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Sorry to highjack but while where on the subject.
I know of a chassie dyno pretty close to me and not very expensive but...
The guy have not lowered the rollers into the floor. So the car would be very tilted forward.
Would that effevt the carb in abad way???
I belive so cause the float levels would be very off.
What do you guys think???

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Agree that tilted forward will effect the carb. A tilt back would at least be similar to the effects of acceleration. Floats are fairly centered and should not be too much effected but the fuel levels relative to the emulsion holes, etc will be - and this will effect the fuel curve. Likewise the fuel level above the front jets will be lower. Not ideal for a baseline.

To the OP: Useful - yes. Degree of usefull depends on planning the test sessions. It's usually a lot more $ than going to the track, but it lets you focus on tuning. So I think its a good start if you can afford it.

Bring jets, secondary springs if relevant, etcs. Inertia only dyno is really best for tuning WOT in 3rd or 4th gear. My preference now is to take a two runs and then disconnect the secondaries and jet in the primaries. Then add in the secondaries. Possibe detours include adjusting the timing and adjusting bleeds.

On the ride back home, be prepared for the possiblilty that the primary jets are too lean during steady highway cruising - the engine will surge as it comes off the transistion (somewhere around 3000 rpm). For this reason, I now tend to err on the side of rich when on the dyno.

In my experience, having the Innovate WBO2 will provide a quicker and more detailed response curve for AFR. Tailpipe sniffer is OK, but the bungs are nice for street and strip use. However it is almost a requirement to also have rpm recorded. With a typical dynojet WBO2, expand the vertical scale so AFR from 12:1 to 14:1 takes up at least half the screen. With AFR I'm looking for a flat stabile line and the AFR number is mostly a reference point to best overall torque and HP curves. As you can see in the above image, at least with dynojet - sometimes its easier to read using the MPH vs. HP. Ask for a copy of the files and software reader.

Here's an Innovate data overlay showing that the primaries providing a flat AFR curve but the secondary side is not. Dynojet data shows the same thing. I'll try to attach.

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I use my engine shops chassis dyno often.
It is extremely useful for comparison use . I dont get goo wound up over actual rwhp shown . I look at afr to get in the ballpark . Comparison on changes , gain or loss .
Best use is repeatability right in front of you . You can do jetting and timing loops quickly and easier.

Tex

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The drag strip is so packed anymore that you are lucky to get 3 or 4 runs in, and they are usually hours apart making it hard to see consistent back-to-back comparisons. On the chassis dyno, I can change jetting and timing several times in an hour, and at least have a known starting point on the tuning.
On the 500" stroked 400, i re-used the 950HP carb and jetted it richer for the larger engine just to be safe. Took the car to the chassis dyno, and ended up with about the same jetting the 451 was using. What the chassis dyno did not show was the carb wanted a bit more accelerator shot, so at the track, I changed the pump cam to the green one and it helped a slight stumble off the line.

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If i go i will try to find the best power with timing and to get a flat a/f curve.
Then change jets at the track for most mph.

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