I am getting ready to modify my govener to get a later shift. Instead of guessing I have thought about getting the car on a dyno first. Would it be worth the extra $$ to be sure?? John
The dyno is a great tool to figure out your shift points. I'd spend the cash and do it, make sure you get a printout with wideband so you can check your tuning. Dyno time is also great to figure out your optimal converter size :Brow: Don't get disappointed by low hp/tq numbers, if your air fuel ratios are correct it will dyno lower than a car that's lean, but run better at the track. I went 11.6 in my C5 with only 334 RWHP, at a 3400 lb race weight....
Waste of money Hi John: I don't feel that dyno to determine shift point would help much. I have altered Govenors for years and found that these big block are about as strong as they can get at or about 5500 RPM with a good cam and carb setup. With a great cam and carb setup, 5800RPM to 6200rpm. Stock valve train and carb 4800 to 5000 rpm is a fair guesstimate. If you: 1. Drill 4 -.250 holes in your fly weights one just inside each corner of the weight. Drill one in the middle if you need more rpm's. 2. Cut 1.50 rings off your weight springs. Don't cut your springs unless you need more than 5000RPMs 3. Grind the sides of the inner spring retainer plates inward to the spring positioning risers. With these mods you are at 5500 to 5800RPM, right where you want to be. Start small and drill and grind until your engine likes it then quit. If you screw it up govenors are cheap, do it again for practice. Weekender :TU:
Weekender, Thanks for the input. I all ready bought a mod kit, but I may break out the drill first, I have a couple governors. TH350, the 455 has high miles and a mild cam. Stock valve train. Qjet is jetted nicely. Dave's HEI and nice exhaust through manifolds. I think the 4800 shift is hurting my times, but I do not want to rev it to high. I am thinking 5200rpm. Dyno is $140 for an hour. JP
Why don't you try holding it in first gear manually to 5200, and see if your ET improves? A simple test-n-tune at the track might be cheaper than a dyno session (although you can learn other things on a dyno too). -Bob Cunningham
I want to do this modification also........I wonder if it would affect the part throttle 1-2 shift also? o No:
Part throttle shifts are not affected but you might wanna firm up the shifts because the wot shifts with the "slow" stock shifting gets a little hard on the trans in a heavy car. I have yet to break anything but the shifts "feels wrong"
John are you using the TH-350 trans.? If so adjusting the kick-down clip at the pedal will change your shift points as well. Obviously this is quicker and easier than governor modifications. Another note, lighten the governor weights for later shift but only mess with the springs if your 1-2 and 2-3 shift points vary. You may want your shift points early for the dyno...to get a wider rpm reading, this will help keep the kick-down from kicking down. Then re-set the kick-down clip (again if you have the TH-350).
TH350. Lite throttle shifts are quick. Mid throttle is about right. WOT is to soon. Kick down works perfect. Shifts are tight thanks to the trans-go shift kit. It will turn the tires going into 2nd and I have even had third gear chirps on a smooth freeway surface. JP
I hope you rent the dyno for ALL day. Getting into the trans is always followed by getting into the trans. I would recommend setting your 1-2 wot/auto shift on the road. This won't cost you a dyno day. This will be easily done without a ticket, depending on your exhaust system's advertising ability. When 1-2 is set, 2-3 will be within 300rpm wouldn't you say? You can always manually shift 2-3. You have enough time to do so. Save the coin and aggrivation.
Why would someone need to sit on a dyno all day and take their car apart there? Making 3 pulls on the dyno will be enough to show where the engine is making power, and you calculate the optimum shift point. After you have the numbers, then you can adjust the shift points later. Making sure the shift points are where you want them on the road will be trial and error, there's no reason to sit at the dyno for that. The dyno is good for collecting the required data to get the most out of your combination.
I misunderstood. I've never heard or setting shift points from dyno data. I thought everybody did the same thing I did by setting shift points at max desired engine redline. Did not know I was doing it wrong. Also, I thought the reason the dude wanted to set shift points ON the dyno was to avoid street drag racing to wot a 2-3 at 80mph. Anyway, when you get your dyno data and your have your graph in your hand, how do you determine at what rpm you want your trans to shift? 300rpm after peak power? Wouldn't you feel the motor lay down on the street and shift it by the seat of the pants? It's a waste of money plain and simple. It's not about data collection and analysis at a later time. It's about feeling what your Buick is doing and shifting when it starts to lay down. You don't need to watch your tach. It will be the same rpm every time. Stick around C5, you'll learn. Buick guys are just a little more down and dirty than your Corvette owners.
Well i know in a normal dyno session the car isnt right thru the gears at WOT, its usually worked up slowly then floored in high gear, i know you can have them do it whatever way u like. when i did my governor i ground the weights put it back in and took it out for a ride, and repeat till you get the results you desire. i'd say get it as close to 5500 as you can, the best thing about doin this is you can drag race in D and not have to worry bout missing a shift.
I'm with Shawn on this one.......I've never driven down a dragstrip but never turn down a good challenge :Brow: Last time I raced someone, I was so glued on the road, I up-shifted way too late.......I didn't see my tach but I had to be revving at least 6 grand.......I didn't plan on revving my new motor that high but it sure felt good blowing past that Pontiac with full guns blazing.......and he even had a head start, I didn't think he wanted to race! Looking back, I was so surprised at how bad I spanked that thing that I could well have slipped her into N from L1 instead of L2........that would have been embarassing.
The whole idea of adjusting my governor is so I do not have to shift the car. I almost blew it up once trying to shift it. Call me a p_ss, I don't care. If I dyno the car the guess work would be done, plus I would know what my car has. I guess it was a dumb question. I found a shop that will do 60 minutes or about three pulls for $70. In my book there is a value to being able to floor board the car and have it shift where the power is. I am just trying to get my rag top as close to 14 flat as possible. Thanks for the replies. John
I've found that the best shift point is about 10% past your peak power RPM. For example, if max power is at 5000, you would want to shift at 5500. The data gained from a dyno pull would be useful to calculate the shift point, which is the point I attempted to make. I have enough experience on the track trying to get every last hundredth out of whatever car I'm racing. Doing your homework pays off, sometimes you put together a combo and it's almost dead on but I'd rather know for sure. My C5 ran the 11.63 with a stock engine(valve covers never off), gears, torque converter, and tuning through stock exhaust manifolds, cats and pre-cats. I guess the dyno time paid off. With regards to your "down and dirty" comment, you'd be surprised just how into it I have already been. Most Corvette owners are a bunch of non-driving waxers who don't know one end of a wrench from the other, but don't lump them all together. I did all the work on my C5, with the exception of computer programming(expensive equipment), myself. That doesn't matter a whole lot anymore since the C5 is sold already, and I'm right back into my Buicks again where I started. I simply used the C5 as a point of reference to show that dyno time and other research pays off when you want to realize the full potential of any combination. If you'd like to further debate this, shoot me an email as I enjoy technical debates with individuals like yourself who can present their viewpoints in an intelligent manner :TU:
