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Discussion Starter · #1 ·
I have a 383 bored .30 over with a Hydraulic comp cam and aluminum 440 stealth heads with pro comp roller rockers. Stock mechanical fuel pump, double roller timing chain and gears. edelbrock performer intake with quickfuel 600cfm carb. Headers as well. I am running a chrysler electronic distributer with orange box and with a MSD coil. 727 transmission with stock converter. My cam Duration @ .006 TAPPET LIFT IS 268 280 and Duration @ .50 is 224 230 so not a heavy cam so I am thinking my stock converter should be fine.

I am having issues with complete lack of power till I hit 2800 rpm ish. It idles fine and seems responsive when pedal is depressed. I have tried several carbs from 600cfm up to 850 cfm demon carb. I just replaced the distributer springs for lighter ones to adjust the curve. I still cannot get this car to spin a tire unless I am taking a corner when it leans. It has a bit of a stumble. What should I start off with initial timing and what should my A/F be set to for a good starting point. Any help would be awesome.
 

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I have a 383 bored .30 over with a Hydraulic comp cam and aluminum 440 stealth heads with pro comp roller rockers. Stock mechanical fuel pump, double roller timing chain and gears. edelbrock performer intake with quickfuel 600cfm carb. Headers as well. I am running a chrysler electronic distributer with orange box and with a MSD coil. 727 transmission with stock converter. My cam Duration @ .006 TAPPET LIFT IS 268 280 and Duration @ .50 is 224 230 so not a heavy cam so I am thinking my stock converter should be fine.

I am having issues with complete lack of power till I hit 2800 rpm ish. It idles fine and seems responsive when pedal is depressed. I have tried several carbs from 600cfm up to 850 cfm demon carb. I just replaced the distributer springs for lighter ones to adjust the curve. I still cannot get this car to spin a tire unless I am taking a corner when it leans. It has a bit of a stumble. What should I start off with initial timing and what should my A/F be set to for a good starting point. Any help would be awesome.
Actaully it goes the other way a lighter car needs more stall speed to delay the converter hooking up thus the engine is free to get higher in its power band. A heavier car forces a greater delay bfore the converter transfers power.

Gears you need to know what's in the rear end, big blocks came with as little as 2.76 and as much as 3.91. As the cam and the heads got bigger the RPM power band went up. If this is a high ratio rear the engine just doesn't have the torque multiplication through the gears to get this launched hard.

Bogie
 

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Is Cam advanced straight up or retarded? What are the header primary lengths and diameter? What was the piston to deck height ? 600 carb is way too small ( a 600 would be right for a 273), Needs 3.91 or 4.10 gears or high stall converter! What are you looking for out of this engine? If its just to burn rubber put short tires on it!!

Heres a good low budget 383 build to make a comparison to what you have done, factory early block bored 0.030 with the stock internally balanced forged crank turned and polished 0.010-0.010 oil feeds chamfered, TRW 11:1 forged pistons (or similar) with floating pin and 0.010 deck, bush stock rods (6 pack rods are best choice)for the floating pins, 906 heads exhaust port matched to max wedge gaskets and intake ports matched to the intake used, Shim type head gaskets , open plenum Mopar intake, at least a 750 carb double pump Holley suggested, Mopar purple cam .509 lift , stock rockers are fine, 2800 stall and torqueflite big block 727 , 3.91 gear, 275/60 tires MT ET Streets are good, 1 7/8 long tube headers (match header flange to exhaust ports) 18 inch collector, 2 inch primary headers kill bottom end if advancing the cam or straight up, If retarding the Cam go to 2 Inch primary's and higher stall speed and bigger gears!! 10/30 oil (20/50 or 15/50 is a HP loss), run a high volume pump Not high pressure, no by pass! Mallory dual point 4 lobe Revpole , Packard gold strand wires non resistor and copper core plugs, Initial timing around 14 and centrifugal advance about 38 in by 2800 depending on octane of fuel! In a heavy body car like the sport fury 3 it should crack low 12s in a light Body it should be 11s in the quarter! Thats a budget build blue print down to the tires I did a lot of those for street strip cars yrs ago LOL

Now if you could give us as much info as you can on your build like I did we could help you much better!

And do NOT show that blue print to anyone its our secret LOL

Jester (Chris)
 

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Discussion Starter · #4 ·
New issues

Well I may have found a reason as to why the lack of power. I have 440 source stealth aluminum heads with PRW aluminum roller rockers installed. On saturday it was running poorly and this car has been burning blue out the pipes for a bit. Took for a ride and dropped an exhaust valve on 1st bank number 5 cylinder. I shut car off immediately. Pulled valve cover and inspected and saw that a rocker failed. The pin holding the roller snapped and the roller broke free. Found it in the valve cover. Then the rocker forced down and pushed spring enough that the keeper backed out and valve dropped. Pulled the head and 2 small marks in top of piston. Valve was mildly bent. I am replacing it. Then pulled valve cover on other head. Another rocker failed. The pushrod adjustment screw backed out and the force snapped the pin holding roller in as well. Found them in the valve cover as well. The pushrod was laying down in the valley but never fell into openings by the cam. Pulled the head an inspected it. Appears to have been like that for some time as the exhaust valve was coated with oil and the plug was also. hence all the smoke. I am thinking this is why my car has been running soo poorly. I have inspected the cam lobes on both valves and they appear ok visually. What else should I check?

The engine was bored over .30 with stock oversized pistons and molley ring set. Cam is a Hydraulic flat tappet Comp cam with 110. lobe seperation and 268 and 280 duration. My rear end gears are 3.91 I think. They are low gears as at 110kms/hr I am at 3800RPM. The trans is a 727 auto running stock converter.
 

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Well I may have found a reason as to why the lack of power. I have 440 source stealth aluminum heads with PRW aluminum roller rockers installed. On saturday it was running poorly and this car has been burning blue out the pipes for a bit. Took for a ride and dropped an exhaust valve on 1st bank number 5 cylinder. I shut car off immediately. Pulled valve cover and inspected and saw that a rocker failed. The pin holding the roller snapped and the roller broke free. Found it in the valve cover. Then the rocker forced down and pushed spring enough that the keeper backed out and valve dropped. Pulled the head and 2 small marks in top of piston. Valve was mildly bent. I am replacing it. Then pulled valve cover on other head. Another rocker failed. The pushrod adjustment screw backed out and the force snapped the pin holding roller in as well. Found them in the valve cover as well. The pushrod was laying down in the valley but never fell into openings by the cam. Pulled the head an inspected it. Appears to have been like that for some time as the exhaust valve was coated with oil and the plug was also. hence all the smoke. I am thinking this is why my car has been running soo poorly. I have inspected the cam lobes on both valves and they appear ok visually. What else should I check?

The engine was bored over .30 with stock oversized pistons and molley ring set. Cam is a Hydraulic flat tappet Comp cam with 110. lobe seperation and 268 and 280 duration. My rear end gears are 3.91 I think. They are low gears as at 110kms/hr I am at 3800RPM. The trans is a 727 auto running stock converter.
So are these rockers PRW or Pro Comps as stated in the first post?

Bogie
 

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Discussion Starter · #6 ·
PRW aluminum roller rockers. I just got full warranty on them so may upgrade to the steel set instead. Is that a better option?
 

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PRW aluminum roller rockers. I just got full warranty on them so may upgrade to the steel set instead. Is that a better option?
Yes the steel rocker is a better option, they are less subject to fatigue failures which sound like the root cause of the problems you had with the aluminum rockers.

Bogie
 

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. Did this engine ever have good power? Some random thoughts on reading above info... The little 600 carb. prolly have the vacuum secondaries opening way to soon, at too low an RPMs... use 650-750 CFM carb. for best power... the 440 heads may have bigger chambers than 383 heads and lowering compression ratio making the engine feel soggy powerwise... the stock converter my have too low a stall RPMs for that cam size, need about 2500 stall minimum, but correct carb. secondaries adjustment should keep bogging to a minimum... 1970 Charger is a beautiful car but heavy for a 383" size engine, making tire spin harder... taller than stock rear tires reduce effective rear end ratio... stiffer valve springs than needed for cam size can break rocker arms... as can overreving the engine which pumps up the lifters so valves hit pistons, bending valves and breaking rocker arms...


. Shoving pistons into valves can crack pistons, smoosh rod bearings, bend rods, and twist crankshaft... hopefully, none of that happened, you lucked out, and new valves and rocker arms can fix the problems... and maybe different valve springs...
 

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Are those adjustable rockers, and how are you setting your lash on the MOPAR 383 ?

The 383 (and the 426 wedge and even the 413 though both obsolete by then) was blowing the doors off 440s back in the day during actual road tests !! Performance 383s had great RPM, 440s were limited, and the Performance 383s still produced very good torque at that time running on little 6 inch wide stock tires!! The 440s in 74 dropped compression and had great deck to piston clearances No more 383s then only 400s and 440s, The 383 mopars compared to the 440s just like a chevy 70 350 LT1 370 hp stock compares to a 400!

Actual test no mods: Motor Trend magazine page 89 Dec 99.

Stock 71 Roadrunner 383 300 hp 0-60 6.7 1/4 mile 14.8 94.5

Stock 71 Roadrunner 440 triple carbs 385 hp 0-60 6.7 1/4 mile 15.0 96.0 mph

Motor trend was startled and both cars tested had 3 speed auto trans.

Thats an 80 HP difference and the 383 just out revved the 440 !! Now just imagine if they both ran 6 packs LOL:mwink:

Jester (Chris)
 

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An aluminum head with the same size chamber can cause a loss in power if you don't tighten up the compression; give the aluminum head a bigger chamber, and a serious loss in performance can be the result.
 
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