Hot Rods 383 chev quad webers falls short on the dyno 200hp 248ftlbs

Yep lol

 

How far are the mixture screws "out" from lightly seated? More than 7/8 , and you might have too small idle jet. Opening them more, is over compensating for too small idle jet.

 

Half turn on each from full seat verified the floats even used the Gunson colour tune on it which shows me rich however I'm not going to jet anymore until I get larger chokes 785ccs per cylinder I need larger chokes/venturis I should be running 51idas and I may have these opened up to 51mm bore but this is all just more stuff I'm playing with in my head mind you and I am also looking at these raptor venturis which combines the main and alternate Venturi and basically just dumps gas and air directly in it and gives you the largest diameter you can run with 48idas

 

3/4 to 7/8 is ideal. If your at 1/2 turn, your idles might have to be leaned out. You can run the IDA's on bbc and not have to have 51mm bore. 51 seems kinda extreme for your 383. You could stand to go up to the 40mm chokes and tune around them. Before I'd do another ch***is dyno, I would invest in a wide band O2 sniffer. Less than a day cost on the dyno, and it yours to use when ever you want. The 14.7 to 1 that is mentioned "perfect" might be a bit lean on the top end if you get your air correctors too big. 12-13:1 air/fuel would be safer.

 

The dyno cost isn't that bad my buddy runs the one I just went to so I get a little more play time then the average customer

 

But yah I'm picking up what your saying I've been told 42mm from a guy on the gt40s site since that is where most of the weber folks hang out and trouble shoot and there is an individual who has a build sheet for this "As an indication I have a build sheet for a 365 cu in chevy with 48's, 11 to 1 comp, no jetting info unfortunately. Cam on 112° lobe centers, 300° duration, .465" lift, 76° overlap. 491hp / 405 tq. As Howard suggests you might have a spring issue, is there any visible standoff or reversion above the trumpets thru the rev range."

 

Back in the Can-Am days of 67-68 those mild 350's that Bartz & Traco were building, put out 525 hp all day long using the 48's

You are leaking about 200 +hp someware and even if it is dead rich you should be up a ton more than 200 ?

Hope you find your problem

 

Me too lol I know I've read lots about webers on fords and chevs and vws putting down decent numbers on the dyno so I know I am losing somewhere but where that is the question too many variables to pinpoint

 

Are the IDA's synchronized? That's one of the details of tuning multiple carb setups that trip up a lot of people. If they aren't opening and closing at the same time, you'll experience all kinds of weird tuning gremlins.

 

Yes fully synced with my synchrometer and shops sync both read the same across all 8 barrels and no drop before we ran on the dyno

 

Pretty much covered already but yes.. venturi's are too small and wide lobe separation (112-114) with webbers and I also think a good wide band is the best tuning tool you can own.

 

I has a recent discussion on "Speed Talk" about the effect of gear ratio on ch***is dyno power readings. it seems very little effect . I run my race bike on the dyno a lot and usually in third gear on a Superflow inertia dyno.. The experienced operater says gear ratio isn't important... http://speedtalk.com/forum/viewtopic.php?f=1&t=44142

 

I applaud your will to test, test, test, and then test more. Tires; is there any chance that there's a slippage issue? I'm asking because of the difference YOU feel in YOUR car vs what the machine says. I will say, like others have, the drag strip is the best dyno on Mother Earth. MPH NEVER LIES. Throwing more **** in the game, some drive lines eat way more power than others. A 9" Ford gear is far less efficient than a 10 or 12 bolt GM due to pinion placement. Even 4 spds (direct mechanical connection) can **** away power. Just hearing it in those short vids I'd never think you're losing that much TQ by the time it gets to where the rubber meets the road. I suppose a test n tune strip night is out of the question due to lack of safety equipment (roll bar, 5 pt harness, etc), but if you have any powersports connections they use radars and GTechs like was suggested earlier in the topic. As I recall both are very accurate. I used to know the equation for converting 1/4 mi MPH to HP, maybe have it in a book somewhere. I don't like ch***is dynos for some reason, maybe because I'm jaded by their use on snowmobiles which I never felt was anywhere near as accurate as a good 1/4 mile blast and a calculator. Engine dyno? Sure, real deal but still can be fudged.

Love the Webers too. Once tuned I'm not sure anything tops their ability for naturally aspirated HP, and that goes for the other styles as well (Dellorto, etc). Not sure any of my comments will net you a single thing, but good luck and thanks for sharing.

 

Man you really think you need 51's for a stroked small block? Something majorly funky is going on somewhere in your set up.....those 48's should be more than enough for your motor. Like others have said those Ford GT 40's had no problem making HP and wining races...as well as the Shelby Cobras. My experience with them were on VW motors...my car idled great, and had plenty of power through out aall rpm ranges

 

Thanks that was very interesting.
It sent me off on reading extravaganza to learn more about dynos.
There's a bunch of stuff that logically just doesn't make sense, I thought I understood it but now I realize it's quite the iceberg.

One particular discussion I came across had showed that a change to numerically higher gear ratios actually calculated to less torque and HP on the dyno but resulted in both a faster ET and a bump in MPH. The proof is in the time slip, the wonderment is on that dyno sheet.

 

On the dyno I hit 140mph in 13 seconds on the graph I can get a chart from the shop that shows that we don't have a track near my local and the car draws enough heat so I'm an angel when driving it ... Lol

 

For more info just Goggle "does gear ratio effect dyno power reading " There's a lot more info... I find the dyno a helpful tuning tool that got me ahead of the compe***ion with just a few changes at the track. Tuning for wide open LSR is easier than for a street engine that must have good low speed manners.

 

IR, 27 posts, no cam specs...

Speedtalk is where I go when I have an engine tech question...

 

Be curious to hear solution to your problem, that should make 350/400 HP 400 torque, no problem, no way do you loose 1/2 thru driveline loss to tires, do not know anything about that type of carburetion, try different intake, carb, check cam timing, a retarded cam let's the motor run, will sound OK, but will kill perfomance, just a suggestion, understand your frustration.

 

If its a comp, and its not a 'race" cam or "thumpr", its on 110.

Man, I don't even wanna THINK about what a complete cluster **** a Thumpr would be with IR. Narrow LSA AND a delayed exhaust closing...

 

Pull the motor and do a flywheel hp dyno pull.