I have a big block and I just got a th400 built and have a 2600-2800 stall, gear 3:90 and a single plane intake. Its a street/strip car but the car see more of the street than the track
Some Modulators are adjustable, small screw inside tube where Hose connects. It will give a small 3-5mph range.
For more adjustment you'll need a Governor Recalibration Kit. B&M Governor Recalibration Kits 20248 - SummitRacing.com
Modulator needs Full Manifold Vac, not Ported/Timed Vac source.
Really? There are NO provisions on that intake?
There is usually one on the rear face of the manifold, below the carb mounting flange. If not, that's where I would CAREFULLY drill and tap a 1/8" NPT hole for a small vacuum hose-barb.
You may be able to do this by simply removing the carb and taping off the intake runners to prevent any material getting away on you. Drill and tap the hole, and then vacuum up the debris.
Use extreme care when tightening any pipe thread fittings on an aluminum intake, as the the thread is tapered and can crack the intake if over-tightened.
I recently did the governor mod on my th 350. Im all smiles now. Regular part throttle shifts with full throttle 5500 rpm shifts. It actually gets in to an rpm range the cam likes.
Yup, you need the governor recalibration kit. Easy to do, but you basically have to guess the springs and weights, then test drive it.
Took me 4 tries to nail mine down.
I was lucky, got it first try. Used stock springs and IIRC I went 4 grams total lighter on the weights. The original weights that were on the governor were a lot lighter than i expected.
What is the rear gear ratio? If you're talking about part throttle, low throttle shifts, they do tend to be very quick if there's no load on the engine. The best way around this is to shift it manually. It will always shift through the gears quick if left in Drive, under low load, light throttle settings.
Yeah, w/those 3.90 gears it's gonna shift through the gears quick under light throttle/light load conditions. It's normal for it to do that. Holding the gears manually is about the only way around it.
You can drill and tap a port at rear for vacumn connection ,be shure you have Heavy grease on drill bit to catch alumimum shavings ,i would also remove carb and duct tape on inside where you will be drilling. or you can buy an aluminum spacer plate to go under carb with vucumn port already in it ,I have one but do not know how to put pictures on this sight ,if you cant find one i will posy picture in my picture albumn Also do you have the elactric kick down connected if not it will shift to early part throttle or WOT
I had the same problem multiple times. This is what i did.
I checked out the tag on the trans to see what it originally came from. IE bigger car usually ment lower rear gears, and earlier shifts for comfort.
Then made sure i had a new red line (adjustable) vacuum modulator. I drove my car and checked the vacuum while the car was at cruising speed. I set my modulator to start pulling in at this measurement. that way when the car is under light throttle it shifts smooth and a lil early but then under heavy throttle it's a lot more firm and a little later.
Normally running anything over 3.42 you have to do governor work. Buy a governor recalibration kit. and start playing with springs and weights. I use a scale and weigh all the weights and compare them to the ones that are original. I also make a graph to record my findings on each combination. also you can remove weight off the outer weight which will help raise your shift points under light loads. inner weight under heavy loads, and the springs separate the shifts.
I went from a 55g outer weight to a 44g. 14g inner weight to a 9g. and 2 step heavier spring. on a 67 firebird 400 th400 3.42 rears. heavy load 1-2 shift 5500, 2-3 shift 5200 rpm.
Also a thing to note is instead of picking 5500 rpm to shift at, you should choose a shift point that correlates with your engine peak torque and hp rpms.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Hot Rod Forum
2.2M posts
175.6K members
Since 2001
A forum community dedicated to hot rod owners and enthusiasts. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!