383 help!!!! our motor combo needs suggestions

[c00nhunterjoe]

Its hard to say what will definatly clear since you don't know exactly what pistons are in it.

The cost of a solid vs hyd cam is irrelevant. The added cost comes with the required adjustable valvetrain.

[694life]

sorry thats what I meant by whats the cost. I shoulda been more clear.

[c00nhunterjoe]

The cams cost about the same.  For a good set of rockers count on about 700 bucks. Also don't forget you will probably need different length pushrods.

[694life]

ouch so what needs to be done for that hydro voodoo 303 cam to work on the stock 906 heads? I see the exhaust lift is .513

[c00nhunterjoe]

It may clear. My cam is 510 lift but I dnt know what pistons are in your engine and what your deck height is or if your heads have been milled. if your "509" cam hasn't hit there is a decent chance that the .513 will clear as well but its purely a guess

[Challenger340]

.509 MUST BE installed at 104-105*, NO LATER.
Dunno if you have enough Piston to Valve to advance it ? If you.... can that will pick up the pressure a bit for some more Torque and get the .509 coming on a bit earlier.
Also,
2.02" 60 Ft ??
Anything "lost", or conversely "Gained" in 60 ft time, can pretty much be doubled off the E.T.
example;
go to an honest 3800-4000 stall and you should see 1.7's 60 ft, thats 3/10 faster than the 2.02, so the E.T. should drop around 6/10th to 12.70's right there...
and,
with the advanced Cam I'll guess another 3 mph for around 12.50's @ 105mph.

NOT your low 12's but closer.......and still cheapest way to 12 sec street car.

[c00nhunterjoe]

That would put his car at the same et's and trap speed as mine. Sounds very achievable. The key will be if he has the valve clearance.

[694life]

I think were done with the 509 cam. It is a street car and hits the track maybe 2 times a year so far ( might go more if it gets more impressive). Looking at doing the voodoo 60303 like firefighter suggested. Is there 12's in that  combo with that cam. BTW thank you guys so much for all this it really is a huge help

[firefighter3931]

Anything "lost", or conversely "Gained" in 60 ft time, can pretty much be doubled off the E.T.
example; go to an honest 3800-4000 stall and you should see 1.7's 60 ft, thats 3/10 faster than the 2.02, so the E.T. should drop around 6/10th to 12.70's right there...

Bingo....your 60ft times are killing ET. That cam is too big for the compression stall and gear you're using in the car/engine combo.  The 509 is going to have a very narrow powerband, especially in a 383ci based build. Figure 4500-6500 is where it will be happiest. Not the best choice for a dual purpose car. 

A shorter duration cam with a wider LSA will broaden the powerband and make lots of additional power at lower engine speeds. Tuning will also be a lot easier ! 

Here's a good thread to read about how a mismatched (overcammed/low compression) combination can be a nightmare...pay close attention to the dyno numbers before vs after : http://www.dodgecharger.com/forum/index.php/topic,6000.0.html

I think were done with the 509 cam. It is a street car and hits the track maybe 2 times a year so far ( might go more if it gets more impressive). Looking at doing the voodoo 60303 like firefighter suggested. Is there 12's in that  combo with that cam. BTW thank you guys so much for all this it really is a huge help

The VooDoo 303 will fit fine....if the 509 clears the pistons then this one will too. The duration plays a significant role in piston to valve clearance. A cam with less duration and wider lobe centers will have more piston to valve clearance. The 303 uses a 3 bolt upper gear so you will need to swap out the timing set when you do the cam swap. The Comp Magnum timing set is reliable and cheap (under $50) so go that route if you decide to use the 303 Lunati stick. 

With hyd cams you're limited to 6000rpm anyway (lifter pump = valve float) and the 303 will pull hard to 6k but will make a lot more bottom end power and torque to help launch the car. You will see a nice improvement in the 60ft and 1/8 mile ET's which will translate to better 1/4 mile ET's and possibly increased trap speeds. 

For you use this is the cam I would pick given the displacement/compression/stall speed/gearing & tire diameter. 


Ron

[694life]

Thank you guys so much we are going with the 60303. like I said a dont know mopar but I have a 9 sec turbo buick. Unfortunatly my buddy went off some mopar sheet or book that has this 509 combo for low 12's in a 383. I will let ya know how we make out. Again thank you guys

[c00nhunterjoe]

Your book is correct, you can get low 12s with a "509" but you need a little more motor then what you have to do it with.

I think you will see a night and day difference when you swap to the 303 cam. Will that alone get you what you want? I doubt it. Still too much tire vs your gears.

[694life]

We may be able to get our hands on some 4:30 gears cheap. Also what spark plugs and gap do you recommend for this combo

[694life]

We got a chance to check some stuff on the car tonight. first off its got 28" tires. Second timing was coming in late and cranking the motor over the cylinder pressure was 92lbs. any thoughts? should we still lock out the distributer at 40deg total with the 303 cam?

[c00nhunterjoe]

I have 4.30's in mine with a 28 inch tire. 40 mph@2000, 50mph @2500, 60 mph @ 3000. Its very cruisable still and the car is a beast when I launch. 


92psi!!!!? I really hope you forgot to hold the throttle open while testing each cylinder.


What type of ignition are you running again? Helps with plugs and gaps

[Chryco Psycho]

compression readings should be more in the 145-160 range but the long duration cam will bleed off a ton of pressure especially at low cranking speeds ,

[firefighter3931]

Wow...92 psi    No wonder this thing is a Slug out of the hole ! 

I wouldn't swap the gears until after you do the cam change 

Get a degree wheel on it when you install the cam and shoot for a 106* installed intake centerline.

I like the NGK XR5 plugs and gap them @.035 with conventional electronic ignition or a little wider with a MSD multispark box. For timing it'll like 18-20 at idle and 36-38 total all in by 2500-2800.

The Lunati stick is most assuredly a step in the right direction. 


Ron

[BSB67]

cranking the motor over the cylinder pressure was 92lbs.

Never saw that coming.    That would be the missing 50 hp for getting to mid 12s at 107.

Be sure to let the cylinder hit the compression stroke 4 or 5 times to get the reading.  Also be sure to do all of the cylinders.  I doubt that all eight were 92 psi..  If they were, try another gauge.

If the cylinder pressure is really this low, this make Ron's suggestion spot on.  Consider installing the cam 6 degrees advanced, and maybe a dual plane intake as well

[c00nhunterjoe]

Again, was the throttle held wide open while testing?

[694life]

  didnt even think of holding the throttle open!! We will have to do thsat and report back thanks for all the help still

[firefighter3931]

Holding the throttle open will help somewhat in getting a more accurate reading but don't expect it to increase significantly. One word of caution if you're using a mechanical fuel pump ; disconnect the fuel line because when you spin the engine over with the throttle wide open it will dump fuel and wash down the cylinder walls.

A flattop piston with no valve reliefs is basicly a replacement piston and it will sit low below the deck surface. A good example is the SpeedPro L2315 "replacement" forged piston that is commonly used....it usually sits .050-.060 below deck depending on factory tolerances. It won't be remotely close to 10.5:1 static....especially with an 88cc open chamber head. I'd be very surprised if it was anything more than 9:1 unless the block has been decked (a lot) and the heads have been milled significantly (.060-.080).

A 248*@.050 cam with a 108 lsa is going to bleed off a TON of cylinder pressure and couple that with a modest 383ci displacement...this explains the results.  

With low compression and modest displacement you need a cam that closes the intake valve early to trap more pressure in the hole and make some power at lower engine speeds.  



Ron

[Cooter]

Well, I see too much cam, not enough motor.

Too tall a tire with not enough gear...Without the motor, you need the gear. With enough motor, you don't need the gear.

Those 4.10's are morel ike 3.50's with those tall ass 29" tires.

[694life]

I made a mistake they are 28" tires. As far is the pistons he got the car when he was 15 and had the motor built when hes was 16 he is 31 now and was told they are 10.5 to 1 but that was only said never confirmed. Its got a 6a ignition box with a blaster 2 coil. He had another cam in it that lost a lobe 7yrs ago and thats when the 509 cam was put in.

[BSB67]

I made a mistake they are 28" tires. As far is the pistons he got the car when he was 15 and had the motor built when hes was 16 he is 31 now and was told they are 10.5 to 1 but that was only said never confirmed. Its got a 6a ignition box with a blaster 2 coil. He had another cam in it that lost a lobe 7yrs ago and thats when the 509 cam was put in.

FWIW, I don't think there was ever a 10.5:1 piston for a 383. All of the flat top 383 pistons that I'm aware of for the past 30 years are at best an actual 9:1 and could be less than 8:1.  Add sunk valves, a .040 or ,.050 gasket and the actual CR can be very dismal.   Retest the cylinder pressure.  It is worth the time to know this for every cylinder, and is important for future decisions.

Also, losing a cam lobe can be tuff on piston skirts and cylinder walls if the motor was not disassembled and cleaned.  Some guys do get away with it.

[firefighter3931]

FWIW, I don't think there was ever a 10.5:1 piston for a 383. All of the flat top 383 pistons that I'm aware of for the past 30 years are at best an actual 9:1 and could be less than 8:1. 

There was a 10.5:1 piston for the 383 but it wasn't a flat top. Many years ago i bought a 383 shortblock from a co-worker who bracket raced at the time. That motor had big domed TRW "race" pistons that were +22cc and with the 906 heads and Felpro head gasket we figured 10.5:1 measuring & calculating. I stuffed a Crane FireBall cam (old timers will remember those grinds  ) in there and it ran pretty descent. Quite an improvement VS the stock (tired) 383 that was in the car originally. 


Ron

[BSB67]

FWIW, I don't think there was ever a 10.5:1 piston for a 383. All of the flat top 383 pistons that I'm aware of for the past 30 years are at best an actual 9:1 and could be less than 8:1.  

There was a 10.5:1 piston for the 383 but it wasn't a flat top. Many years ago i bought a 383 shortblock from a co-worker who bracket raced at the time. That motor had big domed TRW "race" pistons that were +22cc and with the 906 heads and Felpro head gasket we figured 10.5:1 measuring & calculating. I stuffed a Crane FireBall cam (old timers will remember those grinds  ) in there and it ran pretty descent. Quite an improvement VS the stock (tired) 383 that was in the car originally.  
Ron

The domed pistons I put in my 383 were rated at 12.0:1 IIRC (it was 1978).  I bought these because you could not buy the factory correct compression height forged TRW/Speed Pro (i.e. NHRA approved) piston for the 68/69 383.   You know, the one that would be 0.020" proud when blueprinted. The dome on the piston I bought were almost .500 tall.  I had them milled down to about .180 and figured them to be about 11:1.  With a 906 head and the old "Hemi Grind" cam, it blows 210 psi still today.

I remember the Fireball cams....I went with the Racer Brown SSH-25