1994 k1500 383 tbi

[Road Trip]

@PlayingWithTBI doesn't a crank of 3.750 toss and a rod of 5.7 give you a different cubic inch ratio? Well depends on compression? Not actually utalising the true stroke. Block cleanances have to be machined for the 6.0 rods where 5.7 doesn't? So which is a true 383? Short stroke a 4.030 block with a 5.7 rod and raise the compression? Or use the 6.0 rod for actual total long stroke of a 383? I am thankful for all input. I learning also

Hi Taz069,

Here's 3 photos showing the clearance 'hot spots' when you stroke a SBC. One thing to keep in mind is that you can have clearance issues with either 5.7" or 6" rods:


SBC oil pan rail + bottom of bore ground to allow adequate clearance for connecting rod nut swinging past at 100 times per second at 6K rpm (close up)

You must be registered for see images attach

(Credit: Motortrend SBC stroker build article -- recommended read: (LINK)


Same as above, big picture view.

You must be registered for see images attach

(Credit: Motortrend SBC stroker build article -- recommended read: (LINK)


But even after clearancing the oil pan rail and the bottom of the bores for the stroker rotating assembly,
we still aren't completely out of the woods yet. The bigger stroke = parts moving in a bigger circle the
full 360° of rotation, so now we also have to check to make sure we don't whack those extra-tall cam lobes we
also decided upon with the connecting rod's bolt heads?

Note: Due to con rod vs cam lobe (firing order) phasing, most lobes successfully 'timeshare' the same space, but there's a couple that want to clash/crash. (!)

You must be registered for see images attach

(Credit: Chevrolet Power Service Manual, 5th edition) Note also that this engineering drawing is showing a big lobe cam versus a 3.48" (350ci) stroke. 383s = extra caution warranted!

****

By the way, from what you mentioned previously it sounds like you are using the 3970010 4" bore, 4-bolt main block.
I've used that same block for builds in the past. (including 383s!) Properly set up, these blocks are a proven-good
foundation for a build like yours.

The bottom line is that you are officially trying to fit 11-lbs of displacement into a 10-lb bag.
It can be done, but attention to detail is what's gonna make or break this build. No doubt
your machinist has several of these 383s under his belt.

Hope all this helps when you are talking to your machinist. Just asking him how did he
ensure that your chosen cam and rods don't interfere using the 3.750 stroke crank
(small base circle cam? capscrew rod? other?) ...will let him know that you better
appreciate what he's put together than most stroker 383 customers, if you know what
I mean.

Can't wait to see photos of this engine back into your truck & running. Good luck!

 

[PlayingWithTBI]

(Credit: Motortrend SBC stroker build article -- recommended read: (LINK)

Nice read!

I still have a headache!

 

[Taz069]

Hi Taz069,

Here's 3 photos showing the clearance 'hot spots' when you stroke a SBC. One thing to keep in mind is that you can have clearance issues with either 5.7" or 6" rods:


SBC oil pan rail + bottom of bore ground to allow adequate clearance for connecting rod nut swinging past at 100 times per second at 6K rpm (close up)

You must be registered for see images attach

(Credit: Motortrend SBC stroker build article -- recommended read: (LINK)


Same as above, big picture view.

You must be registered for see images attach

(Credit: Motortrend SBC stroker build article -- recommended read: (LINK)


But even after clearancing the oil pan rail and the bottom of the bores for the stroker rotating assembly,
we still aren't completely out of the woods yet. The bigger stroke = parts moving in a bigger circle the
full 360° of rotation, so now we also have to check to make sure we don't whack those extra-tall cam lobes we
also decided upon with the connecting rod's bolt heads?

Note: Due to con rod vs cam lobe (firing order) phasing, most lobes successfully 'timeshare' the same space, but there's a couple that want to clash/crash. (!)

You must be registered for see images attach

(Credit: Chevrolet Power Service Manual, 5th edition) Note also that this engineering drawing is showing a big lobe cam versus a 3.48" (350ci) stroke. 383s = extra caution warranted!

****

By the way, from what you mentioned previously it sounds like you are using the 3970010 4" bore, 4-bolt main block.
I've used that same block for builds in the past. (including 383s!) Properly set up, these blocks are a proven-good
foundation for a build like yours.

The bottom line is that you are officially trying to fit 11-lbs of displacement into a 10-lb bag.
It can be done, but attention to detail is what's gonna make or break this build. No doubt
your machinist has several of these 383s under his belt.

Hope all this helps when you are talking to your machinist. Just asking him how did he
ensure that your chosen cam and rods don't interfere using the 3.750 stroke crank
(small base circle cam? capscrew rod? other?) ...will let him know that you better
appreciate what he's put together than most stroker 383 customers, if you know what
I mean.

Can't wait to see photos of this engine back into your truck & running. Good luck!

My hands have been strictly off! This build is by him selecting all the parts and pieces himself. Mr. Pitcher did say the block was to be machined for the rods. You are correct. Over 30 years of motor building and multiple 383's but not many done the way he wanted to do it, this one is his way

 

[Schurkey]

There isn't enough difference in geometry between 5.7" rods and 6.0" rods to make any difference in power.

Piston motion is virtually the same. There ARE differences, but not enough to matter in terms of power production. They're mostly "theoretical" improvements when it comes to power production.

OTOH, if the longer rod allows you to use an off-the-shelf piston that you happen to like, that'd be a viable reason to go that way. Similarly, a longer rod could allow bigger crank counterweights and/or lighter, shorter pistons making for easier engine balance. That's important on BBC applications.

 

[TylerZ281500]

i believe duntov had published some relevant articles back in the day in terms of stroke/rod relationship and efficiency, dwell, quench etc. which is what helped shape the dz302.

 

[Taz069]

My hands have been strictly off! This build is by him selecting all the parts and pieces himself. Mr. Pitcher did say the block was to be machined for the rods. You are correct. Over 30 years of motor building and multiple 383's but not many done the way he wanted to do it, this one is his way

Well I did select the Harold Sharp 1.5 rockers

 

[Schurkey]

I did select the Harold Sharp 1.5 rockers

Harland Sharp, unless they're knockoffs.
www.summitracing.com/search/part-type/rocker-arms/product-line/harland-sharp-original-roller-rockers

Harland Sharp Original Roller Rockers - Free Shipping on Orders Over $109 at Summit Racing

Find Harland Sharp Original Roller Rockers and get Free Shipping on Orders Over $109 at Summit Racing! If you plan on adding performance to your street machine or building a serious racer, Harland Sharp Original Series roller rockers are recommended for you. Using the very latest manufacturing...

www.summitracing.com

 

[Erik the Awful]

Doesn't it give the piston more dwell time at TDC? That, the operating angles throughout the stroke, and it buries the wrist pin up higher into the ring lands which was already mentioned.

Longer dwell time was the thought about twenty years ago, and that longer rods helped prevent detonation and allowed more compression, but since then engine builders have proved time and again that it was all theory and in practice the only advantage of a long rod is reduced angularity on the piston.

 

[Taz069]

Harland Sharp, unless they're knockoffs.
www.summitracing.com/search/part-type/rocker-arms/product-line/harland-sharp-original-roller-rockers

Harland Sharp Original Roller Rockers - Free Shipping on Orders Over $109 at Summit Racing

Find Harland Sharp Original Roller Rockers and get Free Shipping on Orders Over $109 at Summit Racing! If you plan on adding performance to your street machine or building a serious racer, Harland Sharp Original Series roller rockers are recommended for you. Using the very latest manufacturing...

www.summitracing.com

Nope not knock offs heading to Enterprise tomorrow will update with a few pics

 

[Taz069]

The much anticipated update ladies and gents!! To start the cam specs card.