Roush vs 427FE vs Keith Craft

[madmaxx]

Roush engine design is soiid, KC engine design is solid, the problem engine builders run into 85% of the time is component issue. They purchase lifters, camshafts, heads etc and machine and build the engine. The suppliers of aftermarket engine components is where 95% of the problem lies. The builder of the engine pays for it in the end as they should since that is who the buyer pays their money to. I only hope the engine builders hunt down the suppliers and make them pay.

I have had three Roush engines an 2 bare bone stock motors. The Roush engines have some $$$$$ parts in them, ran the sheet out of them. On the flip side ran the sheet out of the stock motors also. A polished Roush engine is a beautiful sight and everyone go's "wow" and the car shows with the Roush name.

As far as FE and stroked small block, the small block will rev much much quicker, probably require less maintenance and be a more durable engine assuming a Dart block. The big block is more authentic.

[blykins]

Just curious, why do you think a stroked small block will rev quicker and be less maintenance than an fe?

[CobraEd]

Originally Posted by blykins

Just curious, why do you think a stroked small block will rev quicker and be less maintenance than an fe?

Much lighter rotating mass much like an aluminum flywheel vs a steel one. The crank and rods are significantly lighter.


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[blykins]

I would have to disagree with that....

Lots of common misconceptions that are passed around....347's use too much oil, long stroke cranks can't rev, etc, etc.

Also, the FE should not require any more maintenance.

[Varmit]

My Roush 427 SR was using quite a bit of oil at 8k. 11k pulled the heads and sent them out. Builder called me, and showed me the valve stems. The bronze valve guides actually wore depressions in the valve stems, allowing oil to flow into the combustion chambers. It was his opinion that the valves were cheap Chinese valves with a substandard manufacturing process. Replaced the valves the engine ran fine. Have a couple of friends, one on here, who had the same engine. It turned into a disaster for him. If he so desires, he can comment on his problems. Decided to get rid of the engine before it became a boat anchor, sold it and bout the KC 482. Great decision as far as I'm concerned.
Some seem to have engines that have done quite well. I can only speak from my personal experience.

[jhv48]

Originally Posted by Varmit

My Roush 427 SR was using quite a bit of oil at 8k. 11k pulled the heads and sent them out. Builder called me, and showed me the valve stems. The bronze valve guides actually wore depressions in the valve stems, allowing oil to flow into the combustion chambers. It was his opinion that the valves were cheap Chinese valves with a substandard manufacturing process. Replaced the valves the engine ran fine. Have a couple of friends, one on here, who had the same engine. It turned into a disaster for him. If he so desires, he can comment on his problems. Decided to get rid of the engine before it became a boat anchor, sold it and bout the KC 482. Great decision as far as I'm concerned.
Some seem to have engines that have done quite well. I can only speak from my personal experience.

Not sure if I've already responded here as I'm not going to read all the posts to see if I did.

I have a Roush 427 SRTW powered SPF. At 12,000 miles, it was using a quart of oil every 250 miles. Did a leak down test. Readings all over the place, from 10-35%. Pulled the heads. Scratches in a couple of bores. No cross hatch showing in the cylinders. Blow-by was coming out the breathers and dipstick. Sent the heads out. Guides worn, valves had ridges in the stems, seals were shot. Tore down the block. Cracked piston ring land. Rings shot. Damaged lifters. Cam going flat. Broken inner valve spring. Rods and crank were fine, whew! Replaced the anemic street avenger with a ProSystems dp and the sidepipes to 3" a long time ago so the thing could inhale and exhale better.

Remember, this is a street only engine. No race time and few runs to 6000 rpm.

Now, after a complete rebuild and dyno tune it scares the living crap out of me. Get into the throttle a little too hard in third gear and it will step out right now! And that's with sticky nitto 315's.

So, now I'm letting brent build me a slightly detuned engine as a backup in case I decide to part with mine.

Personally, I don't think a Roush engine was worth the money.

[CobraEd]

Originally Posted by blykins

I would have to disagree with that....

Lots of common misconceptions that are passed around....347's use too much oil, long stroke cranks can't rev, etc, etc.

Also, the FE should not require any more maintenance.

I agree with you on the oil 347 issue. It is just an old wives tale. I also agree about long stroke vs short stroke, but that has nothing to do with the issue at hand. An FE or 385 series crank and rods are noticably heavier and it takes more power/time to spin them up vs a small block unit. It is about rotational weight and nothing more. Again, think of an aluminum flywheel vs a steel one. A proven scenario over and over again and universally accepted that an aluminum unit will spin up much faster. The exact same physics applies to a heavier crank and rods. The premise cannot apply to one and not the other. Both are about accelerating rotational mass. No difference. :-)



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[blykins]

Originally Posted by CobraEd

I agree with you on the oil 347 issue. It is just an old wives tale. I also agree about long stroke vs short stroke, but that has nothing to do with the issue at hand. An FE or 385 series crank and rods are noticably heavier and it takes more power/time to spin them up vs a small block unit. It is about rotational weight and nothing more. Again, think of an aluminum flywheel vs a steel one. A proven scenario over and over again and universally accepted that an aluminum unit will spin up much faster. The exact same physics applies to a heavier crank and rods. The premise cannot apply to one and not the other. Both are about accelerating rotational mass. No difference. :-)



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My point was Ed, that was too broad of a statement to make: "the small block will rev much quicker"...

Which FE's? Which small block? What does "rev" mean? Peak hp rpm? Sitting at idle and winging the throttle?

I will say that you are correct in that *some* FE's rotating assemblies are heavier, but not all. If you compare the bobweights between a 427W and a 428 FE, depending on what parts you use, the bobweights can be very similar.

I have also built many 4.250" stroke FE's that rev like chainsaws and pull past 7000 rpm.

It is certainly a case of physics, but you just can't make that broad of a statement, because it's not always true...thus being a lot of the issues about forum misconceptions.

BTW, thanks for the bump.

[CobraEd]

Originally Posted by blykins

My point was Ed, that was too broad of a statement to make: "the small block will rev much quicker"...

Which FE's? Which small block? What does "rev" mean? Peak hp rpm? Sitting at idle and winging the throttle?

I will say that you are correct in that *some* FE's rotating assemblies are heavier, but not all. If you compare the bobweights between a 427W and a 428 FE, depending on what parts you use, the bobweights can be very similar.

I have also built many 4.250" stroke FE's that rev like chainsaws and pull past 7000 rpm.

It is certainly a case of physics, but you just can't make that broad of a statement, because it's not always true...thus being a lot of the issues about forum misconceptions.

BTW, thanks for the bump.

Brent Brent Brent . . . . bobweights have nothing to do with it. They just tune the balance. It also has nothing to do with how high the engine will rev. It has to do with how FAST the engine will get to 7,000 rpm. It is about the TOTAL mass difference of the crank and rods. And of course it is a very general statement and cannot be applied to specific engines. Not a determining factor in building/buying an engine but just a general difference that does exist as a minor factor. As a hypothetical example, if you had a 90lb wheel on a hand crank and a 9lb wheel on the same hand crank, which one would take you longer to spin to 7,000? Obviously the 90lb one. They could both reach the exact same rpm (7,000?) but the heavier one would take longer to get there.


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[blykins]

Since you edited yours, I'll edit mine....

I agree with your general statement of how rotational momentum works.

I don't agree with the general statement that a SBF will "rev quicker" than an FE or BBF. Too many variables and I've been around too many big blocks to know better.

It also does depend on the bobweight, and the bobweight isn't just used for balancing. The bobweight consists of the rod weight, the piston weight, the ring weight, the wrist pin weight, etc, etc. The lighter the bob, the less weight you have hanging off of each rod journal.

However, the statement that was made, unless qualified specifically, is wrong.

[Jerry Clayton]

How quick an engine revs has nothing to do with the hp that it makes in a certain time period from throttle application---for an example----a 302 that will rev to 10,000 will be making less horse power than a 427 will at any identical time frame from idle to max rpm.

I don't have any specific dyno sheets to over lay for the comparison but since Brent does, maybe he can/will------

[blykins]

I've got plenty of dyno sheets, but I don't see where they would help.

I still haven't figured out what "a small block will rev quicker than an FE" means. Does it mean that they are zippier? Does it mean that they will peak at a higher rpm?

Either way, it's still a blanket statement, and doesn't hold true.

[Jerry Clayton]

The easiest way to do it is superposing two dyno runs on the dyno computer with say start rpm at 2000 and the runs being deplayed in a time format.As the graph goes across in micro seconds the hp'tq lines will climb and at any time interval the BB FE will have a higher curve than the small block------

[xb-60]

Don't we need to define 'rev'?
If you're revving the engine with no load, then OK an engine with lower rotational mass will rev quicker (all other variables being equal), but when loaded (accelerating on the road), a higher rotating mass won't make a measureable difference.
Cheers,
Glen

[blykins]

Originally Posted by xb-60

Don't we need to define 'rev'?
If you're revving the engine with no load, then OK an engine with lower rotational mass will rev quicker (all other variables being equal), but when loaded (accelerating on the road), a higher rotating mass won't make a measureable difference.
Cheers,
Glen

Yeah, we should have defined "rev" a good bit ago. I'm pretty sure what we're talking about is an engine's ability to accelerate though. There's a lot that goes into that, and as Ed mentioned, the flywheel weights along with the trans, and the rest of the car can affect the engine's ability in the car.

On the dyno, it's a different story though, and it's easy to hear how well an engine accelerates as it's going through its powerband.

You have to also remember that angular acceleration is caused by something. It's caused by torque, or a force applied at a distance.

Rotating assemblies have their own rotational inertia that has to be overcome, but horsepower and torque will easily overcome that and will accelerate the assembly.

FE's are certainly dinosaurs in the fact that they stem back to the late 50's/early 60's, but that doesn't mean that they are all antiquated. You can hamstring them with 40 lb flywheels, numerically low rearend gears, short camshaft duration, low compression, poor intake flow, etc......just like you can a small block.

But....

Just because the rotating assembly is heavier doesn't mean that it won't accelerate quickly or won't seem zippy, and in a lot of cases, I wouldn't even count on the rotating assembly being heavier.

[blykins]

The dyno I use is an older Stuska and the computer doesn't control the sweep. It would be hard to plot that.

If we look at extremes though, I would mention one of Jon Kaase's 820 cube mountain motor pro stock engines. They use an aluminum rod, but they are still 720g, with a piston that's about 4.780" in diameter, and a stroke of 5.750". These engines will peak at over 9000 rpm, and they are about as zippy as they come.

I could also mention a 351W out of a '74 LTD that is indeed a small block, but probably revs like a fat turd.

Now granted, a typical street/strip FE is not an 820 inch mountain motor with aluminum rods and a Sonny Bryant crank, but the same principles still apply, and they can be quite zippy....and still pull to a high rpm peak. Physics indeed apply, but the engines don't know what their rotating assemblies weigh.

[AL427SBF]

Might as well jump into the fray, and generalities do apply because on balance they apply to most engines.

It takes more energy to spin up a BB's rotating mass versus SB rotating mass because the SB has less mass to spin up, basic physics. That energy comes from your motor and is stored as kinetic energy in the rotating assembly.

The BB guys do better at the 1/4 mile because they can rev it up, dump the clutch - and use all that kinetic energy stored in the rotating assembly for a good launch and let the BB HP do the rest.

The SB guys do better on road courses because it's accelerate & brake driving, less rotating mass to slow down and speed up means the SB can stop and go faster as well as corner better*.

Yeah the BB makes more power earlier in the RPM range, but the SB revs faster than the BB (and typically revs higher than the BB). Hypothetically, if one were to stomp it at say 3000 RPM in some gear, if it takes the BB 2 seconds to get to ~5000 RPM, then those 2 seconds will put the SB at ~6000 RPM ( again hypothetical). In other words, both would be at or near their respective peak horse power levels in the same amount of time.

*That can be debated later, but real road course men prefer SBs

[blykins]

Originally Posted by AL427SBF

...but the SB revs faster than the BB (and typically revs higher than the BB)

We may want to start a new thread to get away from taking over this guy's thread.

However, this statement is again a generality that's not true at all.

[jhv48]

Alright you guys, leave Brent alone.

He has engines that need building!

[hercf16]

Originally Posted by blykins

We may want to start a new thread to get away from taking over this guy's thread.

However, this statement is again a generality that's not true at all.

No problem, good discussion on the differences and issues. I am a little color limited in my search; black, black with stripe, silver with stripe, darker blue
With stripe in that order. A few are starting to pop up with different engines
So the more info the better.

Should have bought Sharpatas? Black with champaign stripes and 638 hp
Keith Craft stroker a few years back, brand new in the low 60s

Herc