451 Stroker Questions

[RockyPat]

Hello everyone,

I am doing more research on the 451 stroker combo of a 400 block and 440 crank.

This engine would be for street use only.

Is it much cheaper to find a 440 crank and make everything fit (machining etc.) into the 400 instead of a $2300 451/470 stroker kit?

I have read that a 451 has great characteristics as it revs fast because of the low deck and has good torque similar to a 440. The 400 block is also said to be durable, have the largest bore, and is lighter than a RB.

How well does the 451 compare to a stock 383/440 build?

How durable is a 451 compared to a stock 383/440 build?

Is the extra cost of the 451 worth it compared to a stock/mild 383/440 build?

I think this thread will lead to good discussion on the merits of these engines without going super technical so a person like myself can understand well.

Thanks everyone!

 

[sam dupont]

https://www.forbbodiesonly.com/moparforum/threads/383-stroker-vs-440-stock-rebuild.224981/

 

[Darter6]

All I can say is it's (451) the best dang engine I ever owned.. Built in 2004 over 50,000 miles on it. Drag racing and street driving in 2 cars now still going strong.I had mine pieced together before any kits. I would do a kit today.

 

[Curiousyellow71]

Using a 440 crank the counterbalances are larger
.. I believe 7.4" od verse the 400s 7.3" od. You have to turn the counterbalances down or grind the block out or the crank won't turn. How much grinding depends on the block year... (most trim the counterbalances) .
If you have a decent set of rods and you own the crank, you can do a 452 cheaply. My guess: used crank$200(good luck finding a forged one)/turn the mains down to b $80/trim counterbalances$100, turn rods journals$130. Your in the $500-$600 and a few hundred less then buying a new crank. Aftermarket rods are stronger because they use bigger bolts and maybe $200 over resized oem w arp bolts. Balancing and pistons is not going to be any different for the kit, but you can shop around for the pistons you prefer, kb hyper 452 pistons are cheap for the 400 rod length.

Longevity I think is probably largely dependent on the quality of parts and how much hp. The 452 b-1 we had was 760hp on the dyno. It cracked the crank the first season. The next crank had hundreds of passes when I lost track of it. For the street the smaller b main is just fine..Some shops can line bore the mains for the rb crank...but it is always more $. We run a billet crank now w mains turned down to fit in a 400 with 2.2 chevy rod journals. But it's not a 452....its a 542. 4.375 bore x 4.5" stroked b.
Our 4.25" crank has been in our car for 27 years now... still the same bearings and still going. The original 383 didnt make it 20 years. Longevity I wouldn't worry about any of them. Buy the best parts you can and find a good shop that does mopars with a Honing plate...and knowledgeable about building a Mopar.

 

[68Dart470]

I decided to go with a "kit" and upped it to a 470 for same money. I have a 451 crank even but for the cost, I feel more comfortable hammering a new crank than a 50 year old one.

 

[Lefty71]

How well does the 451 compare to a stock 383/440 build?

At the risk of sounding like a fanboi, I would almost bet that had the cubic inch wars continued instead of stopping at the 440, MaMopar prolly would have made it themselves at some point., since they were most of the way there already.

 

[451Mopar]

The 400/451" combination has all the same bore/stroke/rod ratio geometry as a 440/451" engine, but with pistons that weigh about 1/2 as much as the 440 pistons, and is in a slightly shorter engine block. Back in the 1980's and 1990's the 400/451" combination was popular because 400 blocks were super cheap, and the modified 440 cranks to fit them were affordable. This is back when an aftermarket forged stroker crank cost over $2,000 itself.
Things have really changed since that time. In Chrysler Power magazine (1980's-1990), they did some 451 engines using modified 400 cast pistons because there were no off-the-shelf inexpensive pistons (No KB/ICON pistons.) ROSS pistons was one of the first to offer affordable forged pistons for the 3.75" and 3.91" stroke 400 stroker combinations. Also, there were very few choices for aluminum heads. There was INDY, Mopar Performance, and Brodix. No Edelbrock until a decade or more later.
440 Source and a few others really changed the stroker game by offering stroker kits at affordable prices.
Now you can get a new stroker kit for about what a forged stroker crank used to cost 30 years ago.

Back when I had my first 400/451 I was using the factory 440 rods, which I was worried might be the weak link, but in my application they were fine.
Built four more stroker engines using the 440 Source Kits. As I told my friend, all these new parts have never been together in the engine block, so you have to check and fit everything. A bit more involved than the average rebuild, but nothing that had to be returned.

 

[68Dart470]

The 400/451" combination has all the same bore/stroke/rod ratio geometry as a 440/451" engine, but with pistons that weigh about 1/2 as much as the 440 pistons, and is in a slightly shorter engine block. Back in the 1980's and 1990's the 400/451" combination was popular because 400 blocks were super cheap, and the modified 440 cranks to fit them were affordable. This is back when an aftermarket forged stroker crank cost over $2,000 itself.
Things have really changed since that time. In Chrysler Power magazine (1980's-1990), they did some 451 engines using modified 400 cast pistons because there were no off-the-shelf inexpensive pistons (No KB/ICON pistons.) ROSS pistons was one of the first to offer affordable forged pistons for the 3.75" and 3.91" stroke 400 stroker combinations. Also, there were very few choices for aluminum heads. There was INDY, Mopar Performance, and Brodix. No Edelbrock until a decade or more later.
440 Source and a few others really changed the stroker game by offering stroker kits at affordable prices.
Now you can get a new stroker kit for about what a forged stroker crank used to cost 30 years ago.

Back when I had my first 400/451 I was using the factory 440 rods, which I was worried might be the weak link, but in my application they were fine.
Built four more stroker engines using the 440 Source Kits. As I told my friend, all these new parts have never been together in the engine block, so you have to check and fit everything. A bit more involved than the average rebuild, but nothing that had to be returned.

In a race app, personally, I'd request the "kit" unbalanced and have your shop handle it from my previous experience. Street app their balance work should be fine.

 

[451Mopar]

I agree with the balance mentioned. The three street engines were fine with the 440 source balance.
On my first 440 source kit, the 4.15" stroke crank 400 block 500" (actually 499), I had a new shop I never used before install the BCR Aluminum main caps and girdle, and the "Balanced" the crank. That engine had a slight vibration, and after a season, I took the engine apart and took it to a machine shop I trust. They had to add the weight back to the crank that the other shop took out. So one shop made the balance job worse than delivered.
After that I bough a good scale, and rod fixture to check how close the balance is to what 440 source balanced the crank at.
Anyhow, I guess the local shops can mess up at times too.

Really, the stroker crank/rod/pistons have been pretty easy and reliable.
My issues have been mostly valvetrain problems.
Found that cheap rockers are a waste of money, and good pushrods are worth the $200+ cost.
Use ARP rocker hold down studs if running over 600#+ open valve spring pressure, or expect to buy new valve covers (and rocker shafts when they break.)

 

[68Dart470]

My new crank had to be welded up as well as the balance was off some.

 

[747mopar]

Can't offer any comparisons since I built a 451 for my first and only Mopar classic, it's all I know. I do love it and with 18,000 miles on it I can't say anything negative about it's reliability, it's been a solid motor that runs very well.

On cost, nobody can really say until you get a quote from your machine shop but the clearance work is quite simple. Having my own lathe I clearanced the throws myself, 4 of them had to be cut at a 45 degree angle.. can't remember the amount (I think until the cut was 3/8" wide)?? Other than that (took maybe 30minutes) you have to have the mains turned down to fit the 400 block then have it balanced.

For me the decision was simple, I already had a 71 440 with a forged crank and had traded an a/c unit for a 400..

 

[451Mopar]

My new crank had to be welded up as well as the balance was off some.

I would have sent it back if it had to be welded?

Last year I picked up a 4.25" stroke crank for a 440 and 7.1" I-Beam rods from RPM International. They are still in the box, but I hope to get started on the project in the next month or so.
Anyone else ever used the RPM International parts?

 

[RockyPat]

Wow! Awesome information in this thread as usual. I would like to thank you all for taking the time to comment! I would have to track down a 440 forged crank (get a price range) and get a quote from my machinist and compare it with the 440source kit. I really do like how the 451 sounds on the internet… Lol

 

[747mopar]

I would have sent it back if it had to be welded?

Last year I picked up a 4.25" stroke crank for a 440 and 7.1" I-Beam rods from RPM International. They are still in the box, but I hope to get started on the project in the next month or so.
Anyone else ever used the RPM International parts?

I put a motor together for a friend that used an RPM crank and rods, looked pretty decent. The only thing I remember is playing musical chairs with the rods to get the needed rod side clearance but that's it.. seemed a bit tight in that department.

 

[68Dart470]

I would have sent it back if it had to be welded?

Last year I picked up a 4.25" stroke crank for a 440 and 7.1" I-Beam rods from RPM International. They are still in the box, but I hope to get started on the project in the next month or so.
Anyone else ever used the RPM International parts?

I probably could have asked them to swap out for an "un-balanced" one. I think this was the last one they had on the shelf for the stroke I needed so would certainly have slowed things down. Although 3 months later, the parts / block are still not prepped and out of machine shop hell.....

 

[RockyPat]

Seems like I have to make sure to stay on top of any balancing issues if I decide to stroke a motor for the most part. Thanks guys!