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400 sbc race engine

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400 sbc race engine

tentman1975 tentman1975
New User | Posts: 2 | Joined: 01/10
Posted: 01/05/10
11:10 AM

I have a 400sbc +030. Scat 3.75" crank, 6" rods, keith block flat tops, dart iron eagle platinum 49cc heads, solid cam, 1.5 roller rockers, moroso pan and pump,brezezinski 2 bbl intake,  12:5.1 compression. We recently had it at the dyno and it produced 332 hp at the rear wheels. I need this engine to produce atleast another 100 hp at the wheels to be competetive. Does any one have any ideas? Rules are all cast iron heads, block and manifolds, maximum CI is 410 with a 500 holley 2bbl. No roller cams allowed!  

gtomustang gtomustang
Enthusiast | Posts: 457 | Joined: 06/09
Posted: 01/05/10
01:29 PM

How's the oil control?  Using a crank scraper or windage tray?  Got a V shape shield in the lifter valley to keep hot oil from splashing on the bottom of the intake? Can you use a higher ratio roller rocker?

You probably won't find one part that gets you that needed HP, it may be a combo of things.  Too bad you didn't start with a 400 Mopar, the bigger lifter bores would let you get some radical cam lobe ramps.  Or a Pontiac 400 could allow you some header-style exhaust manifolds.  Or a ford 400M would give you Cleveland head ports.  Or a....

Can you change transmissions to keep the engine in the sweetest part of its powerband?  
Just because you can't do it...doesn't mean its impossible

tentman1975 tentman1975
New User | Posts: 2 | Joined: 01/10
Posted: 01/06/10
07:09 AM

-It has a moroso pan which has a built in windage tray.
-Yes we have a valley tray also.
-We can use any stud mounted rocker we want
-There is a 5000 rpm rev limiter so no advanatge to changing trannys.  

gtomustang gtomustang
Enthusiast | Posts: 457 | Joined: 06/09
Posted: 01/06/10
01:46 PM

I had assumed, from the 2bbl, this is a round track car, that operates in multiple levels of the RPM that correct?

Will a lighter reciprocating assembly help the engine rev faster to its power potential, or is the torque you need evenly spread across the RPM range?

you may be able to lesson the friction on the reciprocating assembly, which means the car won't slow down when you let off the gas in the corners, you'll need to rely more on the brakes.  But, in the 80's, it was theorized a CSB eats up to 100hp in friction.  Piston rings, valvetrain, so on.  Who knows if its that much?  But a crankcase evacuation system will create vacuum in the crankcase, which could allow you to run thinner piston rings, and thus less friction.

Redrilling the cam bearing openings in the block, to run roller bearings, is excessive...but it helps. It gives you the excuse--if your class allows it--to move the cam further up the block, if you want to run shorter pushrods for less weight, or better angularity to reduce friction.  you've got roller rockers, have you played with the intake one's ratios? Three angle valve job on the valves for extra overlap?  Create a siphon on the exaust port to draw in more intake? I'm assuming that 2bbl, for all its work, is going to offer a restriction.  
Just because you can't do it...doesn't mean its impossible

RodsAndWheels RodsAndWheels
New User | Posts: 4 | Joined: 09/12
Posted: 09/21/12
12:27 PM

What work have you done to the heads?  

pepsi1 pepsi1
User | Posts: 81 | Joined: 10/11
Posted: 09/29/12
11:35 PM

welcome tentman1975.

I think the easiest way to help you is for you to help us with the the specs on what you can do. The specs can help us that way. 100HP on a 2BBL carb is along shot to make 100hp with a 2bbl. carb is alot to of horse power to find...

Start with the basic tuning

I would start by up jetting the engine

Don't know what your using for spark plugs? You can run one or to steps colder spark plug, and regap your plugs to .032. Going to .044 and .045 will not help.  Cool  

Check you disributor for operation, free moving weights, and vacuum advance.

Advance the cam. Advance the bottom by 2* then watch your Valve to piston clearance Tongue

Readjust your valve lash settings. Never a total anymore of .008 increase or decrease in your valve train clearance. For Example. intake valve clearence is normally .024 to NO Further then .032... Grin  Cool

Set your timing: If vacuum advance  set base 12* to 14* degrees, and a total of 34* or more all in at 2500RPM. Give your timing more if the engine does not ping.

Get your engine tuned correctly that will help.

Run a colder thermostat a 180* thermostat. Grin  Cool    


revolutionary revolutionary
User | Posts: 76 | Joined: 07/06
Posted: 09/30/12
05:27 PM

Let's look where you are right now. Depending on the dyno, if you are making 332rwhp then that is about 375hp at the crank. Roughly. So that would be 401 lb ft at 5000 rpm. Pretty much 1 lb ft per cube. Not a bad start for a 2 barrel. Best case for a cast iron 4 barrel in otherwise the same would be about 1.35 lb ft per cube or about 548 lb ft. That would be 521 hp at 5000rpm. I'm not saying you can't make 100 more horsepower than you are now with a 2 barrel, but looking at a well sorted 4 barrel at only 120 horses more makes it unlikely. So work with what you have. You don't get RPM so you HAVE to make a lot of torque. Look at the Engine Masters street class engines...
Choosing the cam is going to be key. Get with 2 or 3 different cam grinders and try the best they can give you. Mike Jones makes a really good cam as does Bullet. Comp has some really good lobes tucked away that few people try. I've also seen a LOT of power come from who built the carb. If you want big power increases expect to buy at least 3-4 carbs from top name (not locals) builders to try out. Intake manifold is also a biggie. BRZ is the most popular and does a great job but there are others out there.

dond1965 dond1965
New User | Posts: 48 | Joined: 12/13
Posted: 12/01/13
05:02 PM

have the lifter bores machined to use AMC solid lifters.use the pvc port on the carb to create a big vacuum leak,and increase airflow through the engine.put as much compression ratio in it as possible. can you use 4v intake manifold?if you can make a big open spacer/adaptor to increase plenum volume.going from 12.5 to 1 to 16.5 to compression is worth about 35 lbs. ft. of torque.crower has 1.7 ratio 7/16 stud mount roller rockers. using COMP cam #11-682-47,which has 108 degree LSA,270-276 degree duration at 50,0.638-0.631 gross lift with 1.5 to 1 rockers,the gross valve lift becomes a whopping,0.723-0.715 inch!