Looking for advice on a blueprint engine.

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Heywodja

Heywodja

The Heartbeat Stops Here
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First off this is not a Mopar, but I was hoping the engine GURUS could help me decide on which engine to purchase. Both are in the same HP range, although the 396 does have a couple more points of compression, which may not use pump gas. Both are built from the same new casting 350 block, and both are in the same price and HP range.

I am ordering a long block because I already hve an ignition and pla on using the performer RPM Airgap manifold.

The one I am leaning towards is this one, it is a 350 stroked to 396 with 6.0" rods and a 4.0in" bore. Forged crank, rods, and pistons.

GM SB Compatible 396 c.i. Engine - 491 HP - Long Block

Or

This one which is also a 350 stroked to 400ci" with a 4.125' bore and a 3.75" stroke also using a forged crank, forged rods, and forged pistons.

GM SB Compatible 400 c.i. Engine - 500 HP - Long Block

I am leaning towards the 396 because of the 6" rods, however I have no clue why because I am dumb as a box of rocks on the math of what works or does not work.
I may have read somewhere or picked up from conversations that a 6" rod is preferred.

They should just make one with 6.123 rods and a 4.040 bore and that would be easy, lol.

Thanks in advance!
 
What is the end use/purpose of the engine? What is the torque comparison between the two? Deciding on an engine based on rod length is a lesson in futility.
 
Charrlie_S said:
What is the end use/purpose of the engine? What is the torque comparison between the two? Deciding on an engine based on rod length is a lesson in futility.
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Both engines are similar in hp/tq, this is going in my 58 Chevy Pickup, this will be hot cruiser with a 350 trans and a 2400 stall converter.

It currently has a 77 Camaro front clip with the donor 350. I think it was a whopping 195hp engine when it started out, but no so much today. The rear gear is a 3:08.
 
I'd probably take the one with the smaller cam and longer stroke since you're putting it in a pickup with that gear and converter.

I wonder if Johnny could send you the full dyno sheets for each so you can overlay them to compare graphs.
 
Check out my sweet new crate engine.....

Image preview
 
mopowers said:
I'd probably take the one with the smaller cam and longer stroke since you're putting it in a pickup with that gear and converter.

I wonder if Johnny could send you the full dyno sheets for each so you can overlay them to compare graphs.
Click to expand...

That’s a great idea. I have been reading that the longer rod increases dwell at tdc, thus allowing a little more compression. Uses shorter pistons which reduces rocking in the bore. But puts the wrist in closer to the oil rings. Weird deal is the 396 stroker is a stock bore on a 350 block

I am sure there is some hot rod math out there which tells the story.
 
Horse apiece, keep in mind the difference in torque curves. With a heavy truck, the flatter the torque curve is better. Less piston pin height, the lighter the piston and quicker it will rev. If it was me, I’d balance the crank by shaving it as opposed to drilling holes to balance it.

Then again keep in mind that a 1/8 inch overbore is the same horsepower gain as an inch of increased stroke.

As for the length of the rod, longer it is to a point, the less loading on the thrust side of the bore.
 
For a street vehicle, use the one that's most pump gas friendly.
 
Here is the 396 torque curve from their website. Looks flatter than Kansas to me

IMG_1534.jpeg
 
Heywodja said:
That’s a great idea. I have been reading that the longer rod increases dwell at tdc, thus allowing a little more compression. Uses shorter pistons which reduces rocking in the bore. But puts the wrist in closer to the oil rings. Weird deal is the 396 stroker is a stock bore on a 350 block

I am sure there is some hot rod math out there which tells the story.
Click to expand...
Shorter pistons INCREASE the amount of rock in the bore. Not the opposite. The longer the skirt the more stable the piston is. That being said, I don’t think any of this matter for this application. Like @RustyRatRod said, use the one that is easiest to run on pump gas for a street truck.
 
Heywodja said:
That’s a great idea. I have been reading that the longer rod increases dwell at tdc, thus allowing a little more compression. Uses shorter pistons which reduces rocking in the bore. But puts the wrist in closer to the oil rings. Weird deal is the 396 stroker is a stock bore on a 350 block

I am sure there is some hot rod math out there which tells the story.
Click to expand...
It has a 3.875 stroke and 4.030 bore.
4 inch bore comes out to 387 or close.
4.030 is 395.4 cubic inch.
There's the magic hotrod math answers .
I found them very easily using a compression calculator.
 
Either one of them will probably make our little truck haul ***, guess I’m just gonna flip a coin. I am going to convert the brakes to hydoboost due to the low vacuum at idle which is around 11-12.
 
Thanks, I like the torque curve of the 396 better. Torque is fun on the street.
 
Heywodja said:
That’s a great idea. I have been reading that the longer rod increases dwell at tdc, thus allowing a little more compression. Uses shorter pistons which reduces rocking in the bore. But puts the wrist in closer to the oil rings. Weird deal is the 396 stroker is a stock bore on a 350 block

I am sure there is some hot rod math out there which tells the story.
Click to expand...
you are wrong on the piston length !
shorter pistons will rock faster than longer ones , think about it ...
 
I'm late to the game on this one! I have seen pump gas and octane and compression being mentioned a few times, and that's exactly where my opinion lies also. The 396 likes 93 or better. On paper it's only a touch higher than the 400, but it does like 93 vs 91. Some areas of the country, where fuel composition seems to vary, we even recommend our octane booster on the 396.
BluePrint Engines TrueBlue Performance Octane Booster

The 400 runs On 91 all day and guys love them.

Don't get me wrong, the 396 is a cool engine, but it really only came to exist because way back when we only had oem blocks, it was the way to make more hp and get more cid. Once our new BPE blocks came to be, the 400 was just the next rendition of 500 hp and a big ish cube sb With its bore size of 4.125.

So today my vote is the 400. Or if you do go 396. Grab some of that octane boost with it to be safe. Both are great engines, the 400 just wins for me being it'll be in the lineup for a long time.

Any questions, give me a call or a pm. Or keep posting here. Whatever works! Thanks for the considerstion!
 
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