No power 383- built similar to HOTROD HT383 build

I built a 383 that's almost identical to the HOTROD 383 where they made 460hp and 500 tq. Problem is this things a slouch and doesn't make any power down low, and only slightly more starting at 3000.  By none i mean it pretty much falls flat on its face from a stop or a roll taking 3 or 4 seconds to even get to 3k rpm, feels about like the 190hp sbc that came out of it.

Heres the HOTROD article
http://www.hotrod.com/techarticles/gm_ht383_crate_small_block_tune_up/viewall.html

Its an early sbc in a 76 chevy pickup with

-eagle 383 stroker kit, oprox 9.5-1 compression with vortec heads
-patriot fully assembled vortec heads
-Howards marine cam hydraulic roller tappet

                   1,800-5,400 rpm
Duration at 050    224 int./230 exh.
Valve Lift    0.501 int./0.509 exh.
Lobe Separation    112

-Comp Cams Ultra Gold Aluminum 1.6 rockers
-Converted over to roller hyd lifters
-Edelbrock Performer intake (so i can run my quadrajet)
-Summit $99 cheap long tube headers with dual exhaust
-Quadrajet 750cfm carb (also tried my Demon 750 and the engine did the same thing)
-HEI dist. with all new plugs and wires (the plugs that Patriot said to use with those heads)

-stock turbo 350 trans, 3.73 gears.  I know a higher stall and shift kit would help but i'd rather get the engine running correct before i get into that.

I degree'd the cam and its right on, I have the distributor set up so with the vacuum advance unplugged its 15 deg advanced at idle and 32 deg max.  I went all the way from 28-38 deg advanced and it seemed to like 32 the best.

What could be causing my serious lack of power? The cam and spring pressure should be matched up but its right on the edge, but weak springs shouldn't cause low rpm sluggishness, can it? I know if set up right there is nothing wrong with q-jets and i want the economy they give, my air/fuel ratio meter shows its almost right on the money.  Like i said before, when i put the demon on it, it did the same thing.

any ideas?  

i ran about the same size cam in a 1/2 ton truck a few years ago with the same tranny & gear.   same problem,... the power didnt come in until around 3,000rpm.   imo, trucks can use alot more rear gear cause the tires are taller than a car.   if you want bottom end grunt, get a smaller cam.     just my $0.02.  
JOE,   pro, shade tree, redneck, get her done!...welder

Its a 2wd pickup with 28" tall tires.  If my engine were to have even close to the power as the one in the article (400+  HP at 2500rpm) then i don't think that would be a problem.

thanks for the thought though  

Hi there,
 I would be looking at the exhausts from idle to 3000 with a friend.
 I believe this problem to be associated with fuel supply and a bit
 of timing guess work. Similar is NOT the same. My 2 cents worth is this...

  Set the dizzy at 12* to 32/34*
  Check fuel pressure and pump at all junctions..Take note of +s and -s.
     Stand back from the issue for an hour..Have a DE- Caf Coffee.[ ]
 and re-think the situation before another road test..Good luck..Skyeking
      Hi Junkman and the Gang :        
skyeking

Had that exact same issue with a engine a while ago. I ended up finding that my timing mark on the dampener was slightly off.  that said, my $ is on your torque converter being to low of stall...  It just takes time and lots of tweaking.  

Hi there,
 I can't believe that the cam mentioned needs moore than 2400
 as the gearing is adequate for the O.D of the tyres..Just how
 hard are you going to push this combo..Most of it makes good sense.
   Time for revision in ALL departments. You are so close....  
skyeking

I kinda thought of that too, I went from 28-38 degrees 1 or 2 degrees at a time, and test drove it in between without much improvement.  

For the other replies about stall, i know a higher stall will only make it better, but my old 190 horse engine had maybe 100hp down low and accelerated quicker than this new engine which should have at least 2 or 3 times the power.  

Hi there Agent Splett,
 Work without the stally equation fora while.
 You could try a set of earlier advance weights AND pivot
 bushes or maybe a new KIT...Keepin Touch...Skyeking..  
skyeking

something has got to be off,,,,,,,,,,,, there is no reason that this build should not twist the axles in half!


 I know this may sound amateur but are you absolutely sure the cam is timmed correctly?????

the only time I EVER built a lazy engine was when I timed the cam wrong, (that motor would not spin in wet grass!!!)

however upon checking I found the problem and that changed it into a tire roasting nice street engine.

or even easier,,,,,, are you sure the valves are not too tight??  I have also seen this cause weak engines  

 I dont mind hearing my engines "click" a little when new cause I know my valvtrain is set very close but not too tight.  I always re adjust after the break in

Just food for thought,,,  

I put a cam in a 400 1 tooth off one time and it was so weak it would barely get out of it's own way until I corrected the problem. Made a world of difference. sounds like you have to go back to square one and check everything again.  

Hi there,
 I agree that if the cam is Spot on then the valves can be too tight.
 Don't be afraid of an early start up click that only lasts a few
 seconds as it will hurt 0000.
 If there is no spit back or backfire through the carby then you
 must be close...Without being there I cannot suggest more than the
 other Guys have already mentioned..  Keep in touch...Skyeking  
skyeking

.. Do you have a tach? So you can see what the actual stall RPM is on your torque converter when taking off?

.. This motor is NOT going to have "3 times" the low RPM torque of your previous motor! Make no mistake, it has a rather big cam. Unless you have a premo carb. with annular boosters or EFI, you're not going to see big torque at 2500 RPMs or lower. And we are talking torque, not HP... Out here in the real world, it's going to need at least 3000 RPMs or more to start pulling really hard... also, it should pull hard to 6500 RPMs... not 4500 RPMs like your previous motor... it needs headers and at least 2 1/2" true dual exhaust and turbo mufflers or better... If you had a 350 in there earlier, despite only being "190netHP", it prolly had about 330-350 gross lb.-ft. of torque at 2500 RPMs... as compared to prolly not much more torque, maybe even less, at 2500 with that big cammed 383... maybe around 400 gross lb.-ft. with things adjusted ideally... 400 lb.-ft. at 2500 RPMs also calculates out to 190 grossHP (by co-incidence)... more RPMs are needed for more HP... since HP is a 'calculated number'... RPM x torque divided by 5252 = HP ... RPMs and torque (twisting force) can be measured directly... torque is what you feel taking off... but HP is the result of a calculation...

.. Also, put a 383 under a 350 Q-Jet and the secondaries are prolly going to open too soon and give you a BOG in power... adjust the secondaries air door spring up top so the secondaries air door doesn't start to open till about 3000 RPMs... you'll prolly also need a bit bigger jets in the primaries and thinner rods taper in the secondaries... contact The Carb. Shop or Sean Murphy for recommendations on that...  

The cam is rather big for the application.,. a common mistake that's often made.
Too much cam and too much carburetion, coupled with poor gearing and heavy vehicle = soggy low end performance, every time.

 
When The Flag Drops,,,



The Bull Chit Stops,,,

P. Engineer.,. Engine Builder

+2  



Professional Hi-performance engine builder

.. At least SPlet sensibly went a couple cam sizes smaller with a 224/230 instead of the full race 230/236 used in that article...

.. Hopefully, a secondaries air door adjustment can bring some measure of satisfaction... I suspect that is most of the problem... along with a tight torque converter... maybe the rear isn't actually a 3.73:1... or the torque converter sprague is stripped out...

.. Even with 28" tires, this setup should storm off the line pretty strong, maybe have a slight bog about 20' out as the torque converter multiplication disappears, then pull strong some more as the engine 'comes on the cam', chirp the tires into 2nd, and have an additional 2,000 RPMs in each gear...

.. Where are you located and what kind of speed in MPH does 6500 RPMs give you in 1st gear?