383 SBC quad 48 IDA 200hp 248ftlbs ???

hey do these numbers make sense to you guys
pulled a dyno 200hp and 248ftlbs


383 small block Chev 10.5:1 compression
Brand: COMP Cams
Manufacturer's Part Number: CL12-212-2

Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 2,000-6,000
Intake Duration at 050 inch Lift: 230
Exhaust Duration at 050 inch Lift: 230
Duration at 050 inch Lift: 230 int./230 exh.
Advertised Intake Duration: 280
Advertised Exhaust Duration: 280
Advertised Duration: 280 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.480 exh.
Lobe Separation (degrees): 110
Lifters Included: Yes
Lifter Style: Hydraulic flat tappet

I am running 20 initial 38 advance all in at 3000 rpms
37mm chokes
f7 emulsion tubes
135 fuel and 120 air
120 70f10 idle
 

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Disregarding the Dynojet numbers for a start, at 383ci your a bit small on the venturis (37mm ), my weber data suggests 42mm or even 45mm for a competition car, also you are in Airdrie which is about 3500 ft up to complicate the issue. A change in venturis is going to mean a complete change of all jetting to suit. Some guys on here who have followed the party line on webers will suggest that the 110° lobe center on your cam is not suitable- jury is still out on that one as far as Im concerned.
As a quick check I would borrow a 4bbl intake and ~600-700cfm carb to use as a reference and trouble shoot for other possible engine problems first.

Always wanted to do a quick tour of Canada to visit all the RCAF bases that my Dad trained at during WW2, named some of his race horses after them which was a mystery to us until much later. Think I might have left my run a bit late for more overseas jaunts though.:)
 
Thanks for the response I do have other jets and I'm going to be getting new chokes Can you run weber idas without any chokes in them at all?
 
Gotta have chokes, big fire looking for a place to happen without... apart from the likelihood it wouldn't run much above idle speed, once you crack the throttle blades above fast idle/progression holes signal drops off and as chokes are not there no signal in main venturi means no further fuel flow. !!!!!
Seems to be some discussion on actual HP figures obtained via dynojet and correction factors reqd to equate to flywheel HP and other dynos ( one website suggests adding ~140 to your 200 then divide by .85 which would give you 400hp? ), what is your seat of the pants feeling? I don't really get into dyno results comparisons, prefer to think of them as a tune/fault finding tool after you have checked the basics first, too many variables when comparing car to car especially in hot rod stuff like your example.

Just watched a video from drone/camera taken around and inside hangars at 'Vulcan' base... all empty and about as much snow as we have here at moment... seems such a waste, could do with one hangar here at my place!!!
 
The feeling I get when running the car is it cocks sideways when I I shift from first to 2nd doing 45mph at 6200 rpm and the wife gets butterfly's in her stomache when I mash it now as you can see by the dyno my power stops pulling at 5000rpms but I spin to 6200 all day long and to me it feels it's still pulling so far the only two cars I have had to actually try with when getting on is a 458 Ferrari and I stayed beside him gear for gear then I played with a tuned up Lamborghini mercalago and he pulled away like I locked my brakes up but I bet that car was putting down mad power to the street

By the way these are the jets emulsion tubes I have to play with
F7 f16
120,225 air
135,200 fuel
120 air idle
70fuel
65 fuel

Thanks for the help
 

Glenn B.

Lifetime Supporter
You are WAY under-carbureted! What kind of AFR and exhaust gas temps were you getting?

Yes, you can machine your vents, but the better ones on the market actually have a taper in the throat out to the maximum measurement. Not sure how a straight-through cut would perform in comparision.

What heads are you running? I have a 383 w/ Weber IDA set-up in my Lola. My compression, heads and cam are a bit more radical than yours, but I am running 42 Vents, 170 mains, and 200 airs.
 

Ron Earp

Admin
I've been using Dynojets for 15 years now. I don't own one of course, but dyno tuning has always been a bit part of my racing program. Just with the V6 Mustangs we've been developing we have a combined total of 185 runs with that engine program, not counting all the other cars we've done.

In general it is accepted to be about a 15% driveline loss for most RWD cars and I don't think your GT40 would be significantly different. Additionally, I can't see if your data is SAE corrected or not, but even so that doesn't effect it tremendously unless your density altitude is way off STP. That'd put your SBC at around 230ish crank horsepower which seems really low. It's not even producing a huge amount of torque either.

Naturally I'd defer to Jac about suggestions on the Chebby. I'd inquire with the dyno operator if there were any problems with the drum, tire slippage, or other problems. Tire slippage is detectable in the dyno plots as a change in slope but it won't make a 350rwhp motor show 200rwhp. We have fought some tire slippage on our relatively low hp V6 cars as they're always wearing race slicks and the dyno drum sometimes doesn't do well with them. Good luck and let us know how things turn out.
 
Ok thanks it was a dyno pull at the car show just a base pull he didn't care about how the engine actually performed or what to improve on CF STD smoothing 5 if that makes sense run conditions 84.69f 26.73 in-hg humidity 15% std:1.14 right now my main venturis are 37mm wouldn't just having my machinist buddy open them to 42 and taper to 44? Would that work? I have a another dyno run booked for the 21st at the VW performance shop they deal in webers and VW stuff and have jets in stock that we can run and I can buy what I will use
 
I used to own and run a Dynojet facility so have a modicum of experience. The dynojet software and control system corrects for intake temp, air pressure (inc elevation) and humidity. Results can be output in Din or SAE (slightly different correction factors). Trans losses (negative horsepower) are measured on coastdown. Most of my transaxle experience was with Porsche units which seemed to consume about 35 to 45 bhp ( roughly a 10% loss). If the dyno was being operated correctly it is hard to see how a good 383 could produce less than 400 lb/ft. Could it be that the operator simply wasn't using all the throttle travel for some reason?
 
Yah that's what I was thinking like I was saying before there is no way a 200 hp car keeps toe to toe with a 458 Ferrari unless I'm 800lb car maybe if you check out my Instagram you can hear the operator is not in it all the way but the readout reads 5500rpms so his machine is wonky or my tach is out

29roadster666 Instagram
 
It is possible to set the rpm pickup incorrectly by entering the wrong firing interval. A quick comparison of the dyno rpm readout and the vehicles own tach would show any error.
 
Yah you can see by the video first link he doesn't look at my tach I was waiting for the mashing of the gas pedal that never happened
 
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