3.78 used vs 3.98 scat new?

[wrench87]

i just wanted opinions if you were building a 427 using a genesis block would you go for the original stroke crankshaft used or get a new scat 3.98 stroke? how much extra hp would the little larger crank give you?.

[jared1970]

If you can afford the new scat 3.98, that's the way I would go. There's no replacement for displacement.

[Burgs]

Doesn't the Scat crank have the wider journals, so you can use the stronger rod ends?

[496fe]

If you are going for the Scat, my $.02 would be to go for the 4.25" stroker. If you're really feeling frisky, put the 4.310" pistons for a total of 496 throbbing cubic inches. Sorry, the moniker's already taken.

The Genesis block has plenty of meat for this size bore. Be sure to use a rev limiter, because if your tires are cold, it's easy to over rev and the strokers don't like high revs that much.

Is two pieces of advise @ $.02 = $.04?

Brian

[wrench87]

this is why i get confused on what to do, i set out to build a 427 using all new parts to find out no one makes a new 3.78 crank. with scat i can go 3.98,4.125 or the 4.250 stroke they all cost about the same i wanted a 427 not a 451 or a 468 or a 482. i thought also with the bigger strokers you need a lot more cyl head to feed them the stage 3 heads are over 3k. what type of hp and tourque could you make witht the 3.98 crank, 6.4 rods and a 4.250 bore and a streetable cam?.

[Chaplin]

Originally Posted by wrench87

this is why i get confused on what to do, i set out to build a 427 using all new parts to find out no one makes a new 3.78 crank. with scat i can go 3.98,4.125 or the 4.250 stroke they all cost about the same i wanted a 427 not a 451 or a 468 or a 482. i thought also with the bigger strokers you need a lot more cyl head to feed them the stage 3 heads are over 3k. what type of hp and tourque could you make witht the 3.98 crank, 6.4 rods and a 4.250 bore and a streetable cam?.

You can easily make between 450 and 500 of both hp and tq with bore/stroke combination and still have a very streetable motor, just depends on heads and cam selection.

[Barry_R]

The stroker motor - assuming the same heads and cam - will make more power everywhere below its power peak.

That power peak will be at a lower RPM by - this is a VERY CRUDE estimate - 10 RPM/cube. In other words adding the 3.98 stroke's 25 cubes will pull the peak point down by 250 RPM. Your heads will become a restriction sooner in the RPM range - but on an FE they are already likely to be a restriction...

[Jerry Clayton]

Use a shorter stroke crank with a bigger bore--NASCAR guys ran them at 396 inches in the mid sized fairlane and comet bodies-- I think they used the 3.5 truck crank

This will get rid of ( well lessen ) effect of TOO MUCH bottom end tq and move the power to a higher level.

Jerry

[496fe]

There are few auto quandries older than this. Everything in motor building is about compromises. It sounds like devotion to original specs is the single most important aspect of your engine design. That would beg the question of why a Genesis block?

The original 427 motor was not a very practical street motor - that's one of the reasons Shelby started putting 428's in (also the 428's were cheaper and more plentiful).

All the reputable engine builders on this forum would be happy to discuss your goals and recommend engine packages. Unless you are going to be doing your own wrenching and machining, the money is well spent with them. They know which components work the best with each other to achieve what you want. And they don't make all that much profit (except Roush).

Your questions suggest that you are at the very beginning of your search and decisions. You have decided on the correct platform. The FE motor is physically smaller and lighter than the 429/460, yet for a few bucks, can make some real power.

Welcome to the wonderful world of the FE.

Brian

[Anthony]

Originally Posted by wrench87

this is why i get confused on what to do, i set out to build a 427 using all new parts to find out no one makes a new 3.78 crank. with scat i can go 3.98,4.125 or the 4.250 stroke they all cost about the same i wanted a 427 not a 451 or a 468 or a 482. i thought also with the bigger strokers you need a lot more cyl head to feed them the stage 3 heads are over 3k.

An original 3.78 crank cast/steel will be strong enough for normally aspirated engines. As everybody has eluded to, a stroker crank will give more torque/hp in the lower rpm range, peak hp will be at lower rpm, although absolute peak hp may not be that less.

Whether you run a stock or stroker crank, power can be excessive, and acceleration brutal, deadly.

I actually have a stock stroke 427, cast crank, and had it chassis dyno'd, and it surprised me how much torque/hp it made. 488 rwtq @ 3900 rpm's, which is about 600 at the flywheel, more than what I would have expected from a stock displacement 427. I wanted a stock stroke 427, just like it would have come from Ford/Shelby.

[Jerry Clayton]

Actually the original 427 was a pretty good street engine--the cars weighed nearly 4000 lbs and 400 horsepower with a narrow 14 in wheel / tire combo was about the limit

Now add a few years of developement-Ford battling Chev 396/427. Mopar 426 Hemis-Nascar, sporty car, drag racing--you have more developement in the Ford than the GM or Hemis-- mid risor, high riser,tunnel port, side oiler, sohc, 4v, 6v, 8v intakes-----
then put that into a 2300 lb sport car? of course the 428 was more streetable, cheaper,and of course better suited to put into the street cars----


Jerry