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440 build ?

SGTPaul

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Hi All! I’ve been out of the muscle car mechanics for 20+ years while wrenching on Army helicopters and have a few questions on a 440 that I’m going to be rebuilding and need a little help.

What I have is a 76 440 cast crank automatic from a motor home. Will be going into a 68 Charger R/T 4 speed. Considering a set of 915 heads since that is what I ran on my cars back in the day. Gear will be a 354 posi. I have not settled on a cam but would look for something for street racing.

My questions are:
With the 76 short block will my compression be close to the factory 10:1 for a 67/68 engine with 606 or 915 heads?
I understand the 906 heads have a larger exhaust valves and better flow, but do the 915 heads with the closed chamber make that much difference in performance compared to 906 heads?
I don’t remember if the cast cranks is internally or externally balanced?
Can I use my 68 flywheel on the 76 short block with the cast crank?
If I remember correctly, if I go to a steel / forged crank I will need a damper & flywheel from that type of crank?
Any suggestions for a cam?

Any help would be greatly appreciated!
Thanks,
Paul
 
Cast crank 440's are externally balanced, and most forged cranks are internally balanced. The '68 crank was forged, so you can't use it's flexplate (not flywheel if it's an automatic) on your '76 crank (without having it balanced).

Some late 915 heads had the larger exhaust valve but they seem rarer now, so if you find some without, it's fairly easy to install the bigger valve (and hardened seats as well). 906's were originally the replacement performance head for the 915's (as Mopar started to recognize smog requirements). I would say (many won't agree) that 915's and early 906's flow pretty much the same, but the 915's will have a slight compression advantage, and they are an excellent choice for quench builds (I'm a 915 fan). 516's are another choice as with the bigger exhaust valves installed and some pocket porting they flow nearly as well as 915's. This all assumes you are not going for aftermarket heads.

As far as compression goes, well, it depends on certain factors; if the pistons are flat topped or dished, and how far down in the bore they are. By '76 the smog requirements were well in play. Don't quote me on these numbers, but by 1976 the 440 had a compression of about 8.5:1 while the 68's had maybe 10:1. Using the 915 heads (and the steel shim head gaskets) should bring you up to about 9:1. Again, don't quote me on any of this.
 
I'll hit on your questions then add a description of my recent build.

The cast crank 440 is externally balanced. This is noted by the harmonic balancer with the counter weight. Early steel crank engines are internally balanced so using the 68 flywheel is not possible on the cast crank unless you add a weight or remove weight from the other side (or a combination of both). The adding/removing weight comes from basic balancing theory but I haven't personally tried to use a zero balance flywheel on a cast crank. If you find a steel crank the balancer and flywheel you will use is zero balance.

915 and 906 heads are exactly the same (assuming you have the same valve sizes) except for the obvious closed chamber part. The benefit from the closed chamber, aside from the added compression, is to provide quench in the chamber, which promotes swirl to help the fuel burn more completely. The result is more power and better efficiency. The flow between the 915 and 906 is (should be) exactly the same. Flow - shmow, the real benefit from using the closed chamber heads is the 1/2 point of compression increase and the quench.

Adding the closed chamber heads to the 76 pistons will help but chances are you will not be at 68 CR specs. Even the 68 engines were not quite 10:1. You will need a compression distance of 1.990" (if I remember correctly) to get to 68 specs. My 77 440 in my Belvedere has 2.065" compression distance pistons (same as 440 six pack) and that puts the flat tops to just about zero deck (actually -.015"). I am netting 10.1:1 with 915's and a steel shim gasket.

You won't need a lot of cam to get the job done for street duty. .450"-.480" lift and about 272-280 duration on a 112 LC. The key is to not loose all of your cylinder pressure. Match the cam and compression!!

The 440 in my 66 Belvedere is a 77 block with a steel crank and LY rods. The pistons are KB237 and I'm running 915's with 2.14" / 1.81" valves. It blows 190 PSI of cranking pressure and has the throttle response of a motorcycle. I also pocket ported the heads. The cam is a .455" / 272 Purple Shaft and the intake is an M1 dual plane (exactly like factory cast iron except in aluminum) and a 750 AFB jetted 4% richer in the secondaries. 2" primary Hooker 5906 headers and a TTI 3" full exhaust with Flowmasters. The car is a full bodied bench seat B body with PS, PB, spare tire, jack, and auto with a TCI 11" converter. Leaving the line at 1800 RPM and loosing lots of traction with 255/60/15 street tires I ran a 13.38 @ 109 MPH on 3.55 gears. The MPH is good enough for a low to mid 12 if I can hook it up, which is my next move. My only issue is I have to run better than 91 octane or it will ping at WOT on a hot day. Driving around with 91 seems fine but I can't get on it. Adding 1 gal of 110 Sunoco leaded to 12 gals of pump 91 seems to cure the pinging problem. If I had just a tad less compression I could probably swing the pump gas 100%.

I recently installed a factory cast iron intake and will get some drag radials and 4.10 gears, and with any luck I should hit my target of 12.50.
 
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