440 RPM motor

[GLHS221]

In my 67 Coronet R/T I have a 440, bored .040 over, 452 heads ported myslef, crane adjustable 1.6 rockers, Edelbrock Performer RPM Cam and Intake, petronix ignition, cheapo headers, tti 3" exhaust, orignal carter 4327s carb(750cfm i think), tranny is a 727 with shift kit, 28-3200rpm stall, 3.91 posi. I would like more power form my engine. I was thinking about getting Super comp headers and a 800cfm carb....maybe nitrous. I want to have 500hp....what else should I change? Thanks, Matt

[Walkercolt]

What's your compression ratio? Is this the original engine in the car? IS IT MATCHING NUMBERS? If the answer to questions 2 or 3 is "yes", LEAVE IT ALONE! Ok, back to your question, raising compression will gain bunches of power and torque, but fuel becomes a problem. You'll have to mix race fuel with pump stuff if you go above 9.5:1. Nitrous can/will be risky with a 30 year old motor unless it's built-up from the crank for it. The last 3-4 isssues of Mopar Muscle had an excellent BB build-up series, they got nearly 600HP on a real streetable engine. Remember the old machine shop saying"HP=$$$; How fast can you afford to go?"

[kingjr]

First thing I'd swap is the carb. That thing's gotta be hurtin ya. Probably an 800dp or something in that range. With the right comp. you should easily come close to 500hp, keep tuning!

[GLHS221]

I want to run on pump gas all the time so I really dont want to raise the compression ratio. The motor has been completely rebuilt has all hp parts(forged crank, good rods etc) has about 200 miles on it tops. So I wouldnt see why I couldnt use NOS right? Matt

[PRO]

GLHS funny you should ask......I had a 67 Coronet 440.4spd with a 150 hp shot of n2O that went 11.88 and this was a 8.5:1 motor,ran it for 4 yrs on the bottle and loved every moment,it was most exciting out of the hole,having a best of 1.49 60 ft,which is way too fast compared to the et,it lifted both front tires off the ground!! too fun,anyhow its relatively inexpensive and its safe if you set it up right and you still get to run pump gas.........PRO.....

[Walkercolt]

GLHS, OK, now we have some important info on you motor. Properly set-up nitrous works great, just make certain you can provide the fuel when you on the "squeeze". A lean mixture will knock holes in your pistons fast, and can ruin heads too. I'm getting a bit cautious about the old BB's anymore. They're old castings, we can't always be certain what has been done to them, and too many of these motors have seen serious abuse.

[GLHS221]

I pulled my motor out of an old 4 door chrysler and when I tore it apart it was in great shape, not even a ridge. So i am really not too worried about the block or anything. I am looking at using a "top shot" since I can conseal it in the air filter, if i use nos. What carb would be better that Holley 770 Street Avenger ot Edelbrok 800cfm performer? Matt

[Walkercolt]

Ouch! That's really kinda apples to oranges. The Holley is a more street oriented carb, the Edlebrock more "performence" oriented. I'm certain either jetted properly would work. To find which would be better would take back-to-back testing on your motor with your mods. We're probably talking tenths of a sec. here, and that's where it gets real hard. Even the way you hit the gas pedal will affect the performance of either carb. I'm wondering if your not approaching the needs of chassis/suspension upgrades, which can let you apply the power to the ground better. I can't help on the carb choice, but you're getting there.

[71 scamp]

I always suggest to my friends that they baseline their cars at the strip before making changes, that way you can learn from it.

[DartGT66]

We are in front of the same problem, except that nitrous is outruled. First, I would like to know the real CR. The RPM cam is pretty big and if your true CR is in the 8's it will not like this cam, would run better with a smaller one. The carb should be bigger; my choice would be the 770 Holley. I believe you have it otherwise pretty well. As far as our car goes, it's heavy at 4400 lbs the heads were all out ported iron heads but they cracked, and the CR was around 9.5:1 otherwise about the same as yours except 1.5 ratio rockers and 3.55 gears. This car run 13.6 at 103 mph. Now we will go with the Edelbrock heads, mill the block .090" to bring the pistons to zero deck (have done this before; works). This will result about 10.5:1 CR with valve reliefs and an uncompromised cam with more lift will be used. hopefully this will help some in our case.

[GLHS221]

I would like to know how much of an icrease those edelbrock heads give you, I am considering about getting a set myself. I really dont know my true compression ratio...is there any way to figure it out with out taking apart the motor? Matt

[DartGT66]

I think the rpm heads will not help us much because the iron heads were about the best (iron heads) money can buy. However, they may have been cracked from the beginning since the car never run quite as well as it should have. So the heads might help some, but I believe there is more in the CR increase and a different cam. The RPM cam is somewhat compromised because it had to be a bolt on to stock mopar short blocks without valve to piston clearance problems. Not decided yet about the cam, rpopably a comp cams extreme energy, Hughes or Ultradyne hydraulic will be used.

[Walkercolt]

GLHS, it might be had to find in Fargo, but they make solid state pressure transducers that screw into the plug hole and act as spark plugs, giving you the actual combustion pressure in the cylinder, as well as the dynamic CR. If there is someone who builds top-fuel or funnycar engines in your area, they almost have to have one to keep from blowing the heads off a nitro engine.