Dyno run/ missing out maybe? Low hp/tq

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ScampChamp

ScampChamp

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Hi guys I got a jasper 383 big block with a Holley 750 carb with a weiand high rise dual plane intake/ an long tube headers. I put my car on the dyno and did just one pull. The car when accelerating seems to almost miss out or run a bit rougher from roughly 3,000-5,000 rpms. I don't know if it's from carb adj/ plug and wires/ ign timing I have no clue anyhelp please and thanks. The motor is super clean and runs great besides that and I noticed it accelerating hard on the highway. So it's not only on the dyno run. Ps the numbers where 187 hp at 4300 rpm and 260 torque at 3300 rpm. Thanks guys !!! mopar or no car
 
What's your combination, what tune is on it? Let's start there.
That 104 temp, doesn't help. I take it ,the dyno operator has no cooling fans.
 
What do you mean by combo and tune? Sorry I don't understand and the dyno operator did have cooling fan but the outside temp alone here in stl Missouri area was 97 degrees today super hot Had to leave car show to change my shirt! Lol thanks for response
 
Combo= combination. This refers to camshaft/compression/ cylinder head specifications. If you bought Jasper,should have a detail sheet/ online specification link. The more important part: what kind of carburetor/intake manifold/ distributor/ exhaust (headers /exhaust manifolds? what size exhaust?). . Who assembled it,set timing( at idle total at 2500-3000 r.p.m. /idle smixture & speed. These all work together in harmony,to make you lay rubber & smile. That's why you have one?(lol). Pictures help in place of explanation at times. Give people here the info,good things can happen.Edit: rear tire size,gear ratio and transmission information ,helps.For what it's worth,ignore that quick dyno pull. All it says,you got work to do...
 
Abodybomber said:
Combo= combination. This refers to camshaft/compression/ cylinder head specifications. If you bought Jasper,should have a detail sheet/ online specification link. The more important part: what kind of carburetor/intake manifold/ distributor/ exhaust (headers /exhaust manifolds? what size exhaust?). . Who assembled it,set timing( at idle total at 2500-3000 r.p.m. /idle smixture & speed. These all work together in harmony,to make you lay rubber & smile. That's why you have one?(lol). Pictures help in place of explanation at times. Give people here the info,good things can happen.Edit: rear tire size,gear ratio and transmission information ,helps.For what it's worth,ignore that quick dyno pull. All it says,you got work to do...
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I believe a "Jasper" 383 is a low dollar engine rebuilder. Most likely a bored 383 with maybe a RV cam. I used to sell "Jasper" engines when in the parts business.
 
Seems to me the dyno operator should have been able to give you a lot more info, at least fuel / air ratio Didn't this "dyno" outfit monitor any engine functions?
 
67Dart273 said:
Seems to me the dyno operator should have been able to give you a lot more info, at least fuel / air ratio Didn't this "dyno" outfit monitor any engine functions?
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Excellent post,Del. A single pull,without information shows the problems . Obviously a sales pitch for dyno time. That's o.k.. He needs to know how to solve it.
 
Did you put a good tune on it before the dyno run? Set the timing to optimum settings and adjust the carburetor? It should be in the best tune possible for a dyno run. Do you know where the timing is set?
 
ScampChamp said:
What do you mean by combo and tune? Sorry I don't understand and the dyno operator did have cooling fan but the outside temp alone here in stl Missouri area was 97 degrees today super hot Had to leave car show to change my shirt! Lol thanks for response
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wear did you have it dyno and what did it cost to have it done? i want to do my dart. thanks mopar65
 
You need to give details about trans and converter . Rear gear ratio. Where is base timing? Total timing? Cam specs? Intake and carb set up? My bet is mismatches on parts and timing way out! Then carb will need work. ALOT. Of great guys here to help. Put on ur thick skin and ask questions and be prepared to LISTEN! Then give the guys the info they need to help.
 
First...Abodybomber asked all the right questions! The more specifics you can give us, the better we can help you. :thumbrig:

So, going off the fact that it was a Jasper rebuild, it may very well be a "low" compression version of a 383. That, and the fact that it may well have a standard head with passenger car valve sizes, will not bode well for "big" dyno numbers.

Keep in mind that a "low comp" 383, even with your bolt-on's and a mild cam, will only produce "real net" numbers in the high 200's. I personally knock off 20% for a chassis dyno, so that brings it down to the low 2's. What I'm getting at is, you may not be as far off at this point as you think.

You mentioned it hasn't felt right, and there's no doubt some tuning can bring it up to speed. Don't get discouraged. Just give us any info you can, and everyone hear will do our best to get you some more performance...
 
I know we have members in your area. Maybe a 12 pack and a little dough could get one of them to come help you tune it.
 
RustyRatRod said:
I know we have members in your area. Maybe a 12 pack and a little dough could get one of them to come help you tune it.
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Great idea......no substitute for experience.

Too bad I 'm not closer....my BS alone is worth about 50 hp on the big end ( just kidding' )
 
RustyRatRod said:
Exactly. The last thing he needs is for somebody to say his stuff is embarrassing.
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im not trying to embarrass him at all.do you know how to do a tune up?do you know how to set the timing? things he needs to know in order for someone to help him.he asked for help,then left??
 
Hi guys I got the car a little over a week ago and don't know much about the tune or combo of the car I'm trying hard to find out more. Looking at the machine shop receipt for the head work it shows the heads are from 1973 and elsewhere it states a valve size of 1.74 not sure if that's exhaust or intake. The torque converter is from summit and the part #is APe 54092 which I'm having a hard time finding specs for. The Holley carb is HLY-0-805085A from summit. Camshaft kit from comp cams is crb 280h pp474 the jasper # is 133710-277923. I understand the first set of numbers is the stock#and the latter is production # The transmission is a 727 torque flight I'm not sure on the axle ratio yet and I have not checked my timing yet gonna set that early this week the dyno was 30 bucks for a pull and it was all donated to charity so I understand slightly me not getting much info beside actual power numbers hopefully this info helps you guys a bit more thanks for all of your help guys!! Means a lot. I take all criticism in a constructive way so no offense takin. Just learning as I go. Ps no idea on carb tuning. Thanks guys you are the greatest. I don't know how to post pictures off my phone or I would
 
HemiDenny said:
Great idea......no substitute for experience.

Too bad I 'm not closer....my BS alone is worth about 50 hp on the big end ( just kidding' )
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HAHA, i don't doubt it...

Scamp Champ, these guys are all getting you in the right direction, tuning will help a lot, do some basic searches on here about timing and carb tuning before you start to tinker and keep us in the loop. Hopefully a nearby member will jump in!

JOE
 
ScampChamp, Nice to see another BB A Body and I agree with Rick, about 225 HP is what would be expected on a chassis dyno for what you are describing and with the DA/Heat. (3,000 DA)

Here are the parts described, just trying to get my mind around this:

Convertor: 2800
http://www.summitracing.com/parts/APE-54092/

Camshaft: 2,000 to 6,000 -
http://www.summitracing.com/parts/cca-21-670-4/overview/

Assumption - This is installed straight up - no degreeing

Carburetor: 750 VS
http://www.summitracing.com/parts/hly-0-80508s

Weind Dual Plane 0-6,000 (is there a spacer)
http://www.summitracing.com/parts/w...jOIQoUHgHJl5uebnfZ7DVQi6Lj6vkXjnj8GgIiBPD_BwE

Ignition: Assumption Mopar Electronic

383 - Assumption low compression rebuild (8.5 to 9) with 346 heads (open chamber)

To me and not knowing the gears, your setup in nice and balanced for street cruising and a bit of performance. Should be fun to drive daily.

Please note, I am not a pro, I am simply imparting what I have learned on my BB Dart (440) - there are many schools of thought and people who are much better versed. and I am I am going by the assumption your knowledge level is on the baseline where I started, so if you are more advanced, please take this thread as me having coffee and talking in the wind (or a blog) and disregard. Sometimes typing helps me learn.

My thoughts - First, Mopar electronic ignition has some quirks, so understand them and learn yours. Orange box is said to advance and retard at different RPM's. Distributors have lights springs. This is a great system though, just need to understand it, this took me a bit.

Timing - I like all in at about 2,500 to 2,800 with this ignition setup with 37* as a start. Low compression motor may like more. I set my timing at 2800 with vacuum plugged @ 37*. Start-up and operations below 2800 may be effected, so you need to balance this.

Fuel - Fuel pressure - assumption is your running a stock pump. Once your timing is set, make sure your bowls are not running out at WOT. I like my fuel pressure at 5.5 through operations.

Also - Fuel bowl heat - I like a spacer between carburetor and manifold, but again hood clearance and all the others items need to balance this. Or even a heat shield.

What temperature do you cruise at?
When you get into it, does your temperature go up and you have a problem cooling?

These are signs of lean, retarded timing etc.

What is the size of your air cleaner?

Hope this helps, please keep posting and good luck
 
joeboy said:
HAHA, i don't doubt it...

Scamp Champ, these guys are all getting you in the right direction, tuning will help a lot, do some basic searches on here about timing and carb tuning before you start to tinker and keep us in the loop. Hopefully a nearby member will jump in!

JOE
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I most def will keep everyone updated as I learn more! You guys are all awesome
 
Cazbah 362 awesome and thanks for the mini research and your guided info I do not have a spacer between carb and intake but I can make one (I work in a machine shop) I know I have room for clearance my air filter is 13 inch wide 3 inch tall
 
First things first. Run a compression test on all 8. Record the numbers and get back to us with them. That will give you and us a good idea of what we're workin with. Make sure you do it with the engine at operating temp. Disable the ignition (remove coil wire). Connect the compression gauge to each cylinder and crank the engine over several times with the throttle wide open, then get your reading off the gauge. Do that for each cylinder. Driver's side bank is 1-3-5-7, passenger side bank is 2-4-6-8. Make sure you record them by the correct number cylinder.
 
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