64 3 sp to 77 4/OD Installation
Wow, gotta be the longest post ever^^^^. You must be retired. I'll have to print and read it on my day off. :)
So I have a 64 Val vert, rebuilt 225 head shaved 0.08, Oregon regrind cam, pretty mild, can't remember the specs right now but I think it's about. 430 lift and maybe 252*, pocket ported, gasket matched, hogged out stock exhaust manifold and soon to have full 2.25 exhaust, stock Carter BBS. 3.23 rear with 3 speed 64 tranny. Static timing is about 8-9*.
First time I took the car out after getting it running I accidentally peeled out a couple times from traffic lights. First is pretty steep at 3.09 X 3.23. I'd like to lower the freeway revs but I haven't installed the mini tach yet. It's going to be a driver.
So AJ, my first change is going to be a 65 trunnion mount 4 speed from a 65 cuda (still 3.09 first gear and 3.23 rear) then I'd eventually like to try the 70s OD I have waiting in the wings. What do you think is the better combo for all around driveability ? I have my ideas but curious what you think.
No question about it; the deep-low and 3.23s,65=2880; so taller tires would be better.
Or else the same deep-low trans and 2.94s, with those tiny 13" tires. Those 195/75-13s are about 24.5 tall. They will get you 65=2622rpm, and the starter gear will be 3.09x2.94= 9.08, just barely enough if you rev it up a bit. 35mph will be about 2700 in second; a happy place for the slanty to be with that cam.
Nothing wrong with using the 3.23s for city fun,and if you don't mind slowing down on the hiway,60=2660. I could dig that!
The slanty will love the shorter splits of the 3.09low/direct 4th box. In comparison,the od box will be pitifully slow with a 252* cam and 3.23s.Dreadfully slow.You basically lose 3rd gear to gain the od, an unfair trade in my book, for a little engine. Sell that box now! So you never have the opportunity to try it. The rpm in od with 3.23s will be
65=2100. Good luck pulling that with a 252* cam. Well now, hold on. This is a lightweight early A, right? Yeah ok your slanty might pull that. But I doubt it will get any better gas mileage,lol.
Here is an experiment for you;
After you get your engine all tuned up, do this. Rev it up in neutral until the vacuum no longer rises. This should be your minimum hiway cruise rpm.The minimum. At this rpm your cam and head are finally working together. Reversion has stopped. The header is pulling like it's supposed to. Now you can lean out the carb, and get the timing maxed out. And just maybe that slanty will pull that 65=2100.
>But if your vacuum peak does not arrive until later,long after 2100, then you will be trying to tune while the intake is still all mixed up. You will spend dozens of hours trying different things, and in the end, you will have to drive faster to reach the efficiency that will max out the economy.
Your dad probably told you about his 49 Merc that got best gas mileage at 85 mph. You ever hear a story like that? What do you imagine could bring such a thing about? It's called efficiency. To maximize economy requires maximum engine efficiency at minimum rpm. Both together. At 2100 in od,you got that one pretty close.How about that vacuum-peak?I guess we'll see.
It is better to sacrifice a little rpm to favor efficiency, than the other way 'round.
>You can sometimes shift the vacuum-peak rpm with timing.Once you find that rpm, put the fast idle on so it stays at that rpm. Then reach down and start advancing the timing until the rpm reaches a peak.Kick off the fast idle. Now go find the new vacuum peak, and set the fast idle to that. Again move the dizzy around to maximize the rpm. When you have thus found it, put a timing lite on it and see what the engine wants,at that final rpm.Bring her back to idle and put the timing back to where you first started the test. Let her idle a while to cool off. Then rev her back up to that earlier determined final rpm, and read the timing.
Then go and figure out how to give her what she wants, yet not that she hammers herself to death with detonation.
Upon re-reading this post, it seems to me that it sounds somewhat condescending.That is not my intent.I just don't know how to write it much different without it losing it's message.
So, all the best to you and that 3.09-Direct box,lol.
and yes, semi-retired, working just 24 hours per week, just like my wife.
