64 3 sp to 77 4/OD Installation
Wow AJ, you threw a wet blanket on this one. Slim didn't say what
mill he's running. If he's got his stuff together, I say go for it.
I also have a 64 Valiant with the optional "big" 225. I just rebuilt it and got it running last fall. It's 3 on the tree with the standard 3.23 gear. I put about 400 miles on it before winter and it seems to have plenty of power. I will say the column shift sucks. Even with careful slow granny shifting it tends to jam and I have to pull over and unjam it. I'm going to give it another try because I just bought some new shifter bushings that will enable me to get a more precise adjustment.
But....I've been collecting parts for a 4 speed conversion. As luck would have it, I now have both a 65 4 speed trunnion mount trans with Hurst shifter and a mid 70's OD trans with shifter and the Bellhousings for both. I finally also obtained 2 floor humps. One is a 64-65 round hole and the other is a 66 oblong hole. The earlier one is VERY rusty but has the correct shifter hole. The 66 is much better but has incorrect hole.
My plan is to try the 65 trans first as my trunnion driveshaft is in good shape and is a direct bolt-in. The OD would require a new shaft. I'll probably try both eventually just for fun. This car will be a driver (entered in this year's Carlisle) and I'd like to get decent mileage so it'll be interesting.
If you have the 170 three-speed,then Your combo is off-the-line-peppy, cuz the starter gear is 3.22 x 3.23 =10.40. The 225 has lots of grunt with that combo to motorvate an early-A.
The 225 tranny had ratios of 2.95-1.84-1.00 IIRC. The starter gear for that tranny is thus a little lower at 9.53. The rebuilt 225 will likely be a little stronger as well, with the compression restored.
I highly recommend the 273 4-spd, as it has the 3.09 low in it.The ratios are 3.09-1.91-1.39-1.00 and the splits are waaay tighter than the A903. This gets and keeps your slanty on the pipe longer, for quicker acceleration. With the 3.09 low, and the tighter splits, you may be able to lose some rear gear.
A)Your current gears may be 2.95-1.83-1.00. With a
3.23, roadgears are
9.53-5.91-3.23.
B)With the early-A box,and
2.94s; the roadgears would be........................
9.08-5.61-4.09-2.94.
Notice that the first two gears are very similar, so you lose almost nothing. Then you get a much closer gear going into 3rd, and then you can think of 4th as an od,cruiser-gear only.That 2.94 will drop your Rs about 9%. Generally 1/2 the Rpm drop will be the economy gain; so expect about 4.5% better fuel economy. This is about 3/4 mpg better on a 16 mpg car.
C)The od box may need an increase in rear gear, for the slanty to pull it on the transfers. I would expect it to need
at least 3.55s,and,with those your roadgears will be;
.................10.97-5.93-3.55-2.59.
Notice now that first gear has much more torque multiplication, while 2nd is about the same, and third is still plus 10%. And the od drops your Rs 20% for a 10% mileage improvement.This is about 1.6mpgs on a 16 mpg car.
I tried to keep second the same, cuz if you load up the slanty with too much second gear, it kindof looses steam.
Notice that the
B) combo gives up a little off the line,to get a short 3rd. If you need acceleration in third,this is the best way to get it. The 5.61 will get you 60mph at 4500. So third now is almost a freebie. But; notice at 32mph, your Rs in second will be about 2400, a happy place for the slanty, cuz this is about where it makes peak torque..A shift into third will drag the Rs down to 1727, a very comfortable cruise. Taking second to 45mph and dropping into third; now the Rs are again about 2400, so now 3rd is very useful.Your slanty will have an easier pull to 60 with this combo than with any other listed here. It will hit 60@3240,still pulling pretty hard. Dropping into 4th, the Rs will be 60=2328(25.5 tires). Again near peak torque. I like this combo.
The
C) combo is almost too much first gear.If you shift it when you normally do, it may fall flat going into second; it is just too far away. You may have to rev the engine up 15% higher than before, going into 2nd. Then 3rd is 10% closer, and 4th is strictly for cruising. When you hit that; 65=2220 rpm.
>I hope your slanty can pull that on the transfers, cuz if it gets up on the mains, the whole idea falls apart.I think it will, cuz it is very near peak torque. At this cruising-only rpm, the slanty may be wanting 40 to 45 or more,degrees of timing. There is no way to get that except with the Vcan,which takes a working sparkport. If your engine gets on the mains,the sparkport will be dead, leaving you with just the mechanical, which will be just over half that; goodbye economy.
>This is a
double whammy to fuel economy,cuz you lose the Vcan advance, and the mains will be too rich. They will be delivering enough fuel for nearly full power, cuz they are seeing low vacuum/large butterfly opening. If you reduce the mains, then you are looking for a meltdown when she really is, under full power.
You have to; stay on the transfers which you can tune, and to keep the manifold vacuum up to keep the sparkport alive.
Or go to a really small 2bbl,lol.This is why I have the SuperSix set up. It has metering rods. And a metering rod adjuster built right in.
So this is a fine line to be walking, with these small engines.
Here is an experiment for you;
Pull the carb off and have a look at the transfers.Set the fast idle cam to open the the butterflies to the top of the transfers.Figure out how to index the throttles so you can easily find this point with the carb back on. Now fabricate a two-stage throttle limiter so that you can feel this point on the gas pedal. I used a coat-hanger, bent in a big old S shape to to do the job with a light initial spring and the existing heavier main spring. Now jump in and wind her up to 60mph. Then back off to the set-point and see how many mph you are currently getting from the transfers. If it ain't more than 60mph, then it will be difficult to gain anything with gearing, and with the current carb.
While you are at it put a vacuum gauge on the spark port and bring it into the cab. Take a reading at 60mph, and note the rpm. Stop the car and put a timing lite on it. Check the timing at the rpm that made 60mph. Idle it back down. Now apply the 60mph vacuum to the Vcan and read the timing increase from idle timing. Add those two together.Whatcha got?
60mph should be 2560rpm with 25.5 tires. I would expect about 25* of timing there, and 14 to 20 in the can, so ideally a total of 45*. More would probably be better.If you don't have at least 39* now, it's only gonna get worse, with a lower highway rpm.
End test.
If your numbers are less than 39* now, then there is plenty of room for improvement in the tune,as to economy under steady-state cruising.
With your newly built 2-stage throttle device, you can find a guaranteed same throttle opening time after time. This means you now have a way to tune under steady state conditions. So attack your timing devices and your AFR, and tune for maximum mph.
>I picked a spot on the hiway that was long and flat. I picked some telephone poles as start/finish lines. I got me a stopwatch. And I timed the stretch 5 times in a row,on my way to and from work,windy days excluded. Then I made a change, and next week re-ran the test. In this way I could see improvements or not. If your fueling is at least close,start with timing first. Just crank 4* in and see what happens. If your time improves, add 3 more. If it improves again, add 3 more and so on until it slows down. Then back up 3 and prove it was best.
While your dizzy is cranked of course, you will have to be easy on the gas-pedal to avoid detonation. If you pickup too much speed, you will have to reset your 2-stage.
>Once the magic number is found, and assuming the power-timing was previously established, You will have to make the magic number appear in the Vcan system.
>After that is done, you start on the carb. And if the stopwatch shows consistent improvements, continue until it slows down.
Then revisit the timing.
>By the end of summer you will have maxed out the steady-state fuel economy.
If the car becomes hard to drive with the leaned-out transfers, then you may have to sacrifice some economy.
>If the Vcan gives you grief with detonation, you will have to figure out a way to drop it out faster without reducing its all-in.
Sometimes you have to change the mechanical curve to achieve the same end result.
>I can almost guarantee you, that dialing in your current economy, in this way, will be worth way more than the theoretical 3/4 mpg of combo-B, or the theoretical 1.5 mpg of combo-C.
Whatever you do, don't melt it down, I ain't buying you a new engine!lol
Seriously, happy motoring
