stock sbc block hp limits
Thread Starter
Intermediate
Joined: Oct 2019
Posts: 45
Likes: 3
From: Hilton Head, SC
stock sbc block hp limits
I was thinking of assembling a 2 bolt 84 corvette block but having it machined for a 383 rotating assembly and a supercharger, installed with milodon 4 bolt splayed main caps and arp hardware. Can i run 700hp + with this combo? how strong does converting a factory 2 bolt to a splayed milodon 4 bolt make the block? (My luck is average but i'm not looking to build the block on luck) 
Race Director
Joined: Mar 2018
Posts: 10,702
Likes: 2,166
From: Golden Colorado
Spend the extra money for a Dart or similar aftermarket block. It won’t cost that much more after all the machine work. It will be much stronger AND you can go larger than 383. And you will be much happier with the end result 
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
If your goal is 700, I would look for a aftermarket block. If build 700 in 6 months you will want 800 just sayin. A 010 block they come in 2 and 4 bolt varieties should go to 700. Once you figure machine work : boring, splaying caps, align bore , checking for core shift, square decking, notching block for stroke ...etc you will be close to the cost of aftermarket iron block.
Thread Starter
Intermediate
Joined: Oct 2019
Posts: 45
Likes: 3
From: Hilton Head, SC
Can i get away with using a Dart SHP Iron block? It's the "most affordable" of them all. Dart rates it at 600hp but i've heard from some people that the actual numbers are SHP = 1000 and Little M = 2500
Thread Starter
Intermediate
Joined: Oct 2019
Posts: 45
Likes: 3
From: Hilton Head, SC
) Though that number is heavily optimistic. Heads are Promaxx 190cc Aluminums. 2.02/1.6 valves going to be calling PAC Springs soon to have them help out on some new beehives for the cam. Stud girdles, and custom length pushrods and still debating on rocker choice. Cam powerband is 1800 - 6800rpm and is a small base circle cam.
Melting Slicks
Joined: Mar 2001
Posts: 2,150
Likes: 304
From: Timra, Sweden
I used the stock short block with AFR190 heads, cam and intake. First a few years with Vortech V1 supercharger, about 10 psi boost.
( Stock 1984 block, stock crank, stock rods, stock pistons and stock bolts. )
Then replaced the supercharger with a turbo that made 627 hp to the wheels at 4200 rpm. 800 lbs ft @ 4000 rpm.
I ran 11.14 sec @ 126 mph with a 1.72 sec 60 ft that year.
Next year I had changed to a bigger turbo that made more power but a bit slower to spool up..
I ran 10.86 sec @ 134.5 mph with a slower 1.83 sec 60 ft.
Later that year I opened up the exhaust and that made a big differance until the engine exploded a few days later.
The direct cause was rod failure but the main caps showed sign of major cap walk,
I would say that with a good tune the stock block can last a while at 700 hp. A while can be days or years
That boost controller, is that a type of 'BOV'? If it is then I think that it is the wrong way to control boost on a centrifugal supercharger. The supercharger will actually run harder when the BOV is open.
I my opinion this is the correct way to reduce top end boost.
https://www.hks-power.co.jp/en/produ...estrictor.html
( Stock 1984 block, stock crank, stock rods, stock pistons and stock bolts. )
Then replaced the supercharger with a turbo that made 627 hp to the wheels at 4200 rpm. 800 lbs ft @ 4000 rpm.
I ran 11.14 sec @ 126 mph with a 1.72 sec 60 ft that year.
Next year I had changed to a bigger turbo that made more power but a bit slower to spool up..
I ran 10.86 sec @ 134.5 mph with a slower 1.83 sec 60 ft.
Later that year I opened up the exhaust and that made a big differance until the engine exploded a few days later.
The direct cause was rod failure but the main caps showed sign of major cap walk,
I would say that with a good tune the stock block can last a while at 700 hp. A while can be days or years
That boost controller, is that a type of 'BOV'? If it is then I think that it is the wrong way to control boost on a centrifugal supercharger. The supercharger will actually run harder when the BOV is open.
I my opinion this is the correct way to reduce top end boost.
https://www.hks-power.co.jp/en/produ...estrictor.html
Last edited by JoBy; Jan 27, 2020 at 04:30 PM.
Thread Starter
Intermediate
Joined: Oct 2019
Posts: 45
Likes: 3
From: Hilton Head, SC
I used the stock short block with AFR190 heads, cam and intake. First a few years with Vortech V1 supercharger, about 10 psi boost.
( Stock 1984 block, stock crank, stock rods, stock pistons and stock bolts. )
Then replaced the supercharger with a turbo that made 627 hp to the wheels at 4200 rpm. 800 lbs ft @ 4000 rpm.
I ran 11.14 sec @ 126 mph with a 1.72 sec 60 ft that year.
Next year I had changed to a bigger turbo that made more power but a bit slower to spool up..
I ran 10.86 sec @ 134.5 mph with a slower 1.83 sec 60 ft.
Later that year I opened up the exhaust and that made a big differance until the engine exploded a few days later.
The direct cause was rod failure but the main caps showed sign of major cap walk,
I would say that with a good tune the stock block can last a while at 700 hp. A while can be days or years
That boost controller, is that a type of 'BOV'? If it is then I think that it is the wrong way to control boost on a centrifugal supercharger. The supercharger will actually run harder when the BOV is open.
I my opinion this is the correct way to reduce top end boost.
https://www.hks-power.co.jp/en/produ...estrictor.html
( Stock 1984 block, stock crank, stock rods, stock pistons and stock bolts. )
Then replaced the supercharger with a turbo that made 627 hp to the wheels at 4200 rpm. 800 lbs ft @ 4000 rpm.
I ran 11.14 sec @ 126 mph with a 1.72 sec 60 ft that year.
Next year I had changed to a bigger turbo that made more power but a bit slower to spool up..
I ran 10.86 sec @ 134.5 mph with a slower 1.83 sec 60 ft.
Later that year I opened up the exhaust and that made a big differance until the engine exploded a few days later.
The direct cause was rod failure but the main caps showed sign of major cap walk,
I would say that with a good tune the stock block can last a while at 700 hp. A while can be days or years
That boost controller, is that a type of 'BOV'? If it is then I think that it is the wrong way to control boost on a centrifugal supercharger. The supercharger will actually run harder when the BOV is open.
I my opinion this is the correct way to reduce top end boost.
https://www.hks-power.co.jp/en/produ...estrictor.html
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Le Mans Master
Joined: Aug 2017
Posts: 6,940
Likes: 1,490
From: New Jersey
I would think if you splayed the mains it wouldn't have exhibited cap walk imo. The 010 blocks are nice. Iirc the dart block comes ready to be a 383 it just needs the bores set up. Something to think about also is the block is a bit heavier than a stock casting.
Race Director
Joined: Sep 2001
Posts: 14,676
Likes: 751
From: NEwhere Ohio
Stock block is way stronger than people think.
700 hp easy. You are pushing a 3300 lb sportscar, not a 6500 lb pickup truck with a load of dirt up a hill.
you are wasting $$ with a bottom end build.
you should put that money in the top end.
and dont wimp out and go ls motor. They arent really any stronger.
the only way id consider all that stuff is if i was rebuilding it anyways, or wanted piece of mind during say, an open road race event (100 miles at 200 mph)
700 hp easy. You are pushing a 3300 lb sportscar, not a 6500 lb pickup truck with a load of dirt up a hill.
you are wasting $$ with a bottom end build.
you should put that money in the top end.
and dont wimp out and go ls motor. They arent really any stronger.
the only way id consider all that stuff is if i was rebuilding it anyways, or wanted piece of mind during say, an open road race event (100 miles at 200 mph)
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
That boost controller, is that a type of 'BOV'? If it is then I think that it is the wrong way to control boost on a centrifugal supercharger. The supercharger will actually run harder when the BOV is open.
I my opinion this is the correct way to reduce top end boost.
https://www.hks-power.co.jp/en/produ...estrictor.html
I my opinion this is the correct way to reduce top end boost.
https://www.hks-power.co.jp/en/produ...estrictor.html
Why don't we put the TB before the compressor and control boost with our throttle? Side benefit: Very low load on the compressor/drive when running at part throttle.
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
It also gives us completely different definitions of "big power".
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
Poor throttle response, harder to build idle vacuum, reduced idle air controller/idle valve efficiency, high vacuum pulls oil through the seals and causes premature failure, and difficulty tuning tip-in and acceleration enrichment.
Race Director
Joined: Sep 2001
Posts: 14,676
Likes: 751
From: NEwhere Ohio
My comments about the LS Motor - if you get detonation it will kill it just the same as an SBC.
LS people making big power are doing so having learned from decades of gearheads making mistAkes on the SBC.
inadequate fuel systems, tricking out a coolant temp sensor with a resistor as your ‘sole source’ of providing extra fuel for nitrous or boost (bc no one knew how to tune), lack of meth/water inj (theyve been around for ever but it seems no one used them in the 80s to 90s efi hot rod years), lack of timing retard (again bc noone knew how to tune)...
make the same mistakes on an ls motor and it will fail just the same
LS people making big power are doing so having learned from decades of gearheads making mistAkes on the SBC.
inadequate fuel systems, tricking out a coolant temp sensor with a resistor as your ‘sole source’ of providing extra fuel for nitrous or boost (bc no one knew how to tune), lack of meth/water inj (theyve been around for ever but it seems no one used them in the 80s to 90s efi hot rod years), lack of timing retard (again bc noone knew how to tune)...
make the same mistakes on an ls motor and it will fail just the same
Last edited by dizwiz24; Jan 28, 2020 at 03:55 PM.
Burning Brakes
Joined: Sep 2016
Posts: 1,133
Likes: 319
From: Ohio
Low air speed during idle/cruise means that cracking the throttle open will cause a hesitation until the air makes it to the intake.
This makes throttle body mounted idle air controllers less efficient, since their effect will have a delay and closed loop idle will be harder to maintain.
For the same reason, its hard to tune accel enrichment with EFI (the fuel injected equivalent of the accelerator pump) because the air and fuel are entering at 2 different points.
Tuning accel enrichment fueling with a carburetor is easier on a draw-through setup than a draw through throttle body EFI setup.
Its also harder to build idle vacuum because of the extra plenum volume and multiple possible leak points. Can still be done with the right precautions though.
And on turbochargers and centrifugal superchargers, having the compressor under vacuum for long periods can pull the oil through the seals.
Its a lot worse on a turbocharger since the oil is pressurized so differential pressure is even higher.
It can be done, but its just not worth all of the downsides.