451 Opinions

[TrxR]

Im looking for opinions on a 451 motor? Also looking for price to HP comparison between the 451 and 440?? Also how the 451's breath?? Also do anyone have experience with the muscle motors 451 kit or 440 braket killer??

[jelsr]

For all the bells, whistles, smoke, and mirrors they are the same motor except for the weight of the internal pieces. The pistons are a little over half the weight, the cranks OD is reduced, and the counterweights are lightened for balancing. The block is about 3/4" shorter from main center to deck and everything else is the same. The light internals are good for reliability and superior acceleration. The only difference pricewise is the crankshaft work. Piston prices are the same if you compare forged vs forged and cast vs cast. With equal cam, CR, heads, etc. the 451 will be quicker due to the lighter internals but the HP figures will be nearly the same.

[Hittman55]

Right!!
I think the idea of building a low deck block is for quick revs, A high winding big block cool! I think the power bands will very alot! I bet the 440 would make alot more low end torque apposed to the high enf horses form the 451!

[1969_RT]

I will have a 451 being released from prison (Machine Shop) hopefully with the next 4 weeks. She is going on the Dyno so I will let ya'll know. Machinist guessed 450-500HP w/500 fpt. Here is the Combo

71 (230) Block
Forged Crank
LY Rods reworked with ARP Bolts
Ross 99494 Forged Pistons
Comp Pro Magnum Roller Rockers
Hughes 3038 Cam
906 Heads w/2.14-1.81 Valves Mild Porting
Performer RPM Intake
Holly 770 Street Avenger Carb
Double Roller TC
Milodan HV Water Pump
Melling HV Oil Pump
6Qt Hemi pan 3/8" Pickup (don't think enough material for 1/2" )
1 3/4 Doug Thorley Headers
Mopar Orange Box

[Jims451]

I have a Muscle Motors 451 "B" (low deck or 400 block) stroker engine, toped with Koffels B-1 B/S heads.

The difference in price as posted earlier is really just what it takes to machine the 440 crank to put into the 400 block. Comparing simular "kits" from Muscle Motors it appears this is about $300 (probbably 1/2 the price for the core the remaining for the crank machine work.)
You may be able to save a little bit more money on the 440 if you use cheap stock replacement pistons, but they weigh much more than the aftermarket lighweight pistons.

The lightweight pistons are the main performance attraction to the 451 stroker engine. They allow the engine to rev quicker with less stress on the rods, crank, and engine block. The "B" engine block itself is slightly smaller than a 440 so it fits into tight engine compartments (like the "A" bodies) better than the 440 block.

Here is how two identical built 451 cid engines with 4.375" bore x 3.75" stroke, both with the 440's 6.768" rods would look on paper.
The 440 would require a 0.055" over bore and the 400 a 0.035" overbore.
The piston height (piston pin center to top of engine deck) for zero deck height would be 2.082" for the 440, but only 1.337" for the stroked 400.
This is one reason the 400 pistons are so much lighter weight.

The main bearing diameter of the 400 block is smaller than the 440, which will slightly reduce frictional losses. There does not seem to be any durability problems with the smaller bearing diameter, and in fact, the re-ground crank removes the factory under-cuts at the bearings and the crank is ground with fillets(sp?) which is supposed to make the crank less prone to stress raisers and cracking, but requires a chamfered main bearing set.
Some supposed benifets of the 400 block also are shorter cylinder walls which are supposed to be more ridged because of the geometry of the shorter length. This may help provide a better ring seal at high RPMs? Also, since the main bearings of the 400 block are smaller, there is more material in the main webbing area. This may make the block slightly stronger than the 440? I have no real comparison if this is true, because the 440 crank/pistons heavier weight can not be evenly compared the the stroked 400.

Usually the 440 crank has the counterweight trimed down so the crank fits into the "B" block without needing to notch the block. The extra counterweight material is usually not needed to ballance the stroked 400 because of the light weight stroker pistons.

Because the deck height of the 400 block is almost 3/4" shorter, the engine uses simularly shorter pushrods. The shorter pushrods are less likely to deflect and weigh less, all which helps in high RPM valvetrain dynamics.

I think if you put two identical 451's, both the 440 baised and the 400 baised, onto a DYNO I think the results may look like this:
At a Constant RPM and load they would both make the same power, the 400 stroker engine may make slightly more due to less friction and the stiffer cylinder walls/ring seal?
If the dyno is measuring power while ACCELERATING, the stroked 400 would make more power than 440 because of the lighterweight internal parts.
Under decelleration, the 440's heavier parts may be harder to slow down and may show more torque under this condition?

FWIW, the 451 stroked 400 engine may not be the "best" stroker engine, but it is one of the easiest and least expensive to build.
For example, if I already had a 440 and was just using it for a towing or street/strip engine (under 600 HP and under 6,500 RPM) I would probbably just use it.
If you don't have an engine to start with, the 400 blocks are usually cheap to buy from the junk yard. The high RPM potential of the 451 stroker makes it nice for engine that rev 6,000+ RPM and higher.

[1969_RT]

I forgot to mention that I got my crank done for free and I already had a 71 400 block so that was the only logical way for me to go.

[dkn1997]

jim seems to have a real good handle on this, makes a lot of sense. one real good reason to go this way is the availability of the respective motors. 440's are becoming harder to get, and the 400 does not have the performance image of it's big brother.
hence, as you already know, 400 will be cheaper to start with at least.

another consideration is exterior parts like pulleys/brackets,etc. if this is a swap (in place of a small block or a 6) then you are more likely to get a whole car dirt cheap with a 400. Then, to start, you will have most of what you need to get running once it is installed in your car. most used 440's that I have seen, including the one I bought, are not in a vehicle. I cannot say enough about how hard it is to get all this little stuff when you buy just a motor itself.