I disintegrated the 390 I got the same cam for the replacement 428 and the 428 got completely crooked on me when I hit 2nd at 6000 rpm. The 390 at 6000 on the same street would just keep smoking the tires or do a wheely.

The engines used the same cam, the same 427 dual point dizzy, same intake, same headers, same 10.5 to 1 compression and same 950 3V Vacuum Secondary Holley. Every thing was the same except for a displacement change and a set 1958 352 PI machined combustion chamber heads on the 428.

Same everything else the power difference was massive.

[427]

The 390 would tolerate more rpm. But the 428 would have more tourqe and make a heavy vehicle move quick.

[Dragon]

Totally agree. I spun two 428s to 7000 weekend after weekend and they ate bottom end parts real fast. One I could put my hand through the side of the block and grab the bent rods.

5 390s survived 8000 over twice as long, well 390 stroke but bored any where from stock to 60 over and they lasted with never a blowup as the 428s. The 1000 rpm difference in redlines made up for the smaller engines as the ET was always in the same ballpark of 9.21 avg. with 9.01 and 9.42 as the ends.

To this day I dislike stokers except for pure race motors because of the stress that long strokes cause.

Changing the rear gears to take advantage of the 390 rpm difference dropped me to 9.10 avg.

Don't even try those rpm ranges with stock bottom ends. I used Forged 427 cranks and Aluminum rods most times. Forged pistons finished the bottom with top of the line Clevite 77 bearings.

[FORD428CJ]

I really don't see the need to spin up a 428 to 7,000+ RPM myself. I have spun mine up to 6,000rpms a lot with no problems at all (with stock rods). And it was a daily driver too. I know quite a few people off the Fordfe.com Forum have used 428 cranks and has lived many of years out on the drag strip and still going to this day. Just make sure you have a nice flat bed for it (Mains are true) and clearances are right. Your Rod ratio isnt bad with a 428 crank. Still above the 1.5 rod to stroke ratio. JMHO

[averagef250]

With a 428 stroke, at 7000 RPM your piston speed is approaching light speed times two. The rules of physics sort of dictate you don't spin an engine with that much stroke much over 6000.

[Dragon]

Racing only Racing never street. We spun a Hemi to 9000 in AA/FD you want to talk about piston speed. The only thing that kept the pistons on the rods was the blower.

The rules of physics sort of dictate you don't spin an engine with that much stroke much over 6000.

The rules of Physics don't matter to me when I am out to win. So the engine fails sooner it was pure race A/Gas

4643.333 for a 428 at 7000
5040 for the 390s at 8000
2750 for my new engine(376) when it gets built.
3276 for my current 390 after I put the new cam in.

[FORD428CJ]

if you would like to spin an engine to 8600RPM all day with no problem for years on end..........SNOWMOBILING is where its at!!! JMHO

[Dragon]

I used to work in a motorcycle shop that took in snow mobiles in the summer and rebuilt them. They do LAST.

[KF100TK]

Thanks for the replies guys. An FE with a c-6 auto. could'nt get those kind of rpm's anyhow would they?

[390F100]

If you really like spinning engines to 9000 rpm go buy a honda with a b16 or a b18c1 in it. Those motors are dang near bullet proof, their bottom ends are as solid as they come and 9k all day is extremely fun... but then again, so is the old american muscle

[Dragon]

Thanks for the replies guys. An FE with a c-6 auto. could'nt get those kind of rpm's anyhow would they?

The c6 shifting at 7000 would break most times with the horsepower that is designed into a 7000 rpm 428. But they can spin that fast. They are very well balanced.

[My427stang]

What are your opinions on the difference between a 428PI and a 390 4bbl with a modified cam?
I am debating a swap in my 70 F-100 shortbox 2wd.

What do you want the truck to do?

A 390 with a cam, headers, intake and a little port work will run strong.

The same setup in a 428 will make more torque and peaks will be at a little lower RPM. However, it wont be dramaticly faster , and if you have to go out and buy a 428 but have a 390, it may not be worth the extra dough.

[Dragon]

That is why most of my race engines are 390s.

[KF100TK]

What are your opinions on the difference between a 428PI and a 390 4bbl with a modified cam?
I am debating a swap in my 70 F-100 shortbox 2wd.

What do you want the truck to do?

A 390 with a cam, headers, intake and a little port work will run strong.

The same setup in a 428 will make more torque and peaks will be at a little lower RPM. However, it wont be dramaticly faster , and if you have to go out and buy a 428 but have a 390, it may not be worth the extra dough.

That was the answer i was looking for! My truck is just a summer weekend fun truck .
I need to freshen up the motor(390), but a neighbor has a freshly rebuilt 428 for sale so i was debating if
there was enough difference to warrant the extra money.