K member & 400 B Big Block question.

[Cudaman77]

Hey all, I just bought a 1967 Barracuda that started life as a slant 6 but was converted to a 318. I know there’s a difference between slant 6 and V8 K members but, is there a difference between Small Block and Big Block K members? I’m looking to build my 400 and run it in my Barracuda but was asked if the K members were different. Also does anyone know if the stock 400 crankshaft is good to run 400+ hp? If not what crankshaft is there to run without making it a stroker motor.

 

[RustyRatRod]

Yes big and small block k frames are different. The stock cast cranks are good to 600 HP with good machine work, good balancing, good lightweight parts (like you would use anyway) and good assembly. They will hold up just fine.

 

[Cudaman77]

Yes big and small block k frames are different. The stock cast cranks are good to 600 HP with good machine work, good balancing, good lightweight parts (like you would use anyway) and good assembly. They will hold up just fine.

Thank you for that information. Do you know by chance what size connecting rods I would need for a stock stroke 400? Also where to look for a big block k member?

 

[Oldiron440]

400 cast crank horse power level 500 or less but you can use a 383 crank in the 400 block.

 

[RustyRatRod]

Thank you for that information. Do you know by chance what size connecting rods I would need for a stock stroke 400? Also where to look for a big block k member?

It depends totally on how you build it. Stock length for the 400 is 6.358. Some use the 440 rod. It is 6.760. Pistons are readily available for both, I believe.

 

[Cudaman77]

400 cast crank horse power level 500 or less but you can use a 383 crank in the 400 block.

Any recommendations on finding a forged 383 crank. All sites I’m finding are using a 440 crank and different rods.

 

[Oldiron440]

Any recommendations on finding a forged 383 crank. All sites I’m finding are using a 440 crank and different rods.

Yep that makes a 451.
You just have to keep looking, it should be cheap when you find one because nobody uses a 383 crank anymore. If you really want to find one look for a 413 crank and you will find 6 383 crankshafts.

 

[Car Nut]

aboard!

 

[RustyRatRod]

400 cast crank horse power level 500 or less but you can use a 383 crank in the 400 block.

They'll take more. Chrysler never used "just" cast iron like Chevy. They used nodular iron, which is a good bit stronger. I always give Ford's 351 Cleveland as an example. They never came with a steel crank, but nodular iron. These engines routinely saw 9500 RPM on the NASCAR circuit using the nodular iron crank. Nodular iron cranks can live quite well with good prep work and parts.

 

[Oldiron440]

They'll take more. Chrysler never used "just" cast iron like Chevy. They used nodular iron, which is a good bit stronger. I always give Ford's 351 Cleveland as an example. They never came with a steel crank, but nodular iron. These engines routinely saw 9500 RPM on the NASCAR circuit using the nodular iron crank. Nodular iron cranks can live quite well with good prep work and parts.

But there's no reason to find out, a 383 crank is what you need.

 

[RustyRatRod]

But there's no reason to find out, a 383 crank is what you need.

Yes, they're cheap enough. But plenty of people have done it and already found out. It's no secret. I'm not trying to argue, just stating facts.

 

[Oldiron440]

I see, I've always regretted not using the best parts I could afford in the shortblock. It seams it's one place sooner or later you build for more power and all the sudden your up against the limits of the shortblock. With today's heads it's very easy to build over 500 hp in a big block so why limit yourself?

 

[Mopar-Mitch]

Welcome! from Kentucky!

 

[RustyRatRod]

I see, I've always regretted not using the best parts I could afford in the shortblock. It seams it's one place sooner or later you build for more power and all the sudden your up against the limits of the shortblock. With today's heads it's very easy to build over 500 hp in a big block so why limit yourself?

Oh I don't know? I always thought not having all the money in the world was a good limiter. I'm happy for you that you don't have that limiting factor.

 

[ragtopfury]

You say your car started life as a /6 and is now a 318..... was the K-frame changed for that swap, or did the prior owner use a conversion motor mount? You might still be working with the original /6 K-frame........ Or, and I should know this, but can't remember - are the /6 and 318 K-frames the same?

 

[RustyRatRod]

You say your car started life as a /6 and is now a 318..... was the K-frame changed for that swap, or did the prior owner use a conversion motor mount? You might still be working with the original /6 K-frame........ Or, and I should know this, but can't remember - are the /6 and 318 K-frames the same?

On his (67 forward) I think the slant and small block k members are different. They are the same 66 and back. @Jim Lusk will tell us for sure.

 

[Oldiron440]

Oh I don't know? I always thought not having all the money in the world was a good limiter. I'm happy for you that you don't have that limiting factor.

I've got a 440 first build in 88 it's just a TRW blue printed build. So it's been decked and compression is 9.5 for street use with polished stock rods. There are no trick parts what so ever but this shortblock has over 2000 pass's and a few more street miles. I've run it to 7000 rpm from the second pass on. It's got a pair of 452 heads and a old 557 cam now, we thrue it on the dyno and it made 520 hp 545 tq. I built the 440 at a time when I had no cash and needed to barter all the machine work (I did bodywork and paint). But my point is build a solid shortblock because you might be living with it for awhile.
If your lucky !

 

[RustyRatRod]

I've got a 440 first build in 88 it's just a TRW blue printed build. So it's been decked and compression is 9.5 for street use with polished stock rods. There are no trick parts what so ever but this shortblock has over 2000 pass's and a few more street miles. I've run it to 7000 rpm from the second pass on. It's got a pair of 452 heads and a old 557 cam now we thrue it on the dyno and it made 520 hp 545 tq. I built the 440 at a time when I had no cash and needed to barter all the machine work (I did bodywork and paint). But my point is build a solid shortblock because you might be living with it for awhile.
If your lucky !

I agree 100%. I've always used what I had, because I had to. Only a few of my personal builds had nice stuff in the bottom. Done a good bit for others. Even this 396 I have built. It's a cast crank, cast piston engine. In its defense, the pistons ARE original heavy duty GM pieces. They are pretty nice for cast pistons....very much like the older cast Chrysler pistons. They are stronger than most give them credit for. But I cannot and will not argue your logic. You're 100% correct.

 

[Cudaman77]

The K member is the slant 6 one but the previous owner relocated the motor mount and welded it back on. I know there are motor mount relocation kits from Schumacher can I use those or will it be to much stress on the K member? Thank you guys for all of the help. I have a lot more to think about then I thought. Looking for cheap but at the same time quality parts