Poor Acceleration in Second

I have a freshly rebuilt 318 Poly in a 66 Satellite. It's an auto (refreshed 727), and the motor has a performance cam, some port work on the heads, 4 barrel factory intake, 600 holley vac sec, and factory exhaust manifolds into a dual system. I've probably done about 1000 miles on it and have a concern with the acceleration as follows:
Off the line in D it hits pretty hard (for a 318), and in third on the freeway from say 3000 rpm it also pulls really well, but if I'm cruising at about 50 mph and drop it manually into second (where the revs are still at about 3000), the acceleration is quite tame, maybe only slightly better than when in third gear. It's almost like there is far more torque than power and the engine needs to have something to push against to do it's best (weight off the line and wind resistance at higher speeds). Is it possible that the secondaries aren't opening up and it's more noticeable in second?

kickdown linkage adjusted correctly? Im no expert but its something to check.

whats the rear gear ratio?

Also what are your shift points (rpm) running it in auto? What is the vintage of the 727 in your car (if not stock)? You will reach a point where you won't 'downshift'; but secondary's are to open. A fast check on this is look down the carb engine off and run the throttle all the way back to see the action of the secondary's (opening). Also as mentioned, your kickdown (lever) should be very close to its max travel. Another quick check here is to note location of rod attached to carb at WOT then detach it to see if there's more rod travel to be had. You say fresh trans build, depending on the extent of the build, which could mean some other adjustments were not done or are off. With mine, having installed a shift kit, I get a rather stiff bump into 2nd chirping the tires beginning at about 1/2 throttle. And as to vintage, older 727's, unless tricked, require opening secondary's to downshift.

The gear ratio is 2.92 I think. To clarify, this is not when I'm kicking it down on the throttle. It does kick down ok and I admit the shift points could do with some adjusting to hold the gears longer when it does, but this relates to when I'm manually shifting gears. The transmission shifts up quite early when driving normally, feels great surfing along on the torque. However when I'm cruising along in D and someone comes alongside who might appreciate the noise, or we enter a tunnel, or when my son is with me and wants to hear it rev, I shift manually into 2 and open it up, holding it to 5-6000 rpm (depending on traffic). The car makes a great noise, but the push in the back and the rate we accelerate away from other cars doesn't seem that good, as compared to the doing the same exercise in D at higher speeds without it kicking down. In other words, 3000-4000 rpm acceleration holding it in 2 seems little better than 3000-4000 rpm in D (third), even though we are obviously turning a smaller gear and encountering a lot less wind resistance. The transmission doesn't feel like it's slipping, but that's sort of the effect, the revs are rising but forward progress doesn't seem to match....
This is all subjective and maybe I'm expecting too much, but the engine feels a bit strangled but only in '2'.
I don't know the vintage of the 727, it was serviced, new seals etc but was all in good order apparently. It seems to shift well and gives me no trouble.
I did recently swap the 700 cfm Holley (mechanical secondaries) with a 600 cfm Holley (vac secondaries) and I noticed a huge reduction in throttle response, but as the intake was changed at the same time (from Weiand 7503 to factory 4 barrel), it was hard to know if the change was due to the carb or manifold or a bit of both.

There's more to this; but 1st glance, having the rear gears you have wouldn't let's say be conducive to a lot of pop off the line or out of 2nd gear. I'd think for the thrill you're seeking you'd want to change out the gears or more, a heftier rear end set up.

Assuming all's functioning properly.. it's the gearing coupled with the more restrictive air flow from the closer to stock manifold/ carb combo.

Thanks guys, I think you're right. The old manifold/carb had a huge torque hole at low revs and then a fairly decent top end, but the new combo is smooth all the way off idle to 6000, but doesn't have that same kick up top. I don't want to change the diff ratio because I hate cruising on the freeway at 4000 rpm.

If you still have the aftermarket intake put the 700 on it and give it a try. The last 318 poly factory 4 intake was made in 1962 and utilized a solid lifter cam. You maybe to far out of the torque range for gains with the second gear down shift.

You're in a dead spot in your combo. Did you degree in the cam? Why did you take off the 7503? 700 cfm is probably too big for that motor, the 600 should be fine if it's set up properly. What is the stall speed on the torque converter?

Changing gears is the quickest way to get where you want to be, but if that is out of the question then you need to find other ways to make mid-range torque.

66 Sat said:

This is all subjective and maybe I'm expecting too much, but the engine feels a bit strangled but only in '2'.

I did recently swap the 700 cfm Holley (mechanical secondaries) with a 600 cfm Holley (vac secondaries) and I noticed a huge reduction in throttle response, but as the intake was changed at the same time (from Weiand 7503 to factory 4 barrel), it was hard to know if the change was due to the carb or manifold or a bit of both.

Click to expand...

My guess is there is nothing wrong with 2nd gear, nor is there a motor problem that only presents itself in 2nd gear. I'm thinking that maybe your perception of a problem is simply incorrect.

If you think it was better before the changes in the induction system, maybe switch back to what you had before.

The cam was installed by the local engine builder he hopefully knows what he's doing. The cam specs are 258/.462” ([email protected]”) 110LC. The torque converter is standard, don't know the stall speed but not very high. The engine builder did say that I'd probably need deeper gears and a higher stall speed to get the best out of what he built, but I wanted to see how it went first before spending more money, as the engine was only part of the restoration and I wanted to get the car on the road (and still pay the mortgage etc). Everyone knows how costs can spiral out of control....
The 7503 was changed as apparently it's not the best manifold for mild street use and the factory 4 barrel is far better (apart from the weight). The carb was changed for the same reason - I thought it would be overkill.
The car is a work in progress and I'm hoping that over time with changes such as headers, electronic ignition (to replace the single points), maybe 3.23 gears, the performance will improve. It's not exactly a slug now - I took it out a few nights back and did some testing and it was going pretty well - it took 2.5 secs to rev from 3000-4000rpm in second, and just under 5 secs for the same increment in D (third) at obviously a higher speed which was a surprise. I can't measure using the speedo as the needle waves around too much for any accuracy. You're right about the dead spot though, that's exactly what it feels like.
I'm going to take it over to a local performance guy in the next day or two for a look too and hopefully go for a drive with him to see what he thinks.

Just throwing this out there, but is your mechanical advance working?

I'd have to think, aside from all the great tips here, that could be a salvation, is your rear gearing is too slight for all the tricks done to your motor. A significant miss-match. There's a science here guys are posting about that know more than me. I have a pretty well tricked up poly too in my '63. This included headers/3" exhaust; the latter unnecessary for my motor. (Got talked into this.) The giddy-up is a disappointment; but then my crate motor or BB thoughts I had initially that I didn't follow, are my fault. I also went from 3:23 to 3:55's and that was a disappointment for the expected low-end pop but then now have the irritation of higher RPM cruising. I too think I have a miss-match somewhere with the trans/convertor, as a guess. Anyway, I'm starting to whine about my dilemma. 3:23's I think is a good go to get you more thrills. My 2 pennies.

I think part of the problem is my perception of speed has changed with modern cars. I have a 2 litre turbo 4 wheel drive hatchback as a daily driver that's as fast as most modern V8's up to about 80 mph. I don't regret rebuilding the poly as it looks and sounds great and has good fuel economy, but I do regret not going the stroker option that I was considering, although that had it's own complications and costs. The car is probably fast enough for the brakes, suspension and safety systems anyway - power is just addictive, you always want a bit more!

Truer words never spoken. Have had the exact same thoughts comparing what we have with today's cars and wanting this with old ones. Tell ya, have done a TON to modernize my '63 and the effort has paid off in many respects. The steering, handling, braking, are night and day from before. LED brake lights, headrests, etc. aside from all engine and rear work done. The void is the transmission while in fine operating shape...it's a 3 speed TF of the era. There are many tricks could do; but the expense is a stretch all considered. Maybe later on this. I think my wife's six Sonata could outrun my '63 in about 1100 of the 1320 feet. I got into plenty of trouble in my youth with BB cars so I may be smart with what I did...never could resist testing the power!