Hot Rods 700R4 or Turbo 350

Driving in the mountains, I would run something other than a tunnel ram myself. I had a 700r4 in an '89 vette with 3.08, was great...

 

A guy with a high winding 327, 2 4bbls on a tunnel ram in a TBucket shouldn't be worried about fucking gas mileage or keeping the RPMs down.

A 700r4 Trans will be completely useless in there.
Here's why - mostly the target RPM range and the national speed limit.
Unpacked :::::
Weight of vehicle
Torque of engine multiplied by gear ratios
Rpms to speed limit.

The tunnel ram will want to be above 3000 rpm, You want a 3000 rpm stall converter, you want to be close to those rpm values driving on public roads.
Th350 with 4:56 gears.


With OD Trans you'll need around 6.8 to 7.0 rear gear to target the rpm and public roads.


The low first gear of the 700 Trans will be completely useless with a 7.xx rear gear in a T bucket.

You can play around with all this stuff too, but if you're dead set on the tunnel ram you gotta consider the other stuff too.

That engine will be just fine cruising at 3200-3500 Rpms, it won't care and it will last about 2/3 the life if it were singing along at 2000 Rpms it's also going to suck up close to 2x the fuel to do it. The engine won't care one bit, the T bucket won't care either about the RPM or Gas mileage. Apparently the owner might.

Here's one more- OD Trans and 120 mph.


Th350 and 4.56 and 130 mph

 

RPM through the lights, is how I select gear ratios. Right on...

 

The po-po gets all uppity when I go through the lights at high RPM.

 

That's why I said math is hard earlier. All of your components have to work together.

Math being hard is why people cannot fathom me running 5.14:1 gears on the street.

 

That trans ratio of .5 makes all the difference gimpy!

Almost sounds like the tunnel ram could be questioned.

 

Yeah how do you get to 0.5 final drive gear?


Anyway, for a guy like the original poster here who wants a "light to light" car ,, the biggest kick in the pants is going to be rear gears- hands down that's the biggest bang for the buck improvement. You can anything to run scary fast from this light to that one, Briggs and Stratton included.

The poser tunnel ram could probably hide sequential port EFI very well and then he can have his cake and eat it too.

 

LT1 T56 6-speed:
Gear Ratios : 2.66, 1.78, 1.30, 1.00, .74, .50

The ratios in this transmission are a little "off-beat". It is almost like a conventional first gear was done away with, and replaced with a second, taller overdrive, so the rear ratio needs to be altered accordingly.

For perspective, I ran an S10 T5, with a 0.72:1 overdrive, and 3.55:1 for a few years.

0.72 x 3.55 = 2.556 combined final ratio.

With the T56:

0.50 x 5.14 = 2.57 combined final ratio, but with a MUCH better gear spread.

 

What would be the difference between using a T350, or a 200r4. Turbo 1st is 2.52, 2nd is 1.52, 3rd is 1.0, a 200r4 1st is 2.74, 2nd is 1.57, 3rd is 1.0 with a over of .67. I could use 4.33 gears, it would be turning 2850 rpm's going down the road at 55, or 4.11's and turning 2700 rpm's with the turbo. With a 200r4 I would not have to use the O.D. unless I'm on a freeway, and still turn the same rpm's. Why would I have to be turning 3000 rpm's if I'm only cruising along on the highways. Then I could run 4.33's and be able to drive farther out with it, and still have the rpm's off the line.

Back in the mid 70's. I had a '67 Camaro with a 283 with double hump head, a 350/350 cam, headers, and 2x4 tunnel with afb's on it, 4spd, and stock gears, and road slicks. I drove the tires off it. It ran good, never had any trouble with it running strong.

I thought of using the 700r4, because I have two sitting, with nothing to do.

I have a 350/700r4 with EFI waiting to be put into my '91 S-10.
I don't want EFI on my coupe, unless it's a Hilborn. I sold my 392 with Hilborn injection, that was suppose to go in my coupe. My avatar.

Pat

 

You haven't mentioned cam duration ...A major factor when trying to determine low rpm cruise numbers.
Cam specs?
Converter specs?

 

Include LSA.

 

Maybe there's something missing,
every tunnel ram for a Small block I see listed their RPM range for that at 2900 rpm to 9000 Rpms And that's going to be based on 350 cubes. This has to do with velocity. If the cubes are less like 327 the Rpms would be up or if cubes are more like the 454 bbc the Rpms are less like 2500. These guys are pretty good with that figure. Can you get away with cruising a 283 at 2200 Rpms- ? - apparently you've done this so it can be done enough but I can't fathom it doing this well. There used to be a "pro street" tunnel ram that had narrow runners to cheat some velocity boost on the low end rpm but it choked the engine in high rpm.

Second difference -
What's the stall speed of that 4 spd's manual Trans clutch? When does it lock up?
It's very different than an automatic converter set up is it not?
With a manual clutch you can release the clutch at any rpm you want, let it slip till the cows come home and lock it at any place between that and down to 0 rpm by letting the pedal up. not so with an auto Trans converter.

(Edit: Cleared that up a bit)

 

Silent rick. Yeah, you are crazy good!

 

I have not picked out a cam yet. I have the '66 327 block & crank, & rods in being machined on now. I have double hump heads, flat top +.030 pistons.

I don't have a converter yet, I am still debating which transmission, and gears to use, That's why I'm asking advice on which to use.

I bought my Edelbrock 2x4 tunnel ram new back in '76? Damn. that was 41 yrs ago.

I understand the difference in running a stick vs auto, but I didn't slip the clutch up to rpm's/speed, with the tunnel ram. I did what I could to keep the tires from spinning, with the oem 12 bolt posi & gears. It worked the best with 10 or 12" (don't remember which) street slicks. We did a lot of street racing back then. It helped that I worked on, and clean cop cars at night back then.

I know of someone that's now using a tunnel ram on his sbc, with a T400, with 3## gears, and drives it everywhere. without any problems, in a '30(?) Tudor. He doesn't turn the rpm's up on it, yet runs great for him. I don't know what he has for a cam, I'll have to ask him.

My car is a coupe, not a bucket.

Thanks, Pat

 

Uh oh.....the big V used the But it is what most of us have been saying here.. If you are hell bent on 2 x 4bbls then just use a low rise dual quad intake some small carbs and a couple velocity stacks or something.

 

I can't EVER remember driving down the rode and thinking. Gee i wish i had one LESS gear .

 

I run an overdrive in everything, the truck has a 700r4 with 4.10 gears, 30 in tires, and it does 55 mph at about 2000 rpms. If you need to run higher rpm, shift down a gear. I have a nv3500 5 speed in the roadster with 3.55 gears, and it performs great as well. I doubt that most people running a tunnel ram on the street are doing it because it is the best choice for performance.

 

I get the feeling that I'm way too busy shifting, every time I drive my wife's little sporty car, with it's 6 speed. Although, the motor is so small, it kind of needs all those gears.

Hot rods with big motors just don't need all that shifting.

 

Can some1 tell me where you got those charts? I would like to check out my set-up too.

 

http://www.csgnetwork.com/multirpmcalc.html

There's a bunch of them thru the "Google"

 

Hi Hemi t, I had at one time an impala with large journal 327 and ran a comp cam adv 268 w/460 lift 10to1 pistons dual plane edlbrock intake and 600 cfm carb. The transmission was a th350 with about 2200 stall converter and stock open rear end with street tires it ran 15.8 on the 1/4 mile. It felt like it needed more stall or a lower gear.
(ty vic I checked the numbers n looks like I have decent set-up

 

The gimp is correct here. Quite a big jump across the ravine that separates a blown flatty and a tunnel rammed 327.

If you want the intake to work you got to keep your revs up. Hopefully there is enough engine to run with the intake. If it were me I would stay with the T350 and enough gear to keep it in the operating range (RPM Wise) for the motor. Not knowing how the engine is actually built makes it hardtop guess a gear. If I were a guessing man I would think that with a 28" tire and a 1:1 final a 3.55 or deeper gear is what you are after. Most guys would be thinking a 3.73 for street and strip (stop light). But like I said impossible to say not knowing the rest of the motor.

 

This is exactly why I have a 6-speed in my Falcon.

It has 199-hp, and is built to take the twisty corners. No big hot rod motor here.

 

LMAO they don't care how many revs you are turning if the light is red.

 

It's going through that light that they have the problem with.

 

Pat, what you gotta realize is, that even though none of these guys have run a OD auto with a 4 series gears, or a tunnel ram, they know better than those who have.
do a simple poll, ask the guys posting here if they have done either one, if they don't answer, take that as a "no", and weight what they have to say accordingly.

 

And they thought that their worries were over when I left town.

 

One of us might have but that guy probably doesn't like an AOD, he may not even be too impressed with a tunnel for a street intake either.

 

OD Trans with 4 series gear - yep plenty
Tunnel ram - I've tuned quite a few, I have no need for one so never owned one.
Lots of stories of both success and failures and turning them around. Amongst those is where I learned the importance and relationships of gearing.

It really really really matters on what the intended driver is looking for and expecting and actually understanding what it takes to get it there. The vast majority of folks "think" they want optimal WOT power levels but drive the car less than 1% of time with their foot on the floor. That means that 99% of the seat time in the car leaves them wanting and disappointed.