BJR Racing

Racing Engines & Heads

 

Big Block Cylinder Head Technology


383/400

First the 383/400 as they use the same basic cranks and rod combinations. These engine have to be
treated like the 273/318 engines as they only have .070 more stroke than their A engine counterparts. So when it comes to the cylinder heads, some precautions have to be taken. For these engines I would use a factory iron head such as the 906's, which have 174 cc's from the factory or the 452's which have 180 cc's from the factory. Being that the stroke is so short, over heading these engine is very easy, just as it is to over cam these engines. I would keep the 2.08 intake valve size and also keep the 1.74 exhaust valve size, the reason for this is that with the stroke being so short the time for filling the cylinder isn't very long so port velocity is very critical. By keeping the smaller valves, the velocity will be as high as it can be without major machining. The intake port is fairly straight forward and will more than take care of the needs for the 383/400 engines, both flow wise and volume wise.

 
I would do the following for all street and mild bracket racing engines. First I would gasket match the heads to the stock gaskets, then cut the bowls open and do a good valve job. This should put the flow in the 240-260 range on the intake and 210-220 cfm's of flow on the exhaust side. This is enough flow to make well over 500 HP and close to 500 ft. lbs. of torque. As cams get larger, the need for more flow will be needed, but this can be taken care of with just a bit more port work - such as radiusing the guides and the short turn on both the intake and the exhaust sides. Cutting the pushrod pinch back as far as you can will really help the flows throughout the range. With these modifications the flow should increase to near 280-290 cfm's on the intake side and 220-230 on the exhaust side.

The ports should be in the 184-188 cc range. This is the best size that we've found to work on the 383 engines and 190-195 cc's on the 400 engines. To get 190-195 cc's out of the heads will require a good amount of work to the ports, and this would be more of a fully ported head. The need for heads larger than this isn't needed on the low block engines. The next step in getting more power out of these engines is in the cams and compression. But be careful when choosing a cam, as it is easy to over cam. Cams in the 230 @ .050 range will work best for dual applications such as street/strip. These engines like cams with centerlines in the 110 to 114 range, 112 seems to be best for street/strip cars.

The next thing that I would do is have a good intake manifold and a good exhaust system with headers. The low block engines will like the 1 3/4 header and a M-1 intake manifold for the street, and a 2" header and the M-1 single plane for the strip. Along with this, a 750 or 850 cfm carburator would be best - the 750 should be a vacuum secondary for the street and a double pumper for the strip. This would be the minimum that I would do in either case. Keep in mind that the rear gear and either a clutch or high stall converter will make the heads really come alive. But this will also be cam dependant. This covers the low block engines for mild to street able engines.
 
 
Next - the 440 and RB engines
The 440 engine can use a good bit more cylinder head and more port volume, the need for velocity isn't as great on these engines as the stroke is .370 more than the low blocks. A good 440 engine should have a 220 to 230 cc port runner and flow in the 310-350 range. The head that I would use on this engine would be the Max Wedge head from Mopar, as they come 210 cc's from the factory and flow near 300 cfm's from the factory. They also have fast burn chambers and this helps with the HP output. If you have factory iron from the 70's don't discard them just yet as they do have a purpose. If your looking for a good stump puller and lots of torque then this is where they will be very useful. These heads should be capable of sustaining 5500 rpm's with ease. The small ports will work well with low rpm cams and very large cams with lots of duration and low centerlines if you can't afford the Mopar Max Wedge heads.
 
Modifying these heads will be the same as the low block heads but with a larger exhaust valve. This will need to be changed to the 1.81 exhaust valve from the 1.74 that comes from the factory. This change will create more torque and HP as the larger size of the engine will really like the breathing capability of the bigger exhaust valve. If you have or are going to buy the Mopar performance Max Wedge heads then no other modifications will be needed as they come with the 2.08/1.88 valve sizes. The ports have been radically changed for better flow and performance, also when this change is made the intake manifold will have to be changed also. For this I can only recommend 1 intake manifold as this is all that’s really out at this time - the Indy manifold. This would be more of a race thing than a street thing. The next option that is available is the stage 6 head. This head comes from the factory at 190 cc's and raised runners so the intake manifold will have to be changed here also but they are available through your Mopar dealer. This is the best option and a middle of the road head (as far as cc's go) for the 440 engine. These heads can be made to work very well on the 440 and have a lot of potential. These heads flow in the 310 cfm range but the low lift suffers from the factory as the bowl needs some attention. This, in my opinion, is one of the best heads out there for the B or RB engines. The only thing is that on a very good 440 they may not be enough for higher rpm's of the engine and this is why I stated the use of the Max Wedge heads as the runners are larger and will support more HP and rpm's.
 
As for headers and carburators the same will apply for headers but the cfm of the carburator will have to go up 100-150 cfm's minimum as the larger CI of the engine will require this.
 
Below is a guide of what head and cfm range that I would use and on which engine. This should help in making choices for most all applications and if yours happens to fall in the middle of this then err to caution to the smaller side.

Engine Size Usage Port CC Head Flow CFM Valve Size Intake Exhaust
383/400 Street 175-182 240-260 2.08/1.74 M-1 Dual Plane
or Edelbrock RPM
1-3/4"
36-44" length
383/400 Strip 188-195 290-320 2.08/1.74 M-1 Single Plane
or Edelbrock Air Gap
1-7/8" - 2"
36-40" length
3-1/2" outlet
440 Street 185-195 260-280 2.08/1.81 M-1 Dual Plane
or Edelbrock Air Gap
1-/34"
34-40" length
440 Strip 210-230 320-380 2.14/1.81 M-1 (standard heads)
Indy (Max Wedge heads)
2" - 2-1/4"
30-34" length
3-1/2 - 4"" outlet
 
 
Thanks for having a look at the site and hope that this helps!