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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+1

Keith builds a solid engine.

E

Blykins
 

No personal experience, but from everything I have read here over many years and many many posts, it would seem that Brent (Blykins) builds really good engines and is really good to work with. Just a third option to think about. If I was too lazy to build my own engine, I would personally go with Brent.


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I find it impressive and overly congenial that one of the better engine builders responded in this professional way. I also find it equally surprising that no one has mentioned Brent Lykins as a solid alternative to the original choices as mentioned by the OP.

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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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.

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------

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.

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------

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. :)

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 :)

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.

Alright you guys, leave Brent alone.

He has engines that need building!

AL427SBF gets it. It is not about how high an engine can rev, it is about how fast an engine can rev. And of course you can build a 385 series that can rev faster than a SBF, but the statement assumes all things being roughly equal. Apples to apples. Dynos only show torque and HP (a derivitive of torque) They cannot and do not show how quickly an engine can rev. This is not about selecting parts and assembling engines. It is about internal combustion physics. AL427SBF gets it 100% completely. He is correct.


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Well, he may get *it* but that *it* may not be what we're talking about.

You both are making too many generalizations, and they are all wrong. I'm really sorry, but you can't make a general statement that says all small blocks "out-rev" all big blocks.

That is absolutely incorrect, I don't care what physics books you are reading.

What I *think* you are trying to explain is how well an engine accelerates. You can absolutely tell that on the dyno, and on a dyno that is fully computer controlled, you can plot it.

And Ed, you are correct in that you can build a 385 series engine that can out-rev a SBF. You just proved the generalization wrong.

Now unless we are all talking about different things, which could be entirely possible, I still fully disagree with both of you.

I have a very small displacement FE here in my shop. The crank has been lightened. The pistons weigh less than 375g each. The rods are the same weight as some SBF rods. It can, and it will "out-rev" and out-accelerate many, many SBF's.

I have also built many long stroke Windsors, which is I think what was referred to in the first post that spoke of this, with a Dart block. I've built 427's, 438's, and 445's, and I will tell you *by experience* that some of the bigger FE's that I build out-accelerate them. Hands down.

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:CRY:

Herc

I don't think you understand what the word generalization means because you just contradicted yourself and made an incorrect statement. If the premis were never wrong, it would not be a generalized statement, it would be a specific statement. He is 100% correct



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It doesn't matter if I think generalization means a 3-legged cow, you can't say that all small block Fords out-rev all FE's.

No one said that ALL small blocks rev faster. It was stated as a general rule of thumb. You are looking at specific and indivdual builds not as a general rule of thumb as a class distinction. This is going nowhere given the apples to oranges view of the discussion.

Hope everyone has a great evening.



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