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HK1837 Offline
#1 Posted : Tuesday, 16 October 2018 7:27:37 AM(UTC)
HK1837

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Anyone here had recent experience with Scat crankshafts? Just wondering if they are OK or too good to be true?

To machine, chamfer, radius etc a used crank of unknown history costs around $300 today, and then they are harder to balance. The crank I just pulled out of the 1968 350 engine I am using has been in there for 50 years in a month or so, and it was a truck 350 (like a C20 or C30 or whatever) so has had an unknown life. Journals are 10 thou under but block was standard so it must have had a re-ring and crank grind in its life. Yet a brand new ready to go Scat crank is about $400 in Australia, in either standard 350 stroke (3.48") or 400 stroke (3.75") to suit a 350 block. Even forged steel ones are only $900, and I can even get a 3.5" stroke forged one which pushes the pistons upwards 10 thou so less decking is required to achieve zero deck (makes it 352ci like a Windsor or Cleveland).

I was only going to build a 350 but tempted by the 3.75" stroke crank, especially as they are internally balanced and I haven't bought the pistons yet as the block is being tanked and checked next week. An extra 27ci would be nice, although the TH350 may not agree! Wiseco pistons/rings are the same price for a 350 or 377, just have a slightly bigger dish so the extra stroke doesn't push the compression up with the same heads. The rods I have are low profile aftermarket 5.7" which means very little (if any) clearancing required for the 3.75" stroke.
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abi Offline
#2 Posted : Tuesday, 16 October 2018 1:52:02 PM(UTC)
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Hi HK, Yes Scat cranks and rods are well respected by the engine builders I know, very good machining and the castings are good too, they are the only way to go. Choose the 3.75 stroke at the same time, internal balance and with the 6 inch rod. The 5.7 inch rod 3.75 stroke cranks are all external balance so give them a miss.

ABI
HK1837 Offline
#3 Posted : Tuesday, 16 October 2018 3:04:05 PM(UTC)
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Thanks for that. Sounds like the go.

I will have to use a 5.7 rod though as I already have them (https://www.cnc-motorsports.com/scat-2-icr5700-7-16a-premium-pro-comp-i-beam-connecting-rods-40936.html).

Scat do make 3.75" stroke cranks for a 4" bore block in internal balance. The external balance versions are far cheaper, but they make two internal balance 3.75" stroke cranks for 5.7" rods. The cast one isn't easy to find anymore though meaning they may not make it anymore, but there is also one (935050L) that is partially internal balance (internal front external rear, needs heavy metal in one counterweight only):

Cast: 935050-I
Forged: 435050

Neither is that expensive. The forged one is $900, and the cast one about $400 (if you can find one) both in Australia. The 935050-L crank is only about $300 here, but the forged one would probably just about pay for itself in far less balancing effort.
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abi Offline
#4 Posted : Wednesday, 17 October 2018 10:27:58 PM(UTC)
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Both of those cranks would be the way to go if you can find them. I'd try to avoid the more common external balance cranks for 5.7 rods as the counter weighted balancers are a big turn-off if you want the engine bay to look standard, dead giveaway of 'tinkering'.

ABI
HK1837 Offline
#5 Posted : Thursday, 18 October 2018 4:46:50 AM(UTC)
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I've asked Scat if they still make the 935050-I, but will probably grab a forged one. The -L crank is a one piece rear main seal crank, but that just means grabbing a later block which are easy to find but would end up costing the same as using the block (1968 350 4 bolt) I have plus buying the forged crank instead.
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HK1837 Offline
#6 Posted : Thursday, 18 October 2018 4:48:06 PM(UTC)
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Scat got back to me. The 935050-I is still not ready for release as they cannot get it to a satisfactory weight, and may never do it. The Forged 435050 is fine for internal balance with 5.7 rods.

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HK1837 Offline
#7 Posted : Saturday, 20 October 2018 5:48:46 PM(UTC)
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Block went to rebuilders yesterday for the block to get cleaned and measured. By co-incidence they just finished a 3.75” stroke 4” bore SBC using the same Wiseco pistons and the same alloy LT1 heads I am running. With a hydraulic roller and Quadrajet it made just under 500hp on dyno. Bit much for me! Or at least for the TH350.

Edited by user Saturday, 20 October 2018 8:42:42 PM(UTC)  | Reason: Not specified

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abi Offline
#8 Posted : Monday, 22 October 2018 10:33:03 PM(UTC)
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Alloy LT1? Are we talking 1990s reverse flow heads or the 'Trick Flow double humps'.

Are you looking to run rams horns and stock appearance or extractors and rowdy?

I recon the TH350 would be OK with 500HP, remember its the torque that will kill the auto as well as heat and also slow shifting under heavy load. Too much horsepower is always a good problem to have.
HK1837 Offline
#9 Posted : Tuesday, 23 October 2018 5:39:18 AM(UTC)
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1992-1997 Corvette LT1 heads modified to take early rocker covers.

This engine will not look stock. Planning on Edelbrock air gap dual plane, 1969 350hp Corvette Quadrajet, low height factory GM air cleaner, Milodon electric fuel pump (plus air and steer pumps), extractors and dual 2.5” system with 2.5” Gibson stainless rear chambered muffler (dimensionally same as original). Dizzy is an MSD billet. Will also have a HQ350 radiator and BF electric fan. Converter is a B&M Holeshot 3000 and 3.25 or 3.5 gears.

Idea is the car will look dead stock exterior except for the Pontiac RallyII rims, standard ride height except the Rodtech front end will lower the front 20mm. Tyres are to be redl wall radials in 215/65/15 or 205/60/15. Interior dead stock except for V2 CV8 front seats.

I had thought about trying some Corvette 2.5” Ranshorns as I do not like the look of or noise from extractors. With the Rodtech crossmember they may fit.

Remember this is only a 5litre auto car, and being an early car (June-July '68) it is a banjo diff and 5" rims too. I don't currently have its original engine either and the Powerglide and LSD banjo in it now plus the original exhaust and muffler came from a HK Brougham and the tailshaft from a HG 253 4spd Kingswood sedan. The engine is a dead stock originally dressed 307 from an early 1968 HK. I don't see the point of all of this stuff as none is original to the car, it will come out onto a pallet or two and get wrapped in plastic and get stored away.

Edited by user Tuesday, 23 October 2018 5:46:11 AM(UTC)  | Reason: Not specified

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abi Offline
#10 Posted : Tuesday, 23 October 2018 10:38:46 PM(UTC)
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OK got it, sounds like it will be a nice car when finished.

I cant say for sure but I recall someone trying the 2.5" Vette rams horns on a HK back in the 90's and he told me the outlets slightly interfered with the subframe rails where the two halves(upper and lower rail pressings) come together as a spot welded flange, its a common problem with some headers too. To tuck these outlets in closer to the block you could possibly angle mill the manifolds mounting face and then spot face the manifolds bolt bosses, bit of mucking around but if your subframe is mint in this area....
HK1837 Offline
#11 Posted : Friday, 26 October 2018 2:31:09 PM(UTC)
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I'll try different ideas once get the Rodtech front end in and sit a dummy SBC block in there with the TH350 and sit the LT1 heads in place. I will be using two left side mount adapters though to sit the engine level so that will drop it down a bit on the driver's side relative to the rail. I could also try a pair of block huggers and change the angle of the flange. I know extractors are easy but they are also noisy damn things, I have them on my Hilux and I hate the noise from them there too.
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morsesworld Offline
#12 Posted : Tuesday, 13 November 2018 5:15:58 PM(UTC)
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Hi HK,
I have a good book on rebuilding CSB on a budget by Vizard late edition printed in 2009. Yes he recommends using those late Alloy heads and Scat cranks.
He also recommends using newer model GM Powder forged 5.7 Rods, as they are much stronger, cheap to buy second hand and are virtually balanced from factory saving you a lot of money over getting the old style rods balanced.
Also the book has a big discussion on Scat cranks and stroking 350's, which is very interesting and valuable.

So I would recommend this book to any body building a 350 to 400 SBC.
HK1837 Offline
#13 Posted : Tuesday, 13 November 2018 7:45:19 PM(UTC)
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Will get and have a read.
I have since bought:

Scat forged 3.75” stroke internal balance crank for 5.7 rods.
Scat I beam pro competition profiled 5.7” rods.
Wiseco forged pistons (see link).
https://www.ebay.com.au/...489fa:g:r4kAAOSw9mpZ6g9i

Will give around 10.5:1 with the LT1 heads or 10:1 with 64cc fuelies.
Waiting on cam recommendation from Comp Cams for a hydraulic roller cam.
Looking at a Performer air gap manifold with the 1969 L46 Quadrajet. Picked up an MSD billet HEI and MSD 6A for it too, plus a Milodon electric water pump.
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If we all had the same (good) taste, who would buy all the Fords?
morsesworld Offline
#14 Posted : Wednesday, 14 November 2018 6:04:34 PM(UTC)
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Looks good HK.

The book is SA Book number 57.
The correct Title is ;
How to Build Max-Performance Chevy Small Blocks on a Budget.
2009 By: David Vizard

It also has some sample engine builds in it and a lot of cam shaft Selection Tables in it from the major cam companies for 350's only.
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