What would you change? |
Post Reply |
Author | |
72BoB
Senior Member Joined: 25-January-2011 Location: Atlanta Status: Offline Points: 248 |
Post Options
Thanks(0)
Posted: 08-June-2012 at 2:52AM |
What would you change up about this combination of cam and gearing for my street
car that sees a lot of highway miles, and will see very little if any
track?
1972 Ford Torino ~4000lbs Built C6 with 2400-2500 stall 2" primary and 3 1/2" collector full length headers Bored 460 to 472" Holley 750 (can change if needed) Stealth intake Mildly
worked C9 heads with factory sized valves9.0-9.5 compression (pistons have yet to be determined) Presumably a Comp 280H grind cam (builder didn't know exactly, but said the cam had .530 lift) 3.08 rear gearing ~29" tall tire Would it be best at this point to change the cam to a more street friendly one? Or would it be best to change the rear gearing to something like 3.73 to take advantage of the 280H's power band? Would changing my gears from the 3.08 to 3.73 affect highway driving significantly? ...or what would you do? Edited by 72BoB - 08-June-2012 at 3:59AM |
|
1972 Torino
|
|
Psquare75
Admin Group Member of the Stroker Club Joined: 26-November-2005 Location: United States Status: Offline Points: 4591 |
Post Options
Thanks(0)
|
What intake/carb/etc? rear tire size? torque converter stall rpm? |
|
Paul
77 XR7 460/C6/3.00:1 *SOLD* 78 XR7 523/C6/3.5:1 79 F100 460/TKO500/3.25:1 'I also have some left over potatoes-I understand you can generate electricity from them'- Foote500 |
|
72BoB
Senior Member Joined: 25-January-2011 Location: Atlanta Status: Offline Points: 248 |
Post Options
Thanks(0)
|
Updated OP with extra information.
|
|
1972 Torino
|
|
72GTS351CJ
Senior Member Joined: 30-November-2010 Location: NY Status: Offline Points: 1481 |
Post Options
Thanks(0)
|
Something to consider when changing gears as a rule of thumb I've been told every tenth on the gear ratio is a hundred rpm's. So from 3.08 to 3.73 add about 700 rpm's.Just thought I'd throw that out there.
|
|
72GTS Clint Eastwood Special
|
|
Psquare75
Admin Group Member of the Stroker Club Joined: 26-November-2005 Location: United States Status: Offline Points: 4591 |
Post Options
Thanks(0)
|
If it were me, I'd drop the cam down a notch and the intake to a performer, but I hate 3K+/4K+ on the highway.. it gets old fast.
|
|
Paul
77 XR7 460/C6/3.00:1 *SOLD* 78 XR7 523/C6/3.5:1 79 F100 460/TKO500/3.25:1 'I also have some left over potatoes-I understand you can generate electricity from them'- Foote500 |
|
72BoB
Senior Member Joined: 25-January-2011 Location: Atlanta Status: Offline Points: 248 |
Post Options
Thanks(0)
|
I am considering a custom cam, but I
am waffling back and forth and can't make up my mind. I will also probably change out the intake as well, but I can do that later on my own.
Say I do decide to stick with the current cam, and change gears to something that would utilize the cam more: Obviously, I would be spinning higher rpms on the highway, but how much would that affect mpg? Say I changed from the 3.08, spinning 2800rpms @ 75 on the highway, to 3.50, spinning 3200 on the highway? If it is only a loss of a couple mpgs then I'm not going to worry too much. And anyone out there with a similar build/car have any estimates of what the mpg would be? Consider if I did not mention highway driving, would just changing out the rear gears be the best option? Especially if I am considering getting a G/V overdrive unit in the future? |
|
1972 Torino
|
|
Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6059 |
Post Options
Thanks(0)
|
big difference from Hot Street to Highway Fuel Sipper, that's why the factory combo is such a compromise and every rodder wants to alter it to better suit what they think they need
existing combo looks like Hot Street except for the rear gear, and it's still not far off considering the 460+ should make enough torque to turn a ~3 gear. 2400 stall with a big block is pretty significant, you're stepping right over the stump pulling bottom end and getting right into 'let's move this pig' territory. Stealth intake says it works from idle to 6800, pretty flexible but you can do better if you're looking for more economy or better power in the bottom end but you'll have to weigh the cost vs gain in that dept. same with the carb, lots of different calibrations including venturi diameters & booster styles, can make a big difference how the engine acts at different rpms not to mention how much fuel gets delivered
so what's the desired end result, what bothers you about the current combo?
not enough Hot in Hot Street or are you looking for better highway cruise?
then you throw out the possibility of the Gear Venders unit, it can be a tricky dance to have your cake & eat it too with the stall converter & big block. in O/D you may find yourself below the stall threshold and just be whipping the trans fluid to stay moving. G-V and a gear ain't cheap! just to end up right back where you are most of the time... Edited by Rockatansky - 11-June-2012 at 6:29AM |
|
72 GT Ute
|
|
72BoB
Senior Member Joined: 25-January-2011 Location: Atlanta Status: Offline Points: 248 |
Post Options
Thanks(0)
|
I really don't know what I'm going for, I can't make up my mind.
First off, I think I'll be switching to a Performer intake for hood clearance, so that solves the intake question. I just don't think I'll know exactly what I want until I drive it. I like the idea of "hot street," I guess it all really just depends on drivability and mpg. I know mentioning mpg and a 460 in the same sentence is laughable, but it would be nice. If changing to a more moderate cam profile will only increase mpg by 1 or 2 then I'm not going to worry about it. Otherwise, I'd rather sacrifice a bit of mpg for a more significant bump in power and acceleration with the cam gears.
Edited by 72BoB - 11-June-2012 at 6:53AM |
|
1972 Torino
|
|
Psquare75
Admin Group Member of the Stroker Club Joined: 26-November-2005 Location: United States Status: Offline Points: 4591 |
Post Options
Thanks(0)
|
Not being a jerk. But come back when you do. Otherwise you end up with something you didn't intend, like I did. |
|
Paul
77 XR7 460/C6/3.00:1 *SOLD* 78 XR7 523/C6/3.5:1 79 F100 460/TKO500/3.25:1 'I also have some left over potatoes-I understand you can generate electricity from them'- Foote500 |
|
Rockatansky
Senior Member Joined: 30-July-2010 Location: On The Road Status: Offline Points: 6059 |
Post Options
Thanks(0)
|
these don't come up available every day, if it's what you're looking for? he doesn't even have it listed as a Dual Port and is starting out pretty darn low
|
|
72 GT Ute
|
|
72BoB
Senior Member Joined: 25-January-2011 Location: Atlanta Status: Offline Points: 248 |
Post Options
Thanks(0)
|
Here is a response on 460ford.com from CarsbyCarl:
"My 429 yielded about 13 mpg running ~3000rpm at ~80mph on a six hour drive to a
race last year. This was with 2.75 gears and 27" tires. The 3.25 gears make for about 70mph at 3000rpm which is okay for shorter trips but gets tiring on longer runs. The 3.70's made for about 60mph at 3000rpm, which was just painful." And here is my response: Carl, that is exactly what I wanted to hear...
Considering my mild 302 that is in the car gets maybe around 17 mpg on the highway, and is an absolute dog doing it, the 13 doesn't sound too bad. That doesn't even include the fact that the 302 gets MAYBE about 10 in the city because the car takes so much to get moving (and the 302 is getting pretty tired). I might have made it sound like mpg was a huge factor in my decision. While it is something that I wanted to consider, it isn't the overall goal of this build. I understand that big blocks and mpg don't go together in the same sentence. I just wanted to make sure that I wasn't going to go totally overboard (and 12-13 mpg is fine for me). And I know what it is like to be buzzing along at 3200 rpms for hours on end. Granted, it was not with a big block, but it was with the mild 302 with glasspacks turned down before the rear axle. I guess to the average person it can get annoying, but after doing it for four years I guess that I'm just "special." |
|
1972 Torino
|
|
72BoB
Senior Member Joined: 25-January-2011 Location: Atlanta Status: Offline Points: 248 |
Post Options
Thanks(0)
|
No offense taken, I need someone to tell me how things are from time to time... And I especially don't mind it when money is involved...
And the reason that I didn't know what I wanted to do is mostly in part because I didn't have clarity on a couple very important questions, one of which Carl answered perfectly above. And with that being said, I think I'm just going to sacrifice a couple mpg and upgrade my rear gear. Edited by 72BoB - 11-June-2012 at 10:41AM |
|
1972 Torino
|
|
Post Reply | |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |