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Short Block "Kit" Opinions Wanted

General engine tech -- Drag Racing to Circle Track

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skinny z
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Short Block "Kit" Opinions Wanted

Post by skinny z »

Hi all.
I'm no longer in touch with the machine shop that built or assisted in building several of the engines that have gone through our hands over the last 30years or so. That leaves me in a bit of a quandary regarding the approach to another project.
This one is a Gen 1 383.
I have the heads, hydraulic roller valvetrain (less cam at the moment) and all of the tin. Also the intake, carb and exhaust. That said, those bolt-on/bolt-in bits can be changed to suit. So this isn't really a question about the combination or "what do you think it'll make".
The attached picture is from one of the local speed shops with a "take out" short block. In pieces as I prefer (assembly is not an issue).
Here's the question: Would you take this short block with it's rotating assembly and wring it out at 6000 RPM (maybe 6300 for a measure of overspeed) for let's say what would happen in an open road event? So, several minutes of WOT?
I'm off the opinion that no is the answer.

383.png

Cons:
Low end, albeit forged connecting rods with 3/8" hardware.
Externally balanced with the required weighted damper purchased separately.
Cast steel crank.
Pros:
It's relatively inexpensive and would allow me to get back in the game sooner.

I'm a drag racer at heart and with the expected power levels of <500HP/TQ (the current heads and cam should make peak power at ~6000), I can see this package being effective and reliable. But I'd like some insurance for the next possible step.
I know nothing of the machine shop doing the work but the speed shop itself has a solid reputation.
Thoughts? Opinions?
Thanks in advance.
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skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

Here’s the scoop on the parts supplied:
All parts SCAT.
Kit no. 1-90305BE
Series 9000 Cast Cranks, Pro Stock I-Beam Connecting Rods with 3/8” Cap Screws (5.7”), Premium Forged Pistons (Icon).
Crank: 9-350-3750-5700
Rods: 2-ICR5700
Pistons: Nothing other than Icon Premium Forged. No info on ring pack.

As I said, this is part of a kit and as for the block machining quality I can't comment but I certainly can determine if it's right.
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6sally6
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Re: Short Block "Kit" Opinions Wanted

Post by 6sally6 »

What's not to like?
Well assembled SCAT stuff should perform just fine at 6000 RPM. IMHO
Now 7000+..........might increase the pucker factor.
6sally6
KnightEngines
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Re: Short Block "Kit" Opinions Wanted

Post by KnightEngines »

I've seen those rods fail over 450hp.
I would much prefer to see the pro I beams with 7/16 bolts in there.
The rest is fine for 550hp/7000rpm.
skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

6sally6 wrote: Thu Jun 10, 2021 10:23 pm What's not to like?
Well assembled SCAT stuff should perform just fine at 6000 RPM. IMHO
Now 7000+..........might increase the pucker factor.
6sally6
True that. But as you indicate, the line is getting close. The drag racing 6000 RPM thing doesn't really concern but what about 5 minutes or more flat out (or nearly so as conditions allow)? I'm not so comfortable with that and why I'm soliciting opinions.
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skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

KnightEngines wrote: Thu Jun 10, 2021 10:48 pm I've seen those rods fail over 450hp.
I would much prefer to see the pro I beams with 7/16 bolts in there.
The rest is fine for 550hp/7000rpm.
That's my thought on the rods as well.
I've heard the cast steel cranks are relatively durable. And 500HP @ 6000 is about the target here.

What's the thought on externally balanced (specifically the balancer)? That's a lot to expect of a crank given that it may be a test of endurance rather than a sprint isn't it?
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skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

skinny z wrote: Fri Jun 11, 2021 11:23 am What's the thought on externally balanced? That's a lot to expect of a crank given that it may be a test of endurance rather than a sprint isn't it?
A weighted balancer is part of the kit but it's the stresses that this type of balancing induces is what concerns me. At least that's my understanding. I've got a decent damper now and SFI flexplate but it's an internal balance deal with a 2pc RMS. Plus a pretty good oil pan to go along with it (such is my reasoning for keeping the 2 pc RMS).
Any and all input is appreciated.
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skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

Thought I'd bump this thinking there may be some additional input.
I don't think the rods care entirely suitable as suggested earlier.
The crank, I'm on the fence about.
The externally balanced deal gives me cause for concern.
I'd still like to pin this thing for minutes on end (supporting parts notwithstanding) and not deal with something borderline that requires an annual teardown and inspection. It's not going to be a race car per se but rather a car that I race.
Thanks.
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lefty o
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Re: Short Block "Kit" Opinions Wanted

Post by lefty o »

skinny z wrote: Thu Jun 17, 2021 11:47 am Thought I'd bump this thinking there may be some additional input.
I don't think the rods care entirely suitable as suggested earlier.
The crank, I'm on the fence about.
The externally balanced deal gives me cause for concern.
I'd still like to pin this thing for minutes on end (supporting parts notwithstanding) and not deal with something borderline that requires an annual teardown and inspection. It's not going to be a race car per se but rather a car that I race.
Thanks.
you have listed enough concerns yourself, to look elsewhere.
skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

lefty o wrote: Thu Jun 17, 2021 12:26 pm
you have listed enough concerns yourself, to look elsewhere.
True enough.
Not seeing the forest for the trees I guess.
Thanks.
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steve cowan
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Re: Short Block "Kit" Opinions Wanted

Post by steve cowan »

skinny z wrote: Thu Jun 10, 2021 4:21 pm Hi all.
I'm no longer in touch with the machine shop that built or assisted in building several of the engines that have gone through our hands over the last 30years or so. That leaves me in a bit of a quandary regarding the approach to another project.
This one is a Gen 1 383.
I have the heads, hydraulic roller valvetrain (less cam at the moment) and all of the tin. Also the intake, carb and exhaust. That said, those bolt-on/bolt-in bits can be changed to suit. So this isn't really a question about the combination or "what do you think it'll make".
The attached picture is from one of the local speed shops with a "take out" short block. In pieces as I prefer (assembly is not an issue).
Here's the question: Would you take this short block with it's rotating assembly and wring it out at 6000 RPM (maybe 6300 for a measure of overspeed) for let's say what would happen in an open road event? So, several minutes of WOT?
I'm off the opinion that no is the answer.


383.png


Cons:
Low end, albeit forged connecting rods with 3/8" hardware.
Externally balanced with the required weighted damper purchased separately.
Cast steel crank.
Pros:
It's relatively inexpensive and would allow me to get back in the game sooner.

I'm a drag racer at heart and with the expected power levels of <500HP/TQ (the current heads and cam should make peak power at ~6000), I can see this package being effective and reliable. But I'd like some insurance for the next possible step.
I know nothing of the machine shop doing the work but the speed shop itself has a solid reputation.
Thoughts? Opinions?
Thanks in advance.
Skinny,
You need to pull the trigger and get it done,we will all die of old age otherwise :D
steve c
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Re: Short Block "Kit" Opinions Wanted

Post by novadude »

KnightEngines wrote: Thu Jun 10, 2021 10:48 pm I've seen those rods fail over 450hp.
I would much prefer to see the pro I beams with 7/16 bolts in there.
The rest is fine for 550hp/7000rpm.
Question on this... what was the failure mode, what stroke, and at what RPM? Wondering about this, as I have these rods in my 355.
skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

steve cowan wrote: Thu Jun 17, 2021 3:44 pm
Skinny,
You need to pull the trigger and get it done,we will all die of old age otherwise :D
Isn't that the truth! And I'll probably be the first to go.
Covid kind of sucked the life out of the discretionary spending out of which comes the engine budget. Not to mention the whole house renovation I took on three years ago.
At least it's given me plenty of time to research and hang out on ST. Plus my theory data base has grown exponentially.
With any luck, I might be back in the saddle by this time next year (he said for the umpteenth time).
More questions to come.
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skinny z
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Re: Short Block "Kit" Opinions Wanted

Post by skinny z »

novadude wrote: Thu Jun 17, 2021 3:47 pm
KnightEngines wrote: Thu Jun 10, 2021 10:48 pm I've seen those rods fail over 450hp.
I would much prefer to see the pro I beams with 7/16 bolts in there.
The rest is fine for 550hp/7000rpm.
Question on this... what was the failure mode, what stroke, and at what RPM? Wondering about this, as I have these rods in my 355.
Something I'd like to know myself. I beat the living crap out of stock rods with upgraded hardware but power levels were modest at 400 HP with RPMs less than 6500 with the 355. And that was basically a street/strip car with no endurance punishment dished out.
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KnightEngines
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Re: Short Block "Kit" Opinions Wanted

Post by KnightEngines »

novadude wrote: Thu Jun 17, 2021 3:47 pm
KnightEngines wrote: Thu Jun 10, 2021 10:48 pm I've seen those rods fail over 450hp.
I would much prefer to see the pro I beams with 7/16 bolts in there.
The rest is fine for 550hp/7000rpm.
Question on this... what was the failure mode, what stroke, and at what RPM? Wondering about this, as I have these rods in my 355.
It was a 3.2" stroke 330 cube engine making around 440hp, the beam snapped in the middle when it was hit with a 100 shot of gas.
I guess they're good at 450hp & 6500rpm, but not a lot of safety margin.
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