biggest improvement I've seen is when I went from a 414(360)stock block 230indy cnc heads 10.5compression 630/270@50 cam in the dart it ran10.40s .everything else being the same I built a 436R3 short 13.5comp and 700/276-280@50 cam and ran 9.7s consistent.2points in comp little more cam better block rotating etc picked it up quite a bit.

Which motor, SB,BB or Hemiroid
Tuning and air flow has made the best improvements on my motors
No two men are equal, same thing on race parts

What I know works: less weight, more compression, make the engine as big as you can. So I started out with making my car as light as I could while maintaining the look I wanted. 3350 with me ready to race. Then it got a 15-1 572. The 5th full pass the car ran 9.3x. Since that time (630 passes) it has had engine maintenance parts. But still has the same heads, compression, cam,& rockers, headers, carbs and intake. Learned what lives and what doesn't. Pac valve springs, Isky bushed lifters, Landrum rear coil springs, Molnar crank, US gear pro gear have fixed any problems that have occured. Maintenance is very low. Same type tires (M/T 10.5Wx31) and overall weight. Swapped rear gear from 4.10 to 4.30 no real change. Aluminum high drum replaced a billet steel unit along with lightening the sun shell. This was worth nearly a 7lb reduction. It was also worth close to .10 in the 1/8th. Various converters picked up .20 putting the car in the 9.0x range. Shocks and springs have helped consistency but really haven't made the personal best any better (1.25, 5.72@121, 9.00@150). Though they sure have helped to put the car in the winners circle. In ways I'm a lazy tuner. Never really chased jetting, lash, timing. We've moved it a little with no real improvement. However nearly every trip to the track for us is a race. Our testing is usally limited to put the car on index or adjust for poor track conditions. We are focused on that. Cant win with a car that won't repeat.
Doug

I will totally agree with the converter. couple times I did things that I knew should have picked up the car, but it was like it had a governor on it,. changed the converter and boom several tenths improvement. And I will also say that while I always give all the info asked to the converter companies, I never get the same recommendations from different companies. If the science was good I should get the same basic setup recommendations from every company, but every company gives me a different take on what the car needs. So in my experience you simply have to buy several and sell the ones that don't work out. For example I have asked for advice on camshafts from several companies and the grinds are usually very similar, so I trust those recommendations and just go with the best service. But to answer the post, if you want to see big changes better cylinder heads and more cubic inches, most other things are usually just small increases in performance. And in my experience many times the small things you change may not show quicker ET slips, but I see improvements in consistency, which tells me there was an issue that needed to be fixed.

just throw it together like i do,only people that make over 6 digits can aford dynos and be so anal about everything,im a average working man,i cant spend all that big money

I second second this!

I sealed my 6PK scoop to my carb... worth a tenth and 1.5mph. Removed it and jetted down, lost everywhere...jetted back up and gained some, sealed and gained all back. Jetted up from there with it sealed and lost.
Working on the car, specifically the front and rear suspension, and launch were the biggest gains.

Found the same exact thing with my air pans. Guaranteed 1-1.5 on both cars I tested them on that have 6 pack scoops. The hemi scoops would probably pick up 2 tenths lol.

Never picked up so much for so cheap.

You may have had good results without, and I suspect you have based on your response but wouldn't say dyno time is only for rich people.

Isn't that expensive to baseline your combo and do testing from that point on.

Isn't the track the best dyno?
It took me awhile to figure out I could not make drag race motors get the best tune on a engine dyno sitting still inside a dyno room

Cam tming. We experimented with a symetrical pattern comp cam around .740 Lift with 1.6 arms. We retarded it 4 degrees and picked a solid 1 1/2 tenths no other changes. Easy enough to do with a Jesel belt drive. FWIW the Indy CM3 (Asymetrical) in there now is best straight up. Don't ask me how I know

I agree overall light is right, but placing weight in the correct areas will be a benefit.
I got a few of those weight tubes added lead shot and scaled the car. Got the car to 49% front
51% rear. More consistent 60 foots and a tenth better et.

I agree with the converter comment very much. Also the 727-904 swap is worth ET every time.

If the converter is correct it almost washes out rear gear choice. I went from 3.91 to 4.56 when I broke my 3.91s. The time slip didn't change hardly at all, it was spinning lots more RPM in the traps but that's it. I have seen other people with a good converter do the same type changes and net nothing ET wise. But a car without "enough" or "the right" converter will usually move a fair amount of ET with gear changes.

What worked best for me back in 1991, my '69 Cuda 3300lbs with home built 446ci motor, 6pk bottom end, Team G, 850DP, 9.8:1, 4800 stall, stock 906's, ran a best of 11.2@118+. Did nothing else but bolt on some 2.14/1.81 906's mildly ported to around 260cfm with HS r/rockers and went 10.7@125 first pass NA. Was running the old MCandless .650"/290@.050 sft cam, and they say it needed 12.5:1 to work, how much faster would it have gone@12.5:1, not that much more I doubt, perhaps a 1/10th?...and there was quite a lot wrong with the car, too loose front end, would top out and not enough air in the 32's to name but 2, would've been a 10.5 car with those sorted.

I learned things on the dyno that wouldn't have been nearly as obvious if all I was going by was an ET slip, a really good example being valve train instability issues.

I learned things on the track that the dyno wouldn't reveal, in one example being two carbs that dynoed virtually identical, but the one that had better shift recovery on the track being worth .1+ MPH and .1+ quicker.

The OP mentioned straightening the lifter bores... Assuming he means bushing them along with blueprinting their locations, I understand the oil control benefits. But is there a measurable performance improvement?"

EDIT: This is of interest to me because my current block has had the lifter bores corrected bushed, but it's "tired" and the cylinders couldn't take anything more than a re-hone during the last rebuild. I've got a freshly machined block to replace it, but the one job the shop that did the work wasn't equipped to do was the lifter bores. Not sure if I should plan to haul it somewhere else to get that done, or build it as is.

Another thing I tried was 2 Pro Systems 750's in place of the Eddy 750's Plug check looked good. Gained 1 mph and .05 in ET. Not worth the cost to make the switch.
Doug

Well, straight push rod angles, 55mm cams, vacuum pumps, dry sump systems, rocker arm geometry, heavy vs lightweight crankshafts, steel vs aluminum rods, ring packs, ect. all effect longevity IMO. If you want to make more power, add CI, heads, camshaft, compression, and fuel system that works with the CI you choose. Then match the converter to that combo.
Weight of the car is always a factor as the old saying goes, "less is more". That said, lightweight crankshafts only RPM faster. They don't really make more power unless you're a comp eliminator guy and use 7" converters and even then the improvement is minimal. A center counter weighted crankshaft weight a lot more than a non center counter weight weighted crankshaft, but it is much less prone to cause main cap chatter.
Look at the stock/super stock/comp eliminator guys. They get the most out of their parts, and they are pros at picking the right converter for their combo. That is the key as mentioned early in this thread. JMO
By the way OP, this is the best post I've seen hear in a long time!

Yes and yes.

hoping i cam get my charger out this year, first time since 2007.
hoping i can crack the mid 11's with .030 over 440, 11.5:1 RPM heads, 3.91/29" tire. [or close ]